Isoptin Side Effects Center

Last updated on RxList: 6/23/2022
Isoptin Side Effects Center

What Is Isoptin SR?

Isoptin SR (verapamil HCl) is a calcium channel blocker used to treat hypertension (high blood pressure), angina (chest pain), and certain heart rhythm disorders.

  • The brand name Isoptin SR is discontinued in the U.S.
  • Generic versions may be available.

What Are Side Effects of Isoptin SR?

Common side effects of Isoptin SR (verapamil HCl) include:

  • dizziness,
  • slow heartbeat,
  • constipation,
  • nausea,
  • headache,
  • tiredness,
  • skin rash or itching, or
  • flushing (warmth, itching, redness, or tingly feeling under your skin).

Tell your doctor if you have unlikely but serious side effects of Isoptin SR (verapamil HCl) including:

  • swelling ankles or feet,
  • fever,
  • upper stomach pain,
  • unusual tiredness,
  • unexplained or sudden weight gain,
  • severe dizziness,
  • sweating
  • gasping for breath, 
  • cough with foamy mucus
  • fainting, or
  • very slow heartbeat.

Dosage for Isoptin SR

The starting dose of sustained-release verapamil is 180 mg, given in the morning.

What Drugs, Substances, or Supplements Interact with Isoptin SR?

Verapamil may interact with

  • other blood pressure medications,
  • buspirone,
  • carbamazepine,
  • cimetidine,
  • cyclosporine,
  • digoxin,
  • lithium,
  • lovastatin,
  • phenobarbital,
  • rifampin,
  • theophylline,
  • sedatives,
  • antibiotics,
  • antifungals,
  • beta-blockers,
  • heart rhythm medications, or
  • HIV/AIDS medicine.

Tell your doctor all medications you use.

Isoptin SR During Pregnancy or Breastfeeding

During pregnancy, verapamil should be used only when prescribed.

  • This medication passes into breast milk but it is unlikely to harm a nursing infant.
  • Consult your doctor before breastfeeding.

Additional Information

Our Isoptin SR (verapamil HCl) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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.


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Isoptin Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives; difficult 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;
  • fever, upper stomach pain, not feeling well; or
  • lung problems--anxiety, sweating, pale skin, wheezing, gasping for breath, cough with foamy mucus.

Common side effects may include:

  • nausea, constipation;
  • headache, dizziness; or
  • low blood pressure.

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.


Salt and sodium are the same. See Answer
Isoptin Professional Information


Serious adverse reactions are uncommon when verapamil therapy is initiated with upward dose titration within the recommended single and total daily dose. See WARNINGS for discussion of heart failure, hypotension, elevated liver enzymes, AV block, and rapid ventricular response. Reversible (upon discontinuation of verapamil) non-obstructive, paralytic ileus has been infrequently reported in association with the use of verapamil. The following reactions to orally administered verapamil occurred at rates greater than 1.0% or occurred at lower rates but appeared clearly drug-related in clinical trials in 4,954 patients.


Constipation 7.3%
Fatigue 1.7%
Dizziness 3.3%
Dyspnea 1.4%
Nausea 2.7%
Bradycardia (HR < 50/min) 1.4%
Hypotension 2.5%
AV Block-total (1°,2°, 3°) 1.2%
Headache 2.2%
2 ° and 3° 0.8%
Edema 1.9%
Rash 1.2%
CHF/Pulmonary Edema 1.8%
Flushing 0.6%

Elevated Liver Enzymes


In clinical trials related to the control of ventricular response in digitalized patients who had atrial fibrillation or atrial flutter, ventricular rates below 50/min at rest occurred in 15% of patients and asymptomatic hypotension occurred in 5% of patients.

The following reactions, reported in 1.0% or less of patients, occurred under conditions (open trials, marketing experience) where a causal relationship is uncertain; they are listed to alert the physician to a possible relationship.

Cardiovascular: angina pectoris, atrioventricular dissociation, chest pain, claudication, myocardial infarction, palpitations, purpura (vasculitis), syncope.

Digestive System: diarrhea, dry mouth, gastrointestinal distress, gingival hyperplasia.

Hemic and Lymphatic: ecchymosis or bruising.

Nervous System: cerebrovascular accident, confusion, equilibrium disorders, insomnia, muscle cramps, parasthesia, psychotic symptoms, shakiness, somnolence, extrapyramidal symptoms.

Skin: arthralgia and rash, exanthema, hair loss hyperkeratosis, maculae, sweating, urticaria, Stevens-Johnson syndrome, erythema multiforme.

Special Senses: blurred vision, tinnitus.

Urogenital: gynecomastia, impotence, galactorrhea/ hyperprolactinemia, increased urination, spotty menstruation.

Treatment of Acute Cardiovascular Adverse Reactions

The frequency of cardiovascular adverse reactions that require therapy is rare, hence, experience with their treatment is limited. Whenever severe hypotension or complete AV block occurs following oral administration of verapamil, the appropriate emergency measures should be applied immediately, e.g., intravenously administered isoproterenol HCl, norepinephrine bitartrate, atropine sulfate (all in the usual doses), or calcium gluconate (10% solution). In patients with hypertrophic cardiomyopathy (IHSS), alpha-adrenergic agents (phenylephrine HCl, metaraminol bitartrate or methoxamine HCl) should be used to maintain blood pressure, and isoproterenol and norepinephrine should be avoided. If further support is necessary, (dopamine HCl or dobutamine HCl) may be administered. Actual treatment and dosage should depend on the severity of the clinical situation and the judgment and experience of the treating physician.

Read the entire FDA prescribing information for Isoptin (Verapamil Hydrochloride Tablet)

© Isoptin Patient Information is supplied by Cerner Multum, Inc. and Isoptin Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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