DRUG INFORMATION SOURCES

From DrugPedia: A Wikipedia for Drug discovery

DRUG INFORMATION SOURCES

Most useful drug information sources are textbooks, drug reference books, drug compendia and journal articles. They provide information about established drugs and furnish information for understanding newer ones. However, they do not include many other details such as trade names, physical and chemical properties, identification criteria, standards of purity and strength, methods of storage and dosage range for therapeutic use which are necessary from a legal point of view for drug control. All these details of drugs are provided by Pharmacopoeias and Formulary. They are collectively known as Drug Compendia. Pharmacopoeias are prepared by a committee, which usually has predominance of physicians. Formulary is prepared by a committee, which usually has predominance of pharmacists. Then there are non-official sources of information.Pharmacopoeia: It is an official code containing a selected list of the established drugs and medicinal preparations with descriptions of their physical properties, identification, purity, potency and the minimum standard required and the average dose for adults. Each country has its own pharmacopeia. For example:

• British Pharmacopeia
• United States Pharmacopeia
• Indian Pharmacopeia
• European Pharmacopeia
• Russian Pharmacopeia
• International Pharmacopeia

Pharmacopeia: Also spelled pharmacopoeia, an official authoritative listing of drugs. Aspirin has, for example, long been in the pharmacopeia. By extension, a pharmacopeia is a collection or stock of drugs.

Formulary: It includes information on drugs, other pharmaceutical products and formulated products in the respective countries.

• British National Formulary is published by the British Medical Association
• National Formulary is published by American Pharmaceutical Association.
• National Formulary of India is published by the Government of India.

Non- Official Compendia

They are secondary sources of drug information which give useful and miscellaneous information about drugs for pharmacists and medical practitioners. They include both generic and trade names of the drugs. The information is not limited to drugs which are approved for use by legally constituted committee of that country. Some examples of non-official compendia are:

1. AMA Drug Evaluation: by American Medical Association 2. Drug Information for the Health Care Profession: by United States Pharmacopeial Convention Inc. Maryland, USA 3. Modern Drug Encyclopedia: by Yorke Medical Books, New York, U.S.A. 4. Martindale Extra Pharmacopeia: by Pharmaceutical Society of Great Britain 5. Physicians' Desk Reference (PDR): by Medical Economies Publication, U.S.A. 6. Remington's Pharmaceutical Science: by Mack Publishing Company, U.S.A. 7. United States Dispensary (USD): by Lippincot Publications, U.S.A.

[edit] SOURCES & NATURE OF DRUGS

Drug is a substance which is used for the following purposes:

• Diagnosis of the disease
• Prevention of the disease
• Treatment or palliation (relief of symptoms) of disease
• Prevention of pregnancy (i.e. contraception)
• Maintenance of optimal health

Sources of drugs are as follows:

I. SYNTHETIC SOURCES

At present majority of drugs used in clinical practice are prepared synthetically, such as aspirin, oral antidiabetics, antihistamines, amphetamine, chloroquine, chlorpromazine, general and local anaesthetics, paracetamol, phenytoin, synthetic corticosteroids, sulphonamides and thiazide diuretics. Advantages of synthetic drugs are:

• They are chemically pure.
• The process of preparing them is easier and cheaper.
• Control on the quality of the drug is excellent.
• Since the pharmacological activity of a drug depends on its chemical structure and physical properties, more effective and safer drugs can be prepared by modifying the chemical structure of the prototype drug.

II. NATURAL SOURCES

Drugs are obtained from the following natural sources:

A- PLANTS:

Following categories of drugs are derived from roots, leaves or barks of plants:

a) Alkaloids

• These are nitrogenous heterocyclic bases, which are pharmacologically active principles of plants.
• They are composed of carbon, hydrogen, nitrogen and oxygen.
• They are bitter in taste and are often poisonous. These are, therefore, used in small doses.
• They are insoluble in water. However, they form salts with acids which are soluble in water.

Some examples of alkaloids and their sources are listed in the table:

ALKALOID	SOURCE
Atropine	Atropa belladonna
Quinine	Cinchona bark
Morphine	Papavarum somniferum
Reserpine	Rauwolfia serpentina
Nicotine	Tobacco
Digoxin	Digitalis lanata
Caffeine	Coffee, Tea, Cocoa

b) Glycosides

• They are ether-like combination of sugar moiety with non-sugar moiety.
• They are called glucosides, if the sugar moiety is glucose.
• Sugar moiety is not essential for the pharmacological activity but it governs the pharmacokinetic properties of the glycoside. In the body it may be removed to liberate aglycone.
• Pharmacological activity resides in the non-sugar moiety that is called aglycone (or genin).
• Some examples are digitoxin, digoxin and ouabain.

c) Oils . They are liquids which are insoluble in water. They are of three types and are used for various medicinal purposes.

i) Essential Oils (or volatile oils): Essential oils are obtained from leaves or flower petals by steam distillation, and have an aroma.

