Nifedipine

A to Z Drug Facts

 Actions Inhibits movement of calcium ions across cell membrane in systemic and coronary vascular smooth muscle and myocardium. Increases CO and decreases peripheral vascular resistance. Minimal effect on sinoatrial and AV nodal conduction. Reduces myocardial oxygen demand; relaxes and prevents coronary artery spasm.

 Indications Treatment of vasospastic (Prinzmetal's or variant) angina, chronic stable angina, hypertension (sustained-release tablets only).

 Contraindications Sick sinus syndrome; second- or third-degree AV block, except with functioning pacemaker.

 Route/Dosage

Capsules: ADULTS: PO 10 mg tid (usual dose range, 10 to 20 mg tid); swallow whole. Some patients (eg, coronary artery spasm) respond only to higher doses administered more frequently (eg, 20 to 30 mg tid to qid; max 180 mg/day). In hospitalized patients, under close observation, dose may be increased in 10 mg increments throughout 4- to 6-hr periods as required to control pain and arrhythmias caused by ischemia. A single dose rarely exceeds 30 mg. Extended-release tablets: ADULTS: PO Procardia XL and Nifedical XL: 30 or 60 mg once daily, titrated over 7- to 14-day period (max, 120 mg/day). Adalat CC (hypertension): Start with 30 mg/day and titrate dose over 7- to 14-day period (max, 90 mg/day).

 Interactions

Barbiturates, rifampin: May reduce nifedipine levels, decreasing the therapeutic effect. Cimetidine: May increase bioavailability of nifedipine. Cisapride, diltiazem: May elevate nifedipine levels, increasing the risk of side effects. Fentanyl, parenteral magnesium: Hypotension may occur. Melatonin: May interfere with the antihypertensive effects of nifedipine. Tacrolimus: Tacrolimus trough concentrations may be elevated, increasing the risk of toxicity. Other hypertensive agents: May have additive effects.

 Lab Test Interferences None well documented.

 Adverse Reactions

CARDIOVASCULAR: Peripheral edema; hypotension; palpitations; syncope; CHF; MI; arrhythmia; pulmonary edema; angina; tachycardia. CNS: Dizziness; lightheadedness; giddiness; nervousness; headache; sleep disturbances; insomnia; abnormal dreams; blurred vision; equilibrium disturbances; weakness; jitteriness; paresthesia; somnolence; malaise; anxiety. DERMATOLOGIC: Dermatitis; rash; pruritus; urticaria; Stevens-Johnson syndrome. EENT: Tinnitus; sinusitis; rhinitis. GI: Nausea; diarrhea; constipation; abdominal discomfort; cramps; dyspepsia; dry mouth; flatulence. GU: Micturition disorders; sexual difficulties. HEPATIC: Hepatitis; hepatotoxicity; elevations of LFT enzymes. HEMATOLOGIC: Anemia; leukopenia; thrombocytopenia; bruising; positive Coombs' test with or without hemolytic anemia. RESPIRATORY: Nasal or chest congestion; shortness of breath; wheezing; cough; respiratory infection. OTHER: Flushing; gingival hyperplasia; sweating; muscle cramps, pain and inflammation; joint stiffness, pain, or arthritis; chills; fever; thirst.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk in small amounts. CHILDREN: Safety and efficacy not established. ELDERLY: May experience greater hypotensive effects. Acute hepatic injury: In rare instances, nifedipine has been associated with significant elevations in liver enzymes, symptoms consistent with acute hepatic injury, cholestasis with or without jaundice and allergic hepatitis. Antiplatelet effects: Nifedipine decreases platelet aggregation and can increase bleeding time in some patients. Beta-blocker withdrawal: Patients withdrawn from beta-blockers while taking nifedipine may experience increased angina. CHF: Use drug with caution in patients with CHF. Edema: Nifedipine has been associated with edema in some cases and should be distinguished from fluid retention secondary to heart failure. Hepatic impairment: Use drug with caution in patients with impaired hepatic function, reduced hepatic blood flow, or hepatic cirrhosis. Increased angina: Occasional patients may have increased frequency, duration, or severity of angina at start of therapy or when dose is increased. Withdrawal: Abrupt withdrawal may cause increased frequency and duration of angina.

 Administration/Storage

• Taper initiation and discontinuation of drug over 7 to 14 days.
• May be administered without regard to meals.
• Have patient swallow sustained-release tablets whole; do not allow patient to chew, divide, or crush.
• Procardia XL and Adalat CC are not rated as generic equivalents; do not be interchanged without health care provider's authorization.
• If beta-blockers are being withdrawn while patient is taking nifedipine, gradually taper beta-blocker dose.
• Start patients with impaired hepatic function with low doses.
• When using immediate-release capsules for treatment of hypertensive emergencies, puncture capsules, and squeeze liquid contents under tongue, or puncture capsule several times and have patient chew.
• Store capsules at room temperature and protect from light and moisture.

 Assessment/Interventions

• Obtain history, including drug history and any known allergies. Evaluate cardiac, endocrine, respiratory, hepatic, CNS, renal, and GI systems.
• Obtain baseline and follow-up vital signs; assess for chest pain.
• If drug is used as antihypertensive, routinely monitor BP and note any orthostatic hypotension.
• Inspect skin for rashes.
• Assess for any unusual bruising or bleeding.
• Check BP at least once daily when patient is taking both nifedipine and cimetidine. If possible, another H₂ antagonist may be prescribed instead of cimetidine.
• Administer sublingual nitroglycerin if breakthrough chest pain occurs. Record frequency and duration of anginal attacks and use of sublingual nitroglycerin.
• If any changes from baseline vital signs occur, notify health care provider.

 Patient/Family Education

• Remind patient that sustained-release capsules must be swallowed whole, not chewed, divided, or crushed.
• Teach patient the importance of good dental care, and advise that patient visit dentist on routine basis because gum swelling may occur.
• Instruct patient to maintain increased fluid intake (if not contraindicated) to avoid constipation.
• Instruct patient that medication must be used chronically to obtain benefit and to notify health care provider if at least 2 doses are missed.
• Teach patient/family to notify health care provider of any changes from baseline evaluation (ie, chest pain, shortness of breath).
• Inform patient that there may be increased chest pain at start of medication and with dose changes, but that this effect is transient. If it persists, notify health care provider.
• If health care provider prescribes coadministration of sublingual nitroglycerin, teach patient how to take nitroglycerin sublingually.
• Explain that when sustained-release form is used, partially undigested tablet may appear in feces but that this effect is no cause for concern.
• Instruct patient to report the following symptoms to the health care provider: ringing in ears, swollen gums, respiratory changes, inability to sleep, fever, or chills.
• Advise patient that drug may cause dizziness, lightheadedness, and blurred vision, and to use caution while driving or performing other tasks requiring mental alertness.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts