UNIT 3: Introduction to Pharmacology
Some common terms
Pharmacology:
It is the science of study of the drugs.
Pharmacology is the study of interactions between chemical substances (drugs) and
the living organism (body system).
Pharmacotherapeutics:
Pharmacotherapeutics is the application of the knowledge of pharmacology in the
treatment of diseased condition. It is the rational and optimal use of drugs in the
exploration or management of diseases or physiological functions.
Pharmacy:
It is the art of preparation of drugs and their formulation into remedies
Drug:
A chemical used in the diagnosis, treatment, or prevention of disease. More generally,
a chemical, which, will modify the behavior of cells exposed to it.
Pharmacodynamics:
The science and study of the biological effects produced by chemical agents; more
specifically, the science and study of how chemical agents produce their biological
effects. In short it is the study of the action of drugs on the body.
Pharmacokinetics:
The study of the factors which determine the amount of chemical agents at their sites
of biological effect at various times after the application of an agent or drug to
biological systems. Pharmacokinetics also includes study of drug absorption and
distribution study of the chemical alterations a drug may undergo in the body, and
study of the means by which drugs are stored in the body and eliminated from it.
Pharmacopoeia:
Large references which contain definitions and adoption of test which establish the
identity, purity, potency of drugs, sources, and preparation and recommendation of
dose size, frequency and indication for each and every drug. – Eg-B.P, USP, E.P, I.P
etc
Half-Life:
The period of time required for the concentration or amount of drug in the body to be
reduced to exactly one-half of a given concentration or amount. Based on the half life
of a drug frequency of its administration is calculated. For example a drug having half
life of 6 hours will be required to be administered every 12 hour inverval.
Dose:
The quantity of drug, or dosage form, administered to a subject at a given time; for
example, the usual dose of aspirin for relief of pain in an adult is 300-600 milligrams.
Dose may be expressed in terms appropriate to a specific dosage form, i.e., one
teaspoonful of a liquid medication, rather than the weight of drug in the teaspoonful.
Dose may be described as an absolute dose (the total amount administered to a
subject) or as a relative dose (relative to some property of the subject as body weight
or surface area, mg/kg, or mg/m2).
Dosage Form:
The physical state in which a drug is dispensed for use. For example: a frequent
dosage form of procaine is a sterile solution of procaine. The most frequent dosage
form of aspirin is a tablet.
Dosage forms
Solid
Semisolid
Powder
Liquid
Solid
1. Tablet: flat circular preparation, contain one ore more dose
2. Bolus (boli): elongated/ oblong preparation, contain one or more dose
3. Pill: spherical, round preparation, contains one dose only
Semisolid
Ointments: oily / fat based preparation for external use
Electuary: medicinal paste for use in mouth
Powder: Preparation that are finely ground for internal or external use
Capsule: powder encapsulated with gelatin. Normally contains preparation that taste
bitter
Liquid
Preparations in liquid form
1. Tincture: alcohol based preparation
2. Mixtures: drug dissolved in water
3. Lotion: antiseptic in water
4. Emulsion: mixture of water and oil
5. Suspension: a dispersion of fine solid particles in a liquid or gas, removable by
filtration
6. Injections: preparation for parental use
Toxic Effects:
Responses to drug, which are harmful to the health or life of the individual. Almost by
definition, toxic effects are "side effects" when diagnosis, prevention, or treatment of
disease is the goal of drug administration. Toxic effects are not side-effects in the case
of pesticides and chemical warfare agents. Toxic effects may be idiosyncratic or
allergic in nature, may be pharmacologic side effects, or may be an extension of
therapeutic effect produced by overdosage. An example of the last of these is the
apnea produced by an anesthetic agent.
Tolerance:
A condition characterized by the necessity to increase successive drug doses in order
for them to produce identical effects. Apparent loss of potency of a drug observed
during the course of successive administrations. "Tolerance" should not be used to
mean "lack of sensitivity" manifested toward a dose of drug. A non-addicted drinker
who is unaffected by several drinks of whisky downed in rapid succession is probably
insensitive to alcohol rather than tolerant to its effect
Pharmacodynamics - The Mechanisms of Drug action
I. Drug Receptors
Most drugs cause their effects by interacting with specific drug receptors. Receptors
are structures on cells that interact with a particular drug because they have chemical
structures that "match" the shape, charge, of the drug(s), much like the relationship
between a key and the lock it opens (or a substrate and the enzyme that acts on the
substrate). The receptor is often named to indicate the type of drug/chemical that
interacts best with it (e.g., a receptor for histamine is called a histamine receptor).
Example below shows how drug reacts with receptor to produce its effect
Drug + Receptor
drug -Receptor Complex
Effect (response)
Cells may have tens of thousands of receptors for certain drugs (or hormones or
neurotransmitters). Cells may have different types of receptors, each of which is
specific for a particular type of drug (or hormone or neurotransmitter). Some drugs
have shapes/structures that "match" the shape of the receptor better or worse than
others, and so activate the receptor better or worse, causing more or less of a response
on that receptor. When there is a poor (or no) "match" between specific drug
molecules and the types or receptors on a particular cell, the drug-receptor interaction
may lead to a weaker response, or no response at all (depending on how well the
drug’s shape and the receptor's shape "match-up"). Some drugs have shapes that allow
them to interact with more than one type of receptor.
II. Agonists
It is defined as a drug (or hormone or neurotransmitter) that interacts with receptors
on cell(s) and causes a response by changing the function of that cell. Agonists have
two main properties namely:
1. Affinity: the ability of the agonist to "bind to" (attach to) the receptor
2. Efficacy: the ability to cause a response via the receptor interaction The maximum
intensity of response to several other wise-similar drugs: if drug A causes a greater
intensity of response than drug B (regardless of dose), then drug A is more efficacious
than drug B
III. The Dose-Response Relationship
The bigger the dose of a given drug, the greater is the effect. Bigger dose means that
more drug molecules are available and able to interact with the many receptors on
target cells, each interaction induce a small response, but collectively leading to a
bigger response than with a lower dose. Dose response relationship is dependent on
affinity, efficacy ED50 and potency.
ED50 (effective dose-50%)
Ed50as the dose of a drug needed to cause 50% of the maximum effect (response) that
the drug can cause. Different drugs that are agonists for the same receptor can have
different ED50s: they can cause the same intensity of the same response(s), it just
takes different doses of the drug (s) to do that
Potency
Potency is a comparison of the ED50s of two or more drugs that cause the same
responses via interacting with the same receptor. The drugs being compared must be
able to cause the same maximum intensity of response (i.e., they have equal efficacy),
regardless of the doses needed to cause that maximum response.
