verapamil hydrochloride

(ver ap' a mill)

Calan, Calan SR, Covera-HS, Isoptin, 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 of transmembrane 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 atrial flutter 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.

        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, 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; T1/2: 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

        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 IV verapamil

        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

        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; liver function tests, 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 SR 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.