Enhanced mydriatic action w/ adrenaline, dipivefrin HCl. Additive β-blocking action w/ catecholamine-depleting drugs eg, reserpine; systemic β-adrenergic blockers eg, atenolol, propranolol HCl & metoprolol tartrate. May induce AV conduction disorder, left ventricular failure or hypotension w/ Ca antagonists eg, verapamil HCl, diltiazem HCl. Increased cardiac conduction disorder w/ digitalis prep eg, digoxin, digitoxin. May increase blood conc w/ CYP2D6 inhibitors eg, quinidine sulfate hydrate, SSRIs.