Pharmacology is the medical science concerned with how drugs – more generally, substances, individual or mixtures of chemicals, whether considered therapeutic or toxic – affect the body and how the body deals with those substances. Pharmacology builds on and integrates with other medical sciences and disciplines, for example, chemistry and biochemistry; endocrinology; anatomy and physiology; neurology; and psychology.
Pharmacology has two main branches. Pharmacodynamics concerns mechanisms of action and effects of drugs on the body, from biochemical interactions to cellular function to major organ systems like the liver, heart, and brain. Pharmacokinetics deals with the mode of administration, absorption, distribution, metabolism, and elimination of drugs. Of great interest and practical application is the correlation in time of the amount of drug present in the body with the drug’s effects, for example, how a drug’s concentrations in blood correspond to the nature and degrees of effects of the substance.