Cardiac electrophysiologic interactions of bepridil, a new calcium antagonist, with enflurane, halothane, and isoflurane

Bepridil is an investigational calcium antagonist that also has fast sodium channel blocking and antidysrhythmic properties. In the present study, the potential interactions of bepridil with volatile anesthetics on cardiac electrophysiologic parameters were evaluated in open-chest dogs. Twenty-four dogs anesthetized with enflurane (n=6), halothane (n=6), isoflurane (n=6), or chloralose (n=6) received 2.5 mg/kg of bepridil intravenously (IV). Twenty-five additional dogs anesthetized with enflurane (n=7), halothane (n=6), isoflurane (n=6), or chloralose (n=6), received bepridil, 5.0 mg/kg, IV. Dogs anesthetized with cloralose served as controls. Cardiac electrophysiologic parameters were measured after the dogs were anesthetized and were repeated 5, 15, 30, 45, and 60 minutes after bepridil infusion. Plasma bepridil concentrations were also determined at the above time points. Synergy between bepridil and enflurane was demonstrated in the following cardiac electrophysiologic parameters: depression of sinus node function as evidenced by severe depression of sinus node automaticity and conduction; depression of atrioventricular function as evidenced by prolongation of the atrial-His bundle interval and the Wenckebach R-R interval; and, prolongation of the atrial effective refractory period. No synergy was demonstrated between bepridil and halothane or isoflurane when compared to bepridil's effects during chloralose anesthesia. It is concluded that significant synergistic cardiac electrophysiologic effects exist between bepridil and enflurane in dogs. It is recommended that caution be used when anesthetizing patients receiving bepridil with enflurane until human data on the use of this combination of pharmacologic agents is available.

Practical application of guinea pig telemetry system for QT evaluation

The purpose of this study was to evaluate a telemetry system for examining QT evaluation in the conscious free-moving guinea pig using 10 reference compounds whose effects on human QT interval are well established: 8 positive references (bepridil, terfenadine, cisapride, haloperidol, pimozide, quinidine, E-4031 and thioridazine), and 2 negative references (propranolol and nifedipine). Pharmacokinetic experiments were also performed for the 8 positive references. Telemetry transmitters were implanted subcutaneously in male Hartley guinea pigs, and the RR and QT intervals were measured. All 8 positive references prolonged QTc (QTc = k x QT/RR(1/2)) 10% or more during the 60 min observation period. When the values of the QTc changes were plotted against the serum concentrations, the resulting curves exhibited an anticlockwise hysteresis loop for all 8 references. In guinea pigs treated with haloperidol, changes of the T-wave shape from positive to flat were observed. The 2 negative references did not prolong the QTc. These findings suggest that the present telemetry guinea pig model is useful for QT evaluation in the early stages of drug development, because of the small body size of guinea pigs and their action potential configuration, which is similar to that of humans.

Free radical-scavenging properties of olive oil polyphenols

Plants in the Mediterranean basin, such as vine and olive trees, have developed an array of antioxidant defences to protect themselves from environmental stress. Accordingly, the incidence of coronary heart disease and certain cancers is lower in the Mediterranean area, where olive oil is the dietary fat of choice. As opposed to other vegetable oils, extra virgin olive oil, which is obtained by physical pressure from a whole fruit, is rich in phenolic components that are responsible for the particular stability of the oil. We have investigated the scavenging actions of some olive oil phenolics, namely hydroxytyrosol and oleuropein, with respect to superoxide anion generation, neutrophils respiratory burst, and hypochlorous acid. The low EC50S indicate that both compounds are potent scavengers of superoxide radicals and inhibitors of neutrophils respiratory burst: whenever demonstrated in vivo, these properties may partially explain the observed lower incidence of CHD and cancer associated with the Mediterranean diet.

Pharmacokinetics of bepridil and two of its metabolites in patients with end-stage renal disease

The pharmacokinetics of bepridil and 2 of its major metabolites (McN-A-2600 and McN-6303) were studied in 6 patients with end-stage renal disease (ESRD) before and after hemodialysis. Patients underwent dialysis 1 day after a single oral 200-mg dose of bepridil hydrochloride; blood was sampled for up to 7 days. The mean (+/- SD) peak plasma concentration, time of peak concentration, and area under the plasma concentration-time curve (0-168 hours) for each agent were as follows: bepridil, 806 +/- 321 ng/mL, 2.6 +/- 1.6 hours, 4.87 +/- 1.21 micrograms.h/mL; McN-A-2600, 57 +/- 16 ng/mL, 4.2 +/- 2.0 hours, 0.53 +/- 0.29 microgram.h/mL; McN-6303, 284 +/- 120 ng/mL, 4.7 +/- 1.5 hours, 4.06 +/- 1.11 micrograms.h/mL. The bepridil area under the curve corrected for dose was similar to that in healthy volunteers, suggesting that plasma clearance was unaffected by severe renal impairment. None of the compounds were removed by dialysis, and no rebound in plasma concentrations was observed after the end of dialysis. The disposition of bepridil appears to be unchanged in patients with ESRD; and is unaffected by hemodialysis. Thus, no dosage adjustment will be required for ESRD patients and those receiving hemodialysis with cuprophane filters.

