Pharmacology: Verapamil reduces pathologically raised blood pressure by dilating the peripheral blood vessels. Peripheral resistance diminishes and the load on the heart is thus relieved.
In coronary insufficiency, verapamil reduces myocardial oxygen consumption directly by intervening in the energy-consuming metabolic processes of the myocardial cell and indirectly by diminishing afterload. Moreover, the decrease of the vascular smooth muscle tone prevents coronary spasms.
Verapamil has a pronounced antiarrhythmic action, particularly in supraventricular cardiac arrhythmias. It prolongs impulse conduction in the AV node and thereby restores the sinus rhythm and/or normalizes the ventricular rate.
Treatment of hypertension.
Adults: 1 tab in the morning, unless otherwise prescribed by the physician. In patients requiring particularly gradual blood pressure-lowering therapy should be initiated with 120 mg (½ tab) of sustained-released Isoptin SR taken in the morning. If required, after about 2 weeks, the dose may be increased up to 2 tabs daily (1 tab in the morning and evening at an interval of approximately 12 hrs).
Patients on long-term treatment should not take >2 tabs daily. Transient dose increase only when directed by the physician.
In patients with impaired hepatic function, the effect of verapamil is intensified and prolonged depending on the severity of the liver disease due to diminished drug metabolism. In these cases, dosage should be adjusted with special care starting with low doses (approximately 30% of the dose given to patients with normal liver function should be administered to severe liver dysfunction patients).
Isoptin SR permits a convenient dosage regimen with the use of fewer tabs and reduction of the dosage interval to once daily-dosage in hypertension.
Administration: The doses of Isoptin SR as prescribed by the physician are to be taken regularly. The tabs are to be swallowed whole with some liquid, preferably with or shortly after meals.
Hypotension (<90 mmHg systolic pressure) or cardiogenic shock.
Complicated acute myocardial infarction (bradycardia, marked hypotension, left ventricular failure). Severe conduction disorders (2nd- and 3rd-degree AV block, sinoatrial block). Sick sinus syndrome (bradycardia-tachycardia syndrome). Patients with atrial flutter or atrial fibrillation with an accessory bypass tract (eg, Wolf-Parkinson-White, Lown-Ganong-Levine syndromes). Patients with known hypersensitivity to verapamil HCl.
When treating hypertension with Isoptin SR, monitoring of the patient's blood pressure at regular intervals is required.
Use in Patients with Attenuated (Decreased) Neuromuscular Transmission: It has been reported that verapamil decreases neuromuscular transmission in patients with Duchenne's muscular dystrophy and that verapamil prolongs recovery from the neuromuscular-blocking agent, vecuronium. It may be necessary to decrease the dosage of verapamil when it is administered to patients with attenuated neuromuscular transmission.
Patients with Impaired Renal Function: About 70% of an administered dose of verapamil is excreted as metabolites in the urine. Verapamil is not removed by haemodialysis. Until further data are available, verapamil should be administered cautiously to patients with impaired renal function. These patients should be carefully monitored for abnormal prolongation of the PR interval or other signs of overdosage.
Care should be taken in slight conduction disorders (1st-degree AV block), heart failure (to be treated by the physician before Isoptin SR is taken).
Effects on the Ability to Drive or Operate Machinery: Depending on individual susceptibility, the patient's ability to drive a vehicle or operate machinery may be impaired. This is particularly true in the initial stages of treatment when changing over from another drug and also with respect to the consumption of alcohol.
Use in pregnancy & lactation: During pregnancy (especially in the 1st trimester) and during lactation, Isoptin SR should not be given unless, in the physician's judgement, it is essential for the patient's well being.
Use in children: Safety and efficacy of Isoptin SR in children <18 years have not been established.
During pregnancy (especially in the 1st trimester) and during lactation, Isoptin SR should not be given unless, in the physician's judgement, it is essential for the patient's well being.
Particularly when given in high doses or in the presence of previous damage, some cardiovascular effects of verapamil may occasionally be greater than therapeutically desired: Reduction of heart rate (AV blockade, sinus bradycardia); lowering of blood pressure (hypotension); reduction of contractile force (more intense symptoms of heart failure).
Constipation is not infrequent and in rare cases, nausea, vertigo, dizziness, headache, flushing, fatigue, nervousness and ankle oedemas may occur.
Allergic skin reactions (erythema, pruritus, urticaria) were reported in single cases; furthermore, a reversible increase of transaminases and/or alkaline phosphatase, which is probably a sign of allergic hepatitis, may occur.
The simultaneous administration of Isoptin SR and cardioactive drugs (eg, β-receptor blockers, antiarrhythmics) or inhalation anaesthetics may lead to a mutual enhancement of the cardiovascular effects (AV blockade, bradycardia, hypotension, heart failure). Until further data are obtained, combined therapy of verapamil and quinidine in patients with hypertrophic obstructive cardiomyopathy should probably be avoided.
IV β-receptor blockers should not be given to patients under treatment with Isoptin SR.
Isoptin SR may intensify the blood pressure-lowering effect of other antihypertensives.
Rises in digoxin plasma levels under concomitant administration of verapamil have been reported. Physicians should be on the alert for symptoms of possible digoxin toxicity. The digitalis level should be determined and the glycoside dose reduced, if required.
There have also been occasional reports on interactions with carbamazepine (potentiated by verapamil), lithium (attenuated by verapamil) and rifampicin (effects of verapamil attenuated).
Phenobarbital therapy may increase verapamil clearance. Verapamil therapy may increase serum levels of cyclosporin. Verapamil may inhibit the clearance and increase the plasma levels of theophylline.
Store in a cool, dry place.
C08DA01 - verapamil ; Belongs to the class of phenylalkylamine derivative selective calcium-channel blockers with direct cardiac effects. Used in the treatment of cardiovascular diseases.
Sustained-release tab 240 mg x 30's.