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Sunday, July 27, 2025

Felodipine


Felodipine is a long-acting, dihydropyridine calcium channel blocker (CCB) primarily used for the treatment of hypertension and angina pectoris. It works by relaxing vascular smooth muscle, leading to arterial vasodilation, reduced peripheral resistance, and consequently lowered blood pressure. Unlike non-dihydropyridine calcium channel blockers (e.g., verapamil, diltiazem), felodipine has minimal effect on cardiac conduction and contractility, making it more suitable in patients with bradycardia or heart failure with preserved ejection fraction (HFpEF).

Felodipine is marketed under several brand names, including Plendil, and is typically available in extended-release (ER) tablets, taken once daily.

Pharmacological Classification

  • Therapeutic class: Antihypertensive, Antianginal

  • Pharmacological class: Dihydropyridine calcium channel blocker

  • ATC Code: C08CA02

  • Legal status: Prescription-only medicine

  • Pregnancy category (UK/US): C – Risk cannot be ruled out

Mechanism of Action

Felodipine selectively inhibits the influx of calcium ions (Ca²⁺) across the L-type calcium channels in vascular smooth muscle. This leads to:

  • Arteriolar vasodilation (peripheral and coronary vessels)

  • Reduction in systemic vascular resistance (afterload)

  • Lowered blood pressure

  • Mild reflex tachycardia due to baroreceptor stimulation

It has negligible inotropic or chronotropic effects, thus preserving myocardial function. Felodipine is highly vascular selective and does not significantly affect AV node conduction or myocardial contractility.

Indications

Approved Uses

  • Essential hypertension (mild to moderate)

  • Stable angina pectoris

Off-label Uses

  • Raynaud’s phenomenon (occasionally)

  • Hypertensive urgency (as an oral agent) – less common due to delayed onset

  • Isolated systolic hypertension in elderly patients

Dosage and Administration

Adults

  • Initial dose: 5 mg once daily (extended-release)

  • Maintenance dose: 2.5–10 mg once daily

  • Maximum dose: 10 mg/day

  • Elderly or hepatic impairment: Start with 2.5 mg/day

Children

  • Not routinely recommended; safety and efficacy in pediatric use have not been established.

Administration advice

  • Take at the same time daily, with or without food

  • Do not crush or chew extended-release tablets

  • Avoid grapefruit juice due to CYP3A4 inhibition

Pharmacokinetics

  • Bioavailability: ~15% (first-pass metabolism)

  • Onset of action: 2–5 hours

  • Peak plasma concentration: ~2.5–5 hours (extended-release formulation)

  • Protein binding: >99%

  • Metabolism: Hepatic via CYP3A4 (produces inactive metabolites)

  • Elimination half-life: 11–16 hours

  • Excretion: Primarily renal (~70%) as metabolites, minor fecal

Contraindications

  • Hypersensitivity to felodipine or other dihydropyridine derivatives

  • Unstable angina or acute myocardial infarction

  • Cardiogenic shock

  • Severe aortic stenosis (may reduce coronary perfusion)

  • Pregnancy (use caution, particularly in first trimester)

  • Severe hepatic impairment (increased exposure due to reduced metabolism)

Precautions and Warnings

  • Hepatic impairment: Dose adjustment required due to reduced metabolism

  • Heart failure: Use with caution; although dihydropyridines may be tolerated in HFpEF, avoid in HFrEF unless indicated

  • Peripheral edema: Common due to precapillary vasodilation

  • Hypotension and reflex tachycardia may occur, particularly with rapid dose escalation

  • Gingival hyperplasia: Rare but documented with long-term use

  • Avoid abrupt discontinuation – may lead to rebound hypertension or angina

Adverse Effects

Very Common (>10%)

  • Peripheral edema (ankles and feet)

Common (1–10%)

  • Headache

  • Dizziness

  • Flushing

  • Palpitations

  • Fatigue

  • Nausea

  • Tachycardia (due to baroreceptor reflex)

Uncommon (0.1–1%)

  • Hypotension

  • Skin rash

  • Myalgia or arthralgia

  • Gingival enlargement

  • Increased frequency of micturition

Rare (<0.1%)

  • Elevated liver enzymes

  • Photosensitivity

  • Allergic reactions (urticaria, pruritus)

  • Gynecomastia (very rare)

Drug Interactions

Enzyme Interactions (CYP3A4)

Inhibitors (↑ felodipine levels and toxicity risk)

  • Grapefruit juice (↑ AUC by ~2–3x) – avoid

  • Ketoconazole, itraconazole

  • Macrolide antibiotics (erythromycin, clarithromycin)

  • Protease inhibitors

  • Cimetidine

Inducers (↓ felodipine levels and efficacy)

  • Phenytoin

  • Carbamazepine

  • Rifampicin

  • Barbiturates

  • St. John’s Wort

Other Interactions

  • Beta-blockers: May increase hypotensive effects; combination used cautiously

  • Other antihypertensives: Additive BP-lowering effect

  • NSAIDs: May reduce antihypertensive efficacy

  • Tacrolimus: Felodipine may raise levels of tacrolimus due to shared CYP3A4 metabolism

Monitoring Parameters

  • Blood pressure: Regular monitoring essential

  • Heart rate: Check for reflex tachycardia

  • Signs of edema: Particularly in lower limbs

  • Liver function tests: In case of long-term use or suspected hepatic dysfunction

  • Gingival condition: Dental exams for long-term users

Use in Pregnancy and Lactation

Pregnancy

  • Not recommended, especially in the first trimester

  • Animal studies show adverse fetal effects

  • Use only if clearly necessary and benefit outweighs risk

Lactation

  • Unknown if felodipine is excreted in human milk

  • Use caution if administering to breastfeeding mothers

Use in Special Populations

Elderly

  • Start with lower dose (2.5 mg/day)

  • More prone to hypotension and peripheral edema

Renal Impairment

  • No dose adjustment required; felodipine is hepatically cleared

Hepatic Impairment

  • Dose reduction required; increased bioavailability due to impaired first-pass metabolism

Comparison with Other Dihydropyridines

Felodipine vs. Amlodipine:

  • Felodipine is shorter-acting unless in ER form; amlodipine has a longer half-life (~30–50 h)

  • Felodipine has lower incidence of reflex tachycardia than nifedipine but higher than amlodipine

  • Felodipine may have less fluid retention than older dihydropyridines like nifedipine

  • Both are effective for monotherapy or combination therapy with ACE inhibitors or ARBs

Patient Counseling Points

  • Take medication at the same time each day

  • Do not crush or chew extended-release tablets

  • Avoid grapefruit juice

  • Monitor for swollen ankles, headaches, flushing

  • Sit or stand up slowly to minimize dizziness

  • Inform dentist about felodipine use due to potential gingival overgrowth

  • Do not stop abruptly without consulting a healthcare provider

Brand Names

  • Plendil® (extended-release)

  • Felodur®

  • Modip®

  • Generic felodipine ER tablets available globally




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