Different effects of exercise on plasma concentrations of nebivolol, bisoprolol and carvedilol

BACKGROUND

In-vitro studies have shown that beta-blockers are taken up into and released from adrenergic cells together with epinephrine and norepinephrine. Consequently, studies in humans revealed an increase in plasma concentrations of propranolol and atenolol, whereas those of carvedilol were not affected by physical exercise. However, nebivolol and bisoprolol never were investigated on this issue.

METHODS

Ten healthy males received oral doses of 5 mg nebivolol, 5 mg bisoprolol, and 50 mg carvedilol daily for one week in a cross-over fashion. Exercise was performed at 3 hours following oral intake of the respective last drugs on the eighth day. Blood samples were taken at rest, during the last minute of exercise, and after 15 min of recovery.

RESULTS

At rest and during exercise, heart rates were as follows: Nebivolol, 57 +/- 7 and 137 +/- 11 beats/min; bisoprolol, 55 +/- 5 and 139 +/- 14 beats/min; carvedilol, 56 +/- 5 and 135 +/- 13 beats/min, with no significant differences between the drugs. Plasma concentrations were as follows: Nebivolol-rest 0.273 +/- 0.029 ng/ml, exercise 0.274 +/- 0.035 ng/ml, recovery 0.272 +/- 0.035 ng/ml (n.s.). Bisoprolol-rest 4.99 +/- 2.73 ng/ml, exercise 6.49 +/- 5.58 ng/ml, recovery 4.90 +/- 3.06 ng/ml ( p < 0.01). Carvedilol-rest 10.3 +/- 9.3 ng/ml, exercise 9.7 +/- 8.2 ng/ml, recovery 6.5 +/- 5.6 ng/ml ( p < 0.05).

DISCUSSION

Plasma concentrations of bisoprolol increased during exercise and returned to baseline during recovery, a behaviour which would have been predicted according to present knowledge. However, exercise had no effect on plasma concentrations of nebivolol and carvedilol, a finding that is in contrast to previous results with other beta-blockers such as propranolol and atenolol. We conclude that both nebivolol and carvedilol are not taken up into and released from adrenergic nerves during exercise, a feature that clearly distinguishes these drugs from other beta-blockers so far investigated.

Differences in the pharmacokinetics of peroxisome proliferator-activated receptor agonists in genetically obese Zucker and sprague-dawley rats: implications of decreased glucuronidation in obese Zucker rats

Genetically obese Zucker rats exhibit symptoms similar to those of obese patients with insulin-resistance or Type II diabetes; therefore, they have been used as a genetic model to study obesity, as well as a pharmacological model for the discovery of new drugs for the treatment of Type II diabetes and hyperlipidemia. In the present study, we compared the pharmacokinetics of two novel peroxisome proliferator-activated receptor (PPAR) agonists, MRL-I [(2R)-7-[3-[2-chloro-4-(4-fluorophenoxy)phenoxy]propoxy]-2-ethyl-3,4-dihydro-2H-benzopyran-2-carboxylic acid] and MRL-II [(2R)-7-[3-[2-chloro-4-(2,2,2-trifluoroethoxy)phenoxy]propoxy]-3,4-dihydro-2-methyl-2H-benzopyran-2-carboxylic acid], in obese Zucker and lean Sprague-Dawley rats following a single intravenous administration. The plasma clearance of both MRL-I and MRL-II was significantly lower in obese Zucker rats (4- and 2-fold, respectively) compared with Sprague-Dawley rats, but without any significant change in the volume of distribution, which resulted in a dramatic increase in the half-life (7- and 3-fold, respectively). The reversible in vitro plasma protein binding of [(14)C]MRL-I and [(14)C]MRL-II was comparable in the two strains, approximately 96% bound. The expression levels of uridine diphosphate-glucuronosyltransferases 1A1, 1A6, 2B1, and CYP2C11 and 3A1 mRNA in liver were lower (30-50%) in Zucker compared with Sprague-Dawley rats, as were the liver glutathione S-transferases (70%), quinone reductase (30%), organic anion-transporting protein 2 (80%), and multidrug resistance-associated protein 2 (Mrp2) (50%) mRNA levels. However, Mrp3 mRNA levels were similar in both strains. Consistent with these observations, the intrinsic clearance (CL(int)), calculated from the V(max)/K(m) of glucuronidation of [(14)C]MRL-I and [(14)C]MRL-II in liver microsomes, was approximately 2-fold lower in obese Zucker rats; the K(m) values were comparable in the two strains for both compounds. In conclusion, differences in the pharmacokinetics of two novel PPAR agonists, both cleared, predominantly, by conjugation, were evident in genetically obese Zucker rats compared with Sprague-Dawley rats. These differences were consistent with changes in the mRNA levels of hepatic drug-metabolizing enzymes and transporters. This information should be considered when comparing pharmacokinetic and efficacious doses in the obese Zucker rats, used as a pharmacological model, with those in Sprague-Dawley rats, which are used widely for drug metabolism and toxicology studies.

