Generic Isoptin Sr

Common use

Isoptin Sr is a Ca2+-channel blocker which relaxes (widens) veins and arteries, which makes it easier for the heart to pump and this way Isoptin Sr reduces its workload. Calcium triggers contraction of smooth muscles and when its entrance to the myocytes, it results in relaxation of the arterial muscles, improved oxygen delivery to the myocardial tissue, and decreased total peripheral resistance, systemic blood pressure, and afterload. Isoptin Sr also decreases the conduction of electrical impulses through the heart that control the coordination of contraction, this slows the rate of contraction. Isoptin Sr is used to treat hypertension, to treat angina, control some types of irregular heartbeats.



Dosage and direction

Take orally with or without food. Daily dose is 180-480 mg which may be taken as a single dose or divided in two or three intakes. Take exactly as prescribed by your doctor, never exceed the dose recommended to you.



Precautions

Avoid drinking alcoholic beverages, grapefruit juice or eating grapefruit. Alcohol is able worsen side effects of Isoptin Sr (drowsiness and dizziness ) while grapefruit interacts with components of the drug. Do not get up too fast from a sitting or lying position as you may feel dizzy.



Contraindications

Isoptin Sr is contraindicated in patients with hypersensitivity to components of the medication, severe left ventricular dysfunction, hypotension (systolic pressure less than 90 mm Hg) or cardiogenic shock, sick sinus syndrome (except in patients with a functioning artificial ventricular pacemaker), atrioventricular block degree II-III (except in patients with a functioning artificial ventricular pacemaker), atrial flutter or atrial fibrillation and an accessory bypass tract (Wolff-Parkinson-White, Lown-Ganong-Levine syndromes).



Side effects

Arpamyl is usually well tolerated. Most common side effects include dizziness, weakness or fainting, swelling of the lower extremities, rash, headache, and constipation. Jaundice, swelling, difficulty breathing, rashes are also possible. If you experience severe side effects listed above seek for immediate medical attention.



Drug interaction

Isoptin Sr inhibits elimination of alcohol, increases the efficacy of doxorubicin both in tissue culture systems and in patients. Cyclophosphamide, oncovin, procarbazine, prednisone (COPP) and the vindesine, adriamycin, cisplatin (VAC) cytotoxic drug regimens are able to decrease absorption of Isoptin Sr. Co-administration of Isoptin Sr with aspiring in rare cases increases risk of bleeding. Correction of digoxin dosage is important in patients treated with Isoptin Sr. Chronic verapamil treatment can increase serum digoxin levels by 50% to 75% during the first week of therapy leading to digitalis toxicity. Co-administration with oral antihypertensive agents results in additive effects. Inform your doctor about all medications you take, especially about Disopyramide, Flecainide, Quinidine, Phenobarbital, Cyclosporin, medications which contain lithium. This medication may change results of certain liver tests to mildly abnormal.



Missed dose

Take the dose you forgot as soon as you remember. If it is almost time for your next intake just skip the next dose and return to your regular schedule.



Overdose

If you experience slow heartbeat and fainting, they may be symptoms of overdose. Seek for immediate medical attention if you suppose that too much of Isoptin Sr was taken.



Storage

Store at room temperature 15-30 C (59-86 F) away from light, moisture, pets and children.



Disclaimer

We provide only general information about medications which does not cover all directions, possible drug integrations, or precautions. Information at the site cannot be used for self-treatment and self-diagnosis. Any specific instructions for a particular patient should be agreed with your health care adviser or doctor in charge of the case. We disclaim reliability of this information and mistakes it could contain. We are not responsible for any direct, indirect, special or other indirect damage as a result of any use of the information on this site and also for consequences of self-treatment.

Clinical Verification

Last Clinically Updated: August 15, 2026

Written By

Dr. Elena Vance, PharmD

Clinical Specialist in Neuropharmacology

Fact Checked By

Marcus Thorne, MS

Biomedical Data & FDA Label Verification

Medically Reviewed By

Dr. Arthur Campbell, MD

Board-Certified Psychiatrist (ABPN)