IV. The three most important properties of any drug used (or being considered for use
in) human or veterinary medicine are:
A. Affinity
The ability to combine on to a receptor of the cell
B. Efficacy
The ability to cause a response via the receptor interaction
C. Safety
Lacks serious adverse effects, at least at doses needed to cause the desired effects
V. LD50 (lethal dose-50%)
LD50 is defined as the dose of a drug needed to cause a lethal effect (kill) in 50% of a
test population of subjects. Depending on the drug(s), the LD50 may be close to, or
much greater than, the ED50 (but obviously the LD50 of a clinically used drug can
never be smaller than the ED50, or it would kill more people / animal than it would
help)
VI. Therapeutic index (margin of safety)
It is defined as the ratio of LD50 and ED50. Reflects the "margin of safety " for a drug
how likely an overdose might cause serious toxicity or death how far above the
average effective dose you would have to go (if someone made a mistake) to start
killing animal with the drug. The bigger the therapeutic index or margin of safety the
more relatively safe a drug is compared to another drug with a lower therapeutic
index. For some drugs the therapeutic index is so small that a toxic dose is barely
above the average effective dose (examples: digoxin, for heart failure; theophylline,
used for asthma). For others, the therapeutic index is so great that it's almost
impossible to kill (or seriously poison) a patient by giving too much (example:
penicillin)
Factors influencing therapeutic index (margin of safety),
Are the factors that make a drug "less safe" than it would be under other conditions,
e.g.
1. Presence/use/administration of other interacting drugs
2. Changes in drug absorption, distribution, metabolism, excretion
VII. Pharmacologic antagonists (also generally called receptor blockers)
These are drugs that can be given as antidotes against certain drug after it has been
given more than what is required or over dose.
Properties of antagonists
1. Have affinity (can bind to a receptor)
2. Have no efficacy -- they do not cause a response of their own; any "effect" you see
after giving an agonist results only from their counteracting the effects of an agonist
Two main types of pharmacologic antagonists
1. Competitive antagonist (surmountable) - the most common, most worthy of your
attention and understanding
2. Noncompetitive antagonist - relatively uncommon
1. Competitive antagonists (examples: atropine, propranolol)
Clinically, these are the most common type of antagonists. Often used (given
afterwards) to overcome excessive or toxic effects of agonists, whether the agonist is
a drug, hormone, or neurotransmitter. Sometimes given before an agonist to prevent
one or several specific unwanted effects of an agonist that is capable of causing
multiple effects
Action of competitive antagonist
Compete with agonist for the same receptor sites. When bound to the receptor(s), the
antagonist prevents the agonist from binding and so prevents the agonists from
causing an effect. Cause an apparent increase in the ED50 of the agonist – a bigger
dose of agonist is needed to cause a response of the same intensity as would be caused
by a lower dose if the agonist were not present that is, whether the antagonist merely
weakens the effects caused by an agonist, or abolishes the agonist's effects altogether,
depends on the dose of both the agonist and the antagonist. Effects of competitive
antagonist can be overcome (surmounted) by giving a greater dose of the agonist so
the agonist molecules can "out compete" the antagonist. Competitive antagonists do
not reduce the maximum effect caused by the agonist - provided the agonist's dose is
increased enough
2. Noncompetitive antagonists
"Permanently" occupy or change receptor so agonist can't interact with it. Effects of
noncompetitive antagonist cannot be overcome by increasing the dose of the agonist
Much less common, in terms of clinical use, than competitive antagonists
Drug Names
a) Generic name:
Names of drugs given by pharmacopoeias, they are mainly based on their chemical
structure
b) Trade name:
Name of drugs given by pharmaceuticals or manufacturers e.g. Bolin for paracetamol
Active Ingredient:
Is the chemical substance in the drug formulation, which bring about the desired
response.
Always look for the active ingredient do get confused with trade name.
Drug Classification:
There is no uniform system of classification of a drug. Drugs are usually classified
according to:
a)
The body system/functions which they most obviously influence (Systemic)eg.
Drugs acting on the nervous system.
b)
The mechanism/mode of action (physical and physiological) egAntimicrobials,
Astringents, Analgesic, antihistaminic, etc.
c)
The chemical structure (Generic) eg- Steriods, Barbiturates,
For practical purposes, we will use a combination of all the systems and classify
drugs into two classes.
A)
Drugs which act on specific systems
B)
Drugs based on the mode of action
A)
Drugs, which act on specific systems
i)
ii)
iii)
iv)
v)
vi)
vii)
Drugs which act on the Digestive system
Drugs, which act on the respiratory system
Drugs, which act on the circulatory system
Drugs, which act on the urinary system
Drugs, which act on the nervous system
Drugs used on the skin
Drugs used in the mammary gland
B)
Drugs, based on mode of action / mechanism of action
i)
2)
3)
Antibiotics/ antibacterials
Sulphonamides
Anthelmintics
4)
5)
6)
7)
8)
9)
10)
11)
12)
Antifungals
Anti protozoans
Antiseptics and disinfectants
Vaccines and antisera
Hormones
Steriods
Antipyretics
Antihistaminics
Vitamins/Minerals/Electolytes
Drug based on specific system they influence
Drugs used in the Digestive system:Antacid:
Are drugs that nuetralises excessive acid formation in the GI tract.
 Magnesium hydroxide
 aluminium hydroxide
 Bismuth carbonate – 2 gm
 Magnesiun carbonate- 2 gm
 Sodium bi carbonate – 2 gm
This mixture is called triple carb and used in gastritis in dogs
 Sodium bi carbonate – 10 % solution. – 200-300 ml half by slow I/V and the other
half by oral route.
This is used in acidiosis in ruminants.
Antizymotic:
These are substances/drugs which prevents the formation of gases in the Intestine and
rumen by decreasing bacterial and enzyme of fermentation. These drugs are used in
case of Bloat/tympanitic colic in horses.
 oil of turpentine – 30 ml in 300-500 ml of linseed oil
 Formaline - 30 ml in 300-500 ml of water.
Astringent:
Are substances, which protect the mucosa of the GI tract from the irritants by forming
a thin film over the mucosa and prevent secretion on fluid into the lumen of intestien.
