Technical Bulletin 6
Medicine Use and Equine Formulary
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Medicine use and Equine Formulary
INDEX
Page
Introduction
Good pharmacy practice
Medicine Use and the Law
Medicine purchase
Medicine storage
Reading the label
Administration of medicines
Disposal
Withdrawal periods
Medicines used in equine practice
Antimicrobials
Anti inflammatories
Endoparasiticides
Ectoparasiticides
Blood Parasite medicines
Antiseptics/Disinfectants
Sedatives
Diuretics
Cardio-respiratory medicines
Others
Drug dosage calculations
Worksheet problems
Answers to problems
Glossary of terms
References
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Introduction
A large part of SPANA's work involves diagnosing disease and illness in equines and
then providing treatment and advice. Much of this treatment is carried out by using
medicines. When SPANA first started over 80 years ago, the medicines available to treat
animals (and humans) were very limited in number and type, in great contrast to the
modern medicines available today. As animal health professionals we have a duty to see
that medicines are used correctly and within accepted guidelines. Medicines can
potentially do harm if used incorrectly, both to the animal being treated, and sometimes
to the vet or technician handling them.
It must also be remembered that medicines alone are unlikely to cure an illness, correct
care and nursing (feed, water, rest, and a good environment) are equally as important. As
far as advice to owners is concerned, the old adage “Prevention is better than Cure” is
most important.
Good Pharmacy Practice
Good practice includes correct storage, utilisation and disposal of medicines. These are
described below in more detail.
A decision to use a particular medicine should be taken by a vet after an evaluation of the
animal and its condition has been made. A full case history followed by a thorough
clinical examination is necessary, before the choice of medicine is agreed. It is
particularly important to establish if any other medicine has been given already by the
owner or another animal health professional, since some medicines can react badly with
others. The use of polypharmacy (using many different drugs) is discouraged as it is
usually due to a lack of a proper diagnosis. A drug should be used only if a valid clinical
reason for its use exists.
Medicine Use and the Law
In many countries, according to the law, only qualified vets can legally buy many of the
drugs listed in this bulletin, and, by law, people who are not vets must only use them on
animals that are under a vets care. You should be aware that, if you buy and use these
medicines and you are not a registered vet, you may be breaking the law.
If you use a medicine in a way that is not included in the manufacturer’s instructions,
even if that way is described in a text book, it is your own responsibility. Such a use
might be giving a medicine to a horse or donkey that has not been licensed for use with
horses and donkeys. If the animal health worker or owner decides to use that medicine
on a horse or donkey, he or she must accept that risk.
Medicine Purchase
Medicines should always be purchased from reputable dealers, preferably licensed. The
premises should be equipped to store medicines correctly. Beware some traders who sell
medicines damaged by being kept in a hot store.
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Only genuine medicines with proper printed labels and, preferably, containing a data
sheet in the box should be used.
The expiry date must be checked when purchasing medicines.
Some makes/brands of medicine are cheaper than others. Another medicine with a
different trade name but the same chemical name may be just as effective and cheaper,
although it is sometimes preferable to go with a trusted name.
The strength/concentration of the medicine must be checked to work out the cost of the
actual amount of medicine in a container. Some medicines with the same chemical name
have more actual medicine in each ml in a bottle
Medicine is often cheaper in larger containers, but it is not necessarily economic to buy
such large containers that it will not be used quickly. Medicine left in a container after
opening is quickly damaged by air and may become contaminated.
Medicine should only be bought in quantities expected to be used well before the expiry
date.
Medicine Storage
Drugs should be kept securely, preferably in a locked cupboard and records must be kept
of their administration to each animal. This is particularly important with potentially
dangerous drugs such as sedatives and anaesthetics.
If medicines are not stored correctly they will become damaged. They may not work and
can become dangerous.
Most medicines require keeping in a cool, dry and dark place. Some must be kept in a
fridge; a few require freezing (certain vaccines). Powdered medicines in particularly do
not want to be anywhere damp. Some medicines are damaged by sunlight; these ones are
often supplied in dark coloured bottles.
It is important to maintain the cold chain once medicines have left the clinic (and
between purchasing the medicines and getting them to the clinic). This probably requires
the use of insulated cold boxes, especially in hot climates.
Medicines must be stored where children and animals cannot gain access to them, and
safe from rodent and insect damage.
Once a bottle of medicine has been opened, it should be used up as quickly as possible,
since it can become contaminated. Some vaccines must be used immediately.
Part used medicines must not be kept in food or drink containers.
Medicines should be used by their expiry dates.
Medicines should be kept labelled and the directions for use kept with them.
A thermometer should be used to keep a check on the storage conditions for medicines.
Most medicines have a maximum and minimum temperature written on the label, and
these should be adhered to.
Transport of medicines in mobile clinic vehicles can pose a particular problem. Cool
boxes MUST be used, if there is not an efficient refrigerator. Cool packs must be used in
the cool box and the lid should be kept on except when removing a medicine to use.
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Reading the Label
Medicines usually have two names; the chemical or generic name e.g. oxytetracycline
and the trade name given by the manufacturing company e.g. alamycin.
