Pharmacologic principles are defined as an understanding of the molecular mechanism of action of a drug and its dose-response characteristics.

1. Drug Action

2. Drug Effect

3. Pharmacognosy

I. Drug Action

Action of a drug is the biochemical physiological mechanisms by which the chemical produces a response in living organisms. It is classified in the following ways:

1. Pharmaceutics is the study of how various drug types influence pharmacokinetic and pharmacodynamic activities. This includes disintegration and dissolution of the drug.

2. Pharmacokinetics is the study fo how the body breaks down a drug after it is administered. It includes the following steps

Absorption

Distribution

Metabolism or biotransformation

Excretion or elimination

3. Pharmacodynamics is the study of how drugs act at target sites of action in the body, i.e., the mechanism of drug action in the living tissues.

II. Drug Effect:

Drug effect is the ability of the drug to produce the desired result. It contains the following term: Pharmacotherapeutics is the study of the use of drugs and their clinical indications to prevent and treat diseases.

III. Pharmacognosy:

Pharmacognosy is the study of natural (plant and animal) drug sources.