VERAPAMIL HYDROCHLORIDE
(ver-ap'a-mill)
Calan, Calan SR, Covera-HS, Isoptin, Isoptin SR, Verelan, Verelan PM
Classifications: cardiovascular agent; calcium channel blocker; antiarrhythmic, miscellaneous
Pregnancy Category: C

Availability

40 mg, 80 mg, 120 mg tablets; 120 mg, 180 mg, 240 mg sustained-release tablets; 100 mg, 120 mg, 180 mg, 200 mg, 240 mg, 300 mg sustained-release capsules; 5 mg/2 mL injection

Actions

Inhibits calcium ion influx through slow channels into cells of myocardial and arterial smooth muscle. Dilates coronary arteries and arterioles and inhibits coronary artery spasm. Decreases and slows SA and AV node conduction without affecting normal arterial action potential or intraventricular conduction. Associated vasodilation of arterioles decreases total peripheral vascular resistance and reduces arterial BP at rest. May slightly decrease heart rate.

Therapeutic Effects

Dilates coronary arteries and inhibits coronary artery spasm, which increases myocardial oxygen delivery and produces an antianginal effect. Also decreases nodal conduction, which results in an antiarrhythmic effect.

Uses

Supraventricular tachyarrhythmias; Prinzmetal's (variant) angina, chronic stable angina; unstable, crescendo or preinfarctive angina and essential hypertension.

Unlabeled Uses

Paroxysmal supraventricular tachycardia, atrial fibrillation; prophylaxis of migraine headache; and as alternate therapy in manic depression.

Contraindications

Severe hypotension (systolic <90 mm Hg), cardiogenic shock, cardiomegaly, digitalis toxicity, second- or third-degree AV block; Wolff-Parkinson-White syndrome including atrial flutter and fibrillation; accessory AV pathway, left ventricular dysfunction, severe CHF, sinus node disease, sick sinus syndrome (except in patients with functioning ventricular pacemaker). Safe use during pregnancy (category C), lactation, or in children (oral) is not established.

Cautious Use

Duchenne's muscular dystrophy; hepatic and renal impairment; MI followed by coronary occlusion, aortic stenosis.

Route & Dosage

Angina
Adult: PO 80 mg q6–8h, may increase up to 320–480 mg/d in divided doses (Note: Covera-HS must be given once daily h.s.)

Hypertension
Adult: PO 40–80 mg t.i.d. or 90–240 mg sustained-release 1–2 times/d up to 480 mg/d (Note: Covera-HS must be given once daily h.s.)

Supraventricular Tachycardia, Atrial Fibrillation
Adult: PO 240–480 mg/d in divided doses IV 5–10 mg IV direct, may repeat in 15–30 min if needed
Child: IV <1 y, 0.1–0.2 mg/kg; 1–15 y, 0.1–0.3 mg/kg (2–5 mg)

Administration

Oral
Intravenous

PREPARE: IV Direct: Given undiluted or diluted in 5 mL of sterile water for injection. Inspect parenteral drug preparation before administration. Make sure solution is clear and colorless.  

ADMINISTER: Direct: Give a single dose over 2–3 min.  

INCOMPATIBILITIES Solution/additive: Albumin, aminophylline, amphotericin B, hydralazine, cotrimoxazole. Y-site: Albumin, amphotericin B cholesteryl complex, ampicillin, mezlocillin, nafcillin, oxacillin, propofol, sodium bicarbonate.

Adverse Effects (1%)

CNS: Dizziness, vertigo, headache, fatigue, sleep disturbances, depression, syncope. CV: Hypotension, congestive heart failure, bradycardia, severe tachycardia, peripheral edema, AV block. GI: Nausea, abdominal discomfort, constipation, elevated liver enzymes. Body as a Whole: Flushing, pulmonary edema, muscle fatigue, diaphoresis. Skin: Pruritus.

Diagnostic Test Interference

Verapamil may cause elevations of serum AST, ALT, alkaline phosphatase.

Interactions

Drug: beta blockers increase risk of CHF, bradycardia, or heart block; significantly increased levels of digoxin and carbamazepine and toxicity; potentiates hypotensive effects of hypotensive agents; levels of lithium and cyclosporine may be increased, increasing their toxicity; calcium salts (IV) may antagonize verapamil effects. Food: Grapefruit juice may increase verapamil levels. Herbal: Hawthorne may have additive hypotensive effects.

Pharmacokinetics

Absorption: 90% absorbed, but only 25–30% reaches systemic circulation (first pass metabolism). Peak: 1–2 h PO; 4–8 h sustained release; 5 min IV. Distribution: Widely distributed, including CNS; crosses placenta; present in breast milk. Metabolism: Metabolized in liver. Elimination: 70% excreted in urine; 16% in feces. Half-Life: 2–8 h.

Nursing Implications

Assessment & Drug Effects

Patient & Family Education


Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug