clinical pharmacology
Drug Interactions
Introduction
Drug interactions are changes in a drug’s effects due to recent or concurrent use of another drug or drugs (drug-drug interactions), ingestion of food ( Nutrient-Drug Interactions ), or ingestion of dietary supplements ( A drug-drug interaction may increase or decrease the effects of one or both drugs. Clinically significant interactions are often predictable and usually undesired (see Some Drugs With Potentially Serious Drug-Drug Interactions* ). Adverse effects or therapeutic failure may result. Rarely, clinicians can use predictable drug-drug interactions to produce a desired therapeutic effect. For example, coadministration of lopinavir and In therapeutic duplication, 2 drugs with similar properties are taken at the same time and have additive effects. For example, taking a benzodiazepine for anxiety and another benzodiazepine at bedtime for insomnia may have a cumulative effect, leading to toxicity. Drug interactions involve Overview of Pharmacodynamics None Overview of Pharmacokinetics None Inpharmacodynamic interactions,one drug alters the sensitivity or responsiveness of tissues to another drug by having the same (agonistic) or a blocking (antagonistic) effect. These effects usually occur at the receptor level but may occur intracellularly. Inpharmacokinetic interactions,a drug usually alters absorption, distribution, protein binding, metabolism, or excretion of another drug. Thus, the amount and persistence of available drug at receptor sites change. Pharmacokinetic interactions alter magnitude and duration, not type, of effect. They are often predicted based on knowledge of the individual drugs or detected by monitoring drug concentrations or clinical signs. 