Pharmacodynamic and pharmacokinetic drug interactions

Drugs may interact with other drugs or any diet or dietary supplement taken at the same time. Interactions may be pharmacodynamic in which interaction is close to the target organ and involves direct antagonism or addition of pharmacological properties. Alternatively interaction may be pharmacokinetic in which one drug, or dietary supplement, alters the absorption, distribution, metabolism or excretion of another drug. The induction or inhibition of drug metabolizing enzymes is a particularly important cause of clinically significant interactions. However, although some interactions may be life threatening, many are only theoretical or clinically trivial. Nevertheless it is always wise to check interactions in an appropriate reference work.