Isoptin Side Effects

Generic Name: verapamil

Please note - some side effects for Isoptin may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Isoptin - for the Consumer

Isoptin SR Controlled-Release Tablets

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 when using Isoptin SR Controlled-Release Tablets:

Constipation; dizziness; fatigue; general feeling of being unwell; headache; lightheadedness; nausea.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; dark urine; fever; lightheadedness, especially upon standing; severe dizziness; shortness of breath; swelling of feet or hands; unusually fast, slow, or irregular heartbeat; yellowing of the eyes or skin.

Side Effects by Body System

Gastrointestinal

Common gastrointestinal complaints include constipation in up to 7% (this can be controlled by increasing dietary fiber) and nausea in 3% of patients. Less common GI side effects--also associated with other calcium channel blockers--include gingival hyperplasia, diarrhea, dry mouth, and dyspepsia.

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

Cardiovascular

Cardiovascular side effects include new or worsened congestive heart failure or pulmonary edema (negative inotropism) in up to 2% of patients. These effects may be particularly important in patients with poor left ventricular function. AV block, including complete AV heart block, has been reported in 1% of patients. The use of verapamil in some patients with depressed left ventricular systolic function and atrial fibrillation is somewhat controversial for these reasons. Vasodilation of vascular smooth muscle by verapamil may result in dizziness or hypotension.

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.

Various conduction disturbances have been reported with verapamil therapy, including bradycardia, AV block, first-, second-, third-degree heart block and left bundle branch block. Dizziness, hypotension, peripheral edema and headache are not uncommon and are related to vasodilation of vascular smooth muscle.

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.

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 buco-lingual 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

Nervous system side effects, such as headache and dizziness, are related to peripheral vasodilation and occur in 1% and 3% of patients, respectively. Lethargy and fatigue have been reported in less than 2% of patients. Rare neurologic complaints, occurring in less than 1% of patients, include paresthesias, sleeping problems, and tremors. 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.

Hepatic

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.

Hepatic abnormalities--elevations of transaminases with or without elevation in serum bilirubin and alkaline phosphatase--have occasionally been reported, and may indicate discontinuation of therapy. The mechanism of injury is not known. Verapamil-associated hepatotoxicity is considered to be idiosyncratic, although some cases indicate a probable hypersensitivity mechanism.

Renal

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.

In general, nephrotoxicity has not been associated with verapamil except for rare cases of oliguria and worsened renal function in patients with preexisting chronic renal failure.

Genitourinary

Genitourinary complaints appear to be limited to rare cases of sexual impotence and loss of libido among males.

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

Endocrine

Verapamil may rarely affect the endocrine system. Although the mechanism is not known, verapamil may interfere with the release or synthesis of prolactin inhibitor factor in the hypothalamus. Due to verapamil-induced hyperprolactinemia, rare cases of galactorrhea have been reported in both sexes. Verapamil does not appear to adversely affect the serum lipid profile. A single case of hyperglycemic metabolic acidosis has been associated with sustained-release verapamil.

Respiratory

Respiratory side effects include dyspnea in 1.4% of patients. 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.

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.

Musculoskeletal

Musculoskeletal complaints are limited to a handful of reports of bizarre perceptual symptoms most closely described as cold extremities.

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.

Psychiatric

Psychiatric side effects are limited to rare cases of depression.

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