Simultaneous determination of the novel neuroprotective agent KR-31378 and its metabolite KR-31612 using high performance liquid chromatography with tandem mass spectrometry in human plasma

An LC/MS/MS method for the simultaneous determination of a neuroprotective agent for ischemia-reperfusion damage, KR-31378 and its N-acetyl metabolite KR-31612 in human plasma was developed. KR-31378, KR-31612 and the internal standard, KR-31543 were extracted from human plasma by liquid-liquid extraction. A reverse-phase HPLC separation was performed on Luna phenylhexyl column with the mixture of acetonitrile-5 mM ammonium formate (55:45, v/v) as mobile phase. The detection of analytes was performed using an electrospray ionization tandem mass spectrometry in the multiple reaction monitoring mode. The lower limits of quantification for KR-31378 and KR-31612 were 2.0 ng/ml. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.

Direct absorption of acylated anthocyanin in purple-fleshed sweet potato into rats

Absorption of acylated anthocyanins in purple-fleshed sweet potato (Ipomoea batatas cv. Ayamurasaki) in rats was studied to obtain evidence that the acylated anthocyanins themselves could exert a physiological function in vivo. Peonidin 3-caffeoylsophoroside-5-glucoside (Pn 3-Caf*sop-5-glc) in purple-fleshed sweet potato was directly absorbed into rat and present as an intact acylated form in plasma. After oral administration of the purple-fleshed sweet potato anthocyanin (PSA) concentrate containing 38.9 micromol of Pn 3-Caf*sop-5-glc/kg of body weight, Pn 3-Caf*sop-5-glc was detected in the plasma, and the C(max) value and t(max) were estimated as 50.0 +/- 6.8 nmol/Lof plasma and 30 min, respectively. Furthermore, the plasma antioxidant capacity was significantly elevated from 58.0 +/- 12.0 to 89.2 +/- 6.8 micromol of Trolox equivalent/L of plasma 30 min after the administration of the PSA concentrate.

Integrated effects of the vasodilating beta-blocker nebivolol on exercise performance, energy metabolism, cardiovascular and neurohormonal parameters in physically active patients with arterial hypertension

OBJECTIVE

The present study was designed to investigate the integrated effects of the beta-1-selective blocker with vasodilator properties, nebivolol, on systemic haemodynamics, neurohormones and energy metabolism as well as oxygen uptake and exercise performance in physically active patients with moderate essential hypertension (EH).

DESIGN AND METHODS

Eighteen physically active patients with moderate EH were included: age: 46.9 +/- 2.38 years, weight: 83.9 +/- 2.81 kg, blood pressure (BP): 155.8 +/- 3.90/102.5 +/- 1.86 mm Hg, heart rate: 73.6 +/- 2.98 min(-1). After a 14-day wash-out period a bicycle spiroergometry until exhaustion (WHO) was performed followed by a 45-min submaximal exercise test on the 2.5 mmol/l lactate-level 48 h later. Before, during and directly after exercise testing blood samples were taken. An identical protocol was repeated after a 6-week treatment period with 5 mg nebivolol/day.

RESULTS

Nebivolol treatment resulted in a significant (P < 0.01) decrease in systolic and diastolic BP and heart rate at rest and during maximal and submaximal exercise. Maximal physical work performance, blood lactate and rel. oxygen uptake (rel. VO(2)) before and after nebivolol treatment at rest and during maximal and submaximal exercise remained unaltered. Free fatty acid, free glycerol, plasma catecholamines, beta-endorphines and atrial natriuretic peptide (ANP) increased before and after treatment during maximal and submaximal exercise but remained unaltered by nebivolol treatment. In contrast, plasma ANP levels at rest were significantly higher in the presence of nebivolol, endothelin-1 levels were unchanged.

CONCLUSIONS

Nebivolol was effective in the control of BP at rest and during exercise in patients with EH. Furthermore, nebivolol did not negatively affect lipid and carbohydrate metabolism and substrate flow. The explanation for the effects on ANP at rest remain elusive. This pharmacodynamic profile of nebivolol is potentially suitable in physically active patients with EH.

