Verapamil
The antihypertensive effect of verapamil, stems from a decrease in peripheral vascular resistance without an increase in heart rate as a reflex response.It has a marked antiarrhythmic effect, particularly in supraventricular arrhythmias.It delays impulse conduction in the A.V. node. Due to Ca-antagonistic effect on the smooth vascular muscles of the coronaries, verapamil enhances myocardial blood flow, even in poststenotic areas,and relieves coronary spasms which contributes to its anti-ischaemic & anti anginal efficacy in all types of coronary artery diseases.Chronic coronary insufficiency, angina pectoris, coronary spasms vasospastic angina, angina after M.I, hypertension. Tachycardias such as paroxysmal supraventricular tachycardia, atrial fibrillation/flutter with tachyarrhythmia, premature beats.
Adults: Oral: 40-80 mg 3-4 times a day. Max. 480 mg daily. I.V.: 5 mg initially, if desired effect is not achieved, further 5 mg after 5-10 minutes. Children: Oral: Less than 6 years up to 40 mg BD or TID. 6-12 years: 40-120 mg BD or TID. Max. 360 mg/day. I.V.: 1-5 years: 2-3 mg, 6-14 years 2.5-5 mg only at onset.
Cardiovascular shock, acute M.I. (bradycardia, hypotension, L.V.F.), severe conduction disorders (2nd & 3rd degree A V block, sinoatrial block) sick sinus syndrome.
Ability to drive or operate machinery may be impaired. Hepatic or renal impairment. Paediatrics: Reduced dose necessary. Pregnancy: Not recommended. Lactation: Drug passes into the breast milk. But at normal doses adverse effects on the baby are unlikely. Elderly: No special problems.
Constipation,nausea, vertigo or dizziness, headache, flushing, fatigue, nervousness, ankle oedemas, erythromelalgia and paresthesia.
Beta-blockers, other antihypertensives, neuromuscular blockers, digitalis, carbamazepine potentiated. Quinidine reduces blood levels & combination may result in profound cardiac depression. Phenobarb, rifampicin, phenytoin increase metabolism. Potentiates neurotoxicity by carbamazepine.
