Dilzem

Action

Inhibits calcium from entering myocardial and vascular smooth-muscle cells, thereby depressing myocardial and smooth-muscle contraction and decreasing impulse formation and conduction velocity. As a result, systolic and diastolic pressures decrease.

Availability

Capsules (extended-release, sustained-release): 60 mg, 90 mg, 120 mg, 180 mg, 240 mg, 300 mg, 360 mg, 420 mg

Injection: 5 mg/ml in 10-ml vials, 100-mg Monovial

Tablets: 30 mg, 60 mg, 90 mg, 120 mg

Indications and dosages

➣ Angina pectoris and vasospastic (Prinzmetal's) angina; hypertension; supraventricular tachyarrhythmias; atrial flutter or fibrillation

Adults: 30 to 90 mg P.O. three to four times daily (tablets), or 60 to 120 mg P.O. b.i.d. (sustained-release), or 180 to 240 mg P.O. once daily (extended-release), adjusted after 14 days as needed, up to a total daily dosage of 360 mg. Or 0.25 mg/kg by I.V. bolus over 2 minutes; if response is inadequate after 15 minutes, may give 0.35 mg/kg over 2 minutes; may follow with continuous I.V. infusion at 10 mg/hour (at a range of 5 to 15 mg/hour) for up to 24 hours.

Dosage adjustment

• Severe hepatic or renal impairment

• Elderly patients

Off-label uses

• Unstable angina, coronary artery bypass graft surgery

• Tardive dyskinesia

• Migraine

• Hyperthyroidism

• Raynaud's phenomenon

Contraindications

• Hypersensitivity to drug

• Atrial flutter or fibrillation associated with shortened refractory period (Wolff-Parkinson-White syndrome, with I.V. use)

• Recent myocardial infarction or pulmonary congestion

• Cardiogenic shock, concurrent I.V. beta-blocker therapy, ventricular tachycardia, neonates (with I.V. use, because of benzyl alcohol in syringe formulation)

• Sick sinus syndrome, second- or third-degree atrioventricular block (except in patients with ventricular pacemakers)

• Hypotension (systolic pressure below 90 mm Hg)

Precautions

Use cautiously in:

• severe hepatic or renal impairment, heart failure

• history of serious ventricular arrhythmias

• concurrent use of I.V. diltiazem and I.V. beta blockers

• elderly patients

• pregnant or breastfeeding patients

• children (safety not established).

Administration

• When giving I.V., dilute in dextrose 5% in water or normal saline solution.

• Give I.V. bolus dose over 2 minutes; a second bolus may be given after 15 minutes.

• Administer continuous I.V. infusion at a rate of 5 to 15 mg/hour.

See When giving by continuous I.V. infusion, make sure emergency equipment is available and that patient has continuous ECG monitoring with frequent blood pressure monitoring.

• Don't crush tablets or sustained-release capsules; they must be swallowed whole.

• Withhold dose if systolic blood pressure falls below 90 mm Hg, diastolic pressure is below 60 mm Hg, or apical pulse is slower than 60 beats/minute.

Adverse reactions

CNS: headache, abnormal dreams, anxiety, confusion, dizziness, drowsiness, nervousness, psychiatric disturbances, asthenia, paresthesia, syncope, tremor

CV: peripheral edema, bradycardia, chest pain, hypotension, palpitations, tachycardia, arrhythmias, heart failure

EENT: blurred vision, tinnitus, epistaxis

GI: nausea, vomiting, diarrhea, constipation, dyspepsia, dry mouth

GU: urinary frequency, dysuria, nocturia, polyuria, gynecomastia, sexual dysfunction

Hematologic: anemia, leukopenia, thrombocytopenia

Metabolic: hyperglycemia

Musculoskeletal: joint stiffness, muscle cramps

Respiratory: cough, dyspnea

Skin: rash, dermatitis, flushing, diaphoresis, photosensitivity, pruritus, urticaria, erythema multiforme

Other: unpleasant taste, gingival hyperplasia, weight gain, decreased appetite, Stevens-Johnson syndrome

Interactions

Drug-drug. Beta-adrenergic blockers, digoxin, disopyramide, phenytoin: bradycardia, conduction defects, heart failure

Carbamazepine, cyclosporine, quinidine: decreased diltiazem metabolism, increased risk of toxicity

Cimetidine, ranitidine: increased blood level and effects of diltiazem

Fentanyl, nitrates, other antihypertensives, quinidine: additive hypotension

HMG-CoA reductase inhibitors, imipramine, sirolimus, tacrolimus: increased blood levels of these drugs

Lithium: decreased lithium blood level, reduced antimanic control

Nonsteroidal anti-inflammatory drugs: decreased antihypertensive effect of diltiazem

Theophylline: increased theophylline effects

Drug-diagnostic tests. Hepatic enzymes: increased levels

Drug-food. Grapefruit juice: increased blood level and effects of diltiazem

Drug-behaviors. Acute alcohol ingestion: additive hypotension

Patient monitoring

• Check blood pressure and ECG before starting therapy, and monitor closely during dosage adjustment period. Withhold dose if systolic pressure is below 90 mm Hg.

See Monitor for signs and symptoms of heart failure and worsening arrhythmias.

• Supervise patient during ambulation.

Patient teaching

• Instruct patient to swallow extended-release capsules whole and not to crush or chew them.

• Advise patient to change position slowly to minimize light-headedness and dizziness.

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

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