Antihypertensive effects and pharmacokinetics of felodipine combined with a beta-blocker and a diuretic

Felodipine. A review of the pharmacology and therapeutic use of the extended release formulation in older patients

Felodipine is a dihydropyridine calcium antagonist which may be administered once daily in an extended release (ER) formulation. As monotherapy in older patients with mild to moderate essential hypertension, felodipine ER once daily provides effective control of blood pressure (BP). The drug has also been effective, either as monotherapy or in combination with other antihypertensive medications, in comparisons with other antihypertensive agents, and does not adversely affect lipid profiles or, in patients with diabetes mellitus, glycaemic control. Results in patients with angina pectoris and congestive heart failure indicate a potential role for felodipine ER in these indications and data also suggest the drug reduces left ventricular hypertrophy. In addition, felodipine ER appears suitable for use in patients with concomitant respiratory disease, renal or hepatic dysfunction, cerebrovascular or peripheral ischaemic disease, or gout, making it particularly useful in the elderly who often have more than one significant clinical condition. Felodipine ER has generally been well tolerated by older patients in clinical trials, although further confirmation in the long term is desirable. Thus, felodipine ER effectively lowers BP in older patients with essential hypertension with the added convenience of once daily administration. It may be used as monotherapy or in combination with other antihypertensive agents and is a practical advance in the treatment of hypertension in the elderly.

Felodipine clinical pharmacokinetics

Absorption of felodipine is rapid and complete. A pronounced first-pass metabolism results in a bioavailability of 15%, irrespective of the oral formulation used. The peak plasma concentrations and area under the plasma concentration-time curve are linearly related to the dose. The variability in plasma concentrations is wide, and individualization of the dosage is recommended. Plasma felodipine concentrations are increased in the elderly, and in patients with congestive heart failure or liver cirrhosis; in these patients felodipine should be started at a low dosage. Food intake has no clinically significant effect on felodipine absorption. Serum digoxin concentrations are increased by felodipine in plain tablet form, but not when it is administered as extended release tablets. Activators, inducers and inhibitors of the cytochrome P450 system affect the plasma concentrations of felodipine. No displacement reactions with high affinity protein binding drugs have been observed. There is a significant correlation between plasma concentration and haemodynamic effect. The mean elimination half-life of 24h together with the extended release formulation of felodipine favours once-daily dosage in patients with hypertension.

Felodipine: a new dihydropyridine calcium-channel antagonist

Felodipine, a dihydropyridine calcium-channel antagonist, significantly reduces systolic and diastolic blood pressure (BP) in patients with hypertension and has been associated with beneficial hemodynamic effects in patients with chronic stable angina pectoris or congestive heart failure (CHF). In hypertensive patients, felodipine does not appear to significantly affect glomerular filtration rate, creatinine clearance, glucose tolerance, or plasma lipoprotein concentrations. Studies comparing felodipine with other agents as monotherapy in mild to moderate hypertension have demonstrated felodipine to be at least as efficacious as hydrochlorothiazide (HCTZ) and HCTZ plus amiloride hydrochloride in combination. Comparisons of felodipine with other agents as adjuncts to beta-blocker or diuretic therapy have shown felodipine to be at least as effective as HCTZ, propranolol hydrochloride, prazosin hydrochloride, and nifedipine. Evaluations of patients with chronic stable angina are limited, and additional studies are needed before felodipine can be recommended for the routine management of angina pectoris. Similarly, additional studies are essential to delineate the role of felodipine, if any, in the management of CHF. In the management of hypertension, felodipine 5-40 mg/d significantly reduces systolic and diastolic BP. Although some patients may be controlled throughout the entire dosing interval when felodipine is administered bid, many patients will require more frequent dosing to obtain adequate BP control. Adverse effects associated with felodipine are similar to those of other dihydropyridine calcium-channel antagonists and include peripheral edema, headache, dizziness, flushing, and fatigue. A potentially clinically important drug interaction was observed when felodipine was administered concomitantly with theophylline aminopropanol; significant decreases in theophylline concentrations were noted. In summary, felodipine appears to be safe and effective for the management of hypertension when used alone or in combination with other antihypertensive agents. The efficacy of felodipine in the management of chronic stable angina pectoris and CHF requires further investigation.

Acute haemodynamic effects of felodipine, verapamil and hydralazine in the anaesthetized dog

Felodipine, a potent dihydropyridine calcium antagonist with a pronounced vascular selectivity, was given intravenously (0.006-0.025 mumol kg-1) to anaesthetized, open-chest dogs with denervated hearts. The result was a dose-dependent decrease in mean arterial pressure (MAP) and total peripheral resistance (TPR), while heart rate (HR), stroke volume (SV) and left ventricular end-diastolic pressure remained relatively unchanged. Cardiac tension work (TTI) and oxygen consumption (MVO2) were reduced, probably due to the decrease in afterload. The relative reduction of the coronary vascular resistance (CVR) was greater than that of TPR. The hypotensive effect of verapamil (0.05-0.20 mumol kg-1) was small and MAP decreased mainly via a decrease in HR and SV. Higher doses of verapamil which induced vasodilatation could not be given without the development of complete atrio-ventricular dissociation. Hydralazine (11-45 mumol kg-1) decreased TPR and CVR in parallel but the decrease in MAP was partly counteracted by a powerful increase in HR, SV and cardiac inotropy which was associated with elevated catecholamine levels in plasma. When MAP and HR were maintained constant by means of aortic balloon inflation and atrial pacing, felodipine markedly increased coronary blood flow and coronary sinus oxygen saturation while SV, TTI, inotropy and MVO2 remained relatively unchanged. It is concluded that felodipine markedly dilates peripheral resistance vessels, and in particular those in the coronary vascular bed, without any cardiodepressant effects.

