PHARMACOKINETIC DRUG INTERACTIONS

Clinical experience highlights oral hypoglycaemic agents, anticoagulants, and the use of barbiturates as especially hazardous areas and clinical Pharmacology units could contribute much to the understanding of these problems.

Abstract

Sometimes, one drug affects the Summary absorption, distribution, metabolism, or excretion of another. These " pharmacokinetic interactions" are becoming increasingly important now that patients are often prescribed more than one pharmacologically active drug. Absorption of one drug can be affected by a second drug which alters pH or gut motility. Some drugs compete for shared protein-binding sites in plasma, and when this happens the effective biological concentration of the displaced drug can rise dramatically. Many drugs and other chemicals stimulate the microsomal enzymes which control drug metabolism in the liver, the usual effect here being to reduce pharmacological and toxic effects: other compounds inhibit metabolism leading to increased plasma concentrations. Yet other drugs affect renal excretion of pharmacologically active compounds. Despite an increased awareness of the problem at the experimental level, little is known about pharmacokinetic interactions in man. However, clinical experience highlights oral hypoglycæmic agents, anticoagulants, and the use of barbiturates as especially hazardous areas. Clinical Pharmacology units could contribute much to the understanding of these problems.