A medicine label should provide the following information either on the bottle, or on an
enclosed label:












The trade name of the medicine
The chemical name of the medicine
Dose; this is usually given in mg/kg bodyweight
The concentration/strength of the medicine (i.e. how much actual drug is in each
ml of medicine in the bottle)
Which animals the medicine can be used in
Instructions about special care required when using the medicine and
contraindications for its use
How to give the medicine, how often to give it and for how many days
Withdrawal period for meat and milk, this is to prevent the medicine affecting
people if animal products are fed to people
The total quantity of medicine in the bottle
The date the medicine was manufactured
The expiry date –medicines should not be used after this date; it may not work
properly and can help to allow resistant microbes to develop in the case of
antimicrobials or parasiticides
The name of the manufacturer
Administration of medicines
Manufacturer’s instructions should be followed when deciding on the route of
administration of a medicine, but also note the individual drug entries in this bulletin.
Owners are not given injections to administer themselves, but if any medicine is given to
an owner to administer in food or on the skin for example, they must be given very clear
instructions as to how to do this.
Medicines which have lost their label must not be used.
Strict hygiene should be employed when medicines are given, particularly with
injections. This involves using a new sterile needle for each animal, swabbing the top of
injection bottles with surgical spirit/alcohol and cleaning the injection site on the skin.
Large quantities of injectable medicines must not be given all at the same site on an
animal with intramuscular injections. Usually the maximum quantity of any medicine
that can be given at one site is 20mls for an adult horse. Again it is important to follow
the manufacturer’s advice on this.
The correct dose must always be given; in order to do this the weight of the animal must
be estimated using a weigh tape or the formula in the SPANA Guide to Animal Care.
Overdosing can be dangerous for the animal and under dosing (particularly with
antibiotics or anthelmintics) and may lead to the development of resistant organisms.
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Disposal
Medicines which are past their expiry date or medicines that have changed colour or look
damaged should be disposed of.
Drug bottles should be disposed of carefully to avoid injury. It is preferable to remove
the label and/or break the bottle to prevent misuse of the contents at a later date.
Incineration is the best method of disposal, but is not always practicable. An alternative
is to bury used containers in a deep hole. This should not be within 50m of a water
course to prevent leakage and contamination.
Withdrawal periods
This is the period after administration of a medicine during which products from the
animal (milk, meat, eggs etc) may not be consumed by people. These mostly relate to
medicines in food producing animals, but must be taken into consideration if there is any
chance that the equine may end up in the food chain. This is probably not relevant to
most of SPANA’s patients.
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Medicines used in equine practice
A. Antimicrobials/antibiotics
Criteria to be considered when selecting an antibiotic regime in horses include:
 The presence or likelihood of an infectious process.
 Type of infectious process.
 Bacteria most likely to be isolated.
 Age and immune status of the animal.
 Antibiotic characteristics- the bacteria must be susceptible to the drugs mode of
action, an appropriate concentration of drug must be achieved at the site of
infection and maintained for a sufficient time to kill the organism, the
microenvironment at the infection site must be favourable for the antibiotic
action.
 Cost of antibiotics.
 Ease of administration.
 Potential toxic effects.
1. Penicillin G
Penicillin is widely used in many conditions, and is active against gram positive bacteria.
It is excreted by the kidneys and concentrated in urine.
It is inactive in respiratory secretions.
Poor systemic absorption after oral administration.
Allergy to penicillin is seen occasionally as acute anaphylaxis. Immune mediated
anaemias are also seen rarely. Neurological signs are occasionally seen with the procaine
form (due to the procaine, not the penicillin)
i. Sodium penicillin
This crystalline salt is used when a rapid effect and high concentration are desired.
Dose
20 000 iu/kg every 6 hours.
Route of Administration
iv or im
ii. Procaine penicillin
Trade names available locally
Combi-kel 40 (penicillin 200 000 iu/ml + streptomycin 200 mg/ml)
Pen & Strep (penicillin 200 mg/ml + streptomycin 250 mg/ml
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This is possibly the most used antibiotic in equine practice, often used in combination
with an aminoglycoside antibiotic to broaden the spectrum of activity.
Dose
20 000 iu/kg every 12 hours.
Route of Administration
im only
iii. Benzathine penicillin
Trade names available locally
Shotapen (benzathine penicillin 100 mg/procaine penicillin 100mg/streptomycin 0.164
iu/100ml)
Slow absorption and low peak serum concentrations, therefore generally not useful in
equines, but can be effective against very susceptible organisms with low MICs
(minimum inhibitory concentrations) involving the urinary tract.
Dose
20 000 iu/kg every 24-48 hours
Route of Administration
im only
2. Aminoglycosides
Used for their gram negative aerobic antibacterial action.
Generally used in combination with penicillins.
Must be given parenterally (not orally) to achieve systemic therapeutic concentrations.
Indicated in the initial treatment of life threatening infections caused by gram negative
aerobic bacteria.
The major toxic effects are nephrotoxicity and ototoxicity. Nephrotoxicity can be
potentiated by the use of other nephrotoxic drugs, loop diuretics (furosemide),
hypotension and age. Care must therefore be taken in animals with already compromised
renal function.
i. Streptomycin
Trade names available locally
Combi-kel 40 (penicillin 200 000 iu/ml + dihydrostreptomycin 200 mg/ml)
Shotapen (benzathine penicillin 100mg/procaine penicillin 100mg/streptomycin 0.164
iu/100ml)
Pen & Strep (procaine penicillin 200 mg/ml, streptomycin 250mg/ml)
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More nephrotoxic than gentamicin.
