Pilot study of the uricosuric effect of DuP-753, a new angiotensin II receptor antagonist, in healthy subjects

The uricosuric effect of DuP-753, a novel, specific angiotensin II receptor antagonist, has been explored in a healthy male Japanese volunteers, given single oral doses of 25, 50, 100 or 200 mg (n = 6), or 100 mg (n = 6) or placebo (n = 3) once daily for 7 consecutive days. In the single-dose study, serum uric acid measured at 4 h after dosing showed a dose dependent decrease; the reductions from the corresponding pre-dose values were: 0.32 (25 mg), 0.77 (50 mg), 1.25 (100 mg) and 1.33 mg.dl-1 (200 mg). The urinary excretion of uric acid within the first 4 h after treatment was also increased in a dose-dependent manner, whereas the urinary excretion of creatinine remained unchanged. In the multiple-dose study, DuP-753 significantly decreased the serum uric acid concentration measured 4 h both after the first (pre-dose value: 5.68 vs 4 h after: 4.48 mg.dl-1) and last administrations (4.42 mg.dl-1). Simultaneously, the ratio of urinary uric acid to creatinine excretion was significantly increased within the first 4 h both after the first (DuP-753: 1.190 vs placebo: 0.576) and last administrations (1.02 vs 0.576). The findings suggest that DuP-753 possesses a uricosuric effect both after single and multiple doses in healthy subjects. The effect should be further examined in hypertensive patients.

The pharmacokinetics of the beta 2-adrenoceptor agonist, tulobuterol, given transdermally and by inhalation

We have studied the pharmacokinetics of tulobuterol given transdermally or by aerosol inhalation in healthy male volunteers. Tulobuterol was rapidly absorbed after inhalation, with a tmax of 0.8-1.5 h. The Cmax and the AUC increased linearly with dose. Tulobuterol was well absorbed after transdermal administration, with an absorption lag-time of about 4 h. The Cmax and AUC increased linearly with dose and the tmax was about 9-12 h. The mean percentage of drug absorbed during the application of a patch for 24 h was 82-90% after a single dose and 82-85% during repeated dosing. The mean urinary recoveries as unchanged drug after a single inhalation and patch application were 3-4% and 5-6% respectively. Tulobuterol did not accumulate during repeated inhalation or transdermal application. It was well tolerated, except for an increase in heart rate of 10-20 beats.min-1 after five repeated applications of a 4 mg patch.

Synthesis of carbapenam skeletons using a ruthenium-catalyzed cyclization

Carbapenam is a very important skeleton of beta-lactam antibiotics, and it has a highly strained structure. When enynes 9 were treated with RuH(2)CO(PPh(3))(3) (10 mol %) in toluene upon heating, carbapenams 10 were obtained in good yields.

Pharmacokinetics and safety of a novel recombinant soluble human thrombomodulin, ART-123, in healthy male volunteers

The safety and pharmacokinetics of a novel recombinant soluble human thrombomodulin, ART-123 were evaluated in single- and multiple-dose studies involving 16 healthy male volunteers. ART-123 was administered by intravenous infusion over 2 hours. The single-dose study indicated that plasma ART-123 levels at doses of 0.03, 0.1, and 0.3 mg declined biexponentially and those half-lives were approximately 4 hours (t1/2 alpha) and 20 hours (t1/2 beta), respectively. The mean plasma peak concentration and area under the plasma concentration-time curves increased in proportion to the given doses. Mean urinary recovery within the first 48 hours was between 54.3% and 59.8% of dose. In the multiple-dose study, ART-123 was administered at a dose of 0.2 mg once daily for 3 days. ART-123 did not accumulate as judged from plasma concentrations and urinary recovery. There were no abnormal findings in objective symptoms and laboratory findings, including blood pressure, heart rate, electrocardiogram, body temperature, hematology, bleeding time, coagulation and hemostatic parameters, blood chemistry, and urinalysis. There were no significant adverse reactions or abnormalities in physical and laboratory examinations that could definitely be attributed to the drug at a dose of 0.3 mg as a single administration and at a dose of 0.2 mg once daily for 3 days. These results indicate that ART-123 is safe at doses up to 0.2 mg once daily for 3 days and may have clinical application. Further studies are needed, however, to evaluate the safety and pharmacokinetics of ART-123 in the targeted population.

