Verapamil ER

Last Reviewed: Sep 16, 2024

Warnings

Verapamil (Calan SR) Risks, Warnings, and Complications

Verapamil can cause or worsen health problems in some people. Talk to your doctor or pharmacist about other medications for chest pain, high blood pressure, and irregular heartbeat if you are at an increased risk of adverse reactions from this drug.

HEART FAILURE: Verapamil can cause pulmonary edema (fluid buildup in the lungs) and congestive heart failure. Before starting verapamil, tell your doctor if you have a history of heart problems such as left ventricular dysfunction (weak heart muscle cells). Also, tell your provider if you are on beta blockers. Your doctor may prescribe digitalis and/or diuretics (water pills) for heart failure before starting verapamil therapy.
SEVERE HYPOTENSION: Verapamil can occasionally lead to an over-correction of high blood pressure, resulting in significant hypotension (low blood pressure). Tell your doctor if you have dizziness or lightheadedness, especially when going from a sitting or lying position to standing (this is called orthostatic hypotension). Your doctor may lower your verapamil dose.
LIVER INJURY: There are reports of elevated liver enzymes in patients receiving verapamil. These changes are usually mild and temporary and sometimes go away even when verapamil treatment is continued. However, some people develop clinical symptoms of liver damage, such as low energy, fever, and/or right upper stomach pain along with elevated liver enzymes on blood tests. Tell your doctor if you have a history of liver problems or kidney disease. Your doctor may want to periodically monitor liver function while you are taking verapamil.
ABNORMAL HEART RHYTHM: Verapamil can cause heart rhythm abnormalities including ventricular fibrillation or excessive bradycardia in some people. This medication is contraindicated in people with sick sinus syndrome, second or third-degree AV block, and atrial fibrillation or flutter with an accessory pathway (Wolff-Parkinson-White syndrome or Lown-Ganong-Levine syndrome). Tell your doctor if you have a history of heart rhythm abnormalities before starting treatment. Your doctor may recommend against taking verapamil or prescribe a lower dose.

Precautions Before Starting Verapamil (Calan SR)

Tell your doctor if you have ever had an allergic reaction to verapamil, any of the active or inactive ingredients in verapamil formulations, other calcium channel blockers, or any other medications. Your pharmacy can give you a list of ingredients.

Give your doctor and pharmacist a complete list of your medications, including prescription medications, over-the-counter medicines, vitamins, dietary supplements, and herbal products. This can help avoid possible interactions between verapamil and your other medicines.

Give your doctor a complete medical history. Verapamil may not be safe for people with certain medical conditions such as a narrowing or blockage in the digestive tract, heart failure, heart disease, kidney or liver disease, muscular dystrophy, or myasthenia gravis.

Tell your doctor if you are pregnant, could be pregnant, plan to get pregnant soon, or are breast-feeding.

Precautions During Use of Verapamil (Calan SR)

Keep all your medical and lab appointments while on verapamil. Your doctor may adjust your dose based on your response to the medicine.

Verapamil can cause dizziness, weakness, and blurred vision. Alcohol can make these side effects worse. Be careful while driving and doing other hazardous activities until you know how verapamil affects you. Get up slowly from a sitting or lying position to standing to prevent falls due to lightheadedness and low blood pressure.

Tell your doctor if you become pregnant while on verapamil.

Tell all your healthcare providers you are on verapamil before any surgery, including dental procedures.

Verapamil (Calan SR) Drug Interactions

Patients receiving concomitant verapamil and certain other medicines can experience severe adverse effects. Possible interactions with other medicines can also affect how well verapamil works. The following medications may have drug interactions with verapamil:

Aspirin
Alpha blockers such as prazosin (Minipress)
Antifungal agents such as itraconazole (Sporanox, Onmel) and ketoconazole (Nizoral)
Antibiotics such as clarithromycin (Biaxin, in Prevpac), telithromycin (Ketek), and erythromycin (E.E.S., Erythrocin, Eryc)
Beta blockers such as metoprolol (Toprol XL, Lopressor, in Dutoprol), atenolol (Tenormin, in Tenoretic), propranolol (Innopran, Inderal, in Inderide), nadolol (Corgard, in Corzide), and timolol (Blocadren, in Timolide)
Antiepileptic drugs such as carbamazepine (Tegretol, Carbatrol, Equetro, Epitol) and phenobarbital
H2 blockers such as cimetidine (Tagamet)
Immunosuppressants such as cyclosporine (Neoral, Sandimmune)
Heart medications such as digoxin (Lanoxin)
Antiarrhythmics such as disopyramide (Norpace), quinidine (in Nuedexta), and flecainide
Diuretics or water pills
Certain HIV medications such as indinavir (Crixivan), ritonavir (Norvir, in Kaletra), and nelfinavir (Viracept)
Psychiatric medications such as lithium (Lithobid)
Other antihypertensives (medications used to treat high blood pressure)
Antidepressants such as nefazodone
Diabetes medications such as pioglitazone (Actos, in Duetact, in Oseni)
Tuberculosis medications such as rifampin (Rifadin, Rimactane)
Respiratory medications such as theophylline (Theochron, Theolair, Uniphyl)

The above list may not include all the potential interactions of verapamil with other drugs. Give your doctor or pharmacist a complete list of your medications. This includes prescription drugs, nonprescription drugs, dietary supplements, and herbal remedies. Also, tell your healthcare professional if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription medications.

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