Pharmacology (Pharmacon, Greek - medicinal, Logos, Greek - study) is a branch of natural sciences which studies the action of chemical compounds on living organisms. Pharmacology mainly studies the effects of chemical substances employed for treatment and prevention of various diseases and pathological conditions. One of the most important tasks of pharmacology consists of search for new effective medicines and chemical compounds to prevent illness.

The range of pharmacological studies is very wide. Studies include the effects of chemical compounds on biological systems (total body to subcellular structures), subcellular metabolism, and regulation of biological systems by receptors and enzymes.

Pharmacology is closely related to theoretical and practical medicine and has significantly influenced the development of several biomedical disciplines, particularly physiology and biochemistry. For example, the mechanism of the synaptic transmission produced by acetylcholine and nor epinephrine have been discovered through the use of vegetropic substances. Development and production of agents that block certain enzymes or accelerate their synthesis had stimulated advances in enzymology. Several of the complex functions of the central nervous system have been discovered through the use of psychotropic substances.

Pharmacology has been particularly important for practical medicine. A wide spectrum of highly effective medicines, has revolutionized the treatment of most diseases. Pharmacological preparations are used to inhibit or stimulate the central and peripheral nervous systems, increase or decrease blood pressure, stimulate cardiac output and pulmonary activity, regulate blood cell production, and modify blood coagulation and metabolic processes. Pharmacologic agents are widely used and are essential in practical medicine.

Progress in pharmacology has greatly affected the development of clinical medicine. The discovery of narcotics and anesthetics has stimulated progress in surgery. Psychotropic substances have led to progress in psychiatry. Isolation and synthesis of hormones has considerably improved the diagnosis and treatment of patients with endocrine disorders. Effective treatment of infectious diseases became possible only after the introduction of antibiotics and sulfanilamide. Organ transplantation surgery has become possible only after obtaining immunosuppressive medicines.

Because of the important role of pharmacotherapy to practical medicine, medical doctors of any specialty must have strong knowledge in pharmacology. Modern medicines have very high biological activity. Any tiny imprecision in their prescription might cause considerable negative effect on the patient's condition.