Usage
- Felodipine is prescribed for the management of hypertension (high blood pressure) and chronic stable angina pectoris (chest pain).
- Pharmacological Classification: Dihydropyridine Calcium Channel Blocker.
- Mechanism of Action: Felodipine inhibits the influx of calcium ions into vascular smooth muscle cells and cardiac muscle cells. This leads to vasodilation (widening of blood vessels), reducing peripheral vascular resistance and blood pressure. In angina, it improves coronary blood flow, reducing oxygen demand and relieving chest pain.
Alternate Names
- International Nonproprietary Name (INN): Felodipine
- Brand Names: Plendil, Plendil ER, Felodipine ER, Renedil, Vascalpha among others (brand names vary by region).
How It Works
- Pharmacodynamics: Felodipine primarily affects vascular smooth muscle, causing vasodilation and lowering blood pressure. It has minimal negative inotropic effects (weakening of the heart’s contractions) compared to other calcium channel blockers.
- Pharmacokinetics:
- Absorption: Almost completely absorbed after oral administration, but bioavailability is around 15-20% due to extensive first-pass metabolism in the liver. High-fat meals can increase absorption.
- Distribution: Highly protein-bound (99%) with a large volume of distribution.
- Metabolism: Extensively metabolized in the liver, primarily by CYP3A4 enzymes, into inactive metabolites.
- Elimination: Primarily excreted in urine (70% as metabolites) and bile (10% of the administered dose). Less than 0.5% is excreted unchanged in the urine. The elimination half-life is around 25 hours.
- Mode of Action: Felodipine selectively blocks L-type calcium channels in vascular smooth muscle and cardiac muscle. This prevents calcium influx, leading to relaxation of the muscle cells and vasodilation.
- Receptor Binding: Binds to the alpha-1 subunit of L-type calcium channels.
- Elimination Pathways: Predominantly hepatic metabolism via CYP3A4 followed by renal excretion of metabolites.
Dosage
Standard Dosage
Adults:
- Hypertension: Initial: 5 mg orally once daily. Maintenance: 2.5 to 10 mg orally once daily. Dose adjustments should be made at intervals of at least 2 weeks. Maximum dose is usually 20 mg/day.
- Angina: Initial: 5 mg orally once daily. May increase to 10 mg once daily if necessary.
- Administration: Extended-release tablets should be swallowed whole and not crushed or chewed. Can be taken with or without food, or with a light meal.
Children:
- Felodipine is not FDA-approved for use in children. Off-label use is not generally recommended due to limited safety and efficacy data, though some guidelines suggest a starting dose of 2.5 mg for children over 6 years with hypertension, not to exceed 10mg per day.
Special Cases:
- Elderly Patients: Start with a lower dose (2.5 mg once daily) and titrate cautiously due to increased plasma concentrations. Maximum dose is usually 10 mg daily.
- Patients with Renal Impairment: No dosage adjustment is typically required.
- Patients with Hepatic Dysfunction: Start with 2.5 mg once daily and titrate cautiously. Contraindicated in severe hepatic impairment.
- Patients with Comorbid Conditions: Monitor patients with heart failure closely. Use with caution in patients with other conditions affecting blood pressure.
Clinical Use Cases
- Felodipine is not typically used in acute clinical settings like intubation, surgical procedures, mechanical ventilation, ICU, or emergencies. It’s intended for chronic management of hypertension and angina. Short-acting intravenous medications are generally preferred in these settings.
Dosage Adjustments
- Dose adjustments should be based on individual patient response and blood pressure control. Close monitoring is necessary, especially in elderly and hepatically impaired patients.
Side Effects
Common Side Effects:
- Headache, flushing, dizziness, peripheral edema (swelling in ankles and feet), palpitations (rapid heart rate).
Rare but Serious Side Effects:
- Exacerbation of angina, allergic reactions, hypotension (low blood pressure).
Long-Term Effects:
- Gingival hyperplasia (gum overgrowth).
