Frequently Asked Questions

Verapamil Hydrochloride

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Calan

Calcium channel blocking agents Group IV antiarrhythmics


Pronunciation

Verapamil is used for:

Treating supraventricular tachycardia, a rhythm disturbance of the heart. It is also used for controlling heart rate response to other rhythm disturbances, specifically atrial fibrillation and atrial flutter. It may also be used for other conditions as determined by your doctor.

Verapamil is a calcium channel blocker. It works by slowing the electrical conduction in the heart, slowing heart rate, and/or normalizing heart rhythm.

Do NOT use verapamil if:

  • you are allergic to any ingredient in verapamil
  • you have certain heart problems (eg, left ventricular dysfunction, sick sinus syndrome, second- or third-degree heart block and do not have a pacemaker), very low blood pressure, or moderate to severe congestive heart failure (CHF)
  • you have atrial fibrillation or flutter and a pre-excitation syndrome (extra conduction pathway in the heart), such as Wolff-Parkinson-White (WPW) syndrome or Lown-Ganong-Levine (LGL) syndrome
  • you have shock due to serious heart problems
  • you are taking dofetilide, or you have taken disopyramide within the past 48 hours

Contact your doctor or health care provider right away if any of these apply to you.

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Before using verapamil:

Some medical conditions may interact with verapamil. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

  • if you are pregnant, planning to become pregnant, or are breast-feeding
  • if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • if you have allergies to medicines, foods, or other substances
  • if you have heart failure or a recent heart attack with lung congestion, low blood pressure, or heart problems (eg, a very slow heart rate, heart block, heart valve disease)
  • if you have kidney or liver problems, muscular dystrophy, or a neuromuscular disease
  • if you are taking another blood pressure medicine or you are being treated for cancer

Some MEDICINES MAY INTERACT with verapamil. Tell your health care provider if you are taking any other medicines, especially any of the following:

  • Beta-blockers (eg, propranolol), clonidine, disopyramide, ketolides (eg, telithromycin), macrolides (eg, erythromycin), or ritonavir because they may increase the risk of verapamil's side effects
  • Phenobarbital, rifampin, or St. John's wort because they may decrease verapamil's effectiveness
  • Aldosterone blockers (eg, eplerenone), aspirin, carbamazepine, colchicine, cyclosporine, digoxin, dofetilide, doxorubicin, dronedarone, eletriptan, erythromycin, everolimus, flecainide, HMG-CoA reductase inhibitors (eg, lovastatin, simvastatin), lithium, narcotic pain relievers (eg, fentanyl), paclitaxel, quinazolines (eg, terazosin), quinidine, ranolazine, theophyllines, or tolvaptan because the risk of their side effects may be increased by verapamil

This may not be a complete list of all interactions that may occur. Ask your health care provider if verapamil may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use verapamil:

Use verapamil as directed by your doctor. Check the label on the medicine for exact dosing instructions.

  • Verapamil is usually given as an injection at your doctor's office, hospital, or clinic. If you will be using verapamil at home, a health care provider will teach you how to use it. Be sure you understand how to use verapamil. Follow the procedures you are taught when you use a dose. Contact your health care provider if you have any questions.
  • Do not use verapamil if it contains particles, is cloudy or discolored, or if the vial is cracked or damaged.
  • Keep this product, as well as syringes and needles, out of the reach of children and pets. Do not reuse needles, syringes, or other materials. Ask your health care provider how to dispose of these materials after use. Follow all local rules for disposal.
  • If you miss a dose of verapamil, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.

Ask your health care provider any questions you may have about how to use verapamil.

Important safety information:

  • Verapamil may cause dizziness. This effect may be worse if you take it with alcohol or certain medicines. Use verapamil with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
  • Do not drink alcohol or use medicines that may cause drowsiness (eg, sleep aids, muscle relaxers) while you are using verapamil; it may add to their effects. Ask your pharmacist if you have questions about which medicines may cause drowsiness.
  • Verapamil may cause dizziness, lightheadedness, or fainting; alcohol, hot weather, exercise, or fever may increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Sit or lie down at the first sign of any of these effects.
  • Tell your doctor or dentist that you take verapamil before you receive any medical or dental care, emergency care, or surgery.
  • Lab tests, including liver function, kidney function, complete blood cell counts, electrocardiogram (ECG), and blood pressure, may be performed while you use verapamil. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
  • Use verapamil with caution in the ELDERLY; they may be more sensitive to its effects.
  • Verapamil should not be used in CHILDREN; safety and effectiveness in children have not been confirmed.
  • PREGNANCY and BREAST-FEEDING: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using verapamil while you are pregnant. Verapamil is found in breast milk. If you are or will be breast-feeding while you use verapamil, check with your doctor. Discuss any possible risks to your baby.

