Principles of Pharmacology

Pharmacology (Gr. pharmakon – a drug or poison, logos – word or discourse) is the science dealing with actions of drugs on the body (pharmacodynamics) and the fate of drugs in the body (pharmacokinetics). It overlaps with pharmacy, the science of preparation of drugs; much of it deals with therapeutics (Pharmacotherapeutics), the treatment of disease.

Toxicology is the branch of pharmacology dealing with the “undesirable” effects of drugs on biological processes (in the case of a nerve gas the bad effect may be a desired one).

Branch of pharmacology

Two important and interrelated areas are: pharmacodynamic and pharmacokinetics.

Pharmacodynamic

Pharmacodynamic (what drug does with the body) are the study of the molecular, biochemical, and physiological effects of drugs on cellular systems and their mechanisms of action.

Such studies also correlate the mechanism of action of a drug and may correlate the drug actions with their chemical structure.

Pharmacokinetics

(Greek: Kinesis—movement)—What the body does to the drug.

Pharmacokinetics (what body does with the drug) deals with the absorption, distribution, and excretion of drugs.

It also deals with all processes involved in the changes of concentration of the drug in the body. The concentration of drug available at the site of action or in biological fluid is termed as bioavailability.

Clinical Pharmacology

This branch of pharmacology deals with the study of drugs on human beings (both in volunteers and patients).

Pharmacotherapeutics

It is the application of pharmacological information together with knowledge of the disease for its prevention, mitigation or cure. It consists of rational pharmacotherapeutics and empirical Pharmacotherapeutics.

Rational Pharmacotherapeutics:

It include the rational use of drug for example, adrenaline is used in bronchial asthma; Why it is used that is well known mechanism.

Empirical Pharmacotherapeutics:

It includes the use of drug in particular disease but its mechanism of action is unknown. For Example, colchicines was at one time used in treatment of gout but how it act, was unknown.

Therapeutics :

It deals with the use of drugs in the prevention and treatment of disease.

Pharmacoeconomics

It deals with the cost, i.e. economic aspects of drugs used therapeutically.

Pharmacogenomics

It is a branch of pharmacogenetics which deals with the use of genetic information in selecting drugs for a person

Pharmacoepidemiology

It is the study of both the useful and adverse effects of drugs on large numbers of people.

Pharmacovigilance

It is a branch of Pharmacoepidemiology which deals with the epidemiologic study of adverse drug effects.

Toxicology

It deals with the adverse effects of drugs and also the study of poisons, i.e detection, prevention and treatment of poisonings (Toxicon=poison in Greek).

Chemotherapy

It is the use of chemicals for the treatment of infections. The term now also includes the use of chemical compounds to treat malignancies.

Pharmacopoeia:

(in Greek Pharmacon = drug; poeia=to make) is the official publication containing a list of drugs and medicinal

Drug

Drug : A chemical substance that is used for diagnosis, prevention & treatment of disease. (French: Drogue -Dry herb)

As per WHO Drug is an “Any substance or product that is used or intended to be used to modify or explore the physiological system or pathological state for the benefit of the recipient”

Nomenclature of Drugs

A drug generally has three categories of names

Examples of Chemical, Generic, Brand Names

Generic/Non-Proprietary Name

Given by USAN Council (United States Adopted Name)
Advantages-
World-wide acceptance, name remains the same in all countries.
Usually have similar suffix in a group.
Economical than Branded/Proprietary Medicines.
Disadvantages-
Naming of Fixed Dose combinations

Brand Name/Proprietary Name

Name given by Pharmaceutical company for commercial purpose.
Advantages-
The consistency or Pharmacokinetics or efficacy does not change with same brand.
Single brand name for a Medicine with multiple ingredients.
Bioavailability remains same where a patient is maintained on a particular brand.
Disadvantages-
Branded Medicines are costlier.
Multiple brands for a same Medicine

Drug Categories

Two categories:

SCOPE OF PHARMACOLOGY

• It provides the rational basis for the therapeutic use of the drug. Before the establishment of this discipline, even though many remedies were used, but doctors were reluctant to apply scientific principles to therapeutics.
• In 1920s, many synthetic chemicals were first introduced and the modern pharmaceutical companies began to develop.
• Scientific understanding of drugs enables us to predict the pharmacological effect of a new chemical that will produce a specified therapeutic effect.
• The scope of pharmacology has expanded greatly over the last decade to incorporate many new approaches such as computer-assisted drug design, genetic screens, protein engineering and use of novel drug delivery vehicles including viruses and artificial cells.
• Our society needs pharmacologists who understand the basis of modern therapeutics for careers within academic, pharmaceutical and governmental laboratories to study and develop tomorrow’s drugs.