Dose
10 mg/kg once daily (CM)
2 mg/kg bid (Rose)
Route of Administration
im
ii. Gentamicin
Trade names available locally
Totamicine (3g/100ml = 30mg/ml) Not indicated for equines
Gentamycin 50 (50mg/ml)
Commonly used in equine medicine, often along with procaine penicillin. Once daily
dosing is recommended.
Dose
6.6 mg/kg once daily.
Route of Administration
iv or im. iv is generally recommended as im use can cause local myositis. If the
medicine is given im it must be given at several sites due to the generally large volume
required.
3. Potentiated sulphonamides.
Trade names available locally
Trisulmix poudre
Bactrim forte tablets (human) (800mg/160mg per tablet)
Avemix 150
Kombitrim 240 (sulfamethoxazole 200mg/ml + trimethoprim 40mg/ml)
Borgal (200mg/ml sulphadoxime and 40mg/ml trimethoprim)
Norodine
A broad spectrum antibiotic mixture consisting of Trimethoprim with one of the
sulphonamide drugs. Not used for difficult gram negative or serious anaerobic infections,
but a good choice for minor skin wounds, respiratory infections and foal diarrhoea.
Rarely immune mediated crystallurea has been found as a side effect.
There have also been reports of sudden death occurring when intravenous potentiated
sulphonamides have been used alongside the alpha 2 adrenergic sedatives detomidine and
romifidine.
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Dose
Recommended dose rates in text books vary but as a general guide:
15 mg/kg every 12 hours if used intravenously.
30 mg/kg every 12 hours if given orally.
These are the total doses of trimethoprim plus the sulphonamide component.
Route of Administration
Intravenous and oral forms are available. The oral form, usually a powder.
4. Tetracyclines
A broad spectrum bacteriostatic drug, which can also be used against mycoplasma
infections.
Some resistance has been reported.
Excreted in kidneys and in the bile.
Avoid tetracycline use in animals with renal failure.
Use with care in young animals as it can cause bone and teeth abnormalities.
These drugs were rarely used in the past with equines as they were said to cause
diarrhoea. Recent evidence suggests they are no more likely to cause diarrhoea in the
general population of equines than other antibiotics, although it is not advised to use the
long acting or high concentration preparations commonly used in ruminants.
i. Oxytetracycline.
Trade names available locally
Terramycine 50 (5g/100ml = 50mg/ml)
Alamycin 10 (100mg/ml)
Dose
5 mg/kg every 12 hours.
Or 10 mg/kg once daily.
Route of Administration
Usually iv. Injection site reactions have been reported.
5. Metronidazole
Trade names available locally
Metronex (oral paste 10g syringe)
Flagyl (human preparation in tablet form)
Used for anaerobic infections. Metronidazole is well absorbed orally and also from the
rectum. It is excreted by the liver and kidneys. Toxicity is uncommon although anorexia
has been reported as a side effect.
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Dose
15 mg/kg every 6 hours
Route of Administration
Orally, usually in paste or tablet form.
Can also be given rectally.
The above information relates to antibiotic preparations for oral or parenteral use. There
are many other topical and ophthalmic antibiotic preparations available.
B. Anti-inflammatories.
1. NSAIDS (Non Steroidal Anti-Inflammatory Drugs.
NSAIDS are drugs that inhibit part of the cyclo oxygenase (COX)enzyme systems that
convert arachidonic acid into prostaglandins, thromboxanes and leukotrienes. There are
two COX enzyme systems:
 COX I enzymes are those responsible for producing prostaglandins which are
necessary for some normal physiological processes and have protective effects on
the gastro-intestinal tract and kidneys. We do not want to inhibit these COX1
enzymes.
 COX II enzymes play a major part in inflammation, and these are the ones we
want to inhibit.
 The ideal NSAID would inhibit COX II, but have no effect on COX I. At the
present time, there is no ideal NSAID that does this.
 However there are NSAIDS that have only small effects on COX I while
inhibiting COX II, these include meclofenamic acid.
 NSAIDS that have a greater effect on COX I are more likely to lead to toxicity,
these include aspirin.
Side effects of all NSAIDS can include the following:
Local irritation
it is advised not to administer by the im route.
Gastric irritation
gastric ulcers
acute enterocolitis
protein losing enteritis
Renal effects
although rare.
Bone marrow suppression
pancytopaenia, occasionally seen in horses treated with
phenylbutazone, or aspirin.
Do NOT use NSAIDS together as the side effects are cumulative.
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i. Phenylbutazone
Trade names available locally
Equipalazone
Phenylarthrite (200mg/ml)
Butosyl (Fort Dodge 186mg/ml)
Equizone powder (1g)
Arthricidine (200mg/ml)
*Dexatomanol (70mg/ml phenylbutazone + dexamethasone, cinchocaine, ramifen)
*Dexaphenylarthrite (180mg/ml phenylbutazone, + dexamethasone)
*The above two products are examples of polypharmacy and should be avoided. It is not
generally recommended to use steroids and NSAIDS at the same time.
Phenylbutazone (Bute as it is often known) is the most commonly used NSAID in
equines. It has the advantage of being relatively cheap. It is used particularly in
musculoskeletal problems, in particular low grade lameness. It also has an antipyretic
effect.
It must not be used in animals that may be used for human consumption.
