Drug Interaction Report

MONITOR: The risk of bradycardia and atrioventricular (AV) block may be increased during initiation of fingolimod treatment in patients receiving beta-blockers, calcium channel blockers, digitalis, or other drugs that can slow the heart rate or AV conduction such as alectinib, atazanavir, flecainide, ivabradine, lacosamide, lithium, mefloquine, moricizine, propafenone, succinylcholine, thalidomide, H2-receptor antagonists, tricyclic antidepressants, and anticholinesterase or cholinergic agents. Fingolimod can cause a decrease in heart rate during initiation of therapy that is apparent within an hour of the first dose and maximal at approximately 6 hours postdose in most cases, but occasionally up to 20 hours after the first dose. Further, but smaller decreases in heart rate may occur after the second dose, although heart rate eventually returns to baseline within one month of chronic treatment. The mean decrease in heart rate in patients receiving fingolimod 0.5 mg at 6 hours after the first dose was approximately 13 beats per minute (bpm). Heart rates below 40 bpm were rarely observed. In controlled clinical trials, adverse reactions of symptomatic bradycardia (hypotension, dizziness, fatigue, palpitations, chest pain) following the first dose were reported in 0.5% of patients receiving fingolimod 0.5 mg, compared to no patient on placebo. Initiation of fingolimod treatment has also resulted in transient AV conduction delays. First- and second-degree AV block (prolonged PR interval on ECG) following the first dose were each reported in 0.1% of patients receiving fingolimod 0.5 mg, compared to no patient on placebo. In a study of 698 patients with available 24-hour Holter monitoring data after their first dose, second degree AV blocks, usually Mobitz type I (Wenckebach), were reported in 3.7% of patients receiving fingolimod 0.5 mg and 2% of patients receiving placebo. Bradycardia and conduction abnormalities were usually transient and asymptomatic, and resolved within the first 24 hours on treatment, but they occasionally required treatment with atropine or isoproterenol.

MANAGEMENT: Fingolimod has not been adequately studied in patients receiving other drugs that can slow the heart rate or AV conduction. Close monitoring is recommended during initiation of fingolimod treatment in these patients. The first dose should always be administered in a setting where resources to appropriately manage symptomatic bradycardia are available. Patients should be observed for a period of six hours after the first dose for signs and symptoms of bradycardia with hourly pulse and blood pressure measurement. An electrocardiogram should be obtained prior to dosing and at the end of the observation period. Additional observation is recommended if the heart rate 6 hours postdose is less than 45 bpm or is at the lowest value postdose, or if the ECG 6 hours postdose shows new onset second-degree or higher AV block. Should postdose symptomatic bradycardia occur, initiate appropriate management, begin continuous ECG monitoring, and continue observation until the symptoms have resolved. Should a patient require pharmacologic intervention for symptomatic bradycardia, continuous overnight ECG monitoring in a medical facility should be instituted, and the first-dose monitoring strategy should be repeated after the second dose of fingolimod. The same precautions are applicable if, after the first month of treatment, fingolimod is discontinued for more than two weeks and then restarted, since the effects on heart rate and AV conduction may recur on reintroduction of fingolimod. Within the first 2 weeks of treatment, first-dose procedures are also recommended after interruption of one day or more; during week 3 and 4 of treatment, first-dose procedures are recommended after treatment interruption of more than 7 days.

H2 antagonists may alter the pharmacokinetic disposition of some nonsteroidal anti-inflammatory drugs (NSAIDs), resulting in increased or decreased plasma concentrations. Data have been varied, even for the same NSAID. The mechanism may involve inhibition of metabolism, changes in gastric pH resulting in altered absorption, and/or reduced urinary elimination of the affected NSAIDs. Statistically significant changes have been small and of limited clinical significance when interactions have been observed.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.

H2 antagonists may reduce the clearance of nicotine. Cimetidine, 600 mg given twice a day for two days, reduced clearance of an intravenous nicotine dose by 30%. Ranitidine, 300 mg given twice a day for two days, reduced clearance by 10%. The clinical significance of this interaction is not known. Patients should be monitored for increased nicotine effects when using the patches or gum for smoking cessation and dosage adjustments should be made as appropriate.