Felodipine is a vascular selective calcium antagonist, which lowers arterial blood pressure by decreasing peripheral vascular residence. Due to the high degree of selectivity for smooth muscle in the arterioles, felodipine in therapeutic doses has no direct effect on cardiac contractility or conduction.
It can be used as monotherapy or in combination with other antihypertensive drugs, e.g. β-receptor blockers, diuretics or ACE-inhibitors, in order to achieve an increased antihypertensive effect. Felodipine reduces both systolic and diastolic blood pressure and can be used in isolated systolic hypertension. In a study of 12 patients, felodipine maintained its antihypertensive effect during concomitant therapy with indomethacin.
Because there is no effect on venous smooth muscle or adrenergic vasomotor control, felodipine is not associated with orthostatic hypotension.
Felodipine has anti-anginal and anti-ischaemic effects due to improved myocardial oxygen supply/ demand balance. Coronary vascular resistance is decreased and coronary blood flow as well as myocardial oxygen supply are increased by felodipine due to dilation of both epicardial arteries and arterioles. Felodipine effectively counteracts coronary vasospasm. The reduction in systemic blood pressure caused by felodipine leads to decreased left ventricular afterload.
Felodipine improves exercise tolerance and reduces anginal attacks in patients with stable effort induced angina pectoris. Both symptomatic and silent myocardial ischaemia are reduced by felodipine in patients with vasospastic angina. Felodipine can be used as monotherapy or in combination with β-receptor blockers in patients with stable angina pectoris.
Felodipine possesses a mild natriuretic/diuretic effect and generalised fluid retention does not occur.
In a randomised, double-blind, 3-week, parallel group study in children aged 6-16 years with primary hypertension, the antihypertensive effects of once daily felodipine 2.5 mg (n=33), 5 mg (n=33) and 10 mg (n=31) were compared with placebo (n=35). The study failed to demonstrate the efficacy of felodipine in lowering blood pressure in children aged 6-16 years.
The long-term effects of felodipine on growth, puberty and general development have not been studied. The long-term efficacy of felodipine as therapy in childhood to reduce cardiovascular morbidity and mortality in adulthood has also not been established.
Felodipine is well tolerated in patients with concomitant disease such as congestive heart failure well controlled on appropriate therapy, asthma and other obstructive pulmonary diseases, diabetes, gout, hyperlipidemia impaired renal function, renal transplant recipients and Raynaud's disease. Felodipine has no significant effect on bland glucose levels or lipid profiles.
Haemodynamic effects: The primary haemodynamic effect of felodipine is a reduction of total peripheral vascular resistance which leads to a decrease in blood pressure. These effects are dose- dependent. In patients with mild to moderate essential hypertension, a reduction in blood pressure usually occurs 2 hours after the first oral dose and lasts for at least 24 hours with a trough/peak ratio usually above 50%.
Plasma concentration of felodipine and decrease in total peripheral resistance and blood pressure are positively correlated.
Electrophysiological and other cardiac effects: Felodipine in therapeutic doses has no effect on cardiac contractility or atrioventricular conduction or refractoriness.
Renal effects: Felodipine has a natriuretic and diuretic effect. Studies have shown that the tubular reabsorption of filtered sodium is reduced. This counteracts the salt and water retention observed for other vasodilators. Felodipine does not affect the daily potassium excretion. The renal vascular resistance is decreased by felodipine. Normal glomerular filtration rate is unchanged. In patients with impaired renal function glomerular filtration rate may increase.
Felodipine is well tolerated in renal transplant recipients.
Site and mechanism of action: The predominant pharmacodynamic feature of felodipine is its pronounced vascular versus myocardial selectivity. Myogenically active smooth muscles in arterial resistance vessels are particularly sensitive to felodipine.
Felodipine inhibits electrical and contractile activity of vascular smooth muscle cells via an effect on the calcium channels in the cell membrane.