Electrophysiological effects of felodipine

Electrophysiologic effects of the calcium antagonist isradipine, a double-blind placebo-controlled study

The electrophysiologic effects of the calcium channel antagonist isradipine in comparison to placebo were evaluated in a double-blind study with 9 patients in each group. The two patient groups were not different with respect to their cardiac disease, baseline electrophysiologic parameters, or blood pressure. Isradipine significantly decreased the systolic (P less than 0.01) and diastolic (P less than 0.05) blood pressure, whereas sinus cycle length was significantly (P less than 0.05) decreased in the placebo group and the isradipine group with no difference between the groups. The influence of isradipine and placebo on sinus node recovery time, effective refractory period of the atrioventricular node, intranodal conduction time (AH interval) and PR interval were not significant. In conclusion, isradipine significantly decreased systolic and diastolic blood pressure. The decrease in sinus cycle length after intravenous isradipine was not significantly different from the decrease seen in the placebo group. Atrioventricular conduction was not significantly affected.

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.

Twenty-four hour profile of the hypotensive action of felodipine in essential hypertension

Felodipine, 10 mg twice daily, and placebo were administered for 5 weeks to ten untreated essential hypertensives in a double-blind, random-order, crossover study. At the end of each phase patients were assessed by 36 hours of continuous intraarterial blood pressure recordings, both during normal activities and specified activities. Patients were also assessed by 36-hour Holter analysis, maximal exercise testing, radionuclide cardiac scan, and measurement of endogenous creatinine clearance and 2-hourly vasoactive hormones. Arterial pressure was significantly reduced by felodipine, with mean falls in blood pressure of 25.1 mmHg and 12.5 mmHg (systolic and diastolic, respectively) over 24 hours. Blood pressure was reduced by felodipine during moderate and maximal exercise and mental stress. There were no significant changes in heart rate, exercise capacity, ventricular ectopy, endogenous creatinine clearance, or vasoactive hormones.

Felodipine, pharmacodynamics and pharmacokinetics in the isolated rabbit heart

Myocardial pharmacodynamics of the Ca2+-antagonist felodipine, a structural analogue of nifedipine, were studied in isolated, spontaneously beating and retrogradely perfused rabbit hearts. The concentration of felodipine in the Krebs-Henseleit perfusion liquid was stepwise increased from 0.7 ng/ml to 90.4 ng/ml (1.8 to 235.3 nmol/l). Increasing felodipine concentrations from 0.7 to 3.6 ng/ml produced an increase of up to 115% in coronary flow rate, which then decreased at higher concentrations to 84% of the control value. Oxygen consumption decreased progressively to 28% at concentrations from 3.6 to 90.4 ng/ml. Myocardial contractility measured by amplitude and rate of contraction decreased progressively to 45.7 and 41.5%, respectively, at concentrations from 0.7 to 9.4 ng/ml and further to 4.0 and 3.0%, respectively, at 90.4 ng/ml. Myocardial efficiency expressed as the percentual ratio of contraction amplitude times frequency to oxygen consumption decreased to 11% at the highest concentration of felodipine. Heart beat frequency decreased simultaneously to 45.6%. The electrocardiographic PQ and QRS intervals increased at the highest concentration to 174 and 111%, respectively, whereas the QT interval decreased to 86.6%. Asystolia occurred in several cases at felodipine concentrations of 90.4 ng/ml. Both myocardial accumulation and disposition pharmacokinetics of the drug showed one-compartment characteristics with half-lives of about 97 min. for both processes. Apparent Vd was about 480 ml/g myocardial tissue, which expresses a very pronounced binding and accumulation of felodipine in the rabbit myocardium in vitro. The findings demonstrate that lower concentrations of felodipine produces coronary vasodilation in the isolated rabbit heart accompanied by a marked negative inotropic effect and a less than proportional reduction in oxygen consumption. The drug seemed to cause direct cardiotoxic effects at higher concentrations.

Acute haemodynamic effects of felodipine in congestive heart failure

The haemodynamic effects of felodipine 0.1 mg/kg p.o., a new arteriolar dilator, were studied in 7 patients with severe congestive heart failure of NYHA Class IV (Group A) and in 3 patients in Class II-III (Group B). In Group A, measurements were made before and 1 and 4 h after felodipine administration. There was a substantial fall in systemic arterial pressure, which was not associated with a compensatory tachycardia. In fact, there was a fall in heart rate from 92 to 82 beats/min 1 h after drug administration. The pulmonary capillary wedge pressure was reduced from 22 to 14 mm Hg and the cardiac index and stroke volume index rose significantly. Consequently, there was a marked reduction in systemic vascular resistance. In Group B measurements were performed at rest and during exercise before and 1 h after felodipine. The pulmonary wedge capillary pressure during exercise was lower than in the control situation. Coronary sinus flow was increased and there was a pronounced fall in coronary vascular resistance. The results would suggest that felodipine, by virtue of its ventricular unloading potency, might be a valuable drug in the treatment of congestive heart failure.

Felodipine in hypertension

Felodipine, a selective arteriolar dilator, was given to 13 hypertensive patients to assess its hypotensive effects and duration of action. Nine patients were treated with 5 mg three times a day and 4 with 10 mg three times a day. Mean blood pressures fell with both treatment regimens: 5 mg placebo 170/103 mmHg; 5 mg felodipine 148/91 mmHg; 10 mg placebo 154/93 mmHg; 10 mg felodipine 137/82 mmHg. Heart rates increased as blood pressures fell with both treatments. However, in the patients given 5 mg three times a day this effect was less noticeable after successive doses. Plasma concentrations of noradrenaline, both resting and tilted, increased after felodipine. There was a negative correlation between the fall in blood pressure and the increase in noradrenaline, suggesting that those patients with good baroreceptor reflexes were better able to counteract the effects of vasodilatation. Four of the nine patients treated with 5 mg felodipine three times a day experienced mild and transient adverse effects. Of the four patients treated with 10 mg three times a day, three experienced moderate to severe headache, and for this reason recruitment into this group was stopped. Felodipine at a divided daily dose of 15 mg effectively lowered blood pressure.