verapamil hydrochloride

verapamil hydrochloride

(ver ap' a mill)

Calan, Calan SR, Covera-HS, Isoptin SR, Verelan, Verelan PM

Pregnancy Category C

Drug classes

Calcium channel-blocker

Antianginal

Antiarrhythmic

Antihypertensive

Therapeutic actions

Inhibits the movement of calcium ions across the membranes of cardiac and arterial muscle cells; calcium is involved in the generation of the action potential in specialized automatic and conducting cells in the heart, in arterial smooth muscle, and in excitation-contraction coupling in cardiac muscle cells; inhibition oftransmembrane calcium flow results in the depression of impulse formation in specialized cardiac pacemaker cells, slowing of the velocity of conduction of the cardiac impulse, the depression of myocardial contractility, and the dilation of coronary arteries and arterioles and peripheral arterioles; these effects lead to decreased cardiac work, decreased cardiac energy consumption, and in patients with vasospastic (Prinzmetal's) angina, increased delivery of oxygen to myocardial cells.

Indications

·        Angina pectoris due to coronary artery spasm (Prinzmetal's variant angina)

·        Effort-associated angina

·        Chronic stable angina

·        Unstable, crescendo, preinfarction angina

·        Essential hypertension

·        Parenteral: Treatment of supraventricular tachyarrhythmias

·        Parenteral: Temporary control of rapid ventricular rate in atrial flutter or atrial fibrillation

Contraindications and cautions

·        Contraindicated with allergy to verapamil; sick sinus syndrome, except with ventricular pacemaker; heart block (second- or third-degree); hypotension; pregnancy; lactation.

·        Use cautiously with idiopathic hypertrophic subaortic stenosis, cardiogenic shock, severe CHF, impaired renal or hepatic function, and in patients with atrialflutter or atrial fibrillation and an accessory to bypass tract.

Available forms

Tablets—40, 80, 120 mg; SR tablets—120, 180, 240 mg; ER tablets—120, 180, 240 mg; SR capsules—120, 180, 240, 360 mg; injection—2.5 mg/mL; ER capsules—100, 120, 180, 200, 240, 300, 360 mg

Dosages

ADULTS

Oral

Immediate release

·        Angina: 80 mg q 6–8 hr; may increase by 80 mg at weekly intervals until control is achieved. Maintenance 240–480 mg daily.

·        Arrhythmias: 240–480 mg/day. In digitalized adults: 240–320 mg/day.

·        Hypertension: 40 mg to 80 mg PO tid.

ER

·        Capsules: 120–240 mg/day PO in the morning. Titrate dose to a maximum 480 mg/day.

·        Tablets: 120–180 mg/day PO in the morning. Titrate to a maximum 240 mg q 12 hr.

SR

·        120–180 mg/day PO. Titrate up to a maximum 480 mg PO in the morning.

Parenteral

IV use only. Initial dose, 2.5–10 mg over 2 min; may repeat dose of 10 mg 30 min after first dose if initial response is inadequate.

PEDIATRIC PATIENTS

IV

< 1 yr: Initial dose, 0.1–0.2 mg/kg over 2 min.

1–15 yr: Initial dose, 0.1–0.3 mg/kg over 2 min. Do not exceed 5 mg. Repeat above dose 30 min after initial dose if response is not adequate. Repeat dose should not exceed 10 mg.

GERIATRIC PATIENTS OR PATIENTS WITH RENAL IMPAIRMENT

Reduce dosage, and monitor patient response carefully. Give IV doses over 3 min to reduce risk of serious side effects. Administer IV doses very slowly, over 2 min.

Pharmacokinetics

Route	Onset	Peak	Duration
Oral	30 min	1–2.2 hr	3–7 hr
IV	1–5 min	3–5 min	2 hr

Metabolism: Hepatic; T_1/2: 3–7 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

IV facts

Preparation: No further preparation required.

Infusion: Infuse very slowly over 2–3 min.

Y-site incompatibilities: Do not give with albumin, ampicillin, nafcillin, oxacillin, sodium bicarbonate, amphotericin B, hydralazine, aminophylline.

Adverse effects

·        CNS: Dizziness, vertigo, emotional depression, sleepiness, headache

·        CV: Peripheral edema, hypotension, arrhythmias, bradycardia; AV heart block

·        GI: Nausea, constipation

·        Other: Muscle fatigue, diaphoresis, rash

Interactions

Drug-drug

·        WARNING: Risk of serious cardiac effects with IV beta-adrenergic blocking agents; do not give these drugs within 48 hr before or 24 hr after IVverapamil

·        Increased cardiac depression with beta-adrenergic blocking agents

·        Additive effects of verapamil and digoxin to slow AV conduction

·        Increased serum levels of digoxin, carbamazepine, prazosin, quinidine

·        Increased respiratory depression with atracurium, gallamine, pancuronium, tubocurarine, vecuronium

·        Decreased effects with calcium, rifampin

Drug-food

·        Decreased metabolism and risk of toxic effects if combined with grapefruit juice; avoid this combination

Nursing considerations

Assessment

·        History: Allergy to verapamil; sick sinus syndrome; heart block; IHSS; cardiogenic shock, severe CHF; hypotension; impaired hepatic or renal function; pregnancy, lactation

·        Physical: Skin color, edema; orientation, reflexes; P, BP, baseline ECG, peripheral perfusion, auscultation; R, adventitious sounds; liver evaluation, normal output; LFTs, renal function tests, urinalysis

Interventions

·        WARNING: Monitor patient carefully (BP, cardiac rhythm, and output) while drug is being titrated to therapeutic dose. Dosage may be increased more rapidly in hospitalized patients under close supervision.

·        Ensure that patient swallows SR tablets whole; patient should not cut, crush, or chew them.

·        Monitor BP very carefully with concurrent doses of antihypertensives.

·        Monitor cardiac rhythm regularly during stabilization of dosage and periodically during long-term therapy.

·        Administer SR form in the morning with food to decrease GI upset.

·        Protect IV solution from light.

·        Monitor patients with renal or hepatic impairment carefully for possible drug accumulation and adverse reactions.

Teaching points

·        Take sustained-release form in the morning with food; swallow it whole, do not cut, crush, or chew it. Do not drink grapefruit juice while using this drug.

·        You may experience these side effects: Nausea, vomiting (eat frequent small meals); headache (adjust lighting, noise, and temperature; request medication); dizziness, sleepiness (avoid driving or operating dangerous equipment); emotional depression (reversible); constipation (request aid).

·        Report irregular heartbeat, shortness of breath, swelling of the hands or feet, pronounced dizziness, nausea, constipation.

Adverse effects in Italic are most common; those in Bold are life-threatening.