EPILAT RETARD TABLETS

Indications

• Hypertension
• Angina pectoris
• Vasospastic angina
• Raynaud's phenomenon

Dosage

Children: Refer to the BNF for Children for specific pediatric dosing recommendations.

Adults: Refer to specific guidelines or consult the BNF for appropriate dosing recommendations.

Mechanism of action

Nifedipine selectively inhibits the influx of calcium ions through L-type calcium channels in the vascular smooth muscle, resulting in relaxation of vascular smooth muscle and vasodilation. This decrease in intracellular calcium leads to reduced peripheral vascular resistance and decreased blood pressure. Additionally, it decreases the contractility of cardiac muscle which helps in managing angina.

Pharmacodynamics

The primary pharmacodynamic effect of nifedipine is the relaxation of vascular smooth muscle, which results in a decrease in systemic vascular resistance and blood pressure. The drug also helps to relieve anginal symptoms by reducing myocardial oxygen consumption. The onset of action can vary, but typically, the effects can be observed within 30 minutes to 2 hours after administration, with a duration of action lasting several hours, particularly with extended-release formulations.

Pharmacokinetics

Nifedipine is well absorbed from the gastrointestinal tract, but undergoes extensive first-pass metabolism in the liver. The bioavailability varies but is significantly reduced after the first pass. The drug has a volume of distribution of approximately 0.5 to 1 L/kg and is highly protein-bound (about 95%). Nifedipine is metabolized primarily by cytochrome P450 enzymes, particularly CYP3A4, and excreted as metabolites in urine. The elimination half-life is around 2 to 5 hours for immediate-release formulations and can be longer for extended-release formulations.

Contra-indications

• Known hypersensitivity to nifedipine or any of its components
• Severe hypotension or cardiogenic shock
• Unstable angina
• Recent myocardial infarction

Adverse effects

• Headache
• Dizziness
• Flushing
• Peripheral edema
• Gastrointestinal disturbances (nausea, constipation)
• Palpitations
• Fatigue
• Rash

Interactions

• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin) may increase nifedipine levels
• CYP3A4 inducers (e.g., rifampicin, St. John's Wort) may decrease nifedipine levels
• Nitrates may enhance the hypotensive effect
• Beta-blockers may have additive effects on heart rate and blood pressure

Precautions

• Use with caution in patients with hepatic impairment
• Monitor blood pressure regularly during therapy
• Assess for signs of hypotension
• Caution in patients with heart failure or severe aortic stenosis

Pregnancy

Nifedipine should be used during pregnancy only if clearly needed, as safety in pregnancy has not been established.

Breast-feeding

Nifedipine is excreted in breast milk; caution is advised when administered to breastfeeding women.

Storage

Store at room temperature, away from moisture and heat, in a tightly closed container.

Formulations

• Immediate-release capsules
• Extended-release tablets
• Sustained-release formulations