Possible side effects of verapamil:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Dizziness; fatigue; headache; lightheadedness; mild pain, redness, or swelling at the injection site.

Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; fainting; lightheadedness, especially when standing; severe dizziness; shortness of breath; swelling of the feet or hands; symptoms of liver problems (eg, yellowing of the skin or eyes, dark urine, pale stools, severe or persistent stomach pain, fever, general feeling of being unwell); unusually fast, slow, or irregular heartbeat.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately. Symptoms may include decreased mental status; dizziness; loss of consciousness; shortness of breath; slow or irregular heartbeat.

Proper storage of verapamil:

Store the undiluted solution of verapamil at room temperature, between 59 and 86 degrees F (15 and 30 degrees C). Because the product does not contain a preservative, any unused portion should be discarded. Verapamil is stable for 24 hours when added to compatible intravenous (IV) solutions at 77 degrees F (25 degrees C). Protect from heat, light, and moisture. Keep verapamil out of the reach of children and away from pets.

General information:

  • If you have any questions about verapamil, please talk with your doctor, pharmacist, or other health care provider.
  • Verapamil is to be used only by the patient for whom it is prescribed. Do not share it with other people.
  • If your symptoms do not improve or if they become worse, check with your doctor.
  • Check with your pharmacist about how to dispose of unused medicine.

This information should not be used to decide whether or not to take verapamil or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about verapamil. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to verapamil. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using verapamil.

Issue Date: February 4, 2015
Database Edition 15.1.1.002
Copyright © 2015 Wolters Kluwer Health, Inc.

Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using this medicine.

It is possible that some side effects of verapamil may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to verapamil: oral capsule extended release, oral capsule extended release 24 hr, oral tablet, oral tablet extended release, oral tablet extended release 24 hr

Other dosage forms:

  • intravenous solution

As well as its needed effects, verapamil may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking verapamil, check with your doctor immediately:

Less common
  • Blue lips and fingernails
  • blurred vision
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • chest pain
  • confusion
  • coughing that sometimes produces a pink frothy sputum
  • difficult, fast, noisy breathing, sometimes with wheezing
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
  • increased sweating
  • lightheadedness, dizziness, or fainting
  • pale skin
  • shortness of breath
  • slow or irregular heartbeat
  • sore throat
  • sweating
  • swelling in legs and ankles
  • unusual tiredness or weakness
Rare
  • Chills
  • cold sweats
  • feeling of warmth
  • redness of the face, neck, arms and occasionally, upper chest

Some verapamil side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common
  • Difficulty having a bowel movement (stool)
  • headache
Less common
  • Acid or sour stomach
  • belching
  • difficulty in moving
  • heartburn
  • indigestion
  • joint pain
  • muscle aching or cramping
  • muscle pains or stiffness
  • nausea
  • rash
  • stomach discomfort, upset, or pain
  • trouble sleeping
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
  • swollen joints

For Healthcare Professionals

Applies to verapamil: compounding powder, intravenous solution, oral capsule extended release, oral tablet, oral tablet extended release

Gastrointestinal

Constipation due to verapamil appears to be related to a delay of colonic transit and not to an effect on upper gastrointestinal transit.[Ref]

Gastrointestinal side effects have included constipation (up to 11.7%), nausea (up to 2.7%), dyspepsia (up to 2.7%), and diarrhea (up to 2.4%). Nausea (0.9%) and abdominal discomfort (0.6%) have been reported with intravenous verapamil. Nonobstructive, paralytic ileus (reversible upon discontinuation) has been reported infrequently. Diarrhea, dry mouth, gastrointestinal distress, and gingival hyperplasia have been reported during open trials/postmarketing experience.[Ref]

Cardiovascular

Cardiovascular side effects have included hypotension (up to 2.5%), new or worsened congestive heart failure (CHF) or pulmonary edema (negative inotropism; 1.8%), bradycardia (heart rate less than 50/minute; 1.4%), atrioventricular (AV) block (first-degree; up to 1.7%), AV block (total first-, second-, and third-degree; 1.2%), AV block (second- and third-degree; 0.8%), and postural hypotension (up to 0.4%). Symptomatic hypotension (1.5%), bradycardia (1.2%), and severe tachycardia (1%) have been reported with intravenous verapamil. In studies related to control of ventricular response in patients taking digoxin who had atrial fibrillation or atrial flutter, ventricular rate less than 50/minute at rest (15%) and asymptomatic hypotension (5%) were reported. Dizziness, hypotension, peripheral edema, and headache are not uncommon and are related to vasodilation of vascular smooth muscle. Verapamil may accelerate conduction of anomalous AV conduction tissue, as in the Wolff-Parkinson-White syndrome, which can result in worsened tachycardia, including malignant ventricular tachyarrhythmias or accelerated junctional tachycardia. Because of this potentially fatal side effect, verapamil is not recommended in patients with atrial fibrillation and premature ventricular depolarizations. Angina pectoris, AV block (second- and third-degree), atrioventricular dissociation, CHF, pulmonary edema, abnormal ECG, chest pain, claudication, hypertension, myocardial infarction, palpitations, and purpura (vasculitis) have been reported during open trials/postmarketing experience.[Ref]

