Nature and Nomenclature of
Drugs
Nature of drugs
Physical Structure



Solid (aspirin)
Liquid (nicotine, ethanol)
Gas (nitrous oxide)
Chemical structure
 Protein, lipid, carbohydrate
 Weak acid or weak base
 Amine (primary, secondary, tertiary)
Characteristics of an Ideal Drug?
 Selective (e.g. if you give a drug for heart, it should only
work on the heart)
 It should have minimum adverse effects
 Temporary (it does not change the function permanently)
 It should be highly effective (efficacious) at low doses
(potent)
 Dose-related (controllable)
 It should be safe in a wide range of doses (therapeutic
index)
 It should have convenient dosing regimens
How are Drug Responses Produced?
• Drug actions are mediated by 3 ways:
1. Acting on somatic or psychic processes or functions
2. Correction of deficiencies
3. Toxic action on pathogenic microorganism
How are Drug Responses Produced?
By interaction with active binding sites called
Drug Targets (e.g. receptors, enzymes, ion
channels etc.)
Drug may be agonist or antagonist for the
receptors
DRUG REACTIVITY AND DRUGRECEPTOR BONDS
Drugs interact with receptors by means of chemical forces or bonds. These are of
three major types:
1.
Covalent: Covalent bonds are very strong and in many cases not reversible
under biologic conditions.
2.
Electrostatic: Electrostatic bonds are weaker than covalent bonds.
Electrostatic bonding is much more common than covalent bonding.
Electrostatic bonds vary from relatively strong linkages between permanently
charged ionic molecules to weaker hydrogen bonds
3.
Hydrophobic: Hydrophobic bonds are usually quite weak and are probably
important in the interactions of highly lipid-soluble drugs. Drugs that bind
through weak bonds to their receptors are generally more selective than
drugs that bind by means of very strong bonds.
Drug Properties Influencing Drug
Actions
Drug Size
✐ The molecular size of drugs varies from very small (lithium ion, MW
7) to very large (eg, alteplase [tPA], a protein of MW 59,050).
✐ However, most drugs have molecular weights between 100 and
1000.
✐ The specificity of drug action requires a drug molecule must be
sufficiently unique in shape, charge, and other properties
✐ To achieve such selectivity, a molecule should be at least 100 MW
units in size.
✐ Drugs much larger than MW 1000 do not diffuse readily between
compartments of the body
Drug Shape
• The shape of a drug molecule must be such as
to permit binding to its receptor site via the
bonds just described.
• Optimally, the drug's shape is complementary
to that of the receptor site in the same way
that a key is complementary to a lock.
Criteria for drug classification
Drugs can be classified in many ways based on
1. Chemical structure
 Cholinesters
 Organophosphates
 Catecholamines
2.
Location of action
 Cardiac glycosides
 Autonomic drugs
Criteria for drug classification
3.
Purpose of medication




4.
Antihypertensive
Diuretic
Antiemetic
Analgesic
Name of plant



Opium alkaloids
Cardiac glycosides
Belladonna alkaloids
Prescription vs Over the Counter Drugs
Prescription Drugs
These drugs that cannot be obtained from a pharmacy without a
registered physician’s prescription.
Over-the-Counter (OTC) Drugs
These drugs are available without a physician’s prescription for
self-treatment of a variety of complaints. Some drugs are
approved as prescription drugs but later are found to be very safe
and useful for patients without the need for prescription.
Potential problems with OTC drugs
1.
2.
3.
Taking these drugs could mask the signs and symptoms of
underlying disease making diagnosis difficult
Taking these drugs with other drugs can result in drug interactions
Can result in drug overdoses
Sources of drugs
☛
Natural Sources: Substances obtained directly
from nature





Plants
Animals / Humans
Micro-organisms
Minerals
Inorganic metals
☛
Semi-synthetic
☛
Synthetic
☛
Bio-synthetic
Sources of drugs
Natural from Plants
Active principles are found in roots, leaves and
seeds in 3 forms:
 Glycosides

Cardiac glycoside Digoxin ( from the Foxglove plant)
 Alkaloids



Morphine (from Poppy capsules),
Atropine (from Belladonna leaves)
Quinine (from bark of Cinchona tree)
 Castor oil (from castor seed)
Sources of drugs
Natural from animals / humans
 Hormones