• They have no caloric or food value.
• They do not form soaps with alkalies.
• They do not leave greasy stain after evaporation.
• On prolonged stay, they do not become rancid (foul smell).
• They are frequently used as carminatives and astringents in mouth-washes.
• Some of these oils are solid at room temperature and sublime on heating e.g. menthol and camphor.
• Other examples are clove oil, peppermint oil, eucalyptus oil and ginger oil.

ii) Fixed oils are glycerides of stearic, oleic and palmitic acid.

• They are obtained from the seeds that are present within the cells as crystals or droplets.
• They are non-volatile and leave greasy stains on evaporation.
• They have caloric or food value.
• They form soaps with alkalies.
• On prolonged stay, they become rancid.
• They do not have marked pharmacological activity and have little pharmacological use except castor oil (purgative) or arachis oil (demulcent).
• They may be of vegetable origin e.g. olive oil, castor oil, croton oil and peanut oil or of animal origin e.g. cod liver oil, shark liver oil and lard .

iii) Mineral Oils are mostly petroleum products and extracted by fractional distillation.

• These are mixtures of hydrocarbons of the methane and related aliphatic series.
• These are extracted in various consistencies - hard paraffin, soft paraffin and liquid paraffin.
• Hard and soft paraffins are used as vehicles for preparation of ointments while liquid paraffin is employed as a purgative.

d) Gums are colloidal exudates from plants which are polysaccharides chemically and yield simple sugars on hydrolysis.

• Upon addition of water, some of them swell or dissolve or form adhesive mucilage or remain unchanged.
• Uses: - In gut agar and psyllium seeds act as hydrophilic colloids and function as bulk purgatives.
• Gum acacia and gum tragacanth are used as suspending agents in making emulsions and mixtures.

e) Resins are ill-defined solid substances found in plants, and are polymers of volatile oil.

• They are produced by oxidation and polymerization of volatile oils.
• They are insoluble in water but soluble in alcohol, chloroform and ether.
• Examples: oleoresins (aspidium); gum resins (asafoetida); oleogum resin (myrrh); balsams (benzoin, tolu, peru); benzoin shellac, podophyllum.

• Uses:
• Benzoin is used as inhalation in common cold.
• Tincture benzoin is applied as antiseptic protective sealing over bruises.
• Colophony (an oleoresin) is used as an ingredient in various plasters.
• Shellac (from Lucifer lacca) is used for enteric coating of tablets.
• Balsams are used in the treatment of cough and bronchitis for their antiseptic and protective properties.
• Podophyllum is used as an irritant purgative.

f) Tannins are non-nitrogenous phenolic plant constituents which have an astringent action.

• Pyrogallol tannins are glycosides of glucose that occur in oak galls.
• Pyrocatechol tannins are sugar-free derivatives of catechol that are present in catechu and eucalyptus.
• Tannic acid is a tannin that is obtained from oak galls and is used for treating burns and diarrhoea.

B-ANIMAL SOURCES

Some animal sources continue to be used to procure some modern drugs because of cumbersome and expensive procedures for the synthesis of such chemicals. For example:

• Insulin, extracted from pork and beef pancreas, is used for the treatment of diabetes mellitus.
• Thyroid powder for treating hypothyroidism.
• Heparin is used as an anticoagulant.
• Hormones and vitamins are used as replacement therapy.
• Vaccines (cholera, T.B., smallpox, polio and antirabic) and sera (antidiptheria and antitetanus) are used for prophylaxis/treatment.

C-MICROBIOLOGICAL SOURCES

Many life-saving drugs are obtained from fungi, moulds and bacteria e.g. penicillin from Penicillium notatum, chloramphenicol from Streptomyces venezuelae, grisofulvin (an anti-fungal drug) from Penicillium griseofulvum, neomycin from Streptomyces fradiae and streptomycin from Streptomyces griseus.

