Nifedipine

Nifedipine is a medication used to manage angina, high blood pressure, Raynaud’s phenomenon, and premature labor. It is one of the treatments of choice for Prinzmetal angina. It may be used to treat severe high blood pressure in pregnancy. Its use in preterm labor may allow more time for steroids to improve the baby’s lungs and time to transfer the mother to a well qualified medical facility before delivery.

Molecular Structure

Nifedipine

Class of Drug

Calcium channel blocker.

Mechanism of Action

Inhibits calcium movement across cell membranes.

Indications / Dosage / Route

Routes of Administration: Oral only.

Condition: Hypertension

Dose: Adults: individualized: 30-60 mg/d. Maximum: 180 mg/d.

Condition: Angina

Dose: Adults: 30-120 mg/day

         Elderly: 30-120 mg/day

Adjustment of Dosage

Kidney disease: None.

Liver disease: Use with caution. Monitor carefully.

Elderly: Use with caution.

Pediatric: Safety and efficacy have not been established.

Onset of Action Peak Effect Duration
0.5-1 h 2 h 8 h

Food and Drug Interactions

Food: No restrictions.

Pregnancy: Category C.

Lactation: Probably appears in breast milk. Potentially toxic to infant. Avoid breastfeeding.

Contraindications: Hypersensitivity to calcium blockers.

Warnings / Precautions

> Use with caution in patients with CHF, severe left ventricular dysfunction and in those concomitantly receiving β blockers or digoxin, liver disease.

> Do not withdraw drug abruptly, as this may result in increased frequency and intensity of angina

> For the diabetic patient, the drug may interfere with insulin release and therefore produce hyperglycemia.

> Patient should be tapered off β blockers before beginning calcium channel blockers to avoid exacerbation of angina from abrupt withdrawal of the β blocker.

Clinically Important Drug Interactions

> Drugs that increase effects/toxicity of calcium blockers: cimetidine, β blockers, cyclosporine.

> Drugs that decrease effects of calcium blockers: barbiturates.

Adverse Reactions

> Common: headache, edema.

> Serious: CHF, arrhythmias, hypotension, depression

Parameters to Monitor

> BP during initial administration and frequently thereafter. Ideally, check BP close to the end of dosage interval or before next administration.

> Status of liver and kidney function. Impaired renal function prolongs duration of action and increases tendency for toxicity.

> Intake of fluids and urinary and other fluid output to minimize renal toxicity. Increase fluid intake if inadequate. Closely monitor electrolyte levels.

> Efficacy of treatment for angina: decrease in frequency of angina attacks, need for nitroglycerin, episodes of PST segment deviation, anginal pain.

> If anginal pain is not reduced at rest or during effort reassess patient as to medication. GI side effects: Use alternative. ECG for development of heart block. Symptoms of CHF.

Advice to Patient

> Use two forms of birth control including hormonal and barrier methods.

> Change position slowly, in particular from recumbent to upright, to minimize orthostatic hypotension. Sit at the edge of the bed for several minutes before standing, and lie down if feeling faint or dizzy. Avoid hot showers or baths and standing for long periods.
Male patients should sit on the toilet while urinating rather than standing.

> Avoid driving and other activities requiring mental alertness or that are potentially dangerous until response to drug is known.

> Use OTC medications only with approval from treating physician.

> Determine BP and heart rate aproximately at the same time each day and at least twice a week, particularly at the beginning of therapy.

> Be aware of the fact that this drug may also block or reduce anginal pain, thereby giving a false sense of security on severe exertion.

> Include high-fiber foods to minimize constipation.

> Limit consumption of xanthine-containing drinks: regular coffee (fewer than 5 cups/d), tea, cocoa.

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