Veramil

Verapamil is an L-type calcium channel blocker with antiarrhythmic, antianginal, and antihypertensive activity. Immediate-release verapamil has a relatively short duration of action, requiring dosing 3 to 4 times daily, but extended-release formulations are available that allow for once-daily dosing. As verapamil is a negative inotropic medication (i.e. it decreases the strength of myocardial contraction), it should not be used in patients with severe left ventricular dysfunction or hypertrophic cardiomyopathy as the decrease in contractility caused by verapamil may increase the risk of exacerbating these pre-existing conditions.

May increase plasma level with CYP3A4 inhibitors (e.g. erythromycin, ritonavir), cimetidine. May decrease plasma level with CYP3A4 inducers (e.g. rifampicin), phenobarbital, sulfinpyrazone. Increased risk of bleeding with aspirin. May increase bradycardic and hypotensive effect with telithromycin. Increased AV blocking effect with clonidine. May increase plasma level of cardiac glycosides (e.g. digoxin, digitoxin), β-blockers (e.g. propranolol, metoprolol), α-blockers (e.g. terazosin, prazosin), immunosuppressants (e.g. sirolimus, ciclosporin, tacrolimus, everolimus), lipid lowering agents (e.g. lovastatin, simvastatin, atorvastatin), colchicines, quinidine, carbamazepine, imipramine, glibenclamide, doxorubicin, midazolam, buspirone, almotriptan, theophylline. May potentiate hypotensive effect with diuretics, antihypertensives, vasodilators. May increase neurotoxic effect of lithium.

Verapamil is generally well tolerated. The following reaction to orally administered Verapamil appeared clearly drug-related or occurred at rates greater than 1% in clinical trials with approximately 5000 patients.

• Digestive system: Constipation, nausea;
• Cardiovascular system: Hypotension, edema, CHF, pulmonary edema, bradycardia, AV block;
• Respiratory system: Upper respiratory tract infections;
• Nervous system: Dizziness, headache, fatigue;
• Skin: Rash, flashing;
• Hepatic: Elevated liver enzyme.

There are no adequate and well-controlled studies in pregnant women, so this drug should be used during pregnancy only if clearly needed. Verapamil crosses the placental barrier and can be detected in umbilical vein blood during delivery. Verapamil is excreted in breast milk. So nursing should be discontinued while Verapamil is administered.

Care should be taken in 1st degree AV block, bradycardia <50 beats/minutes, hypotension <90 mm Hg systolic pressure, atrial fibrillation/flutter and simultaneous pre-excitation syndrome e.g. WPW syndrome, heart failure (previous compensation with cardiac glycosides/diuretics required). Verapamil may impair ability to drive or operate machinery, particularly in the initial stages of treatment and with concomitant consumption of alcohol. Verapamil markedly slows down the elimination of alcohol and prolongs the duration of the effects of alcohol.

Calcium-channel blockers

Treatment of overdose should be supportive. Beta-adrenergic stimulation or parenteral administration of calcium solution may increase calcium ion flux across the slow channel and have been used in the treatment of overdose with Verapamil. Verapamil cannot be removed by hemodialysis.

Do not store above 30°C. Keep away from light and out of the reach of children.