Interactions between somatic and psychotropic drugs: pharmacokinetic and pharmacodynamic consequences

Many psychiatric patients suffer from somatic comorbidities and therefore, are frequently comedicated with psychotropic and somatic drugs. Despite differing by their indications, they generally share a common fate in the organism. Research in this field is centred on the role of cytochrome P-450 and membrane transport systems (e.g. P-glycoprotein) in the biotransformation and elimination of drugs, respectively. Pharmacokinetic interactions, which may occur at this level, depend on the pharmacogenetic status of the patients, but also on environmental factors such as tobacco smoking. These interactions are often followed by pharmacodynamic consequences, which may either increase the risk for toxic effects (in the case of inhibition of the metabolism or the transport system) or for an inactivation of the drug (in case of an induction of the metabolism or the transport system). These considerations justify the strategy to increasingly include pharmacokinetic and pharmacogenetic tests in pharmacovigilance programs.