Felodipine ER formulation in the treatment of mild hypertension: efficacy and tolerability vs placebo

1. Felodipine is a new calcium-antagonist dihydropyridine derivative with a high degree of selectivity for smooth muscle of arteriolar resistance vessels, as opposed to cardiac cells. 2. In this double-blind, cross-over study the antihypertensive efficacy and tolerability of the new extended release (ER) formulation of felodipine 10 mg, once daily, in patients with mild essential hypertension was evaluated. After a 4-week single-blind placebo period 28 patients (15 males; mean age 48 +/- 12 years) were randomized to receive felodipine 10 mg ER once daily or placebo for 4 weeks and the alternative treatment for a further 4 weeks. Supine blood pressure and heart rate were measured in the out-patients department every 2 weeks, 22-24 h after the last drug administration. 3. Felodipine 10 mg ER induced a significant reduction in blood pressure in comparison with placebo (from 149 +/- 16/97 +/- 6 to 140 +/- 12/89 +/- 6 mm Hg). Heart rate remained unchanged. Seven patients dropped-out; five during felodipine ER administration and two during placebo. 4. A once daily dose of felodipine ER significantly reduces blood pressure in mild hypertensive patients 22-24 h after administration. It is well tolerated and the adverse events are related to its pharmacodynamic effects.

Plasma concentration profiles and antihypertensive effect of conventional and extended-release felodipine tablets

1. The rate and extent of felodipine absorption from an oral solution, conventional and extended-release tablets were investigated in two groups of healthy volunteers (n = 18 + 15). 2. The antihypertensive effect of felodipine conventional tablets twice daily (n = 71) and extended-release tablets once daily (n = 76) were compared in a parallel-group study in hypertensive patients. 3. As from a solution, felodipine was completely absorbed from the two solid dosage forms. The rate of absorption increased in the order extended-release tablets, conventional tablets, solution. 4. The extended-release tablet gave more sustained plasma concentrations than the conventional tablet. 5. The extended-release tablet given once daily gave similar blood pressure control to the conventional tablet given twice daily.

Acute effects of felodipine in exertional angina pectoris

To investigate the antianginal efficacy, duration of action and tolerability of 2 doses of the new calcium antagonist felodipine, 15 patients (14 men and 1 woman, mean age 62 years) with stable exertional angina pectoris and angiographically demonstrated coronary artery disease were randomly given felodipine, 5 and 10 mg, and placebo on 3 different days. A bicycle ergometer exercise test was performed 3 and 10 hours after dosing. In comparison with placebo, felodipine 5 and 10 mg significantly increased resting heart rate and decreased resting systolic and diastolic blood pressure 3 hours after administration (p less than 0.001). Ten hours after administration, only supine systolic blood pressure was still significantly lower (p less than 0.001). Anginal (time to mild chest pain) and ischemic (time to 1 mm ST depression) thresholds, as well as duration of exercise and total work at peak exercise, were higher in comparison with placebo at 3 and 10 hours (p less than 0.001). In comparison with the lower dose, 10 mg felodipine induced a decrease in supine (p less than 0.05) and sitting (p less than 0.01) systolic blood pressure at rest and an increase in total work to anginal threshold (p less than 0.01), as well as in total work and duration of exercise at peak exercise (p less than 0.05). These results suggest that a single administration of felodipine, 5 and 10 mg, may improve exercise capacity over a 10-hour period in patients with stable exercise-induced angina due to atherosclerotic heart disease.

Clinical pharmacokinetics of felodipine. A summary

Felodipine is completely absorbed from the gastrointestinal tract. However, the amount reaching the systemic circulation is reduced to about 15% because of first-pass degradation. The bioavailability is constant within the dose interval of 5 to 40mg orally. The frequency histogram of the area under the plasma concentration-time curve (AUC) seems to be normally distributed. The disposition of felodipine is independent of the administered dose over the intravenous dose interval (1-3 mg). The plasma concentration-time curve declines in 3 distinct phases. The mean elimination half-life of felodipine is approximately 25h. Felodipine is extensively distributed to extravascular tissues. The volume of distribution of felodipine is about 10 L/kg, implying that less than 1% of the amount of drug in the body is localised in the blood. Felodipine is more than 99% bound to plasma proteins. Mean total clearance from the blood is 1 to 1.5 L/min and, therefore, felodipine is considered a high clearance drug. Felodipine is metabolised completely and no unchanged drug is eliminated in the urine. The first step in the metabolism involves oxidation to the corresponding pyridine derivative by the cytochrome P-450 system. Identified metabolites in plasma and urine are devoid of vasodilating activity. Long term treatment, and the presence of hypertension and impaired renal function do not affect the disposition of felodipine. Elderly people may have higher plasma levels than the young and middle-aged. Impaired liver function significantly decreases systemic clearance. Cimetidine and food affect felodipine kinetics, but with negligible clinical implications. Therapeutic concentrations of felodipine do not interact with highly protein-bound drugs and these drugs have no effect on the binding of felodipine to human plasma proteins in vitro. Plasma levels of digoxin and metoprolol tended to increase during felodipine treatment. There is a significant correlation between plasma concentrations of felodipine and haemodynamic effects in both healthy subjects and hypertensive patients during short term as well as during long term treatment.