Overview
Nifedipine is a calcium channel blocker used to treat hypertension and chronic stable angina. It works by relaxing blood vessels to reduce blood pressure and improve blood flow to the heart. The extended-release formulation provides 24-hour control with once-daily dosing.
Mechanism of Action
Nifedipine inhibits the influx of calcium ions across cell membranes in vascular smooth muscle and cardiac muscle, producing relaxation of coronary and peripheral arteries. This reduces peripheral vascular resistance and blood pressure while increasing coronary blood flow.
Indications
- Treatment of hypertension
- Management of chronic stable angina (effort-associated angina)
Common Doses
- 30 mg
- 60 mg
- 90 mg
Dosage
Initiate with 30 or 60 mg once daily, titrate over 7-14 days based on response. Maximum recommended dose is 120 mg daily. Tablets must be swallowed whole, not bitten or divided. Avoid grapefruit juice.
Contraindications
- Known hypersensitivity to nifedipine
Side Effects
- Peripheral edema (10-30% at higher doses)
- Headache (15.8%)
- Dizziness (4.1%)
- Flushing
- Fatigue
- Constipation
- Nausea
- Palpitations
- Muscle cramps
- Rare serious reactions: myocardial infarction, congestive heart failure, severe skin reactions
Interactions
- Grapefruit juice increases bioavailability - avoid coadministration
- Beta-blockers may increase risk of hypotension and heart failure
- CYP3A4 inhibitors (ketoconazole, erythromycin) increase nifedipine levels
- CYP3A4 inducers (rifampin, phenobarbital) decrease nifedipine efficacy
Counseling Points
- Swallow tablets whole - do not crush, chew, or break
- Take at the same time each day
- Avoid grapefruit and grapefruit juice
- Rise slowly from sitting/lying position to prevent dizziness
- Report swelling of feet/ankles, severe dizziness, or rapid heartbeat
- Do not stop abruptly without medical supervision