Dose
4.4 mg/kg every 12 hours on the first day.
2.2 mg/kg every 12 hours after that for up to 4 days.
2.2 mg/kg once daily can be used after the 5th day.
NOTE: many commercially prepared formulations have an incorrect dose given,
the correct dose rate for phenylbutazone is 4.4 mg/kg maximum and the quantity of
drug to be given in mls should be calculated from this only.
Route of Administration
Injections should be given by the iv route only. im injections will cause tissue irritation,
and possible necrosis.
Oral formulations as powders, pastes or tablets are commonly available. This route
avoids the possibility of phlebitis. Peak absorption from the oral route is 6 hours, or
delayed if fed.
ii. Flunixin meglumine.
Trade names available locally
Finadyne
Most commonly used for visceral pain (i.e. colic), as well as endotoxic shock. But note
that the drug can effectively mask the clinical signs of colic, therefore care is required
with its use if surgery is an option.
Do not use with other NSAIDS or within 24hours of another. Avoid in dehydrated or
shocked animals (hypovolaemic shock) as this increases the risk of renal toxicity. Do not
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use in pregnancy. Contra indicated in pre existing renal, hepatic or cardiac disease or
possibility of gastro-intestinal bleeding or ulceration.
Dose
1.1 mg/kg every 12 hours is maximum analgesic dose.
For anti-endotoxic shock properties, the dose is 0.25 mg/kg up to 4 times a day.
Flunixin is not commonly used for long term conditions; it may be given at 1.1 mg/kg
once daily for up to 5 days only.
Route of Administration
iv
An oral form may be available, and oral absorption is rapid (30 minutes, delayed by
feeding).
iii. Dipyrone monohydrate
Trade names available locally
Buscopan
Calmagine (500mg/ml)
Metalgen (500mg/ml)
Often found in conjunction with the spasmolytic hyoscine, and used in cases of colic,
especially low grade spasmodic colic. Dipyrone itself is a weak NSAID, and not a
spasmolytic. It has some antipyretic effect. Do not used with another NSAID. It is a
NSAID for short term use.
Dose
20 mg/kg given once or twice.
Route of Administration
iv usually, although some products claim to be ok by the im route.
iv. Aspirin ( acetyl salicylic acid)
Trade names available locally
Aspirin (human formulation)
Aspirin has a very short half life, and is not so commonly used in equine practice. It has
a narrow therapeutic index, and side effects (due to its inhibition of COX I) of gastric
ulceration are not uncommon. It is a relatively poor analgesic, but is sometimes used for
musculoskeletal problems, uveitis, laminitis and mild abdominal pain. It has a prolonged
effect on clotting time, so care should be taken if it is used with surgery, but its
antiplatelet effect may be useful for laminitis prevention (?), or thromboembolic colic, It
has antipyretic properties and is relatively inexpensive.
Dose
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There is a wide variation of dose rates recommended in the texts. A reasonable average
would be:
30 mg/kg every 12 hours
Route of Administration
Generally given orally, as tablets or ground tablets hidden in food or mixed to a paste
with yoghourt or syrup.
v. Meclofenamic acid.
Trade names available locally
Dynoton (100mg/ml) Licensed only for cattle.
??????? (Syria diclofenamic acid)
Useful for musculoskeletal problems, including laminitis. Available orally or for
injection
Dose
2.2 mg/kg once daily for 5-7d, then 2.2 mg/kg every other day.
Route of Administration
Oral powders available.
Injections generally for iv use.
vi. Other NSAIDs.
 Ketoprofen 2 mg/kg sid iv
 Sodium phenyl-dimethyl-pyrazole-methylamino-methane sulphonate (novalgin,
novasul) – said to be analgesic, antipyretic, antirheumatic, spasmolytic
 Also viscalgine
2. Corticosteroids.
Very strong anti inflammatory agents, that stop prostaglandin synthesis right at the top of
the chain, thus both COX I and COX II are inhibited.
Indications for use include:
 Allergic disease
COPD and allergic skin disease.
 Neurological disease traumatic or inflammatory CNS conditions.
Corticosteroids must be administered very early in the course of the disease.
 Non-septic joint disease
 Cyasthostomosis, infiltrative bowel disease
 Myocarditis
 Shock corticosteroids must be given early on. This short term use (48hrs) has
few side effects.
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Side effects of corticosteroids include:
 Suppression of adrenal function
 Immunosuppression
 Laminitis
 Cushings syndrome
 Delayed and poor wound healing
Short acting succinate and phosphate preparations of corticosteroids are generally used in
acute conditions such as shock, anaphylaxis and allergic reactions.
Longer acting acetate preparations act as depot preparations.
Of the two most commonly used corticosteroids in equine medicine, prednisolone has the
shorter duration of action, which may be better if side effects occur. Some horses
however, respond better to dexamethasone.
Corticosteroids should not be used in conjunction with NSAIDS, due to an increased risk
of COX I inhibition problems such as gastro-intestinal ulceration and renal toxicity.
Dose rate:
Very individual, need to titrate dose depending on severity of condition. Apart from one
off doses for shock, dose should be decreased gradually over time.
i. Prednisolone sodium succinate
Short acting preparation used in acute cases.
Dose
1 mg/kg once daily
Shock - up to 30 mg/kg one off dose
Route of Administration
Generally iv
ii. Prednisolone
Sometimes used for lower airway disease and inflammatory bowel disease in the long
term.
