NIFEDIPINE

(nye-fed'i-peen)

Adalat CC, Procardia, Procardia XL
Classifications: antianginal, antihypertensive, calcium channel blocker;
Therapeutic: antiarrhythmic (class iv); antianginal
Pregnancy Category: C

Availability

10 mg, 20 mg capsules; 30 mg, 60 mg, 90 mg sustained release tablets

Action

Calcium channel blocking agent that selectively blocks calcium ion influx across cell membranes of cardiac muscle and vascular smooth muscle without changing serum calcium concentrations. Reduces myocardial oxygen utilization and supply and relaxes and prevents coronary artery spasm; has little or no effect on SA and AV nodal conduction with therapeutic dosing. Decreases peripheral vascular resistance and increases cardiac output.

Therapeutic Effect

Class IV antiarrhythmic. Decreased peripheral vascular resistance, leading to a rise in peripheral blood flow, the basis for use of this drug in treatment of Raynaud's phenomenon.

Uses

Vasospastic "variant" or Prinzmetal's angina and chronic stable angina without vasospasm. Mild to moderate hypertension alone or in combination with a diuretic.

Unlabeled Uses

Esophageal disorders; vascular headaches; Raynaud's phenomenon; asthma; cardiomyopathy; primary pulmonary hypertension.

Contraindications

Known hypersensitivity to nifedipine; unstable angina; acute MI; cardiogenic shock; aortic stenosis; GI obstruction. Safety during pregnancy (category C) or in children is not established.

Cautious Use

Concomitant use with hypotensives; GERD; CHF; lactation.

Route & Dosage

Angina
Adult: PO 10–20 mg t.i.d. up to 180 mg/d

Hypertension
Adult: PO 10–20 mg t.i.d. up to 180 mg/d or 30–90 mg sustained release once/d

Administration

Oral

Do not give within the first 1–2 wk following an MI.
Use only the sustained release form to treat chronic hypertension. Ensure that sustained release form is not chewed or crushed. It must be swallowed whole.
Discontinue drug gradually, with close medical supervision to prevent severe hypertension and other adverse effects.
Store at 15°–25° C (59°–77° F); protect from light and moisture.

Adverse Effects (≥1%)

Body as a Whole: Sore throat, weakness, fever, sweating, chills, febrile reaction. CNS: Dizziness, light-headedness, nervousness, mood changes, weakness, jitteriness, sleep disturbances, blurred vision, retinal ischemia, difficulty in balance, headache. CV: Hypotension, facial flushing, heat sensation, palpitations, peripheral edema, MI (rare), prolonged systemic hypotension with overdose. GI: Nausea, heartburn, diarrhea, constipation, cramps, flatulence, gingival hyperplasia, hepatotoxicity. Musculoskeletal: Inflammation, joint stiffness, muscle cramps. Respiratory: Nasal congestion, dyspnea, cough, wheezing. Skin: Dermatitis, pruritus, urticaria. Urogenital: Sexual difficulties, possible male infertility.

Diagnostic Test Interference

Nifedipine may cause mild to moderate increases of alkaline phosphatase, CPK, LDH, AST, ALT.

Interactions

Drug: beta blockers may increase likelihood of CHF; may increase risk of phenytoin toxicity. Herbal: Melatonin may increase blood pressure and heart rate. Ginkgo, ginseng may increase plasma concentrations. St. John's wort may decrease plasma concentrations. Food: Grapefruit juice (>1 qt/d) may increase plasma concentrations and adverse effects.

Pharmacokinetics

Absorption: Readily absorbed from GI tract; 45–75% reaches systemic circulation (first pass metabolism). Onset: 10–30 min. Peak: 30 min. Distribution: Distributed into breast milk. Metabolism: In liver. Elimination: 75–80% in urine, 15% in feces. Half-Life: 2–5 h.

Nursing Implications

Assessment & Drug Effects

Monitor BP carefully during titration period. Patient may become severely hypotensive, especially if also taking other drugs known to lower BP. Withhold drug and notify physician if systolic BP <90.
Monitor blood sugar in diabetic patients. Nifedipine has diabetogenic properties.
Monitor for gingival hyperplasia and report promptly. This is a rare but serious adverse effect (similar to phenytoin-induced hyperplasia).

Patient & Family Education

Keep a record of nitroglycerin use and promptly report any changes in previous pattern. Occasionally, people develop increased frequency, duration, and severity of angina when they start treatment with this drug or when dosage is increased.
Be aware that withdrawal symptoms may occur with abrupt discontinuation of the drug (chest pain, increase in anginal episodes, MI, dysrhythmias).
Inspect gums visually every day. Changes in gingivae may be gradual, and bleeding may be exhibited only with probing.
Seek prompt treatment for symptoms of gingival hyperplasia (easy bleeding of gingivae and gradual enlarging of gingival mass, especially on buccal side of lower anterior teeth). Drug will be discontinued if gingival hyperplasia occurs.
Research shows that smoking decreases the efficacy of nifedipine and has direct and adverse effects on the heart in the patient on nifedipine treatment.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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