Clinical pharmacokinetics and tolerance of fleroxacin in healthy male volunteers

The tolerance and pharmacokinetics of fleroxacin were studied in healthy male adult volunteers. The peak serum concentrations of unchanged fleroxacin were about 1.5, 3 and 5 mg/l at 1-2 h after single oral doses of 100, 200 and 400 mg, respectively. The apparent serum elimination half-life was about 10 h, independent of the dose. Fleroxacin, demethyl fleroxacin and fleroxacin N-oxide excreted in urine over 3 days accounted for about 75%, 5% and 5%, respectively, of the doses. The urine concentrations of unchanged drug were dose-related; the mean concentrations, sustained over 24 h, were about 50, 100 and 150 mg/l after 100, 200 and 400 mg doses, respectively. Food intake did not significantly influence the serum concentration and urinary excretion. Steady state serum concentrations were achieved from day 3 onwards by repeated doses of twice-a-day dosage regimen and were 2-4 and 5-9 mg/l after 200 and 400 mg bid, respectively. The mean concentrations of unchanged drug in urine were about 200 and 300 mg/l at the respective dosages. The pattern of urinary metabolites was not changed by repeated doses and 90% of repeat doses was recovered in urine, including metabolites. The serum protein binding of fleroxacin was 32%. The saliva concentration was 40% of the total serum concentration or 60% of the free serum concentration. The faecal recovery over 3 days was 3% of the dose following a single 200 mg dose after a meal. The unchanged drug concentrations in faeces during 400 mg repeated dosing were 100-150 mg/kg. No severe dose-related side-effects were observed during the study.

Experimental studies and clinical report on the electrical alternans of ST segment during myocardial ischemia

During myocardial ischemia produced in 43 dogs by occlusion of left coronary artery, electrical alternans developed in 34 experiments. The most common was alternans of ST-T complex. Surface and intracellular electrograms were recorded simultaneously from contiguous sites in the ischemic area. The alternans of ST-T complex in the surface electrogram corresponded to that of the rate of repolarization of the membrane action potential. The development of this alternans is localized in 2 relatively small area and transient. This may be the reason why electrical alternans of ST-T is clinically rare. A clinical case showing electrocardiographic changes of electrical alternans of ST-T complex without any change in the QRS complex is reported. Myocardial infarction and hypokalemia is considered as a cause of the alternans. The present results support the hypothesis that the mechanism of electrical alternans will be an alternation of the rate and extent of the ions transported across the myocardial cell membrane.

Effect of dietary fat content on oral bioavailability of menatetrenone in humans

The purpose of this investigation was to determine the effects of fat content and frequency of meals on the oral bioavailability of menatetrenone (2-methyl-3-all-trans-tetraprenyl-1,4-naphthoquinone), a vitamin K2 with four isoprene units. In the first series of studies, menatetrenone (15 mg) was administered at breakfast time to 18 healthy male volunteers after meals with three different fat contents (meals A, B, and C) on three occasions in a crossover design. The three types of meals had almost the same calorie content (721-746 kcal) with varied fat contents (A, 8.8 g; B, 20.0 g; C, 34.9 g). The area under the plasma menatetrenone concentration-time curve within the first 24 h (AUC0-24) increased with increase of fat content: 371 +/- 194, 485 +/- 150, and 1024 +/- 341 ng.h/mL (mean +/- SD, n = 18) after meals A, B, and C, respectively. On the fourth occasion, the same dose of menatetrenone was administered to all volunteers after taking meal B, but in this case the lunch 5 h after drug administration was omitted from the protocol. The time profile of plasma menatetrenone showed a single peak when lunch was not taken, whereas it showed two peaks with lunch. On the fifth occasion, 12 out of 18 volunteers took the same dose of menatetrenone after a meal with the highest fat content (53.8 g of fat and 789 kcal; meal D), showing that AUC0-24 was almost the same as that for meal C, 1027 +/- 389 and 991 +/- 392 ng.h/mL (n = 12) for meals C and D, respectively. The oral bioavailability of lipid-soluble vitamin K was influenced by the fat content of a meal, although the increase in bioavailability seemed to reach a peak when the lipid content of the meal was > 35 g.