Dose
Starts at 1 mg/kg every 12 hours, then will decrease.
For example:
Week 1:
1.0 mg/kg every other day
Week 2:
0.7 mg/kg every other day
Week 3:
0.5 mg/kg every other day
Week 4:
0.3 mg/kg every other day
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Route of Administration
Generally oral
iii. Dexamethasone
Trade names available locally
Colvasone (2 mg/ml)
Cortamethasone (1 mg/ml)
Dexasone (2 mg/ml)
Dexacortyl (1.52 mg/ml)
*(Dexaphenylarthrite 0.35 mg/ml, +phenylbutazone)
*(Dexatomanol 0.5 mg/ml + phenylbutazone, cinchocaine, raminef)
*(Diurizone 0.5mg/ml +hydrochlorothiazide)
*Examples of polypharmacy and not advisable.
Probably the corticosteroid most commonly used, and often over used.
Dose
0.1 mg/kg once daily to start with, then will decrease.
For example:
Days
Dose mg/kg
1
0.1
3,7,11,15
0.08
19,23,27,31
0.06
35, 39, 43, 47
0.04
51, 55, 59, 63
0.02
Route of Administration
iv and im preparations available, also oral.
C. Endoparasite medicines
For internal parasites. Non chemical control methods should be used wherever possible,
such as removing faeces from grazing areas, moving stock to “clean” grazing areas
during periods where larval survival is likely to be minimal. Deworming schedules
should be devised to maximise health while minimising anthelmintic use.
Ideally treatments should be targeted at animals that have significant faecal egg counts
requiring regular faecal examinations. Treatments should also be strategic, for example
eliminating cyasthostome burdens before the season of the year that is optimal for
parasite development on pasture.
1. Benzimidazoles
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i. Fenbendazole
Trade names available locally
Panacur 100 (100 g/l = 100 mg/ml)
Effective against large and small strongyles (Cyathostomes) and ascarids.
Effective against migrating large strongyles and encysted cyasthostome larvae when used
at higher doses for 5 days.
Resistance to the drug is becoming common.
Dose
5 mg/kg
10 mg/kg once daily for 5 days for encysted cyasthostome larvae.
Route of Administration
Orally, liquids and pastes available.
ii. Mebendazole
Trade names available locally
Telmin
Effective against large and small strongyles, oxyuris.
Dose
9 mg/kg
Route of Administration
Oral. Paste, liquid.
iii. Oxfendazole
Large and small strongyles, parascaris, oxyuris
Dose
10 mg/kg
Route of Administration
Oral. Paste, powder, suspension.
2. Avermectins
i. Ivermectin
Trade names available locally
Noromectin injection (1% w/v)
Vermic injection (10mg/ml, 1%).
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Dectiver injection (10 mg/ml, 1%)
Dectiver paste (4.8 mg/ml)
Atlamec-gel (2 mg/ml)
Large and small strongyles, (adult and migrating larvae),parascaris, oxyuris, lung worm,
strongyloides, gastrophilus, onchocerca filaria, habronema, (+ some external parasites)
NOT for tapeworms, adult onchocerca or encysted cyasthostome larvae.
Dose
0.2mg/kg once for internal parasites.
(0.2 mg/kg repeated after 4d for lice/mange.)
Route of Administration
The only licensed preparations for equines are oral forms, usually in pastes. However,
the injectable form for cattle can be given sc to horses and also orally at the same dose
rate.
ii. Moxidectin
Trade names available locally
Cydectin (1% injection for cattle 10 mg/ml)
Large and small strongyles, parascaris, oxyuris, T.axei, habronema, onchocerca,
gastrophilus, + possibly larval forms of large and small strongyles in mucosa.
Use with caution in young animals, and debilitated ones. Do not in foals less than
4months old.
Faecal egg counts are suppressed longer with moxidectin than ivermectin.
Dose
0.4 mg/kg
Route of Administration
Oral
3. Piperazine
Trade names available locally
Ascazine (360g / kg powder)
Ascazine (188g / l liquid)
Parascaris equorum, and ? small strongyles
Dose
110 mg/kg
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Route of Administration
Oral
4. Pyrimidines
i. Pyrantel
Trade names available locally
Strongid-P (520 mg/ml oral paste)
Large and small strongyles, parascaris, oxyuris, tapeworms
Dose
6.6 mg/kg
Require double this dose for tapeworms
Route of Administration
Oral
D. Ectoparasite medicines
1. Avermectins
i. Ivermectin
Trade names available locally
Noromectin injection (1% w/v)
Vermic injection (10mg/ml, 1%).
Dectiver injection (10 mg/ml, 1%)
Dectiver paste (4.8 mg/ml)
Atlamec-gel (2 mg/ml)
For lice and mange.
Dose
0.2 mg/kg repeated after 4 days for lice/mange.
Route of Administration
The only licensed preparations for equines are oral forms, usually in pastes. However,
the injectable form for cattle can be given sc to horses and also orally at the same dose
rate.
ii. Moxidectin
Trade names available locally
Cydectin (1% injection for cattle 10 mg/ml)
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For control of lice and mange.
Dose
0.4 mg/kg
Route of Administration
Oral
2. Fipronil
Trade names available locally
Frontline spray.
Not licensed for equine use, but has been used successfully as a topical spray on the
lower limbs to control Cheyletiella infestations.
