CARDIAC-GLYCOSIDES - DRUG-INTERACTIONS OF CLINICAL-SIGNIFICANCE

Several commonly coadministered drugs interfere significantly with the pharmacokinetics or pharmacodynamics of cardiac glycosides. Only a fe w of these interactions (e,g. amiodarone, propafenone, quinidine) take place consistently, and although their extent may vary in individual patients, digitalis dosage adjustments should be made to avoid underdi gitalisation or toxicity. In other instances the appearance of clinica lly significant interactions depends on individual pharmacokinetic/met abolic characteristics (e.g. erythromycin, tetracycline), and the resu lt cannot be anticipated on clinical grounds. Some interactions are co ntroversial, having not been confirmed by all studies; others have bee n shown only in healthy volunteers but lack the definition of their re levance in the context of disease states. In view of the possible impa ct on the individual patient, close clinical monitoring (which may be supplemented with evaluation of digitalis plasma concentration) is rec ommended when prescribing cardiac glycosides with other therapeutic ag ents for which the possibility of an interaction has been reported.