felodipine (Plendil)

Introduction

Tradename: Plendil.

Indications

• hypertension
• angina pectoris
• Prinzmetal angina
• left ventricular diastolic dysfunction
• Raynaud's phenomenon

Contraindications

• NOT for use in controlling ventricular response to atrial fibrillation
  • does NOT block AV nodal conduction
  • increases AV nodal conduction

pregnancy category = c

safety in lactation = ?

Dosage

start: 2.5-5 mg PO QD, max 10 mg QD

Tabs: 2.5, 5, 10 mg. Do NOT crush, split or chew tablets!

Pharmacokinetics

• oral bioavailability is about 20%
• significant 1st pass metabolism
• > 99% of drug bound to plasma proteins
• metabolized in the liver by cyt P450 3A4
  • 6 inactive metabolites are excreted in the urine
• elimination 1/2life is 11-16 hours

elimination via liver

1/2life = 11-16 hours

Adverse effects

• headache
• flushing
• dizziness
• nausea
• heartburn
• muscle cramps
• peripheral edema
• hypotension

• drug adverse effects of calcium channel blockers
• drug adverse effects of renin-angiotensin-aldosterone system inhibitors (RAAS inhibitors)
• drug adverse effects of antihypertensive agents

Drug interactions

• barbiturates decrease felodipine bioavailability
• erythromycin increases pharmacologic effect of felodipine
• beta-blockers increase adverse effects of felodipine
• carbamazepine in combination increases carbamazepine levels & decreases felodipine levels
• grapefruit increases absorption of felodipine (40%)
• digoxin levels may be increased by felodipine
• any drug that inhibits cyt P450 3A4 may increase levels of felodipine
• any drug that induces cyt P450 3A4 may diminish levels of felodipine

• drug interaction(s) of calcium channel blockers with ARBs
• drug interaction(s) of calcium channel blockers with ACE inhibitors
• drug interaction(s) of calcium channel blockers with diuretics
• drug interaction(s) of calcium channel blockers with erythromycin
• drug interaction(s) of calcium channel blockers with clarithromycin
• drug interaction(s) of renin-angiotensin-aldosterone inhibitors with trimethoprim-sulfamethoxazole
• drug interaction(s) of beta-adrenergic receptor antagonists with calcium channel blockers
• drug interaction(s) of NSAIDs & antihypertensives

Mechanism of action

• dihydropyridine Ca+2 channel blocker
• decreases peripheral vascular resistance
• slightly increases heart rate, contractility & AV nodal conduction

More general terms

• dihydropyridine
• calcium channel blocker (CCB)

Additional terms

• cytochrome P450 3A4 (cytochrome P450 C3, nifedipine oxidase, P450-PCN1, NF-25, CYP3A4)

Component of

• enalapril/felodipine (Lexxel)

Database

• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=3333
• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=636806