Comparative study of pharmacokinetics of two new fluoroquinolones, balofloxacin and grepafloxacin, in elderly subjects

Comparative pharmacokinetics and tolerability were studied in healthy elderly volunteers for two new fluoroquinolones, balofloxacin (Q-35) and grepafloxacin (OPC-17116), the main excretion routes being the renal and hepatic routes, respectively. Both agents were well tolerated in elderly subjects. In comparison with previously reported data from healthy younger adults, the absorption of balofloxacin was slightly delayed and urinary excretion was delayed and diminished. As a significant linear correlation was observed between renal clearance of balofloxacin and creatinine clearance, the delayed and diminished urinary recovery was attributed to the reduced renal function of the elderly subjects enrolled in the study. The absorption of grepafloxacin was also delayed, and the maximum plasma drug concentration and area under the plasma drug concentration-time curve were increased in the elderly by 31 and 48%, respectively, over those in younger adults on the basis of dose normalized to body weight. The plasma terminal elimination half-life and urinary recovery remained unchanged. Decreases in distribution volume and total body clearance in the elderly were considered to be the primary factors contributing to these differences.

Pharmacokinetics and safety of a new parenteral carbapenem antibiotic, biapenem (L-627), in elderly subjects

The pharmacokinetics and tolerability of a new parenteral carbapenem antibiotic, biapenem (L-627), were studied in healthy elderly volunteers aged 65 to 74 years (71.6 +/- 2.7 years [mean +/- standard deviation], n = 5; group B) and > or = 75 years (77.8 +/- 1.9 years, n = 5; group C), following single intravenous doses (300 and 600 mg), and compared with those of healthy young male volunteers aged 20 to 29 years (23.0 +/- 3.5 years, n = 5; group A). The agent was well tolerated in all three age groups. Serial blood and urine samples were analyzed for biapenem to obtain key pharmacokinetic parameters by both two-compartment model-dependent and -independent methods. The maximum plasma concentration and area under plasma concentration-versus-time curve (AUC) increased in proportion to the dose in all three groups. Statistically significant age-related effects for AUC, total body clearance, and renal clearance (CLR) were found, while elimination half-life (t1/2 beta) and percent cumulative recovery from urine of unchanged drug (% UR) remained unaltered (t1/2 beta, 1.51 +/- 0.42 [300 mg] and 2.19 +/- 0.64 [600 mg] h [group A], 1.82 +/- 1.14 and 1.45 +/- 0.36 h [group B], and 1.75 +/- 0.23 and 1.59 +/- 0.18 h [group C]; % UR, 52.6% +/- 3.0% [300 mg] and 53.1% +/- 5.1% [600 mg] [group A], 46.7% +/- 7.4% and 53.0% +/- 4.8% [group B], and 50.1% +/- 5.2% and 47.1% +/- 7.6% [group C]). A significant linear correlation was observed between the CLR of biapenem and creatinine clearance at the dose of 300 mg but not at 600 mg. The steady-state volume of distribution tended to be decreased with age, although not significantly. Therefore, the age-related changes in parameters of biapenem described above were attributable to the combination of decreased lean body mass and lowered renal function of the elderly subjects. However, the magnitude of those changes does not necessitate dosage adjustment in elderly patients with normal renal function for their age.

