Nifedipine

nifedipine (nye fed' i peen) Adalat, Adalat CC, Adalat XL (CAN), Apo-Nifed (CAN), Gen-Nifedipine (CAN), Nifedical XL, Novo-Nifedin (CAN), Procardia, Procardia XL 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; inhibition of transmembrane calcium flow results in the depression of impulse formation in specialized cardiac pacemaker cells, in slowing of the velocity of conduction of the cardiac impulse, in the depression of myocardial contractility, and in the dilation of coronary arteries and arterioles and peripheral arterioles; these effects lead to decreased cardiac work, decreased cardiac energy consumption, and increased delivery of oxygen to myocardial cells. Indications

• • • •

Angina pectoris due to coronary artery spasm (Prinzmetal's variant angina) Chronic stable angina (effort-associated angina) Sustained-release preparation only: Treatment of hypertension Orphan drug use: Treatment of interstitial cystitis

Contraindications and cautions

• •

Contraindicated with allergy to nifedipine. Use cautiously with lactation, pregnancy.

Available forms

ER tablets—30, 60, 90 mg; capsules—10, 20 mg Dosages ADULTS

Initial dose, 10 mg tid PO. Maintenance range, 10–20 mg tid. Higher doses (20–30 mg tid–qid) may be required, depending on patient response. Adjust over 7–14 days. More than 180 mg/day is not recommended. Sustained-release

30–60 mg PO once daily. Adjust over 7–14 days. Usual maximum dose is 90– 120 mg/day. Pharmacokinetics Route Oral SR

Onset 20 min 20 min

Peak 30 min 2.5–6 hr

Metabolism: Hepatic; T1/2: 2–5 hr Distribution: Crosses placenta; enters breast milk Excretion: Urine and feces Adverse effects

• • • • •

CNS: Dizziness, light-headedness, headache, asthenia, fatigue, nervousness, sleep disturbances, blurred vision CV: Peripheral edema, angina, hypotension, arrhythmias, AV block, asystole Dermatologic: Flushing, rash, dermatitis, pruritus, urticaria GI: Nausea, diarrhea, constipation, cramps, flatulence, hepatic injury Other: Nasal congestion, cough, fever, chills, shortness of breath, muscle cramps, joint stiffness, sexual difficulties

Interactions

Drug-drug • Increased effects with cimetidine Nursing considerations Assessment

• •

History: Allergy to nifedipine; pregnancy; lactation Physical: Skin lesions, color, edema; orientation, reflexes; P, BP, baseline ECG, peripheral perfusion, auscultation; R, adventitious sounds; liver evaluation, normal GI output; liver function tests

Interventions

•

• • •

Monitor patient carefully (BP, cardiac rhythm, and output) while drug is being adjusted to therapeutic dose; the dosage may be increased more rapidly in hospitalized patients under close supervision. Do not exceed 30 mg/dose increases. Ensure that patients do not chew or divide sustained-release tablets. Taper dosage of beta-blockers before nifedipine therapy. Protect drug from light and moisture.

Teaching points

• •

•

Do not chew, cut, or crush sustained-release tablets. Swallow whole. These side effects may occur: Nausea, vomiting (eat frequent small meals); dizziness, light-headedness, vertigo (avoid driving, operating dangerous machinery; take special precautions to avoid falling); muscle cramps, joint stiffness, sweating, sexual difficulties (reversible). Report irregular heartbeat, 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.