CHF or pulmonary edema may be particularly important in patients with poor left ventricular function.

Various conduction disturbances have been reported with verapamil therapy, including bradycardia, AV block, first-, second-, third-degree heart block, and left bundle branch block.

One study of patients with the Wolff-Parkinson-White syndrome (WPW) has shown that patients with a history of WPW complicated by atrial fibrillation and a history of reciprocating tachycardias with rapid conduction over an accessory pathway during atrial fibrillation are more susceptible to ventricular fibrillation after verapamil than those without a history of a rapid ventricular response. A small series of patients with WPW complicated by atrial fibrillation and a rapid ventricular response who developed cardiac arrest within 1 to 10 minutes after receiving intravenous verapamil has been reported.

The mechanism by which verapamil may enhance the ventricular rate response to atrial fibrillation is not known. Verapamil may directly shorten the refractory period of the accessory pathway or cause reflex tachycardia indirectly by causing peripheral vasodilation.[Ref]

Nervous system

A 70-year-old man with supraventricular tachycardia began to experience uncontrollable, irregular, and symmetrical jerking movements in his extremities and torsional movements in his trunk 10 months after beginning verapamil. Both myoclonic and dystonic movements occurred during activity and rest. An electroencephalogram was normal. The movements were not initiated by photic stimulation, hyperventilation, or acoustic stimuli. Once diltiazem was substituted, the movements gradually resolved over the ensuing three weeks. There was no rechallenge.

A 28-year-old woman was treated for supraventricular tachycardia with 10 mg of intravenous verapamil for 3 days in a row. After the third dose, the patient experienced involuntary movements in the buccolingual and neck muscles which made language articulation difficult. The patient also experienced episodes of compulsory neck extension and spasmodic movements of the eyes going upwards. The patient was treated with diazepam parenterally and the symptoms disappeared after 24 hours.[Ref]

Nervous system side effects have included headache (up to 12.1%), dizziness (up to 4.7%), lethargy (up to 3.2%), fatigue (up to 4.5%), sleep disturbances (up to 1.4%), paresthesia (up to 1%), and rare neurologic complaints (including paresthesias, sleeping problems, and tremors; less than 1%). Dizziness (1.2%), headache (1.2%), sleepiness, vertigo, and rare cases of seizures during injection have been reported with intravenous verapamil. Rare cases of muscle fasciculations in patients with underlying neuromuscular diseases, stroke associated with verapamil-induced hypotension, exacerbation of myasthenia gravis, and myoclonic dystonia have been reported. Cerebrovascular accident, confusion, equilibrium disorders, extrapyramidal symptoms, insomnia, paresthesia, shakiness, somnolence, syncope, and tinnitus have been reported during open trials/postmarketing experience.[Ref]

Other

Other side effects have included flu syndrome (up to 3.7%), peripheral edema (up to 3.7%), edema (up to 3%), pain (up to 2.4%), fatigue (1.7%), accidental injury (up to 1.5%), ankle edema (up to 1.4%), and flushing (up to 0.8%). Asthenia has been reported during open trials/postmarketing experience.[Ref]

Immunologic

Immunologic side effects have included infection (up to 12.1%).

Respiratory

A 26-year-old man with rheumatic heart disease, mitral stenosis, and supraventricular tachycardia became apneic following a 5 mg intravenous bolus of verapamil. His heart rhythm at the time was supraventricular tachycardia at 290 beats per min; his blood pressure is not reported. The patient responded to assisted ventilation, oxygen, and DC cardioversion. The authors of this case report have located two other such cases, one of which had "stable hemodynamics," but died due to intravenous verapamil-associated acute respiratory arrest.