These are used as antidiarroheal
 Tannic acid
Kaolin
Pulv Ginger
– 15 gm
- 30 gm
- 15 gm
Mixture to be administered t.i.d for 3-5 days orally
 Commercial Astringent – Neblon Powder- 30 -50 gm orally
Collutoria:
Are antiseptic used as mouth wash in case of stomatitis and mouth lesions e.g. in
FMD
 2 % Alum
 1:10000 Potassium Permanganate
 Boroglycerine/ Idoglycerine
Carminative:
Drugs that help in the expulsion of gas from the GI tract by its antifoaming action.
These drugs are used in tympany in ruminants and tympanitic colic in horse.
 Oil of Turpentine – 30 ml in 300-500 ml of linseed oil/ vegetable oil
 Vegetable oil/water emulsion – 200-500 ml of oil in 500-1000 ml of water as
drench
 Timpol – 100 gm in 500 ml of water as drench
Emetic:
Are drugs, which induce vomition as a means of removing toxic materials/foreign
bodies (Poisoning cases).
Category
Irritant emetics
Mode of action
Irritates the gastric mucosa
thereby increasing the
gastric contraction and
motility
Example
Common salt either as a solid placed
on the back of the tongue or as a
saturated solution –(1-2 tsf in a cup of
water)
Zinc sulphate- 0.6 gm in 60ml of water
Central emetics
Stimulate the vomition
centre in the brain
Sodium carbonate (Washing soda)
Apomorphine Hcl3 mg S/c or 6 mg orally in dogs.
Antiemetic
Drugs which control vomition by inhibiting the vomition centre.
Category
Mode of action
Example
Central antiemetic
Local gastric
sedative
Inhibits the vomition centre
Coats, protect and lubricate the
gastric mucosa, acid neutralization
Metaclopramide – 1 mg/kg body
weight orally tid.
Trifluropromazine/chlorpromazine
Promethazine / promazine,
acepromazine
Triple carb
Enemas:
Are drugs used for the removal of contents from rectum and colon in small animals.
 Warm soapy water
 Glycerine
Large volume is infused into the rectum. The fluid helps to soften the faecal mass and
the distension and slight irritation caused by the fluid stimulates contraction of colon
and rectum.
Laxative/Purgative
Purgatives are drugs that cause marked intensification in the intestinal activity that
results in the expulsion of intestinal content from the colon and rectum. Laxative has
similar action but the action is milder than that of a purgative. These are used in case
of constipation or when purgation is necessary.
Laxative/purgative are of three categories depending upon their mode of action.
Category
Lubricant laxative
Bulk/saline purgative
Irritant purgative
Mode of action
Lubricates the intestinal mucosa and the
food mass.
Absorbs water resulting in distension of the
intestinal wall. This brings about increased
intestinal motility. Also water softens the
Irritates intestinal mucosa which results
into increased intestinal motility
Example
Liquid Paraffin
Magnesiun sulphate
Linseed oil/castor oil
Rumenotorics
Drugs that promote or enhance the function of the rumen.
 Himalayan Batisa
Appetite stimulant
Drugs that promote the intake of feed in animals. Normally after the recovery from a
disease there is reduced intake or at the time of disease there is anorexia that has to be
corrected.
Example. Liv – 52
B-complex with liver extract
Drugs used in the Respiratory system
Expectorants:
Are drugs that increases the fluidity and volume of respiratory secretions, relieve pain
and incidence of coughing in the early stages of inflammation.
Inhalant expectorants:
These agents when dissolved in steaming water are intended for inhalation in a
confined space.
Eg- Oil of turpentine, Tr. Benzoin, eucalyptus oil.
Ingested expectorant:
These agents when administered orally are absorbed through the gut and excreted via
the bronchial mucosa, thereby increasing the bronchial secretion.
Eg- Sodium iodide, Potassium iodide, Ammonium chloride.
Mucolytic expectorant:
Drug dissolve mucous accumulated or removing mucus plug in the respiratory tract.
Eg – Bromhexine- 1 mg /kg body weight in small animals
0.1-0.25-mg/kg body weight in horses and cattle
Commercial expectorant: Caflon powder.
Antitussive:
Drugs, which can diminish the frequency of coughing. This is beneficial when cough
is painful, non-productive, distressing, exhausting. acts at the level of the cough centre
in the CNS.
Demulcent Antitussive: They coat, protect and smoothen the imflammed respiratory
mucosa.
Eg- Honey, Syrup
Direct acting Antitussives:
They depress the afferent sensory nerve of the cough reflex.
Eg- Benzonate
Centrally acting Antitussive:
These agents that depress the cough centre in the medulla oblongata of the brain.
Eg- Codein phosphate, Morphine (These agents are narcotics and carry the risk of
addiction).
Pholcodine, dextrophan dextromethrophan (Non-narcotic)
Respiratory stimulant:
Drugs which stimulates respiration in case of anaesthetic depression or anoxaemia
(carbon monoxide poisoning), drowning, severe pneumonia and pulmonaryoedema
and emphysema.
Local irritants: cause reflex stimulation – eg –Ammonia gas administered by
inhalation.
Analeptics: stimulates the respiratory and vasomotor centres in the medulla. These
agents are administered by I/V or I/M route.
Eg- Nikethamide – 10-20 ml in LA
1-3 ml in SA
Amphetamine – 20 mg in LA
- 1-4 mg in SA
Physiological/Natural Stimulants:
Eg- Oxygen and carbon dioxide
Drugs used in the Urinary system
Diuretic:
Drugs which increases the quantity of urine by reducing tubular reabsorption of water.
They are used in cases of oedema and ascites.
Eg- Mannitol –20 % soln – 1-2 ml/kg bwt I/V in dogs
Frusemide- 1-5 mg/kg/bwt in SA
0.5-1 mg/kg bwt in LA
Urinary antiseptics:
Drugs which renders the urine and urinary tract free of contamination. They are an
alternative to antibiotics and sulphanomides when bacterial resistance excludes the
use of these agents.
Eg- Hexamine (Provided urine pH is acidic)- Sodium acid phosphate (Urinary
acidifier) is administered 20 minutes before the first dose and subsequently at the
same time as hexamine.
Hexamine – 4 gm
Sodium acid Phosphate – 20 gm
This mixture is to be given twice a day.
Nalidixic acid – 10-15 mg /kg bwt orally. (Contraindicated in renal insufficiency)
Urolithiolytics:
Drugs which break down urinary calculi/stones.
Eg- Cystone Tab.
Drugs used in Circulatory system
Haematinics:
Drugs which help in the formation of blood (erythropoiesis) used in Anaemia.
