nifedipine

Absorption: Well absorbed after oral administration, but large amounts are rapidly metabolized, resulting in ↓ bioavailability (45–70%); bioavailability is ↑ (80%) with extended-release forms.

Distribution: Unknown.

Protein Binding: 92–98%.

Metabolism/Excretion: Mostly metabolized by the liver by the CYP3A4 isoenzyme.

Half-Life: 2–5 hr.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO	20 min	unknown	6–8 hr
PO–ER	unknown	6 hr	24 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Sick sinus syndrome;
2nd- or 3rd-degree AV block (unless an artificial pacemaker is in place);
Systolic BP <90 mm Hg;
Coadministration with grapefruit juice, rifampin, rifabutin, phenobarbital, phenytoin, carbamazepine, or St. John's wort.

Use Cautiously in:

Severe hepatic impairment (↓ dose);
History of porphyria;
Severe renal impairment (↓ dose may be necessary);
History of serious ventricular arrhythmias or HF;
Pedi: Safety and effectiveness not established in children;
Geri: Immediate-release formulation appears on Beers list. risk of hypotension and myocardial ischemia in older adults. Avoid use of immediate-release formulation in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: peripheral edema, bradycardia, chest pain, HF, hypotension, palpitations, syncope, tachycardia

Derm: flushing, ↑sweating, dermatitis, erythema multiforme, photosensitivity, pruritus/urticaria, rash, STEVENS-JOHNSON SYNDROME

EENT: blurred vision, disturbed equilibrium, epistaxis, tinnitus

Endo: gynecomastia, hyperglycemia

GI: ↑liver enzymes, GI obstruction, anorexia, constipation, diarrhea, dry mouth, dyspepsia, nausea, vomiting

GU: dysuria, nocturia, polyuria, sexual dysfunction, urinary frequency

Hemat: anemia, leukopenia, thrombocytopenia

Metab: weight gain

MS: joint stiffness, muscle cramps

Neuro: paresthesia, tremor

Resp: cough, dyspnea, shortness of breath

Misc: gingival hyperplasia

Interactions ⬆ ⬇

Drug-drug:

Rifampin, rifabutin, phenobarbital, phenytoin, or carbamazepine may significantly ↓ levels and effects; concurrent use is contraindicated.
Ketoconazole, fluconazole, itraconazole, clarithromycin, erythromycin, nefazodone, nelfinavir, or ritonavir may ↑ levels and effects; consider initiating nifedipine at lowest dose.
Additive hypotension may occur when used concurrently with fentanyl, other antihypertensives, nitrates, acute ingestion of alcohol, or quinidine.
Antihypertensive effects may be ↓ by concurrent use of NSAIDs.
May ↑ serum levels and risk of toxicity from digoxin.
Concurrent use with beta blockers, digoxin, or disopyramide may result in bradycardia, conduction defects, or HF.
Cimetidine and propranolol may ↓ metabolism and ↑ risk of toxicity.
May ↓ metabolism of and ↑ risk of toxicity from cyclosporine, tacrolimus, prazosin, quinidine, or carbamazepine.
↑risk of GI obstruction when used concurrently with H2 blockers, opioids, NSAIDs, laxatives, anticholinergic drugs, levothyroxine, or neuromuscular blockers.

Drug-Natural Products:

St. John's wort may significantly ↓ levels and effects; concurrent use is contraindicated.

Grapefruit and grapefruit juice↑ serum levels and effect; avoid concurrent use.

Route/Dosage ⬆ ⬇

PO (Adults ): Immediate-release: 10–30 mg 3 times daily (not to exceed 180 mg/day); Extended-release: 30–90 mg once daily (not to exceed 90–120 mg/day).

Availability ⬆ ⬇

(Generic available)

Capsules: 5 mg; 10 mg; 20 mg
Extended-release tablets: 30 mg; 60 mg; 90 mg

Assessment ⬆ ⬇

Monitor BP and pulse before therapy, during dose titration, and periodically during therapy. Monitor ECG periodically during prolonged therapy.
- Monitor intake and output ratios and daily weight. Assess for signs of HF (peripheral edema, rales/crackles, dyspnea, weight gain, jugular venous distention).
Patients receiving digoxin concurrently with nifedipine should have routine tests of serum digoxin levels and be monitored for signs and symptoms of digoxin toxicity.
Assess for rash periodically during therapy. May cause Stevens-Johnson syndrome. Discontinue therapy if severe or if accompanied with fever, general malaise, fatigue, muscle or joint aches, blisters, oral lesions, conjunctivitis, hepatitis, and/or eosinophilia.
Angina: Assess location, duration, intensity, and precipitating factors of patient’s anginal pain.

Lab Test Considerations:

Total serum calcium concentrations are not affected by calcium channel blockers.
- Monitor serum potassium periodically. Hypokalemia increases risk of arrhythmias; should be corrected.
- Monitor renal and hepatic functions periodically during long-term therapy. Several days of therapy may cause ↑ hepatic enzymes, which return to normal upon discontinuation of therapy.
- Nifedipine may cause positive ANA and direct Coombs’ test results.

Implementation ⬆ ⬇

Do not confuse nifedipine with nicardipine or nimodipine.
PO: May be administered without regard to meals. May be administered with meals if GI irritation becomes a problem.
- DNC: Swallow tablets whole; do not open, break, crush, or chew extended-release tablets. Empty tablets that appear in stool are not significant.
- Avoid administration with grapefruit juice.
- Sublingual use is not recommended due to serious adverse drug reactions.

Patient/Family Teaching ⬆ ⬇

Advise patient to take medication as directed, even if feeling well. Take missed doses as soon as possible unless almost time for next dose; do not double doses. May need to be discontinued gradually.
- Instruct patient on technique for monitoring pulse. Instruct patient to contact health care professional if heart rate is <50 bpm.
- Advise patient to avoid grapefruit or grapefruit juice during therapy.
- Caution patient to change positions slowly to minimize orthostatic hypotension.
- May cause drowsiness or dizziness. Advise patient to avoid driving or other activities requiring alertness until response to the medication is known.
- Teach patient and family about risk for falls and how to reduce risk in the home.
- Instruct patient on importance of maintaining good dental hygiene and seeing dentist frequently for teeth cleaning to prevent tenderness, bleeding, and gingival hyperplasia (gum enlargement).
- Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to avoid concurrent use of alcohol or OTC medications and herbal products, especially cold preparations and St. John's wort, without consulting health care professional.
- Advise patient to notify health care professional if rash, irregular heartbeat, dyspnea, swelling of hands and feet, pronounced dizziness, nausea, constipation, or hypotension occurs or if headache is severe or persistent.
- Caution patient to wear protective clothing and use sunscreen to prevent photosensitivity reactions.
- Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
Angina: Instruct patient on concurrent nitrate or beta-blocker therapy to continue taking both medications as directed and use SL nitroglycerin as needed for anginal attacks.
- Inform patient that anginal attacks may occur 30 min after administration because of reflex tachycardia. This is usually temporary and is not an indication for discontinuation.
- Advise patient to contact health care professional if chest pain does not improve, worsens after therapy, or occurs with diaphoresis; if shortness of breath occurs; or if persistent headache occurs.
- Caution patient to discuss exercise restrictions with health care professional before exertion.
Hypertension: Encourage patient to comply with other interventions for hypertension (weight reduction, low-sodium diet, smoking cessation, moderation of alcohol consumption, regular exercise, and stress management). Medication controls but does not cure hypertension.
- Instruct patient and family in proper technique for monitoring BP. Advise patient to take BP weekly and to report significant changes to health care professional.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