POTASSIUM-DEPLETING DIURETICS, CALCIUM, QUINIDINE, VERAPAMIL, AMIODARONE, PROPAFENONE, INDOMETHACIN, ITRACONAZOLE, ALPRAZOLAM, AND SPIRONOLACTONE RAISE THE SERUM DIGOXIN CONCENTRATION DUE TO A REDUCTION IN CLEARANCE AND\OR IN VOLUME OF DISTRIBUTION OF THE DRUG, ERYTHROMYCIN AND CLARITHROMYCIN (AND POSSIBLY OTHER MACROLIDE ANTIBIOTICS) AND TETRACYCLINE MAY INCREASE DIGOXIN ABSORPTION IN PATIENTS WHO INACTIVATE DIGOXIN BY BACTERIAL METABOLISM IN THE LOWER INTESTINE, SO THAT DIGITALIS INTOXICATION MAY RESULT. PROPANTHELINE AND DIPHENOXYLATE, BY DECREASING GUT MOTILITY, MAY INCREASE DIGOXIN ABSORPTION. ANTACIDS, KAOLIN-PACTIN, SULFASALAZINE, NEOMYCIN, CHOLESTYRAMINE, CERTAIN ANTICANCER DRUGS, AND METOCLOPRAMIDE MAY INTERFERE WITH INTESTINAL DIGOXIN ABSORPTION, RESULTING IN UNEXPECTEDLY LOW SERUM CONCENTRATIONS. RIFAMPIN MAY DECREASE SERUM DIGOXIN CONCENTRATION, THYROID ADMINISTRATION TO A DIGITALIZED, HYPOTHYROID PATIENT MAY INCREASE THE DOSE REQUIREMENT OF DIGOXIN. CONCOMITANT USE OF DIGOXIN AND SYMPATHOMIMETICS INCREASES THE RISK OF CARDIAC ARRHYTHMIAS. SUCCINYLCHOLINE MAY CAUSE A SUDDEN EXTRUSION OF POTASSIUM FROM MUSCLE CELLS, AND MAY THEREBY CAUSE ARRHYTHMIAS IN DIGITALIZED PATIENTS. ALTHOUGH BETA-ADRENERGIC BLOCKERS OR CALCIUM CHANNEL BLOCKERS AND DIGOXIN MAY BE USEFUL IN COMBINATION TO CONTROL ATRIAL FIBRILLATION, THEIR ADDITIVE EFFECTS ON AV NODE CONDUCTION CAN RESULT IN ADVANCED OR COMPLETE HEART BLOCK. DUE TO THE CAUSE PROLONGATION OF THE PR INTERVAL AND DEPRESSION OF THE ST SEGMENT ON THE ELECTROCARDIOGRAM. DIGOXIN MAY PRODUCE FALSE POSITIVE ST-T CHANGES ON THE ELECTROCARDIOGRAM DURING EXERCISE TESTING. DIGOXIN CONCENTRATIONS IN THE MOTHERS SERUM AND MILK ARE SIMILAR. HOWEVER, THE ESTIMATED EXPOSURE OF A NURSING INFANT TO DIGOXIN VIA BREAST FEEDING WILL BE FAR BELOW THE USUAL INFANT MAINTENANCE DOSE. THEREFORE, THIS AMOUNT SHOULD HAVE NO PHARMACOLOGIC EFFECT UPON THE INFANT. NEVERTHELESS. PEDIATRIC USE : NEWBORN INFANTS DISPLAY CONSIDERABLE VARIABILITY IN THEIR TOLERANCE TO DIGOXIN. PREMATURE AND IMMATURE INFANTS ARE PARTICULARLY SENSITIVE TO THE EFFECTS OF DIGOXIN, AND THE DOSAGE MUST BE INDIVIDUALIZED.