Eg- Iron Injection
Cofecu tab
Haematinic mixture
Ferrous sulphate- 5 gm
Copper sulphate – 1 gm
Cobalt chloride – 0.5gm
Haemostatic:
Drugs, which help in the coagulation of blood and therby, stop haemorrhage.
Eg – as local application - calcium Alginate, Adrenaline with vitamin K
Parenteral - Malonic and oxalic acid
Cardiac stimulants:
Drugs which increases the cardiac output by modulation of rate and force.
Eg- Adrenaline – increases the myocardial contraction and vasoconstriction in the
skin, guts and veins and vasodilatation in the muscles.
Drugs used in the Nervous system
Tranquilizers:
Drugs, which act on the brain and alter the temperament of the animal, making it less
responsive to outside stimulation. This group of drugs is usually used to control
ferocious and nervous animals temperamentally and as a preanaesthetic.
Eg- Chlopromazine, Trifluropromazine Sedatives:
Drugs, which bring about Narcosis - a state of CNS depression that border on
anaesthesia.
This may be used for minor surgery.
Eg- Sub- anaesthetic doses of barbiturates
Morphine
Pethidine Hcl, Fentanyl, Etorphine
Anaesthetics
Drugs which eliminates body sensation.
Anaesthetic
General
anaesthetic
Local
General anaesthetics:
anaesthetic
Drugs, which cause the loss of sensation and the abolition of motor response and also
induce a state of sleep.
Non-volatile
anaesthetics
Volatile
anaesthetic
i) Barbiturates
 Long acting –Phenobarbitone – Anaesthesia last for 1 hour or more.
Medium acting – Pentobarbitone – Anaesthesia last for 15-20 minutes and full
recovery will be achieved after 8-24 hours.
Short acting – Thiopentone sodium – 5 %-.Duration of anaesthesia will depend on the
dose given.
Light anaesthesia- last for upto 10 minutes
Deep anaesthesia – upto 25 min.
Complete recovery takes about 1-2 hours.
Non- barbiturate non-volatile anaesthetic:
 Chloral Hydrate- usually used in horses and cattle as a sedative for minor surgery.15-45 g orally
 Ketamine Hcl – used in cat, for restraint or anaesthetic agent in minor surgery that
do not require skeletal muscle relaxation. Duration of anaesthesia last for 30-45
minutes and complete recovery occurs after several hours
 Xylazine Hcl-2 %- used as anesthetic/ sedative in all species of animals.
Anaesthesia/sedation last for 1-2 hours and complete recovery in 2-4 hours.
Volatile and gaseous anaesthetic:
These are administered in the form of vapour or gases form.
 Chloroform, Ether
ii) Local Anaesthetic
They interfere with the ability of the nerve cells to generate or transmit impulse.
 Lignocaine Hcl.-2% - in large animals for epidural anaesthesia- 5-10 ml
- for local infiltration - 5-10 ml
Drugs used on Skin:
Ointment: Are semisolid preparation containing active ingredient mixed with fat
(animal fat) or greasy substance like soft paraffin applied on skin.
Lotion: Liquid preparation for application on skin or body surface. E.g. Ascabiol
Tincture: are the preparations containing active ingredients dissolved in alcohol. E.g.
Tincture Iodine.
Liniment: irritant solution for application on the body surface to relief pain or
stiffness.
General-purpose drugs
Antibiotics:
An antibiotic is a substance produced by a living organism and which at low
concentration is antagonistic to the growth of another microorganism.
Antibiotics can be divided into two main classes based on their effect.
a) Bacteriostatic:
Tetracyclines
Antibiotics that inhibit/check the growth of bacteria. EgSulfonamides, Erythromycin, chloramphenicol
b) Bacteriocidal:
Antibiotic that kills bacteria. Eg- Penicillin and its derivatives,
Streptomycin, Neomycin, Gentamycin, Cephalosporins,
Nitrofurazone
Antibacterial Spectrum:
Narrow spectrum:
Antibiotics in which the antibacterial activity is restricted to a small number of
organisms. Eg- Penicillin – active only against Gram+ve bacteria
Broad-spectrum antibiotics:
Antibitocs which have activity against both gram + ve and gram - ve bacteria as well
as certain other organisms such as Rickettsia. Eg- Ampicillin, Oxytetracycline,
Streptopenicillin, Gentamycin, Sulphanomides,etc.
Long acting antibiotics:
Depository preparations such as procain penicillin, Benzathin penicillin,
Oxytetracycline
(LA). They are slowly absorbed and have longer duration of
action and are always given by intra-muscular route.
Mode of action of Antibiotics:
The mechanism of action of antibiotics can be summarized as follows:
1)
Antibiotic affecting the synthesis of cell wall – Eg- Penicillin,
Cephalosporins
( Cephlexin), Bacitracin, Vancomycin.
2)
Antibiotics affecting cell membrane permeability- Eg Polymixins,
Aminoglycoside (Streptomycin, gentamycin, dihydrostreptomycin and
Neomycin).
3)
Antibiotic affecting protein synthesis – Eg- Chloramphenicol, Tetracyclines,
Aminoglycosides and Macrolides (Erythromycin, tylosin)
3) Antibiotic affecting nucleic acid metabolism- Rifampicin
5. Competitive antagonism: they interfere with the intermediary metabolism. E.g.
sulphonamide and trimethoprim, folic acid synthesis is inhibited.
Multiple drug therapy:
Use of a combination of antibiotics is indicated in the following conditions.
 Treatment of mixed bacterial infection.
 Therapy of infections where specific etiology is unknown.
 Enhancement of antibacterial activity.
 Prevention of emergence of resistant microorganism.
The use of a mixture of drugs is liable to cause further variation in dose calculation
because of the possibility of a variety of interaction between the components and the
patient. The effect of these interactions could be either a increased response or
decreased response.
Two or more drugs, which elicit the same response, could be administered together.
The final response may be equal to the sum of the expected response had the drugs
been given singly. This response is called as Summation. Should the response be
greater than summation, it is called as Potentiation or Synergism. Eg- Penicillin and
streptomycin, Sulphonamide and trimethoprim. When the response is less than
summation there is said to be antogonism between the drugs. Eg- Sulphonamide (
Bacteriostatic ) and Penicillin ( Bacteriocidal )
Principles in the use of antibiotics:
Drugs are beneficial as long as they are used properly. Among the iatrogenic ailments,
drugs induced conditions take the major chunk of the blame. Over dosage may induce
toxicity and under dosage may lead to organisms developing resistance to the drugs
and may not be effective. Similarly, course of therapy, combination, frequency and
other concurrent conditions are also some important factors to be considered for a
effective therapy.
