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

• Drug actions are mediated by 3 ways:

1. Acting on somatic or psychic processes or functions2. Correction of deficiencies3. Toxic action on pathogenic microorganism

How are Drug Responses Produced?

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 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 on1. Chemical structure

Cholinesters Organophosphates Catecholamines

2. Location of action Cardiac glycosides Autonomic drugs

Criteria for drug classification

3. Purpose of medication Antihypertensive Diuretic Antiemetic Analgesic

4. Name of plant Opium alkaloids Cardiac glycosides Belladonna alkaloids

Prescription vs Over the Counter DrugsPrescription 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. Taking these drugs could mask the signs and symptoms of underlying disease making diagnosis difficult

2. Taking these drugs with other drugs can result in drug interactions3. 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 PlantsActive 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

postmenopausal women

Plasma or serum from blood Thyroxin from Pig or Ox thyroid gland Cod Liver Oil from Cod fish Liver

Natural from micro-organisms

Antibiotics

Penicillin from Penicillium notatum, Streptomycin from Streptomyces griseus, Bacitracin from Bacillus

Sources of drugs

Sources of drugs

Minerals

Calcium, Magnesium, Aluminium, Sodium, Potassium & Iron salts

Liquid paraffin from petroleum.

Inorganic metals Iodine Lithium Radioactive elements: Iodine (I131)

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 synthesis in pharmaceutical laboratories

Sulphonamides Salicylates Barbiturates Benzodiazepines

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 (E-coli) 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 drugs

Sources of Drug Information

☛ Saudi MOH (Ministry Of Health) 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 NomenclatureChemical 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 DrugsGeneric 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

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: Paracetamol or (acetaminophen) Proprietary name: Panadol, Calpol, Adol, Fevadol

Drug Nomenclature

QUESTIONS?

THANK YOU