What it's for (Indications)
- Felodipine is indicated for the management of hypertension, either as monotherapy or in combination with other antihypertensive agents.
- Its primary action is to lower elevated blood pressure, thereby reducing the risk of cardiovascular events.
- It is also approved for the management of chronic stable angina pectorus, where it helps to reduce the frequency and severity of angina attacks by improving myocardial oxygen supply and reducing demand.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | For hypertension, the usual initial dose of felodipine extended-release tablets is 2.5 mg once daily. The dosage should be individualized and adjusted according to the patient's blood pressure response and tolerance, typically in increments of 2.5 mg at intervals of no less than two weeks, up to a maximum recommended dose of 10 mg once daily. For chronic stable angina, the usual initial dose is 5 mg once daily, with the possibility of increasing to a maximum of 10 mg once daily if needed. Doses should be taken without food or with a light meal; high-fat meals should be avoided as they can increase felodipine absorption. Tablets must be swallowed whole and should not be crushed, divided, or chewed to maintain their extended-release properties. |
Safety & Warnings
Common Side Effects
- Common adverse reactions associated with felodipine are generally dose-related and reflect its vasodilatory properties.
- These frequently include peripheral edema (swelling of the ankles and feet), headache, flushing (warmth, redness, or tingling under the skin), and dizziness.
- Palpitations and fatigue are also commonly reported.
- Less common, but documented, side effects can involve gastrointestinal disturbances such as nausea or abdominal pain, paresthesia, and gingival hyperplasia (gum enlargement), which may require careful oral hygiene.
- Severe or persistent adverse effects should prompt consultation with a healthcare professional for evaluation and potential dose adjustment or discontinuation.
Serious Warnings
- Black Box Warning: Felodipine does not carry a specific FDA-mandated Black Box Warning. However, healthcare providers and patients should be aware of several serious warnings and precautions associated with its use. In patients, particularly those with severe obstructive coronary artery disease, there is a potential for paradoxical exacerbation of angina pectoris or, in rare instances, the precipitation of acute myocardial infarction, especially upon initiation of therapy or during rapid dosage escalation. Significant symptomatic hypotension can occur, predominantly in volume-depleted individuals or those receiving concomitant antihypertensive medications, necessitating careful and regular monitoring of blood pressure. As felodipine is extensively metabolized in the liver, patients with severe hepatic impairment require substantial dose reduction and meticulous monitoring due to the risk of greatly increased plasma concentrations and exaggerated pharmacological effects. Furthermore, serious drug-drug interactions are possible; potent inhibitors of the CYP3A4 enzyme system (e.g., ketoconazole, itraconazole, clarithromycin, protease inhibitors) can significantly increase felodipine plasma levels, leading to enhanced hypotensive and vasodilatory effects. Conversely, strong CYP3A4 inducers (e.g., rifampin, phenytoin, carbamazepine) can reduce felodipine efficacy. Patients must be counselled to avoid consuming grapefruit or grapefruit juice, as it is a potent CYP3A4 inhibitor and can substantially elevate felodipine exposure.
- Healthcare professionals should exercise caution when prescribing felodipine to patients susceptible to hypotension, as excessive blood pressure reduction can occur, particularly in volume-depleted individuals or those concurrently receiving other antihypertensive medications.
- While peripheral edema is a common, often benign, and dose-dependent side effect, severe or rapidly progressing edema warrants clinical investigation to rule out underlying cardiac or renal issues.
- Patients with impaired renal function generally do not require dose adjustment, but careful monitoring is advised.
- In patients with severe hepatic impairment, significant dose reduction is necessary, and close monitoring for exaggerated effects is crucial due to decreased drug clearance.
- Concomitant use with medications known to affect the CYP3A4 enzyme system, either as inhibitors or inducers, requires careful consideration and potential dose modifications.
- Patients should be explicitly advised to avoid grapefruit juice, which inhibits CYP3A4 and can significantly increase felodipine plasma concentrations, thereby enhancing the risk of adverse effects.
How it Works (Mechanism of Action)
Felodipine is a dihydropyridine calcium channel blocker (CCB) that selectively inhibits the transmembrane influx of calcium ions into vascular smooth muscle cells, with a lesser effect on myocardial cells. This inhibition leads to a relaxation of arterial smooth muscle, resulting in potent systemic arterial vasodilation and a significant reduction in peripheral vascular resistance. This decrease in peripheral resistance directly contributes to a reduction in blood pressure. In the context of angina pectoris, felodipine's vasodilatory effects decrease cardiac afterload, thereby reducing myocardial oxygen demand. It may also improve myocardial oxygen supply by dilating coronary arteries, leading to relief of angina symptoms.