Repetitive cortical spreading depression in a gyrencephalic feline brain: inhibition by the novel benzoylamino-benzopyran SB-220453

Transient cortical depolarization is implicated in the pathology of migraine. SB-220453 is a potent anti-convulsant which inhibits neurogenic inflammation and cortical spreading depression (SD)-evoked nitric oxide release via a novel but unknown mechanism. This study further investigates the effects of SB-220453 on generation and propagation of repetitive SD in the anaesthetized cat. Vehicle or SB-220453 1, 3 or 10 mg/kg was administered intraperitoneally 90 min prior to induction of SD in the suprasylvian gyrus (SG). Changes in d.c. potential were recorded in the SG and the adjacent marginal gyrus (MG). In vehicle-treated animals (n = 7), a brief exposure (6 min) to KCl induced a median (25-75% range) number of five (four to six) and three (two to four) depolarizations over a duration of 55 min (32-59 min) and 51 min (34-58 min) in the SG and MG, respectively. SB-220453 produced dose-related inhibition of the number of events and period of repetitive SD activity. SB-220453 also reduced SD-induced repetitive pial vasodilatation but had no effect on resting haemodynamics. However, when SD events were observed in the presence of SB-220453, it had no effect on metabolic coupling. These results show that SB-220453 produces marked inhibition of repetitive SD in the anaesthetized cat. SB-220453 may therefore have therapeutic potential in treatment of SD-like activity in migraine.

Trace-level quantitation of iralukast in human plasma by microbore liquid chromatography/tandem mass spectrometry

Iralukast (CGP 45715A) is a potent peptido-leukotriene antagonist that is active in various in vitro and animal models for the treatment of asthma. An analytical challenge was to develop a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method with a lower limit of quantitation (LLOQ) of 10 pg/mL for the analysis of iralukast when administered at low doses during clinical trials. Several issues had to be addressed in order to devise a LC/MS/MS assay for the above compound. First, iralukast appeared to be light sensitive and unstable at room temperature under acidic conditions. Second, a LLOQ of 10 pg/mL was needed to support several clinical trials. Third, positive electrospray ionization of iralukast did not yield the necessary sensitivity required for studies in humans. Consequently, LC/MS/MS conditions were optimized for the negative ion mode of detection. Fourth, sample preparation steps proved to be critical to reduce the possibility of microbore HPLC column (50 mm x 1.0 mm i.d.) obstruction, chromatographic deterioration, and matrix-mediated electrospray ion suppression. While our validated method addressed the above challenges, its major drawback was limited sample throughput capability. Nonetheless, plasma concentration-time profiles for patients with moderate asthma after oral administration of 200, 500, 1000, and 5000 microgram/kg/day of iralukast were successfully obtained.

[Acute beta 1-selective beta-receptor blocker nebivolol poisoning in attempted suicide]

HISTORY AND ADMISSION FINDINGS

A 17-year-old girl had swallowed 80-100 tablets of Nebivolol, 5 mg each, with suicidal intent. She was referred to hospital 8 hours later by an emergency duty physician. On admission she was sweaty and pale, but there were no other obvious abnormalities. Neurological examination revealed decreased responsiveness and slowed movements. She was known to have type 1 diabetes mellitus.

INVESTIGATIONS

Blood pressure was 105/55 mmHg, the ECG showed sinus bradycardia of 55 beats/min. Biochemical tests revealed hypoglycaemia (2.1 mmol/l), hypokalaemia (3.4 mmol/l) and respiratory failure (pO2 6.16 kPa, O2 saturation 82%, pCO2 6.55 kPA). Heart and lung were unremarkable on physical examination as were chest radiogram and echocardiogram. Plasma level of nebivolol was 480 ng/ml on admission (therapeutic range 88-195 ng/ml).

TREATMENT AND COURSE

After gastric lavage and administration of charcoal and sodium sulphate a temporary pacemaker was connected and glucagon infused intravenously as an antidote. The cardiovascular state stabilized with falling plasma level of nebivolol. Glucose was administered initially, but transient intravenous insulin infusion became necessary to counteract hyperglycaemia. The patient was transferred from the intensive care unit in a stable cardiovascular state after 2 days.

CONCLUSION

This case demonstrates that swallowing 400-500 mg nebivolol, resulting in a plasma level of 480 ng/ml, need not be fatal. But the outcome in this patient should not be taken as necessarily applying to similar cases. It depends on the individual patient's metabolic state whether higher plasma levels might be reached with the same amount of ingested nebivolol.

Liquid chromatographic determination of a non-steroidal oral contraceptive CDRI-85/287 in rat serum

A precise and sensitive high performance liquid chromatographic (HPLC) assay method was developed and validated for the quantitation of 2-[4-(2-piperidinoethoxy) phenyl]-3-phenyl-(2H)-1-benzo(b)pyran (compound CDRI-85/287) in rat serum. This method, applicable to 0.5 ml volumes of serum, was validated according to GLP guidelines. It involved double extraction of serum samples with a mixture of hexane and iso-propanol (98:2 v/v) at alkaline pH and the use of UV detection at 332 nm. Linearity, precision and accuracy were acceptable (5-200 ng ml-1. The absolute recovery was more than 75% and the lower limit of quantitation was 5 ng ml-1. Freeze-thaw stability studies up to four cycles showed no apparent differences in the calculated spiked concentrations. However, in-process stability evaluation showed the stability of the processed samples lasted up to 85 h.

