[Digoxin-quinidine and digoxin-amiodarone interactions. Effects on blood levels of the cardioactive glycoside]

With ever increasing frequency potentially dangerous interactions are reported between Cardiac Glycosides and other drugs, particularly the antiarrhythmic one. The AA, carried out this work with the intent of studying the possible modifications produced by Q and A on the SDL. First of all the AA. retrospectively studied the SDL of patients treated with the associations Q-D and A-D and this SDL was compared with the SDL of patients treated with D alone. Then 10 subjects treated sequentially, at first with D alone and after with the Q-D (5 p.) and A-D (5 p.) association, were studied. The results obtained confirm the data of other AA. regarding the Q-D interaction; in fact, in the presence of this antiarrhythmic drug, the SDL increase significantly following the concomitant pharmacological effects of the Cardiac Glycosides. The SDL on the contrary seem not be influenced by the A-D association. The AA. then reviewed the literature about the mechanism of the Q-D interaction. The majority of the AA. agree outlining a reduction of the Volume of Distribution and of D Clearance, in consequence of the concomitant administration of Q, which would explain the high SDL obtained. In conclusion the AA. suggest, when the Q-D association is mandatory, a 50% reduction of the D maintenance dose and to check periodically the ECG and SDL.