Dose
Sufficient spray to wet the hair in the area. Not for general use all over body.
Route of Administration
Topical spray. Use gloves to rub into the hair.
E. Blood parasite medicine
i. Diminazine aceturate
Trade names available locally
Berenil
Trypanodad 3.5mg/kg
Veriben 3.5 mg/kg
For treatment of babesiosis (B. equi and B. caballi) and trypanosomiasis.
This drug is produced for use in cattle and can be dangerous in equines. It is sometimes
used, if nothing better is available.
Dose
3.5mg/kg
Route of Administration
??
ii. Melarsamine
Trade names available locally
Cymerlarsan
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Mainly used in camels to treat trypanosomiasis (Surra)
Dose
0.25mg/kg
Route of Administration
im
iii. Imidocarb diproprionate
Trade names available locally
Imizol 2.4 mg/kg
Carbesia 2.4 mg/kg
To treat babesiosis. In some countries only licensed for cattle use.
Dose
2.4 mg/kg (may need to repeat again in 48 hours for B.equi)
Route of Administration
im (deep into neck muscles, no more than 5 mls to be given at any one site)
F. Antiseptics/Disinfectants
i. Iodine
Trade names available locally
Betadine
Povidone
Used to clean wounds and also to prepare skin for surgery. Inactivated by organic matter.
Concentrated form is irritant. Also added to soaps for surgical scrubs.
Concentration
Dilute 0.1-1%, this actually has better bactericidal activity than the full strength.
Most authors recommend 0.1-0.5% strength, as any stronger can be detrimental to
healing.
Do not use to lavage joints (use sterile saline)
ii. Chlorhexidine
Trade names available locally
Hibitane
Savlon (chlorhexidine + cetrimide)
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To clean instruments (do not soak them or they will rust), to clean wounds and to prepare
skin for surgery. Also with soap ingredient for scrubbing hands before surgery.
Not effective if organic matter like faeces or pus present.
Concentration
0.05% is advised concentration to avoid harmful effects on tissues.
Do not use to lavage joints.
iii. Hydrogen peroxide
Generally considered unsuitable for wound lavage because it is tissue toxic. Its use is
limited to circumstances where anaerobic conditions are likely e.g. irrigation of a deep
wound which might be infected with Clostridium tetani, particularly wounds to the foot.
Concentration
300ml of 3% solution with 1 litre water.
Diluted solutions of 3% or lower concentrations have limited tissue toxicity.
iv. Hypochlorites
Trade names available locally
Bleach
Cheap and effective disinfectant for buildings, floors, tables. Works better in sunlight.
Do not use on animals, and wear gloves when making up solutions. Very irritant.
Concentration
200ml/l for buildings
v. Phenols
Trade names available locally
Jeyes fluid
Dettol
For buildings, floors, tables. Not for skin. Activity maintained even in presence of
organic matter.
vi. Potassium permanganate
Can be used to clean wounds and instruments. Must be very dilute for skin use.
Concentration
1 g/l for wounds.
10 g/l for instruments
22
vii. Gentian violet
Often applied to wounds as a component of antibiotic sprays.
20 g/l is making up solution.
G. Sedatives
i. Xylazine hydrochloride
Trade names available locally
Rompun
Xylaject
Alpha 2 adrenergic agonist.
Properties of sedation, analgesia and muscle relaxation.
Used for standing chemical restraint as well as premedication for anaesthesia.
Can be combined with acepromazine or opioids.
It may be useful in colic due to analgesic effect. Xylazine is shorter action than
detomidine so it does not mask clinical signs as severely. This is good if surgery is an
option.
Xylazine is hypotensive. Use with caution if there is pre existing cardiac disease, in old
horses and in horses suffering from dehydration and shock.
Dose
1.1 mg/kg for donkeys and horses.
1.6 mg/kg for mules.
Needs 5 mins for full effect.
Effect variable.
Lasts 40-60 mins
Route of Administration
SLOW iv injection.
Has also been given im.
If given by epidural route has no sedation but good analgesia.
ii. Romifidine
Trade names available locally
Sedivet
Less commonly used than other alpha 2 adrenergic agonists.
Causes less sedation and ataxia than the other two (xylazine and detomidine), but has a
longer duration of action.
Similar contraindications to xylazine. Care is needed if using in animals with
cardiovascular disease.
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DO NOT use potentiated sulphonamide drugs iv at the same time.
Dose
40-120 mcg/kg (0.04-0.12mg/kg) depending on level of sedation required.
Onset of action 1-2mins
Level of sedation
desired
Dose iv, mcg/kg
Dose in ml/100kg
(of 10mg/ml
sedivet)
Commencement of
effect iv in mins
Duration of action,
hours
Light
Deep
Deep and prolonged
40
0.4
80
0.8
120
1.2
1-2
1-2
1-2
0.5-1
0.5-1.5
Up to 3
Dose with butorphanol
40-120mcg/kg romifidine + 20mcg/kg butorphanol
Route of Administration
SLOW iv injection
iii. Detomidine hydrochloride
Trade names available locally
Domosedan
Alpha 2 adrenergic agonist.
Used for chemical restraint and premedication.
Same physiological effects to xylazine.
Longer lasting than xylazine (less than romifidine)
Can be used with acepromazine or opioids.
Not for use in the last month of pregnancy.