Pharmacokinetics and pharmacodynamics of the leukotriene B4 receptor antagonist CP-105,696 in man following single oral administration

AIMS

CP-105,696, (+)-1-(3S,4R)-[3-(4-phenylbenzyl)-4-hydroxy-chroman-7-yl] cyclopropane carboxylic acid is a potent, novel LTB4 receptor antagonist advanced to clinical trials to determine its efficacy in inflammatory diseases. The pharmacokinetics and pharmacodynamics of CP-105,696 were investigated in healthy male volunteers following oral administration of single doses of 5 to 640 mg.

METHODS

Forty-eight subjects participated in a randomized, double-blind, parallel group study. Plasma and urine concentrations of CP-105,696 were determined at intervals after drug administration. As an indication of LTB4 receptor antagonism following oral administration of CP-105,696, the inhibiton of LTB4-induced upregulation of the neutrophil cell surface complement receptor (CR3), CD11b/CD18, was monitored at 4 h following drug administration using an ex vivo whole blood flow cytometry assay.

RESULTS

Cmax and AUC(0, infinity) increased in a dose-related manner. Respective mean Cmax values were 0.54 to 30.41 microg ml(-1) following doses of 5 to 640 mg. Respective mean AUC(0, infinity) values were 1337 to 16819 microg ml(-1) h for the 40 to 640 mg dose groups. Plasma concentrations declined in a monoexponential manner, with terminal elimination half-lives ranging from 289 to 495 h. Group mean terminal elimination half-lives were dose-independent. Urinary excretion of unchanged drug accounted for < 1% of the administered dose. A linear relationship was observed between CP-105,696 plasma concentrations and inhibition of LTB4-mediated CD11b upregulation on human neutrophils in whole blood. CP-105,696 plasma concentrations of 5-6 microg ml(-1) were necessary to elicit a two-fold shift to the right of the LTB4 concentration response curve for CD11b upregulation.

CONCLUSIONS

These studies demonstrate pharmacologically significant LTB4-receptor antagonism following a single dose of CP-105,696 and pharmacokinetics consistent with once-daily dosing.

Combined effects of dehydroepiandrosterone and EM-800 on bone mass, serum lipids, and the development of dimethylbenz(A)anthracene-induced mammary carcinoma in the rat

Although treatment with dehydroepiandrosterone (DHEA) and the antiestrogen EM-800 alone decreased dimethylbenz(A)anthracene (DMBA)-induced mammary tumor incidence from 95% to 57% and 38%, respectively, approximately 9 months after DMBA administration, only two tumors developed in the group of animals that received the combination of DHEA and EM-800, and these two tumors disappeared before the end of the experiment (P < 0.01 vs. DHEA or EM-800 alone). Average tumor number per tumor-bearing animal as well as average tumor area per tumor-bearing animal were further decreased in animals that received the combination therapy compared with the effect of each treatment alone (P < 0.01). DHEA induced 6.9% (P < 0.01), 10.6% (P < 0.05), and 8.2% (P < 0.01) increases in bone mineral density of total skeleton, lumbar spine, and femur, respectively. The addition of EM-800 to DHEA did not affect the enhancing effect of DHEA on bone mass. The combination of the two drugs had important inhibitory effects on the urinary excretion of calcium and phosphorus as well as on the urinary hydroxyproline/creatinine ratio. Serum total alkaline phosphatase was stimulated by DHEA. Treatment with EM-800 decreased both serum triglyceride and cholesterol levels, whereas DHEA had an inhibitory effect on serum triglycerides. Although treatment with EM-800 caused a marked atrophy of the mammary gland, DHEA alone reduced lobular hyperplasia seen in aged intact rats while causing an androgen-specific stimulation of the same structures in animals already receiving the antiestrogen EM-800. The combination of DHEA and EM-800 lowered ovarian weight by 24% (P < 0.01) and decreased serum estradiol concentrations to intact control levels, whereas each compound alone had no effect on ovarian weight and stimulated serum estradiol levels by 45% (P < 0.05) and 46% (P < 0.05), respectively. Treatment with EM-800 caused a marked inhibition of uterine and vaginal weight. The present data show the additive inhibitory effects of DHEA and EM-800 on the development of DMBA-induced mammary carcinoma in the rat, thus suggesting the potential benefits of such a combination for the prevention of breast cancer in women while preserving or even increasing bone mass and maintaining a favorable lipid profile.