D-MINERAL SOURCES

Minerals or their salts are useful pharmacotherapeutic agents. For example:

• Ferrous sulfate is used in iron deficiency anaemia.
• Magnesium sulfate is employed as purgative.
• Magnesium trisilicate, aluminium hydroxide and sodium bicarbonate are used as antacids for hyperacidity and peptic ulcer.
• Kaolin (aluminium silicate) is used as adsorbent in antidiarrheal mixtures.
• Radioactive isotopes of iodine, phosphorus, gold are employed for the diagnosis/ treatment of diseases particularly malignant conditions.

III. SEMISYNTHETIC SOURCES

Sometimes semi-synthetic processes are used to prepare drugs when the synthesis of drugs (complex molecules) may be difficult, expensive and uneconomical or when the natural sources may yield impure compounds. Some examples are semisynthetic human insulin and 6-aminopenicillanic acid derivatives.

IV. BIOSYNTHETIC SOURCES (genetically engineered drugs)

This is relatively a new field which is being developed by mixing discoveries from molecular biology, recombinant DNA technology, DNA alteration, gene splicing, immunology and immunopharmacology. Some of the recent developments are genetically engineered novel vaccines (Recombinex HB - a hepatitis-B vaccine), recombinant DNA engineered insulins (Humulin- human insulin) for diabetes and interferon-alpha-2a and interferon-alpha-2b for hairy cell leukaemia.

[edit] DRUG NOMENCLATURE

Three types of names are assigned to every drug.

g) CHEMICAL NAME: This name is given according to the chemical constitution of a drug. It indicates the precise arrangement of atoms and atomic groups in the molecule. However, chemical names are too complex and cumbersome to be used in prescription.

h) NON-PROPRIETARY /GENERIC NAME: When a drug has been found therapeutically useful, it is given a non-proprietary name by the United States Adopted Name (USAN) council. These names are used uniformly all over the world by an international agreement through the W.H.O. Non-proprietary name is called official when included in official books such as Indian, British, United States or International pharmacopeia. The non-proprietary name is often referred to as generic name.

i) PROPRIETARY /TRADE/BRAND NAME: The pharmaceutical company, which sells the non-proprietary drug selects the proprietary name and gets it registered. The trade name then becomes the sole property of the pharmaceutical company. Thus a non-proprietary drug may be marketed under many proprietary names by different firms. Proprietary name is usually smaller than the non-proprietary name and it is most widely used by medical practitioners.

Prototype Drug:

Usually, attention is focussed on one or at the most two drugs belonging to a group in order to comprehend and co-relate their pharmacological effects with the other drugs of the same group. . Drugs selected for this purpose are called prototype drugs e.g. chlorpromazine is a prototype drug for anti-psychotic drugs and morphine is a prototypal drug for narcotic analgesics.

CATEGORIES OF DRUGS:

Drugs may be divided into two categories:

A) Prescription Drugs: These drugs are used under medical supervision because these are considered to be unsafe. So they are dispensed only by an order of registered physician. e.g. antibiotics, anxiolytics, antidepressant etc.

B) Non-Prescription Drugs: These drugs are considered relatively safe and can be sold without physician's prescription over the counter (OTC ) e.g. vitamins, antacids, paracetamol etc.

[edit] External links

The following websites offer independent, evidence-based, unbiased (or at least, less biased) information on pharmaceuticals. In the 21st century, despite industry's claim that pharmaceutical reps are an important source of information for doctors, there is little excuse for health care providers relying on biased promotional information. But please note: None of the following comes with free lunch!

Therapeutics Letter (Canada) http://www.ti.ubc.ca/

Established in 1994 by the Department of Pharmacology and Therapeutics at the University of British Columbia "to provide physicians and pharmacists with up to date, evidence-based, practical information on rational drug therapy."

Member of the International Society of Drug Bulletins, and free.

Drug and Therapeutics Bulletin (UK) http://www.dtb.org.uk

A monthly publication giving independent evaluations of, and practical advice on, individual treatments and the management of disease.

Medical Letter http://www.medletter.com

Since 1958 has published critical appraisals of new drugs, prescribing recommendations based on expert consensus. It reviews virtually all new drugs (so who needs drug reps?). By subscription.

Prescriber’s Letter http://www.prescribersletter.com

Prescrire (France) http://www.prescrire.org

Ce site internet est celui de la revue Prescrire, revue de formation permanente destinée aux professionnels de santé : médecins, pharmaciens, infirmiers etc., ainsi qu'aux étudiants de ces disciplines.

Member International Society of Drug Bulletins