Do not use iv potentiated sulphonamides when using detomidine for sedation. There
have been some fatal collapses.
If using with butorphanol, do not use in pregnant animals or those suffering from colic.
Ensure you listen to the heart before administering, and do not give if horse has bradydysrhythmias
Dose
Level of sedation
desired
Dose im or iv,
Light
Moderate
Deep
10-20
20-40
40-80
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mcg/kg
Dose in ml/100kg
(of 10 mg/ml
domosedan)
Commencement of
effect iv in mins
Commencement of
effect im in mins
Duration of action,
hours
0.1-0.2
0.2-0.4
0.4-0.8
3
2
1
5
5
5
0.5-1
0.5-1
0.5-2
Dose with butorphanol (torbugesic)
12 mcg/kg detomidine + 25 mcg/kg butorphanol
NB studies show that a dose of 0.5ml domosedan and 1ml torbugesic is a reasonable dose
for horses over 200kg.
Route of Administration
SLOW iv injection
im injection
Can be given by epidural route, still has (reduced) sedative and ataxic effects by this
route (compare with xylazine).
iv. Acepromazine
Trade names available locally
ACP inj 10mg/ml
No analgesia, use for mild sedation, may help calm nervous horses. Pain and loud stimuli
can rouse apparently sedated horse!
Sedative at the higher dose rates, but also used as premed and as tranquilizing agent at
low doses.
Can be combined with alpha 2 agonists (xylazine, detomidine) or opioids.
Onset of action slow, 20-30mins.
Duration is 4-6 hours.
Used in cases of tetanus (given every 36-48h), also ? laminitis.
Use with caution in old, dehydrated horses or ones with a history of recent haemorrhage,
due to hypotensive effects.
Excessive doses cause restlessness and hallucinatory effects.
Do not give to breeding stallions, due to the possibility of penile paralysis.
Do not give to pregnant mares.
Dose
0.03-0.1 mg/kg
Route of Administration
iv or im
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Oral paste also available.
v. Butorphanol
Trade names available locally
Torbugesic
Used as sedative with detomidine or romifidine, see dosages above.
History of liver disease is contra indication.
Dose
Also used alone as analgesic at 0.1 mg/kg for colic. Can be given every 4hours.
Route of Administration
iv
H. Diuretics
Not commonly required in equine practice.
DO NOT USE in cases of dehydration or in cases of urinary obstruction.
Do not use with aminoglycosides as this can increase the risk of ototoxicity and
nephrotoxicity.
i. Furosemide
Trade names available locally
Furosemide 25 (25 mg/ml)
Dimazon injectable (50 mg/ml)
Lasilix (10 mg/ml human prep)
Frusmicen (50 mg/ml)
Furilan (20 mg vials human prep)
(*Diurizone hydrochlorothiazide 50mg/ml + dexamethasone 0.5mg/ml.
Example of polypharmacy and best to avoid)
Used in oedema due to vascular lesions of allergic, toxic, traumatic or inflammatory
origin, localised.
It’s most common indication in humans and small animals is to alleviate symptoms of
congestive heart failure (i.e. pulmonary oedema and ascites), we are unlikely to be
presented with this in equines, and unlikely to treat it.
It may be used in cases of protein deficiency oedema due to renal proteinuria, liver
lesions with disorders of protein metabolism, parasitism or malnutrition.
May be used to treat pathological oedema of udder and perineum at time of parturition in
mares or preputial or scrotal oedema of males.
In most cases furosemide is used to alleviate symptoms, it is not a cure in itself.
26
In particular furosemide must NOT be used in horses which are, apparently, having
difficulty urinating.
Dose
0.25-1 mg/kg
Route of Administration
iv or im
I. Cardio-respiratory medicines
i. Bromhexine hydrochloride
Trade names available locally
Bisolvon
An aid in the treatment of respiratory disease, helping to shift excess mucous from the
respiratory tract. Only the powder form is licensed for equines.
Dose
0.2-0.4 mg/kg once daily.
Route of Administration
Oral
ii. Clenbuterol hydrochloride
Trade names available locally
Ventipulmin
Lasts 6-8 hrs only.
Treatment of respiratory disease where airway obstruction due to bronchospasm and/or
accumulation of mucous is a factor.
Used for acute, sub-acute and chronic respiratory allergies, COPD.
Long term use is common.
May cause sweating, tremors, tachycardia, hypotension, restlessness.
Do not use at time of parturition as may abolish uterine contractions.
Dose
0.008 mg/kg every 12 hours (can inc to 0.032 mg/kg)
Route of Administration
iv inj.
Oral
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iii. Dembrexine hydrochloride
Trade names available locally
Sputolosin
For symptomatic treatment of acute, sub-acute and chronic respiratory disease where
there is an abnormal amount of mucous of increased viscosity. Often long term use.
Dose
0.2 mg/kg every 12 hours.
Route of Administration
Oral, in feed.
iv. Acefylline heptaminol
Trade names available locally
Vetecardiol
An analeptic, said to be good for:
Cardiovascular problems – shock, surgical or obstetrical shock, cardiac insufficiency,
myocarditis, cardio respiratory failure.
Respiratory problems – bronchitis, flu, and emphysema, acute pulmonary oedema.
Renal insufficiency.
Latest information does not indicate that this drug is of great use in modern equine
medicine.