Pharmacokinetic study of an oral cephalosporin, cefdinir, in hemodialysis patients

The pharmacokinetics of cefdinir were investigated in six hemodialysis patients. For the present study, two tests were carried out, one with 4 h of hemodialysis and the other without hemodialysis. Cefdinir was given orally to each patient in a dose of 100 mg, and blood was collected serially for 48 h after dosing in the test without dialysis and for 72 h in the test with dialysis. In the test without dialysis, the maximum plasma concentration (Cmax) was 2.36 +/- 0.53 micrograms/ml (mean +/- standard deviation) and the time to Cmax was 9.00 +/- 2.45 h. The terminal elimination half-life (t1/2) and area under the concentration-time curve (AUC) were 16.95 +/- 1.20 h and 69.05 +/- 14.84 micrograms.h/ml, respectively. In the test with dialysis, t1/2 during hemodialysis decreased approximately to one-sixth of that obtained in the test without dialysis, although t1/2 in the latter elimination phase did not differ from that in the nondialysis test. AUC was reduced to 43% of that in the test without dialysis. The fractional removal of cefdinir by hemodialysis was 61%. These findings indicate that clearance of cefdinir is prolonged in patients with renal failure, and cefdinir is well removed by introduction of hemodialysis, although t1/2 (during hemodialysis) and AUC were two and eight times higher than the data previously reported for healthy volunteers, respectively. The pharmacokinetic data suggest that 100 mg of oral cefdinir once a day would result in a sufficient concentration in plasma in hemodialysis patients, but this remains to be confirmed by multiple-dose studies.

Pharmacokinetics and tolerability of intravenous infusion of adenosine (SUNY4001) in healthy volunteers

AIMS

To examine the tolerability and disposition of i.v. adenosine (SUNY4001) in healthy male Japanese volunteers.

METHODS

SUNY4001 was infused i.v. for 6 min at 0 (placebo), 60, 100, 120 and 140 microg kg-1 min-1 in a dose-escalating manner in 30 healthy subjects. Adenosine and its metabolites were determined in the plasma and urine.

RESULTS

Only plasma hypoxanthine was increased from 3 min during until 5-10 min after SUNY4001 infusion at the higher rates without any significant dose-related changes in plasma adenosine, inosine, xanthine or uric acid, or in urinary adenosine and all metabolites compared with the placebo. There was a dose-related increase in the incidence of subjective symptoms such as heat sensation, flushed face, dyspnoea, chest discomfort, etc. Transient and self-subsiding episodes of second-degree atrioventricular block were found in two subjects each at the higher doses.

CONCLUSIONS

Adenosine infusion at < or = 140 microg kg-1 min-1 was concluded to be generally well tolerated.

Comparative antiplatelet effects of aspirin, vapiprost and GR144053, a GPIIb/IIIa antagonist, with a special reference to the role of platelet microaggregates

Microthrombi produced have a potential to form larger thrombi, leading to vascular occlusions. Recently, a new device to easily detect microaggregates using laser-light scattering (LS) has been developed. We adopted this device to comparatively evaluate the inhibitory effects of aspirin (1,3 or 10 mg kg(-1)), vapiprost (0.3, 1 or 3 mg kg(-1)) or GR144053 (0.1, 0.3 or 1 mg kg(-1)) on ex vivo aggregation of hamster platelets in relation to their in vivo antithrombotic effects. A transluminal thrombus was produced in the hamster femoral artery by the photochemical reaction. Each compound was injected i.v. as a bolus 10 min prior to the reaction, showing a dose-dependent antithrombotic effect, i.e. they prolonged the time before the artery occluded. At that time cyclic flow reductions occurred more marked when aspirin or vapiprost was given. At the end of experiments, blood was collected to evaluate the platelet aggregation using both the new LS device and the conventional optical density (OD) method. Many more small aggregates were still formed when the highest dose of aspirin or vapiprost was used as compared with that of GR144053, although suppression of the platelet aggregation using the OD method, prolongation of the occlusion time and the bleeding time were quite similar. In conclusion, a GPIIb/IIIa antagonist markedly suppressed the microthrombi and reduced the cyclic flow reduction. This further indicates the importance of small aggregates as triggers of thrombosis and shows that prevention of their formation may result in improved vascular patency after thrombotic insult.

