verapamil

Brand Name

Apo-Verap (CAN), Calan, Isoptin, Novo-Veramil (CAN), Nu-Verap (CAN) 

verapamil hydrochloride
Calan SR, Isoptin SR, Verelan

Class and Category

Chemical class: Phenylalkylamine derivative

Therapeutic class: Antianginal, antiarrhythmic, antihypertensive

Pregnancy category: C

Indications and Dosages

To treat chronic angina pectoris

TABLETS (VERAPAMIL)

Adults and adolescents age 15 and over.

Initial: 80 to 120 mg t.i.d., increased every day or wk, as needed and prescribed.

Maximum: 480 mg daily in divided doses.

Infants and children up to age 15. 4 to 8 mg/kg daily in divided doses.

To manage hypertension

E.R. CAPSULES (VERAPAMIL HYDROCHLORIDE)

Adults and adolescents. Initial: 240 mg daily, increased every day or wk, as needed and prescribed. Maximum: 480 mg daily.

E.R. TABLETS (VERAPAMIL HYDROCHLORIDE)

Adults and adolescents. Initial: 180 mg daily, increased every day or wk, as needed and prescribed, according to following schedule: 240 mg daily in the morning; 180 mg every 12 hr or 240 mg in the morning and 120 mg in the evening; then 240 mg every 12 hr. Maximum: 480 mg daily in divided doses.

TABLETS (VERAPAMIL)

Adults and adolescents age 15 and over.

Initial: 80 to 120 mg t.i.d., increased every day or wk, as needed and prescribed.

Maximum: 480 mg daily in divided doses.

Infants and children up to age 15. 4 to 8 mg/kg daily in divided doses.

To prevent or treat supraventricular tachycardia

TABLETS (VERAPAMIL)

Adults and adolescents age 15 and over.

Initial: 80 to 120 mg t.i.d., increased every day or wk, as needed and prescribed.

Maximum: 480 mg daily in divided doses.

DOSAGE ADJUSTMENT Initial P.O. dosage possibly reduced to 40 mg t.i.d. (120 mg daily for E.R. tablets or capsules) for elderly patients and those with impaired hepatic or left ventricular function.

I.V. INJECTION (VERAPAMIL HYDROCHLORIDE)

Adults and adolescents age 15 and over.

Initial: 5 to 10 mg slowly over 2 min; then 10 mg, as prescribed, if response isn’t adequate after 30 min.

Children ages 1 to 15. Initial: 100 to 300 mcg/kg slowly over 2 min, up to maximum of 5 mg; then 10 mg, as prescribed, if response isn’t adequate after 30 min.

Infants up to age 1. Initial: 100 to 200 mcg/ kg slowly over 2 min.

DOSAGE ADJUSTMENT I.V. drug administered over 3 minutes in elderly patients.

Mechanism of Action

Inhibits calcium movement into coronary and vascular smooth-muscle cells by blocking slow calcium channels in cell membranes. The resulting decrease in intracellular calcium level has the following effects:

• inhibits smooth-muscle cell contractions

• decreases myocardial oxygen demand by relaxing coronary and vascular smooth muscle, reducing peripheral vascular resistance, and decreasing systolic and diastolic pressures

• slows AV conduction time and prolongs AV nodal refractoriness

• interrupts reentry circuit in AV nodal reentrant tachycardias.

Route            Onset             Peak            Duration

P.O.                1–2 hr             30–90 min     6–8 hr

P.O. (E.R.)      1–2 hr             30–90 min     Unknown

I.V.                 1–5 min            3–5 min        10 min–6 hr

Incompatibilities

Don’t mix I.V. verapamil with albumin, amphotericin B injection, hydralazine hydrochloride injection, nafcillin, or sulfamethoxazole and trimethoprim injection. Solutions with pH above 6.0 cause precipitation.

