Drug Interactions between guanethidine and Rapiblyk

Consumer information for this interaction is not currently available.

MONITOR: Sympathetic ganglion-blocking or catecholamine-depleting agents such as guanethidine, reserpine, and monoamine oxidase (MAO) inhibitors may potentiate the pharmacologic effects of beta-blockers, which are thought to competitively antagonize catecholamines at cardiac and other peripheral adrenergic neurons. Combining these medications may increase the risk of hypotension, orthostasis, bradycardia, and heart failure due to excessive reduction of sympathetic activity. A case report describes two elderly patients who developed bradycardia less than 2 weeks after the initiation of phenelzine during treatment with a beta-blocker (nadolol 40 mg/day or metoprolol 150 mg/day). The pulse rates returned to normal following a 50% reduction of the nadolol dosage and discontinuation of metoprolol. In another report, a young woman developed marked orthostatic hypotension following the addition of pindolol 2.5 mg three times a day to an existing regimen of tranylcypromine. The pindolol dosage was reduced to 2.5 mg twice a day until her blood pressure stabilized, then slowly increased to 5 mg three times a day.

MANAGEMENT: Caution is advised if beta-blockers, including ophthalmic formulations, are prescribed in combination with sympathetic ganglion-blocking or catecholamine-depleting agents. Patients should contact their doctor if they experience dizziness, lightheadedness, syncope, bradycardia, shortness of breath, difficulty breathing, edema, and/or chest pain.