Comparative pharmacokinetic and pharmacodynamic properties of oral and intravenous (+)-sotalol in healthy volunteers

The pharmacokinetic and pharmacodynamic properties of (+)-sotalol (BMY-5763) were studied to analyse the relationship between plasma concentration and QTc prolongation in healthy male volunteers given single oral doses of 50, 100, 200 and 300 mg, repeated oral doses of 200 mg twice daily for 6.5 days, and single intravenous doses of 1.0 and 1.5 mg kg-1. The plasma concentration of (+)-sotalol peaked about 3 h after oral administration and declined with a half-life of 7.9-9.7 h. The Cmax and AUC showed dose-related increases, while the urinary recovery as the unchanged form remained constant (66-68% of the dose). During repeated oral administration the plasma concentration of (+)-sotalol reached almost a steady state on the 3rd day and there was no change in renal clearance of (+)-sotalol measured on the 1st, 4th and 7th days. After intravenous administration, (+)-sotalol in plasma decreased bi-exponentially with a terminal half-life of 7.6-8.3 h and the urinary recovery as unchanged drug amounted to 84-88% of the dose. The increase in QT interval was significant after a single oral administration except for the lowest dose, and regression analysis revealed a significant correlation between QTc interval and concentration of (+)-sotalol in plasma. The same correlation was evident with repeated oral doses on the 1st, 4th and 7th days. In the case of single intravenous administrations of (+)-sotalol, a combined pharmacokinetic-pharmacodynamic model was attempted by assuming an effect compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuronal histamine release elicited by hyperthermia mediates tracheal dilation and pressor response

Whether brain histaminergic neurons contribute to the regulation of tracheal tone and peripheral vascular tone under hyperthermia was investigated in anesthetized rabbits. Histamine release from the rostral ventrolateral medulla (RVLM), the raphe nuclei, and the solitary nucleus of the medulla oblongata was significantly increased by hyperthermia. The increased histamine was significantly suppressed by 10−6 M tetrodotoxin microdialyzed in each area. Tracheal pressure and mean arterial pressure were significantly decreased and increased by hyperthermia, respectively. An H1-receptor antagonist, 5 × 10−6 M (+)-chlorpheniramine, bilaterally microdialyzed in the RVLM significantly enhanced histamine release in the RVLM as well as significantly suppressed tracheal dilation and pressor response caused by hyperthermia. These data indicate that histamine release in the medulla oblongata is enhanced by hyperthermia. The enhanced histamine is the neuronal origin and the cause of tracheal dilation and pressor response at least via H1 receptors in the RVLM. Brain histaminergic neurons play important roles in tracheal tone and peripheral vascular tone via H1 receptors in the RVLM and homeostasis on body temperature.

Posterior hypothalamic control of rabbit tracheal tension and involvement of central histaminergic neurons

The hypothalamus is involved in the control of the cardiovascular system, but airway tone is less well defined. In the posterior hypothalamus, histaminergic neuronal cell bodies are located. Effects of electrical stimulation in the posterior hypothalamus on tracheal tension and the cardiovascular system were examined in anesthetized, paralyzed and artificially ventilated rabbits. Tracheal tension was determined from pressure exerted on a balloon inserted in the trachea and measured by a pressure transducer. Electrical stimulation of the posterior hypothalamus caused tracheal tension to decrease, arterial blood pressure to increase, and mild tachycardia followed by bradycardia. The tracheal tension decrease induced by posterior hypothalamic stimulation was not affected by atropine nor by transection of either the superior laryngeal nerve or the vagus nerve, but was depressed by adrenoceptor blockade. Tracheal tension decrease was also reduced by pyrilamine, a histamine H1-receptor antagonist, administered into the fourth ventricle, but was not affected by cimetidine, a histamine H2-receptor antagonist. The stimulation sites where these effects were evoked were interspersed among the loci of histamine immunoreactive cell bodies previously reported. Results suggest that posterior hypothalamic neurons decrease tracheal tension through the sympathetic nervous system, and involve the histaminergic neurons in this route.

