Action

Inhibits calcium ion movement across cell membranes of cardiac and arterial muscles, relaxing coronary and peripheral vascular smooth muscle. This action reduces diastolic blood pressure, enhances left ventricular function, and improves ejection rates; it also reduces mean vascular and systemic vascular resistance, increasing cardiac output and improving stroke volume.

Availability

Capsules: 2.5 mg, 5 mg

Tablets (controlled-release): 5 mg, 10 mg

Indications and dosages

➣ Hypertension

Adults: Initially, 2.5 mg P.O. b.i.d. as monotherapy or combined with a thiazide diuretic (regular-release capsules); may increase in increments of 5 mg/day at 2- to 4-week intervals, to a maximum of 20 mg/day. Or, 5 to 10 mg P.O. (controlled-release) daily as monotherapy or combined with a thiazide diuretic.

Contraindications

• Hypersensitivity to drug or other calcium channel blockers

Precautions

Use cautiously in:

• heart disease, hypotension, hepatic or renal disease, GI hypermotility or obstruction (controlled-release form)

• concurrent use of beta-adrenergic blockers

• elderly patients

• pregnant or breastfeeding patients

• children.

Administration

• Give with or without food.

• Don't give with grapefruit juice.

• Don't crush or break controlled-release tablets. Make sure patient swallows them whole.

Adverse reactions

CNS: dizziness, headache, fatigue, syncope, sleep disturbances

CV: peripheral edema, tachycardia, hypotension, chest pain, arrhythmias

GI: nausea, vomiting, constipation, abdominal pain or distention, dry mouth

GU: nocturia, urinary frequency

Hematologic: leukopenia

Hepatic: hepatitis

Skin: rash, pruritus, urticaria

Other: flushing

Interactions

Drug-drug. Atracurium, gallamine, pancuronium, tubocurarine, vecuronium: increased respiratory depression

Beta-adrenergic blockers: increased cardiac depression

Carbamazepine, digoxin, prazosin, quinidine: increased blood levels of these drugs

Drug-food. Grapefruit juice: increased drug absorption

Patient monitoring

• Monitor vital signs closely, especially blood pressure.

• Assess liver function test results.

• Monitor for arrhythmias and peripheral edema.

Patient teaching

• Tell patient he may take with or without food, but not with grapefruit juice.

• Instruct patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.

• Teach patient with heart, kidney, or liver disease to watch for and promptly report adverse reactions.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and foods mentioned above.