Amiodarone-associated hypothyroidism--a possible cause of digoxin intoxication

The problem of a possible interaction between amiodarone and digoxin is still unsettled. We have recently treated two patients with digoxin intoxication who had received amiodarone for eight and 36 months respectively. Both developed extreme bradycardia requiring temporary pacemakers. The presence of hypothyroidism was confirmed in both cases by laboratory data. Judging by present knowledge concerning the interaction between amiodarone, thyroid function, and digoxin, it is suggested that digoxin intoxication was not the result of its direct interaction with amiodarone. The possibility that amiodarone-induced hypothyroidism precipitated digoxin intoxication seems to be more plausible. Prevention of digitalis toxicity in amiodarone-treated patients would therefore require monitoring of thyroid function every three to six months. Frequent monitoring of digitalis blood levels is also indicated in patients with amiodarone associated hypothyroidism. Early detection of hypothyroidism and digitalis intoxication is necessary in view of the severity of the course of the disease.