Central histaminergic neurons regulate rabbit tracheal tension through the cervical sympathetic nerve

We previously showed that stimulation of the posterior hypothalamus decreases tracheal tension and involves central histaminergic neurons. In the present study, we reveal that central histaminergic neurons project to the rostral ventrolateral medulla and affect cervical sympathetic nervous activity in rabbits. Administration of histamine into the fourth ventricle increased cervical sympathetic nervous activity and decreased tracheal tension. These effects were inhibited by administration of a histamine H receptor antagonist, pyrilamine, into the fourth ventricle. Unilateral injection of DL-homocysteic acid into the tuberomammillary nucleus increased cervical sympathetic nervous activity, an effect was antagonized by bilateral injection of pyrilamine into the rostral ventrolateral medulla. The pulse correlogram between the stimulation pulse applied to the tuberomammillary nucleus and the cervical sympathetic nerve activity showed a mode at 150 to 200 ms, which was reduced by pyrilamine administration into the fourth ventricle. Fibers anterogradely labeled by Phaseolus vulgaris leucoagglutinin (PHA-L) injected into the tuberomammillary nucleus were distributed in the A1, A2, C1, and C2 areas which are determined by tyrosine hydroxylase-immunohistochemistry. PHA-L positive neurons were in close contact with tyrosine hydroxylase-immunoreactive neurons in these four areas. Cell bodies in the tuberomammillary nucleus retrogradely labeled with fluorogold from the rostral ventrolateral medulla were immunoreactive with histamine. These results suggest that an excitatory efferent pathway projects from the tuberomammillary nucleus to the cervical sympathetic nerve and that the histaminergic neurons of this pathway influence tracheal tension through the rostral ventrolateral medulla.

Autoregulation of histamine release in medulla oblongata via H3-receptors in rabbits

The release of histamine (HA) from the rostral ventrolateral medulla (RVL), the raphe nuclei (nR), and the solitary nucleus (nTS) was investigated in anesthetized rabbits using microdialysis and high-performance liquid chromatography. HA release upon electrical stimulation of the posterior hypothalamus (PH), where histaminergic cell bodies are located, was increased to 168% of the baseline level in the RVL (n = 6), 139% of the baseline level in the nR (n = 5), and 166% of the baseline level in the nTS (n = 4). Upon perfusion of thioperamide, an H3-receptor antagonist, via a microdialysis probe, HA release from the RVL, nR and nTS increased. The increase in HA release from the RVL, nR and nTS following thioperamide perfusion was suppressed by co-perfusion of thioperamide and an H3-receptor agonist, imetit. We found that HA is released from the RVL, nR and nTS, that the HA release from all three areas is increased upon stimulation of the PH, and that the HA release is locally influenced in opposite directions by thioperamide and imetit. These results suggest that HA release in the medulla oblongata is controlled by the PH and that H3-receptors participate in the autoregulation of HA release by providing negative feedback locally. Autoregulation of HA release via H3-receptors may be important for maintaining tonic output to the sympathetic nervous system.

Phase I study of Y-20811, a new long-acting thromboxane synthetase inhibitor by oral administration