1. Course of therapy:
The Antibiotics should be administered for a minimum of 3 days and to a maximum
of 7 days depending upon the efficacy of an antibiotic.
2. Dosage
Over dosage and under dosage are not conducive to the well being of the patient. Over
dosage may cause toxicity and under dosage may not be effective and also organisms
may develop resistance against the drugs when expose to the drug at low
concentration for a prolonged time.
3. Combination
As a general rule only the antibiotics under one head can be used in combination for a
course. Never use a combination of bacteriostatic and bacteriocidal antibiotics.
4. Frequency
Frequency of drug administration depends on the plasma concentration and clearance
time (half life). Certain drugs have to be given at a shorter interval whereas some are
given at a longer interval. For example. Strepto-penicillin is given at 24 hourly
whereas Ampicillin is given at 12 hours interval.
Antibiotic resistance:
Means decreased in sensitivity to an antibiotic to an antibiotic. Microorganisms
develop the ability to survive in the presence of antibiotics. Exposure of the microbes
to sub-lethal dose could be the main contributing factor.
Microorganisms can develop resistance against an antibiotic in two ways.
1) Production of inactivating enzymes. Eg- Beta- Lactamase which inactivate
penicillin.
2) Change in permeability or drug uptake.
3) Change in structure of the receptors or target molecules.
4) Development of alternative metabolic pathways.
How to avoid development of resistance to antibiotics
 Avoiding indiscriminate use
 By starting the therapy as early as possible
 Giving adequate dosage at required frequency
 Completing the course of treatment.
Anthelmintics:
Drugs that act against and eliminate the internal parasites/worms. They kill the
worms by interfering with their metabolism.
Anthelmintics are divided into several groups on the basis of their pharmacological
effect on worms.
1)
Benzimidazoles
Eg
- Albendazole, Fenbendazole
2)
Imidazothiazoles
Eg – Levamisole
3)
Tetrahydropurimidines
Eg- Morantel
Organophosphorus compounds
Eg-Trichlophon (Neguvon)
Piperazines
Eg- Piperazine hexahydrate
4)
5)
6)
7)
Avermectins
Eg- Ivermectin ( Ivomac)
Others
Eg- Niclosamide, Rafoxanide, Oxyclozanide, praziquantel
Anthelmintic
Albendazole
/Fenbendazol
e
Tetramisole
Piperazine
hexahydrate
Effective against
Round worms,
flukes and tape
worm. Effective
against larval stage.
All round
worms/lung worm
Round
worms,except
Trichuris spp.
Safety/toxicity
Has a wide safety range
Dose
Round worms-5 mg/kg BW
Tape worm/flukes – 10-20
mg/kg
Toxicity not common at
recommended dosage.
Toxicity not common at
recommended dosage.
The drug can be given
to pregnant animals and
those suffering from
Gastroenteritis.
15 mg/kg BW
Horse and cattle- 0.2 g/kg BW
(Max 80 g in adults,30 g in foal
and 60 g in yearling)
Pig- 1 gm /10 kg BW in three
divided doses.
Poultry- 32mg/kg BW in two
divided doses in feed or water
Niclosamide
Tape worms of
dogs, cats, cattle
Does not pose any
hazards at
recommended dose rate
Oxyclozanid
e
Adult fluke
Rafoxanide
Adult and
immatured fluke
Praziquantel
A wide range of
tapeworm
Effective against
adult and larval
stages of most
nematodes
Animals should not be
slaughtered 14 days
after treatment
Has a wide safety
margin. Should not be
given to milking
animals
Toxicity is not common
at therapeutic dose rate
Well tolerated at
recommended dose rate.
Should not be given to
dairy animals of
breeding age and 7 days
prior to slaughter
It should not be used in
milking animals or 28
days pre-partum and 21
days prior to slaughter
in meat producing
animals.
Levamisole
ivermectin
Effective against a
range of external
parasites such as
Warble, Mange,
Ring- worm, lice,
mites; and internal
nematodes.
Cattle- 50 mg/kg BW
Sheep and goat- 100 mg/kg
Dogs and cats- 500 mg/3 kg
BW
10 mg/ kg BW ( Max of 3.4
gm)
7.5-10 mg/kg BW
5 mg/kg BW
7.5 mg/kg BW ( 1 ml/10 kg in
cattle)
Cattle -1 ml/50 kg BW
Antiprotozoan
Drugs which act against and eliminate the protozoa from the body.
Drug
Quinapyramine
sulphate and
chloride
Indicated in
Prophylaxis and
treatment of
Trypanosomiasis
Dosage
To make suspension
dissolve the powder in 14
ml of distilled water.
0.025 ml/kg BW s/c.
Suramin
Prophylaxis and
treatment of
Trypanosomiasis
Diminazene
aceturate
Treatment of
trypanosomiasis
and babesiosis
Prophylaxis and
Horse- 0.4-0.6 g/45
kgBW iv
Cattle – 12 mg/Kg
BW.Repeat half the dose
after 2 weeks,
0.8-1.6 gm/100 kg/BW
P-toluene-
Prophylaxis- 1 gm/litre
Toxicity/contraindication
Overdosage in young
animals may cause
trembling, sweating
salivation, increased
respiration and heart rate
and collapse.
Potentially very toxic. May
cause liver, kidney and
spleen damage.
Local reactions may occur
sulphonyl
treatment of
betamethoxyethyl coccidiosis
urethane
Amprolium Hcl
Prophylaxis and
treatment of
coccidiosis
of drinking water
Treatment – 4 gm/litre
Poultry- 60 gm/50 litres
of water
Calf –50 mg/kg BW
Antifungals: used against fungal infection. E.g Griseofulvin
Ectoparasiticide: Drug used against the ectoparasites. E.g. BUTOX
Antihistamines: Drug used in allergic reactions due to the release of histamine. E.g.
AVIL
Anti-inflammatory: drugs used to control inflammation. E.g Dexamethasone
Antipyretic/Analgesics: Drugs used to reduce fever and pain e.g. Paracetamol
Antineoplastic: drugs used to treat cancer / tumor. Vincrystine sulphate
Vitamins/Minerals/Electolytes: are preparations used as tonics / supplements
Antiseptics and Disinfectants: substances used to destroy harmful germs on
body/instrument surface e.g. spirit, Tr. iodine
Drugs used on the skin – ointments/liniment/lotions
Ointment: a smooth greasy substance used on the skin to soothe soreness or
itchiness, help wounds heal, or make the skin softer.
