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Isoptin Side Effects

Generic name: verapamil

Medically reviewed by Last updated on Jan 31, 2024.

Note: This document contains side effect information about verapamil. Some dosage forms listed on this page may not apply to the brand name Isoptin.

Applies to verapamil: oral capsule extended release, oral tablet, oral tablet extended release. Other dosage forms:

Serious side effects of Isoptin

Along with its needed effects, verapamil (the active ingredient contained in Isoptin) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking verapamil:

Less common


Other side effects of Isoptin

Some side effects of verapamil may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common

For Healthcare Professionals

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


The most commonly reported side effects include constipation, dizziness, and headache.[Ref]

Nervous system

Seizures occurred rarely with IV administration.

Paralysis/tetraparesis was reported in a patient taking this drug and colchicine concurrently.[Ref]

Very common (10% or more): Headache (up to 12.1%)

Common (1% to 10%): Dizziness, lethargy

Rare (0.01% to 0.1%): Seizures

Frequency not reported: Rotary nystagmus, sleepiness, vertigo, lightheadedness, tingling, numbness, neuropathy

Postmarketing reports: Syncope, cerebrovascular accident, equilibrium disorders, parkinsonism/extrapyramidal symptoms/syndrome, paresthesia, shakiness/tremor, paralysis/tetraparesis, somnolence[Ref]


Cardiovascular side effects may occur with greater intensity at higher doses or in patients with a history of myocardial damage.

Approximately 15% of patients who had atrial flutter/fibrillation and received this drug and digoxin developed resting ventricular rates below 50 beats/min; in the same trial, asymptomatic hypotension occurred in approximately 5% of patients.

Asystole occurred after second/third degree AV block and was usually short in duration, with spontaneous cardiac action returning within seconds in the form of a sinus rhythm.[Ref]

Common (1% to 10%): Symptomatic hypotension/hypotension/abrupt blood pressure fall, sinus bradycardia/bradycardia (heart rate less than 50 beats/minute), severe tachycardia, ankle edema/edema, development/aggravation of congestive heart failure (CHF), atrioventricular (AV) block, peripheral edema

Uncommon (0.1% to 1%): Second-/third-degree AV block, palpitations, orthostasis

Postmarketing reports: Angina pectoris/chest pain, AV dissociation, ECG abnormal, claudication, hypertension, myocardial infarction, sinus arrest with asystole, decreased myocardial contractility, cardiogenic shock, bradyarrhythmia in atrial fibrillation, vasculitis, erythromelalgia[Ref]


Common (1% to 10%): Constipation, dyspepsia, nausea, diarrhea, flatulence

Uncommon (0.1% to 1%): Abdominal discomfort/pain

Frequency not reported: Non-obstructive paralytic ileus/ileus, bloating

Postmarketing reports: Dry mouth, gastrointestinal stress, gingival hyperplasia, vomiting[Ref]

Non-obstructive paralytic ileus was reversible when treatment was stopped.

Gingival hyperplasia occurred when this drug was given over a prolonged period of time, and was reversible once the drug was discontinued.[Ref]


Common (1% to 10%): Pulmonary edema, pharyngitis, sinusitis, rhinitis, dyspnea

Rare (0.01% to 0.1%): Broncho/laryngeal spasm[Ref]

Bronchospasm and laryngeal spasm occurred during hypersensitivity reactions.[Ref]


Common (1% to 10%): Fatigue, tiredness/malaise, accidental injury, pain

Frequency not reported: Infection, flu syndrome

Postmarketing reports: Tinnitus, asthenia[Ref]


Itch and urticaria occurred in hypersensitivity reactions.[Ref]

Common (1% to 10%): Scalp irritation, rash

Uncommon (0.1% to 1%): Itching, urticaria, flushing, exanthema

Frequency not reported: Diaphoresis, photodermatitis

Postmarketing reports: Ecchymosis, bruising, alopecia/hair loss, hyperkeratosis, macules, Stevens-Johnson syndrome, hyperhidrosis/sweating, erythema multiforme, Quincke's edema/angioneurotic edema[Ref]


Common (1% to 10%): Sleep disturbance

Uncommon (0.1% to 1%): Bad dreams, depression/emotional depression

Postmarketing reports: Confusion, psychotic symptoms, insomnia, nervousness[Ref]


Common (1% to 10%): Myalgia

Frequency not reported: Muscle fatigue

Postmarketing reports: Muscle cramps, arthralgia[Ref]


Uncommon (0.1% to 1%): Elevated liver enzymes (transaminases, alkaline phosphatase)[Ref]

Reversible elevations liver enzymes occurred during treatment, and are likely the result of a hypersensitivity reaction (e.g., allergic hepatitis).[Ref]


Rare (0.01% to 0.1%): Hypersensitivity/allergic reactions

Postmarketing reports: Allergy aggravated[Ref]


Frequency not reported: Lowered glucose tolerance

Postmarketing reports: Hyperkalemia[Ref]


Postmarketing reports: Galactorrhea, increased blood prolactin/hyperprolactinemia, increased urination, spotty menstruation, erectile dysfunction/impotence[Ref]


Postmarketing reports: Renal failure[Ref]


Gynecomastia occurred in older male patients on prolonged treatment, and was reversible upon discontinuation of this drug.[Ref]

Postmarketing reports: Gynecomastia[Ref]


Postmarketing reports: Purpura[Ref]


Postmarketing reports: Blurred vision[Ref]


1. (2001) "Product Information. Calan (verapamil)." Searle

2. (2001) "Product Information. Isoptin (verapamil)." Knoll Pharmaceutical Company

3. (2001) "Product Information. Covera-HS (verapamil)." Searle

4. Cerner Multum, Inc. "UK Summary of Product Characteristics."

5. Cerner Multum, Inc. "Australian Product Information."

6. (2010) "Product Information. Verelan PM (verapamil)." Schwarz Pharma

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.