Simultaneous determination of a potassium channel opener and its metabolite in rat plasma with column-switching liquid chromatography using atmospheric pressure chemical ionisation

A specific LC-MS assay was developed for simultaneous determination of Ro 31-7837 (I) and its metabolite Ro 31-6930 (II) in rat plasma, using on-line SPE by column-switching reversed-phase HPLC combined with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry for detection in the selected reaction monitoring mode. The method involved precipitation of plasma proteins with ethanol and automatic injection of a 1-ml aliquot of the supernatant onto a standard bore trapping column (LC-ABZ, 20x4.6 mm) for compound retention. Using the backflush mode, the analytes were transferred onto the analytical column (Kromasil C18, 125x4.0 mm) for chromatographic separation and mass spectrometric detection. The mean precision and accuracy for I and II in the concentration range 0.25-100 ng/ml were found to be 3.7% and 101%, and 3.5% and 106%, respectively. The data were assessed from QC samples during the validation phase of the assay. The lower limit of quantification for both I and II was 0.25 ng/ml, using a 0.5-ml plasma aliquot. This LC-MS method provided the requisite specificity, sensitivity, accuracy and precision to assess the pharmacokinetics of the compounds in the rat.

A pharmacokinetic and pharmacodynamic interaction study between nebivolol and the H2-receptor antagonists cimetidine and ranitidine

AIMS

The study was designed to investigate the effects of the H2-receptor antagonists, cimetidine and ranitidine on the pharmacokinetics and pharmacodynamics of nebivolol in healthy volunteers.

METHODS

Twelve healthy volunteers took part in a randomized placebo-controlled cross-over study. Each subject received on three separate occasions placebo, cimetidine (400 mg twice daily) or ranitidine (150 mg twice daily) for 24 h before and 48 h after a single oral dose of nebivolol (5 mg). Nebivolol and its individual (+) and (-) enantiomers were determined tby h.p.l.c.

RESULTS

Ranitidine had no significant effect on nebivolol pharmacokinetics. Cimetidine, however, resulted in a 21-23% increase in Cmax of unchanged nebivolol and of each enantiomer plus its hydroxylated metabolites. Cimetidine significantly (p < 0.05) increased the AUC [mean +/- s.d. (95% C.I. of differences in mean)] for unchanged (+/-)-nebivolol [7.76 +/- 3.07 ng ml-1 h with placebo; 11.50 +/- 5.40 (1.75, 8.76) ng ml-1 h with cimetidine], (+)-nebivolol plus its hydroxylated metabolites [73.0 +/- 18.0 ng ml-1 h with placebo; 91.5 +/- 25.7 (1.0, 23.1) ng ml-1 h with cimetidine] and (-)-nebivolol plus its hydroxylated metabolites [101 +/- 32 ng ml-1 h with placebo; 123 +/- 38 (3.3, 27.0) ng ml-1 h with cimetidine]. Statistical analysis of the resting blood pressure and heart rate and exercise data did not suggest any consistent effects of ranitidine or cimetidine upon the pharmacodynamic effects of nebivolol.

CONCLUSIONS

There was no interaction between ranitidine and nebivolol. Although cimetidine inhibited nebivolol metabolism, it did not have a significant influence on the pharmacodynamics of the drug.

Gastrointestinal physiology-regulated dogs for bioavailability evaluation of an oral controlled-release dosage form composed of pulsatile release granules

Gastrointestinal (GI) physiology-regulated beagle dogs (regulated dogs) were regulated by a combined treatment using intramuscular pentagastrin and intravenous atropine sulfate. In the regulated dogs, the gastric pH was shifted to around 2, and the GI transit time was prolonged to approximate that in humans. Pranoprofen, an acidic anti-inflammatory agent, was granulated around sucrose seeds, and then coated with low substituted hydroxypropyl cellulose used as a swelling agent to afford plain granules (A-granule). Then, A-granule was coated stepwise with ethyl cellulose used as an outer shell material to afford two kinds of pulsatile release granules (B- and C-granules). In the dissolution study using pH 1.2 and 6.8 media, A-, B- and C-granules exhibited lag times of 0, 1 and 2h, respectively. Even in intact beagle dogs, the absorption profiles for A- and B-granules corresponded with those expected from the dissolution profiles. In contrast, the bioavailability of C-granule was only 35% in the intact dogs, but was 55% in the regulated dogs. Thus, the absorption of pranoprofen from pulsatile release granules after a longer lag time should be influenced by the location in the GI tract. Next, a controlled-release (CR) dosage form of pranoprofen was tentatively prepared by combining A-, B- and C-granules at the ratio of 3:4:3 (w/w in contents of pranoprofen). The bioavailability of the CR dosage form was significantly diminished in the intact dogs, being about 70% as much as that in the regulated dogs. Therefore, the regulated dogs would be superior to the intact dogs in avoiding the underestimation of the bioavailability of a CR dosage form with a pulsatile release property.

