Generic Name: verapamil (oral) (ver AP a mil)
Brand Name: Calan, Calan SR, Isoptin SR, Verelan, Verelan PM
What is Calan SR (verapamil)?
Verapamil is a calcium channel blocker. It works by relaxing the muscles of your heart and blood vessels.
Verapamil is used to treat hypertension (high blood pressure), angina (chest pain), and certain heart rhythm disorders.
Verapamil may also be used for purposes not listed in this medication guide.
What is the most important information I should know about Calan SR (verapamil)?
You should not use verapamil if you have a serious heart condition such as "sick sinus syndrome" or "AV block" (unless you have a pacemaker), severe heart failure, slow heartbeats that have caused you to faint, or certain heart rhythm disorders of the atrium (the upper chambers of the heart that allow blood to flow into the heart).
What should I discuss with my healthcare provider before taking Calan SR (verapamil)?
You should not use verapamil if you are allergic to it, or if you have a serious heart condition such as:
"sick sinus syndrome" or "AV block" (unless you have a pacemaker);
severe heart failure;
slow heartbeats that have caused you to faint; or
certain heart rhythm disorders of the atrium (the upper chambers of the heart that allow blood to flow into the heart).
To make sure verapamil is safe for you, tell your doctor if you have:
congestive heart failure;
low blood pressure;
liver disease; or
a nerve-muscle disorder such as myasthenia gravis or muscular dystrophy.
It is not known whether this medicine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.
Verapamil can pass into breast milk and may cause side effects in the nursing baby. You should not breast-feed while using this medicine.
How should I take Calan SR (verapamil)?
Follow all directions on your prescription label. Your doctor may occasionally change your dose. Do not use this medicine in larger or smaller amounts or for longer than recommended.
Do not crush, chew, or break an extended-release tablet or capsule. Swallow it whole.
If you have trouble swallowing an extended-release capsule whole, ask your doctor or pharmacist if it is safe for you to open the capsule and sprinkle the medicine into a spoonful of applesauce to make swallowing easier. Swallow this mixture right away without chewing. Do not save the mixture for later use. Discard the empty capsule.
Your blood pressure will need to be checked often. Your kidney or liver function may also need to be checked.
If you need surgery, tell the surgeon ahead of time that you are using verapamil.
You should not stop using verapamil suddenly. Stopping suddenly may make your condition worse.
If you are being treated for high blood pressure, keep using this medication even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.
Verapamil may be only part of a complete program of treatment that also includes diet, exercise, and other medications. Follow your doctor's instructions very closely.
Store at room temperature away from moisture, heat, and light.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of verapamil can be fatal.
What should I avoid while taking Calan SR (verapamil)?
If you also take disopyramide, avoid taking it within 48 hours before or 24 hours after you take verapamil.
Verapamil may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.
Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.
Drinking alcohol can further lower your blood pressure and may increase certain side effects of verapamil.
Grapefruit and grapefruit juice may interact with verapamil and lead to potentially dangerous effects. Discuss the use of grapefruit products with your doctor.
Calan SR (verapamil) side effects
Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
chest pain, fast or slow heart rate;
a light-headed feeling, like you might pass out;
shortness of breath (even with mild exertion), swelling, rapid weight gain;
lung problems--anxiety, sweating, pale skin, wheezing, gasping for breath, cough with foamy mucus; or
liver problems--loss of appetite, upper stomach pain, tiredness, easy bruising or bleeding, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).
Common side effects may include:
headache, dizziness; or
abnormal liver function tests.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What other drugs will affect Calan SR (verapamil)?
Many drugs can interact with verapamil. Some drugs can raise or lower your blood levels of verapamil, which may cause side effects or make verapamil less effective. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any you start or stop using, especially:
aspirin, imatinib, lithium, nefazodone, St. John's wort;
all other heart or blood pressure medicines, especially clonidine, digoxin, flecainide, ivabradine, nicardipine, or quinidine;
an antibiotic--clarithromycin, telithromycin;
antifungal medicine--itraconazole, ketoconazole, posaconazole, voriconazole;
antiviral medicine to treat hepatitis or HIV/AIDS--atazanavir, boceprevir, cobicistat, delavirdine, efavirenz, fosamprenavir, indinavir, nelfinavir, ritonavir, saquinavir;
a beta blocker--atenolol, carvedilol, labetalol, metoprolol, nadolol, nebivolol, propranolol, sotalol, and others;
cholesterol lowering medicine--atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin;
drugs to treat high blood pressure or a prostate disorder--alfuzosin, doxazosin, prazosin, terazosin, silodosin, tamsulosin;
seizure medicine--carbamazepine, phenobarbital, phenytoin; or
tuberculosis medicine--isoniazid, rifampin.
This list is not complete and many other drugs can interact with verapamil. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.
See also: Side effects (in more detail)
More about Calan SR (verapamil)
- Side Effects
- During Pregnancy or Breastfeeding
- Dosage Information
- Drug Images
- Drug Interactions
- Support Group
- Pricing & Coupons
- En Español
- 9 Reviews – Add your own review/rating
- Generic Availability
- Drug class: calcium channel blocking agents
Related treatment guides
Where can I get more information?
- Your pharmacist can provide more information about verapamil.
- Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
- Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.
Copyright 1996-2012 Cerner Multum, Inc. Version: 14.01.
Date modified: August 01, 2017
Last reviewed: April 24, 2017