Drug Interaction Report

Consumer information for this interaction is not currently available.

MONITOR: Since acetylcholinesterase inhibitors can cause bradycardia and heart block due to vagotonic effects on the sinoatrial and atrioventricular nodes, additive effects may occur with other agents that also possess bradycardic effects such as beta-blockers, calcium channel blockers, digitalis, some protease inhibitors (atazanavir, lopinavir-ritonavir, saquinavir), amiodarone, dronedarone, moricizine, lacosamide, and mefloquine. A group of French investigators conducted a retrospective analysis of spontaneous reports in the French Pharmacovigilance Database concerning adverse drug reactions (ADRs) associated with use of the acetylcholinesterase inhibitors donepezil, galantamine, and rivastigmine. Two hundred and five cases of potential drug-drug interaction with bradycardic drugs (beta-blockers, calcium channel blockers, amiodarone, digoxin) were identified, 73 of which were associated with serious ADRs including five deaths due to syncope, bradycardia, arrhythmia, or cardiac arrest. However, no details on the individual cases such as patient characteristics or concomitant risk factors were provided, making the contribution of a potential drug interaction difficult to evaluate. The remainder of the cases were of no apparent clinical consequences. In contrast, a phase III trial of donepezil consisting of 1035 patients reported no significant increase in risk ratios for bradycardia during concomitant use of beta-blockers, nondihydropyridine calcium channel blockers, or digoxin.

MANAGEMENT: Caution is advised if acetylcholinesterase inhibitors are used concomitantly with bradycardic drugs. Patients with underlying structural heart disease, preexisting conduction system abnormalities, ischemic heart disease, or cardiomyopathies may be at increased risk for developing cardiac conduction disturbances and atrioventricular block. Patients should be advised to notify their physician if they experience dizziness, lightheadedness, fainting, or irregular heartbeat.

Do not consume grapefruit or grapefruit juice during treatment with dronedarone unless directed otherwise by your doctor. Grapefruit juice can increase the blood levels of dronedarone to dangerous levels. This may increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). Talk to your doctor if you have any questions or concerns. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.