BMS-180448, a novel glyburide-reversible cardioprotective agent, enhances postischemic recovery of contractile function in dogs

BMS-180448 has been found to retain the cardioprotective potency of its chemically related analog, cromakalim, although having significantly less peripheral vasodilating activity. The effect of the ATP-sensitive potassium channel opener, BMS-180448, on postischemic recovery of function (segmental shortening) was determined in open chested, anesthetized dogs instrumented with ultrasonic crystals. The plasma concentration of the effective and ineffective doses of BMS-180448 was compared to concentrations used in isolated rat hearts. BMS-180448 was given as a total dose of 4.2, 1.4 or 0.5 mg/kg over 30 min, starting 15 min before ischemia. Ischemia was initiated by a complete occlusion of the left anterior descending coronary artery for 15 min. Reperfusion was maintained for 3 hr and segmental shortening was measured. During ischemia, systolic bulging was observed in the ischemic region in drug- and vehicle-treated groups. Upon reperfusion, some contractile functional recovery was observed in vehicle-treated controls within minutes, but quickly decreased so that slight bulging was observed up to 3 hr into reperfusion. High dose BMS-180448 significantly improved the recovery of contractile function such that, by 3 hr after reperfusion, segmental shortening had recovered to 60% of base line. The 1.4-mg/kg dose also significantly improved reperfusion function, but 0.5 mg/kg of BMS-180448 was without effect. None of the doses of BMS-180448 significantly affected peripheral hemodynamic status or collateral blood flow. The plasma concentration of the 1.4-mg/kg dose was approximately 3 microM during ischemia. In isolated rat hearts, BMS-180448 significantly increased postischemic function at 3 microM and higher concentrations, which agrees with the dog data. BMS-180448 was protective in a dose-dependent manner in a canine model of stunned myocardium, and the concentrations necessary for protection are similar to that for rats.

The development and cross-validation of methods based on radioimmunoassay and LC/MS-MS for the quantification of the class III antiarrhythmic agent, MK-0499, in human plasma and urine

An analytical method based on radioimmunoassay (RIA) has been developed for the determination of the antiarrhythmic agent, MK-0499, in plasma and urine. Owing to the potency of the drug, the specificity of this assay in human plasma could not be adequately determined using conventional RIA procedures. A highly specific procedure, based on LC/MS-MS, was developed to cross-validate the RIA. The lower quantifiable limits of the RIA and LC/MS-MS-based methods were 0.05 and 0.013 ng ml-1, respectively. Cross-validation data, compared using paired student's t-test regression analysis, showed excellent correlation between methods. The mass spectrometric assay was also used to simultaneously measure plasma concentrations of unlabeled and 14C-labeled MK-0499 following administration of the drug at high specific activity to volunteers.

Stereospecific high-performance liquid chromatographic determination of an S(-)-benzopyran methyl ester derivative (CGP 50 068), its (-)-carboxylic acid metabolite (CGP 55 461) and the related (+)-enantiomer (CGP 54 228) in human and dog plasma

The simultaneous determination of CGP 50 068, S(-)-enantiomer (I), its (-)-carboxylic acid metabolite CGP 55 461 (II) and the related (+)-enantiomer CGP 54 228 (III) by stereospecific high-performance liquid chromatography, in human plasma, is described. The three compounds and racemic acebutolol, used as internal standard, were isolated from plasma by liquid-solid extraction on disposable C18 columns. The resolution and determination of I and the two carboxylic acid enantiomers were achieved by direct chromatography using a Chiral-AGP column refrigerated at 5 degrees C. The mobile phase was tetrabutylammonium iodide in a pH 7 phosphate buffer solution used at a constant flow-rate of 0.5 ml/min. The UV detection wavelength was set at 270 nm. The reproducibility and accuracy of the method were found to be suitable over the concentration range 0.56-28.0 mumol/l for II and III and 2.0-26.7 mumol/l for I.

High-performance liquid chromatographic measurement of the novel anti-HIV agent 7,8-dihydrocostatolide (NSC 661123)

An HPLC assay was used to determine levels of a promising anti-HIV agent 7,8-dihydrocostatolide (DC; NSC 661123) in human and murine plasma. The structurally related compound costatolide (C) was found to be a suitable internal standard. Drug was extracted from human or murine plasma using a solid-phase C18 cartridge. The compound was eluted from an ODS analytical HPLC column using an acetonitrile-water mobile phase. Drug was quantified over the assay range of 19.5 to 625 ng/ml with excellent within- and between-day reproducibility. Data resulting from the use of the assay method for determination of dihydrocostatolide pharmacokinetics in mice are presented. This is the first report of a validated HPLC assay for determining DC levels in human and mouse plasma.

