Diltiazem hydrochloride

diltiazem hydrochloride

(dil tye' a zem)

Apo-Diltiaz (CAN), Cardizem, Cardizem CD, Cardizem LA, Cartia XT, Dilacor XR, Diltia XT, Gen-Diltiazem (CAN), Novo-Diltiazem(CAN), Nu-Diltiaz (CAN), Tiazac

Pregnancy Category C

Drug classes

Calcium channel blocker

Antianginal

Antihypertensive

Therapeutic actions

Inhibits the movement of calcium ions across the membranes of cardiac and arterial muscle cells, resulting in the depression of impulse formation in specialized cardiac pacemaker cells, slowing of the velocity of conduction of the cardiac impulse, depression of myocardial contractility, and 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 in patients not controlled by beta-adrenergic blockers, nitrates

·        ER form: Essential hypertension

·        Parenteral: Paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter

Contraindications and cautions

·        Contraindicated with allergy to diltiazem, impaired hepatic or renal function, sick sinus syndrome, heart block (second or third degree), severe hypertension, cardiogenic shock, acute MI with cardiogenic shock (oral), lactation.

Available forms

Tablets—30, 60, 90, 120 mg; ER capsules—60, 90, 120, 180, 240, 300, 360, 420 mg; LA tablets—120, 180, 240, 300, 360, 420 mg; injection—5 mg/mL; powder for injection—25 mg

Dosages

Evaluate patient carefully to determine the appropriate dose of this drug.

ADULTS

Initially, 30 mg PO qid before meals and hs; gradually increase dosage at 1- to 2-day intervals to 180–360 mg PO in three to four divided doses.

Extended-release

Cardizem CD and Cartia XT: 180–240 mg PO for hypertension; 120–180 mg daily PO for angina.

Cardizem LA: 120–540 mg daily PO for hypertension; 180–360 mg/day PO for chronic, stable angina. May be given with nitroglycerine or nitrate therapy.

Dilacor XR and Diltia XT: 180–240 mg daily PO as needed; up to 480 mg has been used.

Tiazac: 120–240 mg daily PO for hypertension—once daily dose; 120–180 mg PO once daily for angina.

IV

Direct IV bolus: 0.25 mg/kg (20 mg for the average patient); second bolus of 0.35 mg/kg.

Continuous IV infusion: 5–10 mg/hr with increases up to 15 mg/hr; may be continued for up to 24 hr.

PEDIATRIC PATIENTS

Safety and efficacy not established.

Pharmacokinetics

Route	Onset	Peak
Oral	30–60 min	2–3 hr
ER	30–60 min	6–11 hr
IV	Immediate	2–3 min

Metabolism: Hepatic; T_1/2: 3.5–6 hr; 5–7 hr (ER)

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

IV facts

Preparation: For continuous infusion, transfer to normal saline, D₅W, D₅W/0.45% NaCl as below. Mix thoroughly. Use within 24 hr. Keep refrigerated.

Diluent Volume (mL)	Quantity of Injection	Final concentration (mg/mL)	Dose (mg/hr)	Infusion Rate (mL/hr)
100	125 mg	1	10	10
	(25 mL)	—	15	15
250	250 mg	0.83	10	12
	(50 mL)	—	15	18
500	250 mg	0.45	10	22
	(50 mL)	—	15	33

Infusion: Administer bolus dose over 2 min. For continuous infusion, rate of 10 mL/hr is the recommended rate. Do not use continuous infusion longer than 24 hr.

Incompatibilities: Do not mix in the same solution with furosemide solution.

Adverse effects

·        CNS: Dizziness, light-headedness, headache, asthenia, fatigue

·        CV: Peripheral edema, hypotension, arrhythmias, bradycardia, AV block, asystole

·        Dermatologic: Flushing, rash

·        GI: Nausea, hepatic injury, reflux

Interactions

Drug-drug

·        Increased serum levels and toxicity of cyclosporine if taken with diltiazem

·        Possible depression of myocardial contractility, AV conduction if combined with beta blockers; use caution and monitor patient closely

Drug-food

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

Nursing considerations

Assessment

·        History: Allergy to diltiazem, impaired hepatic or renal function, sick sinus syndrome, heart block, lactation, pregnancy

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

Interventions

·        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.

·        Monitor BP carefully if patient is on concurrent doses of nitrates.

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

·        Ensure patient swallows ER preparations whole; do not cut, crush, or chew.

Teaching points

·        Swallow extended-release and long-acting preparations whole; do not cut, crush, or chew; do not drink grapefruit juice while using this drug.

·        You may experience these side effects: Nausea, vomiting (eat frequent small meals); headache (regulate light, noise, and temperature; medicate if severe).

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

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