- Nifedipine, dihydropyridine prototype, inhibits the influx of Ca++ into cardiac and vascular muscle cells similar to other dihydropyridines including Amlodipine, felodipine, Isradipine, and nicardipine.
- Peak serum concentrations is reached within 0.5-2 hours after oral administration as capsules.
- Plasma drug concentrations of extended-release tablet dose reach a plateau at approx six hours after dosing
- Food decrease the rate but not the extent of absorption
- In normal renal and hepatic function, the plasma half-life of nifedipine is about 2 hours with conventional capsules, and about 7 hours with extended-release tablets
- Nifedipine undergoes extensive hepatic metabolism via cytochrome P450 system especially by CYP3A4, to highly polar, inactive metabolites excreted in the urine.
- CCBs target L-type Ca channels found predominantly in muscle cells involved in contraction.
- DHP CCBs binds directly to inactive Ca channels thereby stabilizing their inactive conformation which are more prevalent in smooth muscle cells relative to cardiac muscles.
- The reduction in Ca++ influx by nifedipine causes arterial vasodilation and decreased peripheral vascular resistance which is associated with reduced arterial BP.
- Nifedipine also inhibits the drug efflux pump P-glycoprotein which is overexpressed in some multi-drug resistant tumors
- At therapeutic concentrations, nifedipine has little effect on cardiac myocytes and conduction cells.
- Nifedipine overdoses may form drug bezoar; consider endoscopic removal as a potential treatment option.
- Overdose, generally produce toxic effects that are extensions of their usual adverse effects (dizziness, lightheadedness, giddiness, flushing or heat sensation, and headache) and includes pronounced hypotension. loss of consciousness, heart rhythm disturbances, metabolic acidosis, hypoxia, and cardiogenic shock with pulmonary edema and hyperglycemia that responds to aggressive treatment with intravenous fluids, calcium, and dopamine.
- Acute hepatitis following first exposure to nifedipine has been reported
- Nifedipine is highly protein bound; dialysis is unlikely to be of any benefit
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