Pharmacokinetic behaviour in polymorphonuclear leucocytes of N,N-dimethylcarbamoylmethyl alpha,2-dimethyl-5H-[1]benzopyrano[2,3-b]- pyridine-7-acetate (Y-23023), a new prodrug type of anti-inflammatory agent, and indomethacin after oral administrations in rats

N,N-Dimethylcarbamoylmethyl alpha,2-dimethyl-5H-[1]- benzopyrano[2,3-b]pyridine-7-acetate (Y-23023) is a prodrug developed as a new non-steroidal anti-inflammatory drug (NSAID). Y-23023 is rapidly hydrolysed to an active metabolite, alpha,2-dimethyl-5H-[1]benzopyrano[2,3-b]pyridine-7-acetic acid (M1) following its absorption and then exhibits a strong anti-inflammatory activity. We have examined the pharmacokinetic behaviour in polymorphonuclear leucocytes (PMNs) of M1 and of indomethacin after oral administration to rats of Y-23023 and indomethacin, respectively. Y-23023 was rapidly absorbed, producing a mean Cmax (1.13 micrograms mL-1) of M1 after 1 h in plasma. Indomethacin was less rapidly absorbed, producing a mean Cmax (3.38 micrograms mL-1) after 3 h in plasma. The mean AUC of M1 and indomethacin in plasma were 5.45 micrograms h mL-1 and 22.49 micrograms h mL-1, respectively. The mean tmax, Cmax and AUC of M1 in PMNs were 1 h, 11.1 ng (41 pmol)/10(8) cells and 58.6 ng (164 pmol) h/10(8) cells, respectively. The same parameters for indomethacin in the PMNs were 3 h, 15.4 ng (57 pmol)/10(8) cells and 95.2 ng (266 pmol) h/10(8) cells, respectively. The PMNs/plasma ratio of M1 was about 2.8 times that of indomethacin. These results indicate that the association of M1, an active metabolite of Y-23023, from blood to the PMNs is greater than that of indomethacin.

Reduction in myocardial infarct size by the new potassium channel opener bimakalim

We examined the effect of a new potassium channel opener, bimakalim, on myocardial infarct size (IS) in dogs. Barbital-anesthetized dogs were subjected to 90 min of left circumflex coronary artery (LCX) occlusion followed by 5-h reperfusion. Bimakalim (3 micrograms/kg bolus followed by 0.1 microgram/kg/min intravenously, i.v.) was initiated either 15 min before LCX occlusion and continued throughout the experiments in one group of animals or initiated 5 min before and throughout reperfusion in a second group. A third group of dogs received i.v. vehicle (control) 15 minutes before LCX occlusion and throughout the remainder of the experiment. IS was determined by triphenyltetrazolium histochemical staining, regional myocardial blood flow (RMBF) by the radioactive microsphere technique, and neutrophil migration by measurement of tissue myeloperoxidase (MPO) activity. Bimakalim reduced mean aortic blood pressure (MBP, 25 mm Hg) during the occlusion and reperfusion periods in the group of dogs that received the drug throughout the experiment and reduced in BP, during reperfusion when administered immediately before the reperfusion period. In addition, bimakalim increased LCX coronary artery blood flow (CBF) and increased regional myocardial blood flow (RMBF) primarily during reperfusion in both drug-treated groups, with the greatest increase to the subepicardial region. During occlusion, however, bimakalim had no effect on collateral blood flow to the ischemic region. In all three groups, left ventricular (LV) mass, area at risk (AAR) mass, and percentage of he left ventricle at risk were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of the anti-ischemic activity of nebivolol in comparison with atenolol

The anti-ischemic effect of 5 mg nebivolol o.i.d., a newly developed beta 1-selective adrenoceptor blocking drug with vasodilating properties, was compared with that of atenolol (100 mg o.i.d.) following a treatment period of 6 days. The study was performed in 24 patients with documented coronary artery disease and stable angina pectoris according to a double-blind randomized study, designed using conventional symptom-limited exercise testing. Exercise testing 3 h after the first dose showed a more marked ST-segment reduction by atenolol than by nebivolol (59% vs. 18%). ST-segment depression measured 24 h after administration of the penultimate dose was statistically significantly reduced by nebivolol (from 0.19 +/- 0.07 to 0.13 +/- 0.07 mV; P = 0.0059) but not by atenolol (from 0.17 +/- 0.06 to 0.14 +/- 0.10 mV; P = 0.0703). Approximately 3 h after the last dose, the reduction was comparable (45% and 38% by nebivolol and atenolol, respectively). Exercise duration, exercise time necessary to produce ST-segment depression by 0.1 mV and exercise time to the onset of angina were also prolonged following administration of both drugs. Thus, at steady-state single daily doses of 100 mg atenolol and 5 mg nebivolol were about equieffective when measured at time of maximal effect (i.e. 3 h after drug administration). However, duration of action with respect to the ST-segment depression seems to be slightly longer for nebivolol.