Liniment: a liquid rubbed into the skin to relieve aches or pain, e.g. one
containing alcohol and camphor.
Lotion: a thick liquid preparation that is applied to the skin for cosmetic or
medical reasons
Drugs used in the udder – Intramammary infusion
Factors affecting Dose rate.
1. Body size:
Dosage is related to the body weight and size as this is a indicator of the volume of
drug distribution. Allowances have to be made for fat. If the drug is fat soluble,
increased dosage is necessary to allow for that portion of the drug that is sequestered
in the body fat.
2. Genetic factors:
Certain species and breeds of animals may be unduly sensitive to drug action while
others may be quite resistant. For eg- Cat are very sensitive to phenolic disinfectants.
Such variation could be explained by the variation in the drug detoxifying capabilities.
3. Age:
Very old and very young animals usually require reduced dose. This is because of
senile degeneration of organs like liver and kidney in old animals. In young animals
these organs are not developed sufficiently. Eg- Chloramphenicol is toxic to baby
pigs.
4.Sex:
Anatomical differences and certain physiological states in one sex require a different
approach. For e.g- corticosteriods and purgatives are contra-indicated in pregnant
animals.
5. Pathology:
Sick animals especially with liver and kidney damage have an impaired drug
detoxifying capacity.
Hypoalbuminaemia will reduce drug-binding capacity.
6. Tolerance:
When a drug is given over a long period of time, it is often necessary to increase the
dose in order to maintain a steady level of response. Tolerance to drugs disappears on
withdrawal of the drug.
Drug Toxicity
All the drug can be considered as manifesting a desirable characteristic effect so
called as the main or major effect. All other effects apart from the major effects
whether desirable or undesirable are called as additional effects. These effects are
caused by modifying the cellular functions and in this sense all drugs can be
considered to manifest toxicity. Drug toxicity can be classified as:
Selective toxicity:
Drugs, which destroy the causal organism of disease and yet do not harm the host.
However, such ideal drugs are rare and the vast majority of the drugs possess toxic
effect.
Side effect:
It is the unwanted effect of the drug, which occurs at a normal dosage and depend on
the pharmacological effect of the drug on the sites other than the targeted site.
Secondary effect:
Is the condition when undesirable effect is the consequences of the main action.
Adverse reaction:
Is the undesirable drug effect, which is life, threatening. Such action may follow
accidental overdosing or cumulate. Collectively unwanted drug induced effects are
called as Iatrogenic disease.
Major drug toxicities
1. Hypersensitivity reactions:
Hypersensitivity denotes the allergy or intolerance of an animal to a drug. The
consequences of hypersentivity reactions can range from very trivial to the fatal. The
reaction can be immediate in onset and last for only a few hours (eg- Urticaria and
anaphylaxis) or may be much longer lasting (auto allergy or contact dermatitis). The
antigen is a complex of the drug with an endogenous protein. Such reactions will
occur only in some individuals and are usually related to pre-exposure in suboptimal
quantities or are genetically determined.
2. Drug Dependence:
Drug dependence means a state in which the continued presence of the drug is
essential for the well-being of the patient. Eg- Insulin in diabetic patients. This
includes habit forming narcotic drugs like opium and its derivatives and cocaine.
3. Organ Toxicity:
When a drug is concentrated in any site, the chances of localised toxicity are
increased. This can occur in the kidney where the excreted drug is rapidly
concentrated by the tubular reabsorption of water. Degenerative changes in the
tubules have been seen with many drugs. Eg- several antibiotics. The liver is another
very common site of damage as it receives drugs in high concentration and also
because of its function to remove the toxic substances from the circulation. Eg- fatty
changes in sheep due to carbon tetrachloride even at normal dose.
4. Blood Abnormalities:
Occasionally the use of drugs is followed by disturbances in the blood constituents,
most commonly depression of the white blood cell count as a consequence of bone
marrow depression. Eg- Chloramphenicol
5. Central Nervous system:
Drugs can induce change in the normal pattern of activity of the CNS. Such drugs
commonly CNS depressants. E.g. Sulphonamides, Motor incoordination due to
tranquilization.
6. Reproductive system:
Occasionally some drugs may affect fertility, fecundity, birth weight, and growth of
the newborn.
7. Teratogenicity:
Teratogenicity means the abnormality in the foetus. Some drugs like Aspirin and anti
cancer drugs can induce foetal abnormalities. In veterinary medicine the foetus is
most likely to be affected by induction of abortion due to purgatives and
corticosteroids in late pregnancy.
8. Carcinogenicity:
Certain compounds have the ability to induce neoplastic changes.
9. Mutagenicity:
Mutagenesis is the induced change in the genetic makeup of individuals. Carcinogens
can damage germ cells and cause mutagenesis in the progeny.
10. Imapired Immune response:
Some drugs modify or depress the mechanisms of immunity. Eg- corticosteroids.
Drug Residue:
The existence of drug residue in milk or meat of food producing animals is of great
concern as a public health hazard for eg- Penicillin in milk can induce sensitization in
man and Organochlorine(DDT) residue in body fat. To minimize the danger from
residues, it is essential to observe a withdrawal period ( Time between the last dose of
the drug and the consumption of animal products). For milk and meat producing
animals, a withdrawal period of 72-96 hours is normally recommended.
Drug dosage and dose calculation
Dose calculation:
As under dosage and over dosage are not conducive to the welfare of the patients, it
becomes necessary to stick to the recommended dosage. When determining the dose
of a drug, many factors like body weight, strength of the drug and route of
administration should be considered.
How to calculate the required dose:
Example 1.
Cythion:
Strength of stock solution
50%Ec
Solution required for treatment
1%
Amount of diluted solution required
5 litres
Using the formula given below, we can calculate the amount of concentrated solution.
Required to make a 5-liter solution of 1% strength.
Vol. of stock solution required (ml) = strength of diluted soln X Vol. of diluted
soln req.
-----------------------------------------------------------Strength of stock soln
= 1X 5000 ml
---------------50
= 100 ml
Example 2
Panacur:
Body wt. of cow
Dosage
Conc. of Fenbendazole
Calculation
Volume of drug formulation req.
= 300 Kg
= 5 mg/kg B. wt
= 250 mg/gm panacur powder
= Dose rate x body weight
----------------------------Strength of the drug in the fromulation
5mg x300 / 250 mg/gm
= 6 gm
*6 gms of Panacur is required to deliver 1500 mg of Fenbendazole
Example 3.