Contraindications

Cardiogenic shock, concomitant use of beta blockers (with I.V. verapamil), hypersensitivity to verapamil or its components, hypotension, severe heart failure unless secondary to supraventricular tachycardia that responds to verapamil, severe left ventricular dysfunction, sick sinus syndrome or second- or third-degree heart block unless artificial pacemaker is in place, ventricular tachycardia (with I.V. verapamil)

Interactions

DRUGS

alpha blockers, antihypertensives, general anesthetics (hydrocarbon), prazosin: Hypotensive effects

aspirin: Increased bleeding time

beta blockers: Increased risk of heart failure, hypotension, and severe bradycardia

calcium supplements: Decreased response to verapamil

carbamazepine, cyclosporine, theophylline,

valproate: Increased risk of toxicity from these drugs

cimetidine: Decreased metabolism and increased blood level of verapamil

clonidine: Increased risk of severe sinus bradycardia

cyclophosphamide, oncovin, procarbazine, prednissone (COPP) regimen; vindesine, adriamycin, cisplatin (VAC) regimen: Decreased verapamil absorption

dantrolene: Increased risk of hyperkalemia and myocardial depression

digoxin: Increased blood digoxin level and risk of digitalis toxicity

disopyramide, flecainide: Additive negative inotropic effects

doxorubicin: Increase plasma doxorubicin level

erythromycin, ritonavir: Increased blood verapamil level

lithium: Increased risk of neurotoxicity

neuromuscular blockers: Prolonged recovery from neuromuscular blockade

NSAIDs, sympathomimetics: Decreased antihypertensive effect of verapamil

paclitaxel: Decreased paclitaxel clearance

phenobarbital: Increased verapamil clearance

procainamide: Increased QT interval, additive negative inotropic effects

protein-bound drugs (hydantoins, salicylates, sulfonamides, sulfonylureas, and warfarin and other oral anticoagulants): Altered blood levels of these drugs

quinidine: Increased risk of quinidine toxicity, increased QT interval, additive negative inotropic effects

rifampin: Decreased bioavailability of oral verapamil

telithromycin: Increased risk of bradyarrhythmias, hypotension, and lactic acidosis

FOODS

grapefruit juice: Increased verapamil level

ACTIVITIES

alcohol use: Increased blood alcohol level and prolonged CNS effects

Adverse Reactions

CNS: Asthenia, confusion, disequilibrium, dizziness, equilibrium disorders, extrapyramidal reactions, fatigue, headache, insomnia, paresthesia, psychosis, shakiness, somnolence, stroke, syncope

CV: Abnormal ECG, angina, AV conduction disorders, bradycardia, claudication, heart failure, hypertension, hypotension, MI, palpitations, peripheral edema, tachycardia, vasculitis

EENT: Blurred vision, dry mouth, tinnitus

ENDO: Gynecomastia, hyperprolactinemia

GI: Constipation, diarrhea, elevated liver function test results, GI distress, nausea

GU: Galactorrhea, impotence, increased urination, menstrual irregularities

MS: Arthralgia, muscle spasms

RESP: Dyspnea, pulmonary edema,

SKIN: Alopecia, diaphroesis, ecchymosis, erythema multiforme, exanthema, flushing, hyperkeratosis, rash, Stevens-Johnson syndrome, urticaria

Other: Allergy aggravated

Nursing Considerations

• Administer I.V. verapamil with compatible solutions, including Ringer’s injection, D5W, or normal saline solution.

•Maintain continuous ECG monitoring and keep emergency resuscitative equipment and drugs readily available during I.V. therapy.

• Assess patient with hypertrophic cardiomyopathy or idiopathic hypertrophic subaortic stenosis for early development of hypotension and pulmonary edema because second-degree AV block and sinus arrest can result.

• Assess for bradycardia and hypotension, and notify prescriber if heart rate or blood pressure declines significantly.

• Disopyramide or flecainide shouldn’t be given within 48 hours before or 24 hours after verapamil because additive negative inotropic effects can result.

• Institute measures to prevent constipation, including a high-fiber diet and a stool softener, as prescribed.

PATIENT TEACHING

• Instruct patient not to crush or chew verapamil E.R. tablets or capsules. Inform her that she may break E.R. tablets in half if necessary to aid swallowing.

• Direct patient to check her pulse before taking verapamil and to notify prescriber if it’s below 50 beats/minute or as instructed by prescriber.

• Caution patient about possible dizziness and the need to avoid potentially hazardous activities until drug’s CNS effects are known.

• Inform patient that adverse skin reactions may subside with continued verapamil use. Advise her to notify prescriber if rash persists.

• Encourage patient to increase dietary fiber intake to help prevent constipation. Advise her to notify prescriber if problem becomes persistent or severe.