Adverse Drug Reactions (ADR):
- Angioedema, Stevens-Johnson syndrome (rare but serious skin reaction).
Contraindications
- Hypersensitivity to felodipine, cardiogenic shock, severe aortic stenosis, unstable angina, acute myocardial infarction, decompensated heart failure, pregnancy.
Drug Interactions
- CYP3A4 Inhibitors (e.g., erythromycin, ketoconazole, grapefruit juice): Can increase felodipine levels.
- CYP3A4 Inducers (e.g., rifampin, phenytoin): Can decrease felodipine levels.
- Other Antihypertensives: Additive hypotensive effects.
- Alcohol: Can enhance hypotensive effects.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Contraindicated during pregnancy due to potential fetal harm.
- Breastfeeding: Excreted in breast milk. Not recommended during breastfeeding.
Drug Profile Summary
- Mechanism of Action: Calcium channel blocker, inhibiting calcium influx into vascular smooth muscle.
- Side Effects: Headache, flushing, dizziness, peripheral edema, palpitations.
- Contraindications: Hypersensitivity, cardiogenic shock, severe aortic stenosis, unstable angina, acute MI, decompensated heart failure, pregnancy.
- Drug Interactions: CYP3A4 inhibitors/inducers, other antihypertensives, alcohol.
- Pregnancy & Breastfeeding: Contraindicated.
- Dosage: Adults: 2.5-10 mg once daily. Elderly: Start 2.5 mg. Hepatic impairment: Start 2.5 mg.
- Monitoring Parameters: Blood pressure, heart rate, signs of peripheral edema, liver function tests (if indicated).
Popular Combinations
- Other Antihypertensives (e.g., beta-blockers, ACE inhibitors, diuretics): To achieve better blood pressure control when felodipine alone is insufficient.
Precautions
- Monitor blood pressure closely, especially during dosage adjustments. Good dental hygiene is important to prevent gingival hyperplasia. Caution in patients with hepatic impairment or heart failure.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Felodipine?
A: Adults: Initial 5 mg once daily, maintenance 2.5-10 mg once daily (maximum usually 20mg). Elderly: Start 2.5 mg. Hepatic impairment: Start 2.5 mg. Not recommended for children.
Q2: How does Felodipine differ from other calcium channel blockers?
A: Felodipine is a dihydropyridine calcium channel blocker with more vascular selectivity and less negative inotropic effect compared to non-dihydropyridines like verapamil or diltiazem.
Q3: What are the most common side effects?
A: Headache, flushing, dizziness, peripheral edema, and palpitations.
Q4: Can Felodipine be used in pregnancy?
A: No, Felodipine is contraindicated in pregnancy due to potential harm to the fetus.
Q5: What are the significant drug interactions?
A: CYP3A4 inhibitors (e.g., erythromycin, ketoconazole, grapefruit juice) can increase felodipine levels. CYP3A4 inducers (e.g., rifampin, phenytoin) can decrease felodipine levels. Other antihypertensives can have additive effects.
Q6: How should Felodipine be administered?
A: Extended-release tablets should be swallowed whole once daily, usually in the morning, with or without food. Do not crush or chew.
Q7: What should be monitored in patients taking Felodipine?
A: Monitor blood pressure, heart rate, signs of peripheral edema or heart failure exacerbation. Periodic liver function tests might be warranted.
Q8: Can Felodipine be used in patients with renal impairment?
A: Generally, no dosage adjustment is needed for patients with renal impairment.
Q9: What are the contraindications for Felodipine?
A: Cardiogenic shock, severe aortic stenosis, unstable angina, acute myocardial infarction, decompensated heart failure, hypersensitivity to felodipine, and pregnancy.
Q10: What is the role of Felodipine in managing angina?
A: Felodipine improves coronary blood flow by dilating coronary arteries and reducing vasospasm. This increases oxygen supply to the heart muscle, alleviating angina symptoms.
