How does this medication work? What will it do for me?
Verapamil belongs to the class of medications called calcium channel blockers. The sustained release (SR) form of this medication is used for the treatment of mild-to-moderate high blood pressure, when beta-blockers or diuretics (water pills) are not recommended or have caused unacceptable side effects. The immediate-release form of verapamil may be used to treat certain abnormal heart rhythms, angina (chest pain), and certain conditions where the heart muscle is enlarged, as well as blood pressure. It works to control blood pressure and reduce the number of angina attacks by relaxing blood vessels. It also helps to normalize heart rhythms.
This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.
Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.
Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.
What form(s) does this medication come in?
phl-Verapamil SR is no longer being manufactured for sale in Canada. For brands that may still be available, search under "verapamil". This article is being kept available for reference purposes only. If you are using this medication, speak with your doctor or pharmacist for information about your treatment options.
How should I use this medication?
For most conditions, the dose of verapamil for adults is 80 mg to 120 mg taken 3 or 4 times daily with food. This dose may be increased to a maximum of 480 mg daily. When treating specific conditions where the heart muscle is enlarged and preventing the heart from working efficiently, the dose may be increased to 600 mg or 720 mg of verapamil divided throughout the day.
If you use the sustained-release (SR) tablets, the recommended dose of verapamil ranges from 180 mg to 480 mg daily with food. The SR tablets are to be taken once daily if the dose is 240 mg or less. Doses over 240 mg daily of the SR tablets should be taken in 2 divided doses (morning and evening) with food. Do not chew or crush the sustained-release tablets. Do not take more than 480 mg daily.
Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.
It is important to take this medication exactly as prescribed by the doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.
Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.
Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.
Who should NOT take this medication?
Do not use verapamil if you:
- are allergic to verapamil or any ingredients of this medication
- are suffering from severe congestive heart failure and/or severe left ventricular dysfunction unless it is due to a cause that is treatable by verapamil
- have a very low heart rate
- have certain types of abnormal heart rhythms, including atrial flutter or atrial fibrillation and an accessory bypass tract (e.g., Wolff-Parkinson-White, Lown-Ganong-Levine syndromes)
- have severe low blood pressure
- have second- or third-degree heart block or sick sinus syndrome
- are taking the medication ivabradine
- are taking the medication flibanserin
This medication should not be given to people who are in cardiogenic shock or those who are suffering from certain types of complicated heart attack.
What side effects are possible with this medication?
Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.
The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.
The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.
Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.
- unusual tiredness or weakness
Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
- breathing difficulty, coughing, or wheezing
- irregular or fast, pounding heartbeat
- low blood pressure (e.g., fainting, dizziness, lightheadedness, blurred vision, nausea)
- joint pain
- muscle weakness or cramps
- signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
- skin rash
- slow heart rate (less than 50 beats per minute)
- swelling of ankles, feet, or lower legs
Stop taking the medication and seek immediate medical attention if any of the following occur:
- signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
- signs of a severe skin reaction (e.g., painful red lumps, itchiness, sweating, joint or muscle pain)
Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.
Are there any other precautions or warnings for this medication?
Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Heart failure: Verapamil works partially by reducing the force of the heart’s contractions which can cause the symptoms of heart failure to become worse. If you have heart failure that is not well-corrected, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.
Verapamil may also reduce liver function and can cause liver failure. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.
Low blood pressure and heart rate: Low blood pressure symptoms of tiredness and weakness with faintness have been reported following single doses and even after some months of treatment with verapamil. Some people may require a reduced dose. Verapamil can cause very low heart rate for some people. If you have an abnormally low heart rate (less than 50 beats per minute) or persistent fatigue, tell your doctor.
Neuromuscular disease: If you have a neuromuscular disease such as myasthenia gravis, Lambert-Eaton syndrome, or Duchenne's muscular dystrophy, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Pregnancy: Verapamil reaches the developing baby if it is taken during pregnancy. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: This medication passes into breast milk. If you are breast-feeding and are taking verapamil, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.
Children: The safety and effectiveness of using this medication have not been established for children.
Seniors: Seniors may have a higher risk of side effects with this medication. Your doctor may recommend lower doses to reduce this risk.
What other drugs could interact with this medication?
There may be an interaction between verapamil and any of the following:
- acetylsalicylic acid (ASA)
- alpha-agonists (e.g., clonidine, methyldopa)
- alpha-blockers (e.g., alfuzosin, doxazosin, silodosin, tamsulosin)
- amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
- angiotensin converting enzyme inhibitors (ACEIs; captopril, enalapril, ramipril)
- angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
- antiarrhythmics (e.g., amiodarone, disopyramide, dronedarone, flecainide, propafenone, quinidine)
- anti-cancer medications (e.g., apalutamide, cabazitaxel, docetaxel, doxorubicin, etoposide, ifosfamide, irinotecan, paclitaxel, vincristine)
- anti-psychotics (e.g., chlorpromazine, clozapine, olanzapine, quetiapine, risperidone)
- "azole" antifungals (e.g., ketoconazole, fluconazole)
- barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
- benzodiazepines (e.g., diazepam, lorazepam, midazolam)
- beta-blockers (e.g., propranolol, metoprolol, nadolol)
- other calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine)
- calcium salts (e.g., calcium carbonate, calcium gluconate)
- corticosteroids (e.g., budesonide, dexamethasone, fluticasone, hydrocortisone, prednisone)
- diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
- ergot alkaloids (e.g., dihydroergotamine, ergonovine, ergotamine, methylergonovine)
- "gliptin" diabetes medications (e.g., linagliptin, saxagliptin, sitagliptin)
- grapefruit juice
- hepatitis C antivirals (e.g., elbasvir and grazoprevir, glecaprevir and pibrentasivr)
- HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
- HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
- lumacaftor and ivacaftor
- macrolide antibiotics (e.g., clarithromycin, erythromycin, telithromycin)
- monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, phenelzine, rasagiline, selegiline, tranylcypromine)
- multiple sclerosis (MS) medications (e.g., fingolimod, ponesimod, siponimod)
- narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone, tramadol)
- nitrates (e.g., isosorbide dinitrate, isosorbide mononitrate)
- non-steroidal anti-inflammatory medications (NSAIDS; e.g., ibuprofen, naproxen)
- phosphodiesterase 5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
- protein kinase inhibitors (e.g., bosutinib, dasatinib, idelalasib, imatinib, nilotinib)
- St. John's wort
- "statin" medications (e.g., atorvastatin, lovastatin, simvastatin)
- tricyclic antidepressants (e.g., clomipramine, imipramine)
If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:
- stop taking one of the medications,
- change one of the medications to another,
- change how you are taking one or both of the medications, or
- leave everything as is.
An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.
Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.
All material copyright MediResource Inc. 1996 – 2023. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source: www.medbroadcast.com/drug/getdrug/phl-Verapamil-SR