VERAPAMIL HYDROCHLORIDE

(ver-ap'a-mill)

Calan, Calan SR, Covera-HS, Isoptin, Isoptin SR, Verelan, Verelan PM
Classifications: calcium channel blocker; antihypertensive; antiarrhythmic class iv;
Therapeutic:antiarrhythmic; antihypertensive
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

Action

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.

Therapeutic Effect

Decreases angina attacks by dilating coronary arteries and inhibiting coronary vasospasms. Decreases nodal conduction, resulting in an antiarrhythmic effect. Dilates peripheral arterioles, causing decreased total peripheral vascular resistance with reduction in BP.

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); pregnancy (category C); children <18 y (extended release tablets).

Cautious Use

Duchenne's muscular dystrophy; hepatic and renal impairment; MI followed by coronary occlusion, aortic stenosis; GI obstruction, GERD, hiatal hernia, ileus; IV form in neonates or infants.

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 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: IV 2.5–5 mg initial dose, then 5–10 mg after 15–30 min (max total dose: 20 mg)
Child: IV <1 y, 0.1–0.2 mg/kg q30min prn; >1 y, 0.1–0.3 mg/kg (max dose: 5 mg)

Renal Impairment
Cl_cr <10 mL/min: give 50–75% of dose
Hemodialysis: Supplemental dose not necessary

Hepatic Impairment
In cirrhosis, use 20–50% of normal dose.

Administration

Oral

Give with food to reduce gastric irritation.
Capsules can be opened and contents sprinkled on food. Do NOT dissolve or chew capsule contents.
Give Covera-HS once a day in the evening.
Do not withdraw abruptly; may increase and extend duration of pain in the angina patient.

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, trimethoprim/sulfamethoxazole. Y-site: Albumin, amphotericin B cholesteryl complex, ampicillin, mezlocillin, nafcillin, oxacillin, propofol, sodium bicarbonate.

Store at 15°–30° C (59°–86° F) and protect from light.

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. St. John's wort may decrease efficacy.

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: In liver (CYP3A4). Elimination: 70% in urine; 16% in feces. Half-Life: 2–8 h.

Nursing Implications

Assessment & Drug Effects

Monitor therapeutic effectiveness. Drug should decrease angina frequency, nitroglycerin consumption, and episodes of ST segment deviation.
Establish baseline data and periodically monitor: BP and pulse.
Lab tests: Baseline and periodic liver and kidney functions.
Instruct patient to remain in recumbent position for at least 1 h after dose is given to diminish subjective effects of transient asymptomatic hypotension that may accompany infusion.
Monitor for AV block or excessive bradycardia when infusion is given concurrently with digitalis.
Monitor I&O ratio during IV and early oral maintenance therapy. Renal impairment prolongs duration of action, increasing potential for toxicity and incidence of adverse effects. Advise patient to report gradual weight gain and evidence of edema.
Monitor ECG continuously during IV administration. Essential because drug action may be prolonged and incidence of adverse reactions is highest during IV administration in older adults, patients with impaired kidney function, and patients of small stature.
Check BP shortly before administration of next dose to evaluate degree of control during early treatment for hypertension.

Patient & Family Education

Monitor radial pulse before each dose, notify physician of an irregular pulse or one slower than established guideline.
Adhere to established guidelines for exercise program.
Do not drive or engage in potentially hazardous activities until response to drug is known.
Decrease intake of caffeine-containing beverage (i.e., coffee, tea, chocolate).
Change positions slowly from lying down to standing to prevent falls because of drug-related vertigo until tolerance to reduced BP is established.
Notify physician of easy bruising, petechiae, unexplained bleeding.
Do not use OTC drugs, especially aspirin, unless they are specifically prescribed by physician.

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

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