Pharm 101: Nifedipine

Class

Dihydropyridine Calcium Channel Blocker

Pharmacodynamics

• Blocks vascular L-type calcium channels > cardiac channels:
  • Blocks activated and inactivated L-type calcium channels (alpha-1 subunit)
  • Resultant decreased transmembrane calcium current results in long-lasting relaxation in smooth muscle
  • Note verapamil causes a nonselective block of L-type calcium channel in vessels and heart
• Dihydropyridines blocks smooth muscle calcium channels at concentrations below those required for significant cardiac effects
• No effect on AV conduction

Pharmacokinetics

• Slow-release formulation
• High first pass metabolism, bioavailability 45-70%
• High plasma protein binding
• Extensive metabolism
• Half-life 4 hours

Clinical uses

• Hypertension
• Raynaud’s phenomenon

Adverse effects

• Hypotension, dizziness
• Flushing
• Nausea, constipation
• Peripheral edema

Precautions/contraindications

• Immediate-acting preparation may increased risk of MI in patients with hypertension

Other Dihydropyridines

• Nimodipine has as high affinity for cerebral blood vessels and reduces morbidity after SAH
• Amlodipine has a slower onset, longer half-life (30-50 hours) and longer duration of action than nifedipine