Isoptin SR Special Precautions

Heart Block/First degree AV block/Asystole/Bradycardia (<50 beats/min): Verapamil hydrochloride affects the AV and SA nodes and prolongs AV conduction time. Use with caution as development of second- or third-degree AV block (contraindication) or unifascicular, bifascicular or trifascicular bundle branch block requires discontinuation in subsequent doses of verapamil hydrochloride and institution of appropriate therapy, if needed. Verapamil hydrochloride affects the AV and SA nodes and rarely may produce second- or third degree AV block, bradycardia, and, in extreme cases, asystole. This is more likely to occur in patients with a sick sinus syndrome (SA nodal disease), which is more common in older patients. Asystole in patients other than those with sick sinus syndrome is usually of short duration (few seconds or less), with spontaneous return to AV nodal or normal sinus rhythm. If this does not occur promptly, appropriate treatment should be initiated immediately. See Adverse Reactions.
Anti-arrhythmic and Beta blockers: Mutual potentiation of cardiovascular effects (higher-grade AV block, higher-grade lowering of heart rate, induction of heart failure and potentiated hypotension). Asymptomatic bradycardia (36 beats/minute) with a wandering atrial pacemaker has been observed in a patient receiving concomitant timolol (a beta-adrenergic blocker) eye drops and oral verapamil hydrochloride.
Digoxin: If verapamil is administered concomitantly with digoxin, reduce digoxin dosage. See Interactions.
Heart Failure: Heart failure patients with ejection fraction higher than 35% should be compensated before starting verapamil treatment and should be adequately treated throughout.
Hypotension: Hypotensive symptoms of lethargy and weakness with faintness have been reported following single oral doses and even after some months of treatment. In some patients it may be necessary to reduce the dose of verapamil hydrochloride.
HMG-CoA Reductase Inhibitors ("Statins"): See Interactions.
Neuromuscular transmission disorders: Verapamil hydrochloride should be used with caution in the presence of diseases in which neuromuscular transmission is affected (myasthenia gravis, Lambert-Eaton syndrome, advanced Duchenne muscular dystrophy).
Ventricular Tachycardia: The risk of inducing ventricular tachycardia cannot be excluded.
Other Special Populations: Renal impairment: Although impaired renal function has been shown in robust comparator studies to have no effect on verapamil pharmacokinetics in patients with end-stage renal failure, several case reports suggest that verapamil should be used cautiously and with close monitoring in patients with impaired renal function.
Verapamil cannot be removed by hemodialysis.
Liver impairment: Use with caution in patients with severely impaired liver function (see also Liver Impairment under Dosage & Administration).
Effects on ability to drive and use machines: Due to its hypotensive effect, depending on the individual response, verapamil hydrochloride may affect the ability to react to the point of impairing the ability to drive a vehicle, operate machinery or work under hazardous conditions. This applies all the more at the start of treatment when the dose is raised, when switching from another drug and in conjunction with alcohol. Verapamil may increase the blood levels of alcohol and slow its elimination. Therefore, the effects of alcohol may be exaggerated.