Nifedipine
Mechanism :
Nifedipine is a calcium channel blocker and inhibits the transmembrane influx of calcium ions into cardiac muscle and smooth muscle. The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. Nifedipine selectively inhibits calcium ion influx across the cell membrane of cardiac muscle and vascular smooth muscle without changing serum calcium concentrations.
Indication :
- Hypertension
- Hypertrophic cardiomyopathy
- Raynaud phenomenon
Contraindications :
Known hypersensitivity reaction to nifedipine and pregnancy.
Dosing :
Hypertension:
1 month-18 years: Oral 250-500 mcg/kg daily once or in 2 divided doses upto 1-2 mg/kg/day. Max: 120 mg/day.
Hypertrophic cardiomyopathy:
0.6-0.9 mg/kg/day PO in 3-4 divided doses.
Raynaud phenomenon:
0.2-1 mg/kg/day PO in 3-4 divided doses. Max: 180 mg/day.
Adverse Effect :
Commonly reported adverse effects are peripheral oedema, headache, flushing, heartburn, nausea, tachycardia, palpitations, dizziness, rash, gum hyperplasia. May increase intracranial pressure.
Interaction :
Beta-blockers: May increase cardiovascular adverse effects.
Cimetidine: May increase nifedipine serum concentration.
Digoxin: May increase digoxin serum concentration; monitor digoxin levels and if necessary, reduce digoxin dose.
Rifampicin: Do not use together as effective levels of nifedipine may not be reached.
Bioavailability is increased if taken with grapefruit juice.
Fentanyl: Severe hypotension has been reported during fentanyl anesthesia with concomitant use of a beta-blocker and a calcium channel blocker.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Dose as in normal renal function |
| 10-20 | Dose as in normal renal function. Start with small doses |
| <10 | Dose as in normal renal function. Start with small doses |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in GFR<10 mL/min |
| HD | Not dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Unknown dialysability. Dose as in GFR<10 mL/min |
| CAV/VVHD | Unknown dialysability. Dose as in GFR=10–20 mL/min |
Hepatic Dose :
In hepatic impairment, the elimination half-life is prolonged, and the total clearance is reduced. Thus, dosage reduction and close monitoring of blood pressure is advised in patients with hepatic impairment. The sustained release tablets should be avoided in patients with hepatic impairment.