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Pharmacologic class: Calcium channel blocker
Therapeutic class: Antianginal, antiarrhythmic (class IV), antihypertensive
Pregnancy risk category C
Decreases conduction of sinoatrial and atrioventricular (AV) nodes by inhibiting calcium influx into cardiac and vascular smooth muscle cells, inhibiting excitatory contraction. These effects prolong AV node refractoriness and decrease myocardial oxygen consumption.
Capsules (extended-release): 100 mg, 120 mg, 180 mg, 200 mg, 240 mg, 300 mg, 360 mg
Capsules (sustained-release): 120 mg, 180 mg, 240 mg, 360 mg
Injection: 2.5 mg/ml in 2- and 4-ml vials, ampules, and syringes
Tablets (extended-release): 120 mg, 180 mg, 240 mg
Tablets (immediate-release): 40 mg, 80 mg, 120 mg
⊘Indications and dosages
Adults: Initially, 80 mg (immediate-release) P.O. t.i.d.; may titrate at daily or weekly intervals to 360 mg/day. Or initially, 180 mg (extended-release) P.O. once daily at bedtime, titrated up to 480 mg/day at bedtime.
➣ Supraventricular tachyarrhythmias (SVTs)
Adults: 5 to 10 mg (0.075 to 0.15 mg/kg) I.V. bolus over 2 minutes; may give additional 10 mg after 30 minutes if response inadequate. Or 240 to 480 mg (immediate-release) P.O. daily in three or four divided doses.
➣ To control ventricular rate in chronic atrial flutter or atrial fibrillation in patients receiving digoxin
Adults: 240 to 320 mg P.O. daily in three or four divided doses
Adults: Initially, 180 mg (extended-release tablet) or 200 mg (extended-release capsule) P.O. daily at bedtime. For maintenance, may titrate up to 480 mg (extended-release tablet) or 400 mg (extended-release capsule) P.O. daily at bedtime. Or initially, 80 mg (immediate-release tablet) P.O. t.i.d.; may titrate at daily or weekly intervals up to 360 to 480 mg/day. Or initially, 240 mg (sustained-release capsule) P.O. q day in morning; for maintenance, may titrate up to 240 mg P.O. b.i.d. or 480 mg P.O. once daily in morning. Titrate based on response.
• Renal or hepatic impairment
• Concurrent digoxin therapy
• Ventricular tachycardia
• Migraine headache prophylaxis
• Neurogenic bladder
• Premature labor
• Hypersensitivity to drug or other calcium channel blockers
• Sick sinus syndrome
• Second- or third-degree AV block (except in patients with artificial pacemakers)
• Heart failure, severe ventricular dysfunction, or cardiogenic shock (except when associated with SVTs)
• Atrial flutter or atrial fibrillation associated with accessory bypass tracts (such as Wolff-Parkinson-White or Lown-Ganong-Levine syndrome)
Use cautiously in:
• renal or severe hepatic impairment; first-degree AV block; idiopathic hypertrophic cardiomyopathy; neuromuscular transmission defects (such as Duchenne's muscular dystrophy); respiratory depression; digital ulcers, ischemia, or gangrene
• elderly patients
• pregnant or breastfeeding patients.
• Give I.V. over at least 2 minutes.
• Discontinue disopyramide 48 hours before starting verapamil. Don't restart disopyramide for at least 24 hours after verapamil therapy ends.
CNS: anxiety, confusion, dizziness, syncope, drowsiness, headache, jitteriness, abnormal dreams, disturbed equilibrium, psychiatric disturbances, asthenia, paresthesia, tremor, fatigue
CV: chest pain, hypotension, palpitations, peripheral edema, tachycardia, arrhythmias, heart failure, bradycardia, AV block
EENT: blurred vision, epistaxis, tinnitus
GI: nausea, vomiting, diarrhea, constipation, dyspepsia, dry mouth, anorexia
GU: dysuria, urinary frequency, nocturia, polyuria, sexual dysfunction, gynecomastia
Hematologic: anemia, leukopenia, thrombocytopenia
Musculoskeletal: joint stiffness, muscle cramps
Respiratory: cough, dyspnea, shortness of breath, pulmonary edema
Skin: dermatitis, flushing, diaphoresis, photosensitivity, pruritus, urticaria, rash, erythema multiforme, Stevens-Johnson syndrome
Other: gingival hyperplasia, edema, weight gain
Drug-drug.Antihypertensives: additive hypotension
Aspirin: increased risk of bleeding
Beta-adrenergic blockers, other antiarrhythmics: additive adverse cardiovascular reactions
Carbamazepine, cyclosporine: increased blood levels of these drugs
CYP450-3A4 inducers (such as rifampin): decreased verapamil blood level
CYP450-3A4 inhibitors (such as erythromycin, ritonavir): increased verapamil blood level
Digoxin: increased digoxin blood level, greater risk of toxicity
Lithium: increased or decreased lithium blood level
Neuromuscular blockers (succinylcholine, tubocurarine, vecuronium): prolonged neuromuscular blockade
Theophylline: decreased verapamil clearance, increased blood level, and possible toxicity
Drug-diagnostic tests.Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, blood urea nitrogen, glucose, lactate dehydrogenase: increased levels
Granulocytes: decreased count
Drug-food.Coffee, tea: increased caffeine blood level
Grapefruit juice: increased verapamil blood level and effects
Drug-herbs.Black catechu: increased drug effects
Cola nut, guarana: increased caffeine blood level
Ephedra (ma huang), St. John's wort: reduced hypotensive effect of verapamil
Yerba maté: decreased clearance of this herb
Drug-behaviors.Alcohol use: additive hypotension
• With I.V. use, monitor vital signs and ECG continuously.
• Assess blood pressure when therapy begins and when dosage is adjusted.
• Watch closely for signs and symptoms of heart failure.
Monitor for signs and symptoms of erythema multiforme (fever, rash, sore throat, mouth sores, cough, iris lesions). Report early indications immediately, before condition can progress to Stevens-Johnson syndrome.
• Assess CBC. Watch for blood dyscrasias.
• Monitor blood glucose level. Stay alert for hyperglycemia in diabetic patients.
• Instruct patient to avoid chewing, breaking, or crushing extended-release form.
Advise patient to immediately report rash, unusual bleeding or bruising, fainting, and (in long-term use) fatigue, nausea, or yellowing of skin or eyes.
• Caution patient not to take with grapefruit juice.
• Instruct patient to limit caffeine intake and avoid alcohol.
• Advise patient to seek medical advice before using over-the-counter medications or herbs.
• Tell patient to avoid sun exposure and to wear sunscreen and protective clothing when going outdoors.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, herbs, and behaviors mentioned above.