Oxytetracycline- 200mg/ml
Dose rate = 10 mg/ kg BW
Body weight = 300 kg
Quantity of OTC (in ml)
=
Dose rate x body weight
----------------------------Strength of the drug in the formulation
= 10 mg/kg x 300 kg
= 30 ml
200mg/ml
Example 4.
Thiopentone sodium – 0.5 gm vial
Dose rate
= 25 mg/kg BW as a 2.5 % solution
Body weight of animal = 12 kg
Step 1. Prepare a 2.5 % soln.
2.5 gm in 100 ml = 2.5 %
0.5 gm in X ml = 2.5 %
= 100x0.5/2.5
= 20 ml = 25 mg/ml
Step 2. Calculate the quantity of 2.5 % solution required.
Total dose = Dose x BW/ strength of solution.
= 25mg x12 /25mg/ml = 300 mg /25 = 12 ml
Homework (dose calculation)
1. Gentamicin (antibiotic) is available as 40mg per ml preparation in 30 ml
vials. General dose rate of Gentamicin is 2 mg/kg body weight. Calculate
total dose of Gentamicin in mg and ml for the animals listed below:
Animal
Calf
Dog
Cat
Body weight
50kg
11.5kg
2.5kg
Total (mg)
Total (ml)
2. Triflupromazine is available as 20mg per ml preparation in 5 ml vials.
General dose rate of Triflupromazine is 3 mg/kg body weight. Calculate
total dose of Triflupromazine in mg and ml for the animals listed below:
Animal
Dog
Body weight
7kg
Total (mg)
Total (ml)
Dog
Cat
11kg
3.5 kg
3. Albendazole is available as 400 mg table. Its general dose is 25mg per kg body
weight. Calculate total dose in mg and number of tablet required for the
animals listed below.
Animal
Dog
Cat
Bull
Cow
Body weight
8kg
3.5 kg
350 kg
270 kg
Total (mg)
No. tablet
4. Oxytetracyclin is available as injection, each ml containing 50mg
oxytetracyclin. Its general dose is 6mg per kg body weight. Calculate total
dose in mg and ml required to be given for the animals listed below.
Animal
Cow
Bull
Buck
Dog
Body weight
250kg
315kg
34kg
13 kg
Total(mg)
Total (ml)
5. Ampicillin sodium is available as 250 mg injectable powder in sterile vial.
Prior to injection 3.5 ml distilled water has to be added to make it into 5 ml
solution. General dose of Ampicillin is 5 mg per kg body weight. Calculate
content per ml preparation and total dose in mg and ml to be given to animals
listed below.
Content per ml =
Animal
body weight
total (mg)
total (ml)
Cat
3.5 kg
Rabbit
2.25 kg
Homework (dose calculation) (ANSWERS)
1. Gentamicin (antibiotic) is available as 40mg per ml preparation in 30 ml
vials. General dose rate of Gentamicin is 2 mg/kg body weight. Calculate
total dose of Gentamicin in mg and ml for the animals listed below:
Animal
Calf
Dog
Cat
Body weight
50kg
11.5kg
2.5kg
Total (mg)
100mg
23 mg
5mg
Total (ml)
2.5 ml
0.58ml
0.125ml
2. Triflupromazine is available as 20mg per ml preparation in 5 ml vials.
General dose rate of Triflupromazine is 3 mg/kg body weight. Calculate
total dose of Triflupromazine in mg and ml for the animals listed below:
Animal
Body weight
Total (mg)
Total (ml)
Dog
Dog
Cat
7kg
11kg
3.5 kg
21mg
33 mg
10 mg
1.05ml
1.65ml
0.5ml
3. Albendazole is available as 400 mg table. Its general dose is 25mg per kg body
weight. Calculate total dose in mg and number of tablet required for the
animals listed below.
Animal
Dog
Cat
Bull
Cow
Body weight
8kg
3.5 kg
350 kg
270 kg
Total (mg)
200 mg
87.5 mg
8750mg
6750 mg
No. Tablet
0.5 tab
0.22 tab
21.8tab
16.88 tab
4. Oxytetracyclin is available as injection, each ml containing 50mg
oxytetracyclin. Its general dose is 6 mg per kg body weight. Calculate total
dose in mg and ml required to be given for the animals listed below.
Animal
Cow
Bull
Buck
Dog
Body weight
250kg
315kg
34kg
13 kg
Total (mg)
1500 mg
1890 mg
204 mg
78 mg
Total (ml)
30 ml
37.8 ml
4.1 ml
1.56 ml
5. Ampicillin sodium is available as 250 mg injectable powder in sterile vial.
Prior to injection 3.5 ml distilled water has to be added to make it into 5 ml
solution. General dose of Ampicillin is 5 mg per kg body weight. Calculate
content per ml preparation and total dose in mg and ml to be given to animals
listed below.
Content per ml = 50 mg / ml
Animal
body weight
total (mg)
total (ml)
Cat
Rabbit
17.5 mg
11.25 mg
0.35 ml
0.23 ml
3.5 kg
2.25 k
Routes of drug administration
There are different routes by which drug can be given to an animal patent. Depending
upon the preparations and the form of drug a particular route may have to be chosen.
Different routes for the administration of drug are described below.
1. Oral route: the drug is administered through mouth. Solid form or liquid form
of medicine can be given by this route. Liquid form of medicine can be given
as drench using drenching bottle (Beer bottle is suitable) or bamboo made
drenching bottle in the rural areas where there is bamboo. While drenching an
animal care has to be taken so as to prevent accidental drenching into the
lungs. Other may of giving medicine by this route is mixing the medicine with
feed. It is better to take a small lot of feed, mix the medicine with and give it
to the animal before giving the rest of the feed to ensure that animal consumes
the medicine.
2. Local route: means applying the medicine /drug on the surface of affected
part. For example applying an ointment on the skin wound. This is other wise
called local application.
3. Parental routes: this is the administration of the drug with the help of a
syringe and a hypodermic needle. There are many routes under this which are
as follows:
a. Subcutaneous: is deposition of
medicine beneath the skin.
Normally it is done at the neck
region where there is loose skin. In
small animal dog and cat it is given
at the flank region. This route is
mainly used in deposition of
vaccine, which requires slow
absorption into the circulation.
b. Intramuscular: Is deposition of
medicine deep into the muscle of animal
body. For giving this injection a region
with thick muscle as to be selected. Areas
with
thick
muscles
suitable
for
intramuscular injection are given in the
table below.