Dose suggested
10 mg/kg
Route of Administration
iv, im, sc, ip, ic
v. Diprophylline + heptaminol
Trade names available locally
Frecardyl
Analeptic as above, + heart stimulant effect of heptaminol?
Of limited use in equine medicine.
Dose suggested
10 mg/kg
Route of Administration
iv, im, ip
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Others
J.Atropine
Trade names available locally
Atropcen
Atropine
Parasympatholytic. Anticholinergic.
Topical ophthalmic solutions used. Also used for brady arrhythmias and for diagnosing
av block.
Bronchodilator, but side effects of ileus and constipation, tachycardia, mydriasis and
excitation preclude use.
Used to control excessive salivation, excessive bronchial secretions, premedication in
some species.
Organo Phosphate poisoning treatment. Dose rates repeated until clinical signs of
poisoning received. Atropine only effective several minutes after injection, so there is a
need to wait and see effect before giving more.
Dose
0.02-0.04 mg/kg Repeated as necessary for organophosphate poisoning.
Route of Administration
im, sc
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Worksheets on dosage calculations.
Q1
A mule of approximately 250kg requires an injection of phenylbutazone.
You have a bottle of phenylarthrite or equipalazone or athricidine, all of which state they
have a concentration of 200mg/ml.
The dose rate for phenylbutazone is 4.4mg/kg for the first day. How many mls of the
medicine do you need to give?
Q2
A 300 kg horse requires phenylbutazone medication for tendonitis. After the initial dose
of 4.4 mg/kg, we will reduce the dose to the recommended lower dose rate of
phenylbutazone at 2.2mg/kg. How many mls of medicine does it require?
Q3
A small donkey of 100kg bodyweight is to receive antibiotic treatment for a joint
infection. We decide to give penicillin and gentamicin.
Procaine penicillin dose is 20 000 iu/kg bid
Gentamicin dose is 6.6 mg/kg sid
We have a procaine penicillin preparation containing 200 000iu/ml
We have a gentamicin preparation containing 50mg/ml
What dose in mls of each drug should we give?
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Q4
A 150kg donkey requires worming. You have an injectable ivermectin preparation which
can be given orally (for example Dectiver injection) which is 1 %w/v. How much of the
drug in mls will you give this animal?
Answers to Questions
A1
Animal weight = 250kg
Dose rate for phenylbutazone on day 1 = 4.4mg/kg
Concentration of medicine in bottle =200mg/ml (note always check that the
concentration is given in mg/ml, not mg/bottle)
Total dose required in mg = weight(kg) x dose (mg/kg)
=250 x 4.4 = 1100mg
Quantity in mls required = total dose(mg) / concentration(mg/ml)
=1100/200 = 5.5mls
Therefore the 250kg mule requires 5.5 ml of phenylbutazone solution on day 1.
A one step method of doing this is to use the formula:
ml dose required = weight(kg) x dose(mg/kg)
_________________
concentration(mg/ml)
i.e. in the above example:
ml dose required=
250 x 4.4
_______
200
= 5.5mls
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A2
ml dose required = weight(kg) x dose(mg/kg)
_________________
concentration(mg/ml)
i.e. in this example:
ml dose required=
300 x 2.2
_______
200
= 3.3mls
A3
Procaine penicillin:
ml dose required = weight(kg) x dose(iu/kg)
_________________
concentration(iu/ml)
in this example:
ml dose required=
100 x 20 000
_______
= 10mls bid i/m
200 000
Note we can use the same equation for iu (international units), as we can for mg, as long
as we use the same units for both the dose rate and the drug concentration.
Gentamicin:
ml dose required = weight(kg) x dose(mg/kg)
_________________
concentration(mg/ml)
i.e. in this example:
ml dose required=
100 x 6.6
_______
50
= 13.2mls sid, i/v
32
A4
Note: % w/v is another way of expressing the concentration of a drug. It stands for
weight/volume and is expressed as a percentage. It is the same as the weight of the drug
in g in a litre volume of liquid. E.g. 1% w/v is the same as 10g/1litre (the same as
10mg/ml)
1% w/v ivermectin is therefore the same as 10mg/ml
ml dose required = weight(kg) x dose(mg/kg)
_________________
concentration(mg/ml)
i.e. in this example:
ml dose required=
150 x 0.2
_______
10
= 3mls orally
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GLOSSARY OF TERMS
Qid
Tid
Bid
Sid
Eod
4 times a day, every 6 hours
3 times a day, every 8 hours
2 times a day, every 12 hours
once a day
every other day
(The above latin abbreviations are not commonly used today, but you may come across
them in old text books)
iv
im
sc
ip
po
ic
mg
kg
ml
l
intravenous
intramuscular
subcutaneous
intraperitoneal
by mouth
intra cardiac
milligrammes
kilogrammes
millilitres
litre
REFERENCES
Celia Marr presentations in Morocco, Dec 2003
Compendium of Data Sheets for Veterinary Products 2002-2003
Horse Healthcare
David Hadrill
Manual of Equine Medicine and Surgery
Patrick T. Colahan, I.G. Mayhew, Alfred M.
Merritt, James N. Moore
Manual of Equine Practice 2nd Ed
Reuben J. Rose, David R. Hodgson
Saunders Handbook of Veterinary Drugs
Mark G. Papich
The SPANA Guide to Animal Care
Where there is no vet.
Bill Forse
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