Effects of hemodialysis on plasma protein binding of bepridil

The effects of end-stage renal disease (ESRD) and hemodialysis on the in vitro plasma protein binding of bepridil hydrochloride were investigated. The possible influence of bepridil metabolites on bepridil-protein binding in ESRD patients was also examined. Plasma samples were obtained from six patients with ESRD. Bepridil-plasma protein binding was measured by microequilibrium dialysis after addition of freshly prepared bepridil-14C (239 microCi/mg) at a final concentration of 2 micrograms/mL. The percentage of free bepridil in peripheral venous samples drawn on a nondialysis day was lower (i.e., binding was greater) in the patients with ESRD relative to previous observations in healthy subjects (0.15% +/- 0.04% versus 0.31% +/- 0.05% (mean +/- SD). The plasma concentrations of alpha-1-acid glycoprotein (AAG), the principal bepridil binding protein, were also higher in ESRD patients (110 +/- 32 mg/dL) than previously reported in healthy subjects. Although hemodialysis resulted in significant increases in AAG, total protein, and albumin concentrations, no significant difference in bepridil-plasma protein binding was detected between predialysis and postdialysis peripheral venous samples in the presence (0.16 versus 0.18) or absence (0.20 versus 0.17) of bepridil metabolites. The percentage of free bepridil in plasma from both the arterial and venous limbs of the dialyzer during hemodialysis (means of free bepridil ranged from 0.24-0.28%) was higher than in samples drawn from a peripheral vein. This displacement of bepridil from its binding sites as blood passes through the dialyzer may have been owing to the presence of high local concentrations of plasticizers. Confirmation of this hypothesis will require further investigation.

Dose-dependent red blood cell volume increase induced by bepridil

1. Bepiridil, (beta-[(2-methylpropoxy)methyl]-N-phenyl-N-(phenyl-methyl)-1-py rro lidine-ethanamine), a calcium channel blocker, inhibits sickling of red blood cells (RBC) from patients with sickle cell disease (SCD) at micromolar concentrations in vitro. 2. Bepridil induces dose-dependent osmotic swelling of RBC and a concomitant decrease in mean corpuscular hemoglobin concentration (MCHC). 3. Modest decreases in MCHC greatly lengthen the delay time for polymerization of deoxygenated sickle hemoglobin (Hb S) and inhibit RBC sickling. 4. Equilibrium dialysis studies of bepridil and purified hemoglobin showed a low binding affinity (Kb = 10(3)/M). 5. The partition coefficient (Kp) determined for the interaction of RBC and bepridil was 1-3 x 10(3), which is similar to the Kp determined for other amphipathic molecules, such as chlorpromazine.

Evaluation of bepridil efficacy by electrophysiologic testing in patients with recurrent ventricular tachycardia: comparison of two regimens

The purpose of the study was to evaluate this effect of different doses of intravenous and oral bepridil on the induction of ventricular tachycardia. Thirty-eight patients underwent electrophysiologic evaluation for recurrent ventricular tachycardia (VT). Sustained monomorphic VT was induced by programmed ventricular stimulation, using up to three extrastimuli in all patients. The effects of intravenous bepridil (2 mg/kg) were evaluated during the initial study. Intravenous bepridil prevented the induction of sustained VT in eight patients (21%). Electrophysiologic study was repeated after oral bepridil. In six patients the study was stopped because of adverse effects or VT recurrence. Thirty-two patients underwent repeat study 7 days later, taking oral bepridil, 500 mg/day (n = 16) or 900/day (n = 16). A dose of 500 mg/day of bepridil prevented the induction of sustained VT in only one patient. A dose of 900 mg/day of bepridil prevented the induction of sustained VT in eight patients. There were no significant clinical adverse effects, except in one patient receiving intravenous bepridil. The response to intravenous bepridil did not predict the response to oral bepridil. The response to intravenous or oral bepridil was not related to the plasma level of bepridil but was related to a higher left ventricular ejection fraction. Eight patients (21%) in whom VTs were noninducible on oral bepridil were discharged on 300 mg/day of bepridil if their initial loading dose was 500 mg/day or on 600 mg/day if their initial loading dose was 900 mg/day. They remained free of VT during a follow-up of at least 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Bepridil in combination with anthracyclines to reverse anthracycline resistance in cancer patients

The use of calcium antagonists as multidrug resistance reversing agents is limited by acute cardiac toxicity which, for verapamil, becomes prohibitive when concentrations in plasma approach those required in vitro for its action. A new calcium antagonist, bepridil, is as active as verapamil in reversing drug resistance in vitro. In addition, bepridil has some more favourable pharmacological properties compared with verapamil and other calcium antagonists. 14 patients with progressive advanced cancer, resistant to doxorubicin or epirubicin, were treated with the same anthracycline in combination with bepridil. Bepridil was administered in a continuous 36 h infusion at 22 mg/kg/36 h, with a dose scheme which should result in a steady state plasma concentration of approximately 5 mumol/l, able to reverse anthracycline resistance in vitro. Pharmacokinetic studies demonstrated a median bepridil plasma concentration of 5.3 mumol/l (range 2.6-19.3 mumol/l), at the time of administration of the anthracycline. No acute cardiac toxicity was observed and apparently bepiridil did not induce an increase or change in anthracycline toxicity. However, 2 patients developed overt chronic heart failure after treatment discontinuation, which caused 1 patient's death, and a significant reduction in left ventricular ejection fraction was seen in 4 patients. This chronic cardiac toxicity could be related to the total anthracycline dose received. 5 patients attained short lasting minor responses, 3 had stable disease and 6 progressed. Immunohistochemical studies in 7 tumours failed to reveal P-glycoprotein expression. Further trials with escalating doses of bepridil in combination with multiple drug resistance related anticancer agents are warranted.