Animal
Muscular region
Horse, Buffalo
Rump, thigh, neck
Cattle, yak
Rump, thigh
Sheep, Goat
Thigh
Dog, cat
Thigh
Chicken
Chest
Area for intramuscular injection
c. Intravenous: is deposition of
medicine directly into the blood
circulation through superficial veins.
This route can be used when quick
action is desired and also when a large
volume of preparation like dextrose or
normal saline is required to be given or
for the blood transfusion. The site for giving intravenous in various animals are
given in the table below.
Site for intravenous injection
Animal
Site / vein
Horse, cattle, yak, sheep & goat
Dog & cat
Pig, buffalo, elephant
Chicken
Man
Jugular vein
Cephalic, saphenous veins
Ear vein
Wing vein
Cephalic vein
d.
Epidural: is the deposition of preparation like local anaesthetics into the
spinal chord to desensitise the nerves supplying the hindquarters (detail will be taken
in surgery).
e.
Intraperitoneal: is the deposition of the preparation into the peritoneal
cavity. This is done when fluid therapy can not be done through intravenous route due
to the severe dehydration.
f.
Intrarumenal: Is the deposition of medicine or preparation into the rumen by
rumen puncture.
4. Other routes that may be used are:
a. Intravaginal: placing the medicine into the vagina.
b. Intrauterine: deposition of medicine into the uterus
c. Ocular: placing the medicine into the eyes.
d. Intra-articular: deposition of medicine into the joint cavity
e. Per rectal: deposition of medicine into rectum
f. Inhalation: administration of preparation in the form of vapour though
nasal route.
g. Intramammary deposition of medicine into the mammary gland
Prescription writing
Prescription: is a written order to a pharmacist from a qualified physician containing
precise instructions for dispensing certain drug in fixed amounts giving direction as to
compounding and administration. The ancient physicians started their prescription
with an appeal to the gods for its success. The ancient symbol, Rx, signifying the
appeal, was established centuries ago and has been carried down to the present time.
The importance of the prescription and the need for complete understanding and
accuracy made it imperative that a universal and standard language be employed.
Thus, Latin was adopted, and its use was continued until approximately a generation
ago. Present-day prescription is simpler containing a single ingredient, written in
English, with doses given in the metric system. The ancient "Rx" and the Latin
"Signatura," abbreviated as "Sig.," are all that remain of the ancient art of the
prescription.
Parts of prescription:
A prescription consists of the superscription, the inscription, the subscription, the
signa, and the name of the prescriber - written within the confines of a form.
Superscription: The date when the prescription order is written; the name, address and
age of the patient; and the symbol Rx an abbreviation for "recipe," the Latin for "take
thou."
Inscription: or the body of the prescription contains names of drugs with quantities of
each to be dispensed.
Subscription: is the direction to the pharmacist and it normally written in Latin.
Signature: is the direction to the farmer with regard to the administration of drug to
the animal. This is preceded by abbreviation sig meaning mark or label and the
direction is written in English.
At the right side bottom page the initial of the writer and date should be written.
Name of the owner and description of the animal also should be there at the top of the
page.
Prescription is written in Latin, for the following reasons:
a. Latin is a dead language and it does not change, this allows the
physicians all over the world to use same language
b. Latin has few words that can be easily remembered by the physicians
c. Only the pharmacist and the physicians can understand this language
and this allows maintaining secret between the pharmacist and the
physicians.
Prescription should not be written with pencil for the fear of being altered by some
people and thereby causing trouble later on to the patient. It should be strictly written
in ink and it is a legal document, which mean the animal owner can sue the writer if
the prescribed drug produce adverse reaction in the animal patient or kills it.
NOTE: Be careful when you write a prescription to your patient.
Abbreviation used in prescription writing
Abbreviation
a.c
p.c
alba
aqua bulli
aqua ferv
bol
div.in pulv
div
Latin
ante-cibus
post- cibus
album
aqua bulliens
aqua fervans
bolus
divide in pulveres
divide
Meaning
Before feeding
after feeding
white
hot water
hot water
ball
divide into powders
divide
sig
talis
flavum
ind
od
spts
levis
lotio
m
mite
molles
nigrum
pil
q.r
rep
stat
tr.
qid
q3h
ad
add
dist
sos
ung
Adlib
Elect
Inj
Ft
Ol
Aq
Liq
signa
talis
flavum
in dies
omne die
spiritus
levis
lotio
misec
mite
molles
nigrum
pilula
quantum rectum
repetatur
statim
Tintura
quarter in die
quaque 3 hora
si opus sit
unguentum
adlibitum
electuarium
injectio
fiat
olium
aqua
liquor
mark
such
yellow
daily
daily
spirit
light
lotion
mix
weak
soft
black
pill
right quantity
let be repeated
immediately
tincture
4 times daily
every 3 hourly
make up the volume
add that much volume
distilled
if necessary
Ointment
at pleasure
electuary
an injection
le it be made
oil
water
a solution
Table 1. Common Terms and Abbreviations
Term or Phrase
Abbreviation
Meaning
ad
ad
to, up to
ad libitum
ad. lib.
at pleasure
ana
a.a.
of each
ante cibos
a.c.
before meals
aqua
aq.
water
bis in die
b.i.d.
twice a day
collyrium
collyr.
eye lotion
cum
c.
with
cum aqua
cum aq.
with water
dentur tales doses
d.t.d.
give such doses
dispensa
disp.
dispense
et
et
and
gutta, guttae
gtt.
drop, drops
hora somni
h.s.
at bedtime
in vitro
in vit.
in glass
misce
m.
mix
non repetatur
non. rep.
do not repeat
oculus dexter
o.d.
right eye
oculus sinister
o.s.
left eye
omni die
o.d.
daily
omni mane
o.m.
every morning
omni nocte
o.n.
every night
per os
p.o.
by mouth
placebo
placebo
to please
post cibos
p.c.
after meals
pro re nata
p.r.n.
as the occasion arises
quantum sufficiat
q.s.
sufficient quantity
quater in die
q.i.d.
four times a day
recipe
Rx
take
semis
ss _
one-half
sine
s,s
without
si opus sit
s.o.s.
if necessary
ter in die
t.i.d.
three times a day
trochiscus, torchisci
troch.
lozenge, lozenges
unguentum
ungt.
ointment
ut dictum
ut dict.
as directed