Stereoselective disposition of pranoprofen, a nonsteroidal antiinflammatory drug, in rabbits

The stereoselective disposition of pranoprofen, a nonsteroidal antiinflammatory drug, was studied in rabbits. Plasma levels of S(+)-pranoprofen after oral and i.v. administration of the racemate pranoprofen were always higher than those of the R(-)-isomer. The elimination rate constant of the R(-)-isomer (2.74 h-1), calculated using a 2-compartment model, was significantly larger than that of the S(+)-isomer (2.14 h-1), while no significant difference was observed in the absorption rate constants between enantiomers. Pranoprofen was excreted in the urine exclusively in the form of pranoprofen glucuronide. The glucuronide of R(-)-isomer was excreted more rapidly than the S(+)-isomer. However, no metabolite of pranoprofen was detected in plasma, owing to its instability in liver and plasma. Moreover, the elimination of the S(+)- and R(-)-isomers of pranoprofen was more rapid when the enantiomers were separately administered than when administered as the racemate. The R(-)-isomer showed a significantly higher elimination rate than the S(+)-isomer, compared to what was observed upon the administration of the racemate. No inversion to an R(-)-form or S(+)-form to their corresponding antipode after administration of the isomers separately was detected. Pranoprofen, especially the R(-)-isomer, was significantly distributed in the kidney. An in vitro metabolism experiment of pranoprofen showed the predominant glucuronidation to be in the kidney rather than in the liver because of rapid hydrolysis of glucuronide in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of interaction of pranoprofen with human serum albumin: binding properties of enantiomers and metabolite

The interaction of pranoprofen, pranoprofen glucuronide and pranoprofen methylester with human serum albumin (HSA), was investigated by equilibrium dialysis and spectroscopic techniques. The binding affinities of pranoprofen glucuronide and pranoprofen methylester to HSA were found to be almost the same, although they were remarkably small as compared to that of the parent compound, pranoprofen. Pranoprofen and pranoprofen methylester showed stereoselective affinities to HSA. It was found from the competitive displacement experiments using the fluorescent probes that the specific binding site for pranoprofen was site II, the diazepam site, and that the binding sites of pranoprofen glucuronide and pranoprofen methylester were site I, the warfarin site. In addition, from the binding data with modified HSA, it seemed that tyrosine-411 was specifically involved in the pranoprofen binding. The absorption spectral changes which accompanied the binding of pranoprofen and pranoprofen methylester to HSA or detergents implied that the HSA binding site of pranoprofen consisted of a cationic site on the surface of the albumin molecule with a hydrophobic region to accommodate the aromatic ring and that the binding site for pranoprofen methylester seemed to occupy a wide hydrophobic area. These limited data indicated differences in the location and microenvironments of binding sites for pranoprofen and its glucuronide on the HSA molecule.

Quantitative determination of CGS 18102A, a new anxiolytic, in human plasma using capillary gas chromatography/mass spectrometry

CGS 18102A is a novel hexahydrobenzopyranopyridine that has a mixed pharmacological profile of 5-HT-1A agonist and 5-HT-2 antagonist properties. Based upon these mechanisms, the compound is predicted to have anxiolytic efficacy with possible efficacy in depression. Preclinical studies in the rat have shown the drug to be well absorbed and extensively metabolized. Because of the anticipated low plasma levels in humans a gas chromatography/mass spectrometry (GC/MS) analytical method has been developed and validated to determine plasma concentrations of CGS 18102A in early clinical studies. The method utilizes CGS 18416A as the internal standard. Samples (1 mL) were extracted with pentane:ethyl acetate (75:25, v:v). Extracts were then concentrated and analysed directly by GC/MS. Separation was accomplished on a methylsilicone capillary column (30 m x 0.32 mm i.d.). GC/MS was carried out under positive ion ammonia CI conditions, with selected ion monitoring of the [M + H]+ ions (m/z = 262 and 248) for CGS 18102A and CGS 18416A, respectively. The method was successively applied to the analysis of clinical samples from an ascending multidose safety and tolerability study conducted in six normal healthy male volunteers.

Disposition of the enantiomers of cromakalim in rat and cynomolgus monkey

1. Disposition of the 3R,4S(+) and 3S,4R(-) enantiomers of the racemic antihypertensive drug cromakalim has been studied in rats and cynomolgus monkeys using the 14C-drug labelled in either the 3R,4S(+) or the 3S,4R(-) enantiomer. 2. After oral administration to rat, blood concentrations of the 3R,4S(+) enantiomer were up to fourfold higher than those of the 3S,4R(-) enantiomer. Metabolism of the former was not as extensive as that of the latter and consequently plasma and urinary radiometabolite patterns were quantitatively different. 3. In contrast to rat, there were much greater differences in the disposition of the two enantiomers following oral administration of cromakalim to the cynomolgus monkey. Plasma concentrations of the 3R,4S(+) enantiomer were approximately 100 x those of the 3S,4R(-) enantiomer and the rate of urinary 14C elimination for the 3R,4S(+) enantiomer was much faster than that for the 3S,4R(-) enantiomer. Plasma and urinary radiometabolite patterns were very different for the two isomers. Metabolic end products of the 3R,4S(+) enantiomer were predominantly phase I metabolites whereas the 3S,4R(-) enantiomer was almost entirely metabolized by glucuronidation. 4. A study of the racemic drug alone would have led to a misunderstanding of the fate of the compound in these species.