Drug Interactions between digitoxin and parathyroid hormone

MONITOR CLOSELY: Parathyroid hormone may alter the effects of digitalis glycosides. The inotropic effects of digitalis glycosides are affected by serum calcium levels. Since parathyroid hormone causes a transient increase in serum calcium, it can potentiate the risk of digitalis toxicity if hypercalcemia develops. On the other hand, digitalis efficacy may be reduced if hypocalcemia occurs. Severe cases of both hypercalcemia and hypocalcemia have been reported during treatment with parathyroid hormone. The risk of hypercalcemia is greatest when starting or increasing the dose of parathyroid hormone, whereas the risk of hypocalcemia is greatest when parathyroid hormone is withheld, missed, or abruptly discontinued.

MANAGEMENT: Serum calcium and digitalis levels should be closely monitored during parathyroid hormone therapy, and the digitalis dosage adjusted as necessary. Patients should be advised to seek medical attention if they experience signs of digoxin toxicity such as nausea, anorexia, visual disturbances, slow pulse, or irregular heartbeat.