Sources of Drugs:

Drugs are obtained from many sources. These include natural, synthetic, semi-synthetic and biosynthetic.

Natural source:

• Natural sources provide many important drugs. Natural drugs come mainly from plants, animals, microorganisms and minerals.

Plants:

• Oldest source of drugs
• Also provide constituents for semi-synthetic drugs.
• In addition to pure drugs, the crude extracts of some plants are used in therapeutic today.
• Biological activity of plant is due to presence of specific or more than one chemical constituent which are isolated from plant in crude form and then purified to be used as drug.
• Example: alkaloids, glycosides, atropine

Animals:

• Provides relatively few but some life-saving drugs.
• Drugs from animal sources are called pharmazooticals
• Includes antisera, vaccines, hormones, enzymes, vitamins, coagulants and anti-coagulants, blood and blood components, etc.
• Ex: Bovine pancreas- Insulin

Liver- Heparin

Liver of cod fish- Vitamin A

Pituitary gland- Gonadotrophin

Microorganisms:

• Drugs obtained from microbial sources includes; antimicrobials, anti-neoplastic, vaccines, probiotics and vitamins.
• Antibiotics- valuable in treatment of infectious diseases
• Anti-neoplastic- treatment of tumors
• Vaccines- provides immunity against diseases and tumors.
• Ex: penicillin, chloramphenicol, tetracycline, kanamycin

Minerals:

• Widely used in therapeutics and constitute economical source of drugs.
• Also used as dietary supplements to correct mineral deficiencies causes by various diseases, pregnancy, poor nutrition and certain medications.

Synthetic source:

• Synthetic drugs are prepared by chemists in laboratory from chemical substances.
• Drugs prepared in pharmaceuticals at present are synthetic drugs.
• Chemically pure and more effective than naturally obtained drugs.
• Easier to prepare in standardized units and can be manufactured in bulk to maintain a regular supply line.
• Ex: aspirin, paracetamol, sulfonamides, ampicillin, pethidine, etc.

Semi-synthetic source:

• Synthesized in laboratory by utilizing naturally occurring chemical as a starting material.
• These drugs are neither pure nor pure synthetic substances.
• Several antibiotics such as ampicillin, amoxicillin and cephalosporins are also prepared from semi-synthetic source.

Bio-synthetic source:

• Involves recently introduced techniques of genetic engineering or recombinant DNA technology.
• Used for large scale production of some complex polypeptide drugs, hormones, scarce enzymes and other proteins which are difficult to obtain in pure form from natural animal sources and are also difficult as well as very expensive to synthesize in laboratory.
• Ex: Human insulin