A 66-year-old woman with a 10-year history of hypertension and bronchial asthma was switched from immediate-release verapamil to sustained-release verapamil. The patient developed dyspnea, cough, and wheezing after taking the first tablet. The patient experienced similar reactions on three subsequent occasions with verapamil sustained-release administration.[Ref]

Respiratory side effects have included upper respiratory infection (up to 5.4%), pharyngitis (up to 3%), sinusitis (up to 3%), rhinitis (up to 2.7%), and dyspnea (up to 1.4%). Extremely rare cases of respiratory arrest have been associated with the use of intravenous verapamil. The mechanism is unknown. An acute asthma attack associated with sustained-release verapamil has been reported. Dyspnea has also been reported during open trials/postmarketing experience.[Ref]

Hepatic

Hepatic side effects have included elevated liver enzymes (up to 1.4%), and elevated transaminases with or without elevated serum bilirubin and alkaline phosphatase. The mechanism of injury is not known. Verapamil-associated hepatotoxicity is considered to be idiosyncratic, although some cases indicate a probable hypersensitivity mechanism. Elevated liver enzymes have also been reported during open trials/postmarketing experience.[Ref]

Transient increases in liver function tests may occur but generally resolve following discontinuation of verapamil, although these changes may abate even with continued administration. A hypersensitivity mechanism is suspected since some cases report eosinophilic infiltrations and moderate cholestasis on liver biopsy.

Hepatic side effects may be more likely and more severe in patients with liver disease. It is recommended that verapamil therapy be reconsidered if this patient's liver disease is severe. Monitoring liver function tests during therapy is recommended.[Ref]

Dermatologic

Dermatologic side effects have included rash (up to 1.4%). Diaphoresis has been reported with intravenous verapamil. Arthralgia and rash, exanthema, hair loss, hyperkeratosis, macules, sweating, urticaria, Stevens-Johnson syndrome, and erythema multiforme have been reported during open trials/postmarketing experience.[Ref]

Endocrine

Endocrine side effects have rarely included interference with the release or synthesis of prolactin inhibitor factor in the hypothalamus; however, the mechanism is not known. A single case of hyperglycemic metabolic acidosis has been associated with sustained-release verapamil. Galactorrhea/hyperprolactinemia has been reported during open trials/postmarketing experience.[Ref]

Due to verapamil-induced hyperprolactinemia, rare cases of galactorrhea have been reported in both sexes.[Ref]

Renal

Renal side effects have included rare cases of oliguria and worsened renal function in patients with preexisting chronic renal failure.[Ref]

Rare cases of hypertensive patients with chronic renal failure who developed acute oliguric renal failure after receiving verapamil have been reported. These patients also developed symptomatic hypotension associated with slow cardiac arrhythmias.[Ref]

Genitourinary

Genitourinary side effects have included rare cases of sexual impotence and loss of libido among males. Gynecomastia, galactorrhea/hyperprolactinemia, impotence, increased urination, and spotty menstruation have been reported during open trials/postmarketing experience.[Ref]

After the onset of impotence, one patient elected to discontinue verapamil. His impotence resolved upon drug discontinuation, and recurred upon rechallenge.[Ref]

Musculoskeletal

Musculoskeletal side effects have included myalgia (up to 1.1%) and bizarre perceptual symptoms most closely described as cold extremities. Muscle fatigue has been reported with intravenous verapamil. Arthralgia (with rash) and muscle cramps have been reported during open trials/postmarketing experience.[Ref]

Three case reports have been found by one practitioner. In each case, unusual symptoms of cold extremities and paresthesias without objective evidence of a neuromuscular or cardiac etiology were described. The symptoms resolved upon discontinuation and, in each case, recurred upon drug rechallenge.[Ref]

Psychiatric

Psychiatric side effects have included rare cases of depression. Emotional depression has been reported with intravenous verapamil. Psychotic symptoms have been reported during open trials/postmarketing experience.[Ref]

Hematologic

Hematologic side effects have included ecchymosis or bruising during open trials/postmarketing experience.[Ref]

Hypersensitivity

Hypersensitivity side effects have included aggravated allergy during open trials/postmarketing experience. In rare cases of hypersensitivity, broncho/laryngeal spasm accompanied by itch and urticaria has been reported with intravenous verapamil.[Ref]

Ocular

Ocular side effects have included blurred vision during open trials/postmarketing experience. Rotary nystagmus has been reported with intravenous verapamil.[Ref]

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61. Vazquez C, Huelmos A, Alegria E, Errasti P, Purroy A "Verapamil deleterious effects in chronic renal failure." Nephron 72 (1996): 461-4

62. King BD, Pitchon R, Stern EH, et al "Impotence during therapy with verapamil." Arch Intern Med 143 (1983): 1248-9

63. Kumana CR, Mahon WA "Bizarre perceptual disorder of extremities in patients taking verapamil." Lancet 06/13/81 (1981): 1324-5

64. Dassylva B "Verapamil may cause depression." Can J Psychiatry 38 (1993): 299-300

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