Heparin from Pig or Ox liver,
Insulin from Pig or Ox pancreas
Gonadotrophins from urine of pregnant women
 Plasma or serum from blood
 Thyroxin from Pig or Ox thyroid gland
 Cod Liver Oil from Cod fish Liver
Sources of drugs
Natural from micro-organisms
Antibiotics



Penicillin from Penicillium notatum,
Streptomycin from Streptomyces griseus,
Bacitracin from Bacillus
Sources of drugs
Minerals
 Calcium, Magnesium, Aluminium, Sodium,
Potassium & Iron salts,
 Liquid paraffin from petroleum.
Inorganic metals
 Iodine
 Lithium
 Radioactive elements: Iodine (I131)
Sources of drugs
Semi synthetic drugs
Prepared by chemical modification of natural
drugs in labs.
 Ampicillin from Penicillin-G,
 Semisynthetic cephalosporin's from 7-amino
cephalosporinic acid
Sources of drugs
Synthetic Drugs
Prepared
by
chemical
pharmaceutical laboratories
 Sulphonamides
 Salicylates
 Barbiturates
 Benzodiazepines
synthesis
in
Sources of drugs
Synthetic / semisynthetic Drugs
• Technical advances allow scientists to alter a chemical
with proven therapeutic effectiveness to make it better.
• Sometimes, a small change in chemical’s structure can
make that chemical more useful as a drug – more
potent, more stable, less toxic.
• These technological advance have led to the
development of groups of similar drugs, all of which
are derived from an original prototype, but each of
which have slightly different properties, making a drug
more desirable in a specific situation.
Sources of drugs
Bio-Synthetic Drugs
• Scientists use genetic engineering to alter
bacteria to produce chemicals that are
therapeutic and effective.
• Prepared by cloning of human DNA into
bacteria such as E. Coli.
Sources of drugs
Bio-Synthetic Drugs
Technique is called Recombinant DNA technology
(or Genetic Engineering)
 Cells are obtained from animals or human that
produce required substance (e.g. a hormone)
 Isolation of DNA or DNA fragment encoding the
substance
 Transfer of encoding DNA fragment to bacteria (Ecoli) via plasmids (Gene cloning)
 The transformed E-coli synthesizes the new
substance
Sources of drugs
Examples of Bio-Synthetic Drugs
 Human Insulin
 Human Growth Hormones
 Human Hepatitis B Vaccine
Sources of Drug Information
☛
☛
☛
☛
☛
☛
☛
☛
☛
☛
Saudi MOH Drug List (see notes below)
Pharmacopoeias
“Up to date” website
Elsevier “Gold standard” Clinical Pharmacology website
Micromedex (www.micromedex.com)
Drug labels (see next slide)
Package inserts
Drug references (e.g. Physician’s drug reference)
Journals
Internet (e.g. wikipedia)
Drug Nomenclature
Chemical name
 Based on the chemical composition and structure
Generic name (Official, Approved)
 This is usually the abbreviated form of the chemical name
 This name is used and chosen by official bodies
Proprietary name (Brand name, Company name)
 the name given by the company which markets the drug
 It is the commercial property of a pharmaceutical company
 It indicates a particularly formulation of a particular
substance by a particularly manufacturer
Generic Drugs vs Brand Name Drugs
Generic name:
 When a company brings a new drug onto the market, the firm has
already spent substantial money on research, development,
marketing and promotion of the drug. A patent is granted that gives
the company that developed the drug an exclusive right to sell the
drug as long as the patent is in effect under it’s brand name e.g.
generic name for metformin is “METFORMIN” (used for treating
diabetes)
Brand name:
 Are copies of generic-name. In other words, their pharmacological
effects are exactly the same as those of their generic-name
counterparts e.g. for diabetes “METFORAL” or “GLUCOPHAGE”
 Brand drugs are only cheaper because the manufacturers have not
had the expenses of developing and marketing a new drug….but be
careful about brand drugs from underdeveloped countries
Drug Nomenclature
 Since several companies market the same
drug under different proprietary names,
which creates unnecessary confusion
 Whenever possible drugs should be
prescribed by their GENERIC names

Chemical name: Acetyl-p-aminophenol

GENERIC name:

Proprietary name: Panadol, Calpol, Adol, Fevadol
Paracetamol or
(acetaminophen in the USA)
QUESTIONS?
THANK YOU