The safety, pharmacological action and pharmacokinetics of the thromboxane (TX) synthetase inhibitor Y-20811, a prospective medication for ischemic vascular disorder, were investigated in Phase I clinical trials in which single and repeated doses were administered orally to 32 healthy adult male volunteers. In the single-dose study, subjects were given single doses of 2.5, 5, 10, 25, 50, and 100 mg; in the repeated-dose study, a single dose of 50 mg was administered daily for 5 days. In the repeated-dose study, slight elevation of liver function test parameters in 1 subject was observed, but throughout the trials, no abnormality attributable to the test drug was found in other routine laboratory tests, subjective and objective findings, vital signs (blood pressure, pulse rate, body temperature, respiration rate), ECG, or bleeding time; nor did any finding indicate a problem concerning the safety of Y-20811. In both single- and repeated-dose studies, inhibition of the serum TXB2 production and an increase in the 6-keto-prostaglandin F1 alpha production during whole-blood coagulation, and inhibition of arachidonic acid-induced platelet aggregation were observed from 1 hour after administration of Y-20811. The duration of these actions was long, the former two lasting 168 hours (1 week) and the latter 48-72 hours or more. Slight inhibition of adenosine diphosphate-induced secondary platelet aggregation was also observed. The maximum plasma concentration time (tmax) of Y-20811 was 0.5-1.1 hours. The initial-phase half-life (t1/2 alpha) was 0.8-1.1 hours and the final-phase half-life (t1/2 beta) was 4.7-9.2 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Phase I study of cefixime, a new oral cephalosporin

The tolerance to and pharmacokinetics of cefixime, a new oral cephalosporin, were evaluated in healthy volunteers given the drug in single doses of 50, 100 and 200 mg and repeated doses of 200 mg bid for 14 days. In the repeated-dose study, there were mild and transient subjective symptoms such as soft stools, diarrhea, and anorexia, which disappeared without additional treatment during the dosing period. Slight increases in eosinophil and serum amylase levels were also observed. The serum concentrations of cefixime peaked at 0.71, 1.17, and 2.08 micrograms/mL on average, four to five hours after dosing with 50, 100, and 200 mg, respectively, and the half-lives were 2.54, 2.38, and 2.29 hours. Serum concentrations and urinary recoveries after dosing with 100 mg were little affected by food ingestion. There was no evidence of cefixime accumulation in the body by repeated dosing since mean serum concentrations and urinary recoveries were almost the same on the first, third, seventh, and 14th days of dosing.

Involvement of central histaminergic neurons in polypnea induced by hyperthermia in rabbits

A role of central histamine in the preoptic area/anterior hypothalamus (POA/AH) for the regulation of hyperthermia-induced polypnea was examined in anesthetized, paralyzed, vagotomized and artificially ventilated rabbits. Phrenic nerve activities were recorded to monitor respiratory neuronal output. Hyperthermia increased respiratory frequency by reductions of inspiratory time (T(I)) and expiratory time (T(E)). Pyrilamine, an H1 receptor antagonist, which was applied to the POA/AH reduced polypnea under hyperthermia. The effect of S+alpha-fluoromethylhistidine, a specific inhibitor of histidine decarboxylase, applied in a lateral ventricle was comparable to the effect of pyrilamine on polypnea. Moreover, histamine dihydrochloride applied into the POA/AH at a normal body temperature produced polypnea by reductions of T(I) and T(E). The results suggest that central histamine in the POA/AH contributes to the generation of polypnea in hyperthermia through H1 receptors.

Central mediation of tracheal pressure through H1 and H2 receptors after histamine administration to the fourth ventricle of anesthetized rabbit

Administration of 1.5, 5.0 and 15 nmol histamine (HA) into the fourth ventricle (IVth) decreased tracheal pressure (PT) dose-dependently in anesthetized rabbits. Maximum decrease of PT occurred 0.9 +/- 0.1 min (mean +/- S.E.M., n = 9) after administration of 15 nmol, and recovery occurred at 4.5 +/- 1.0 min (n = 9). The decrease of PT was blocked by the H1 receptor antagonist, pyrilamine administration into the IVth, or intravenous injection of the alpha-adrenoceptor antagonist, phentolamine. Recovery from the PT decrease was delayed by the H2 receptor antagonist, cimetidine. The results suggest that HA centrally decreases PT through H1 receptors, which action is mediated by the sympathetic nervous system, and this decrease may be modulated through H2 receptors.

Pharmacokinetic and pharmacodynamic analysis of a novel leukotriene biosynthesis inhibitor, MK-0591, in healthy volunteers

1. The pharmacokinetic and pharmacodynamic properties of a novel 2-indolealkanoic acid derivative (MK-0591), a potent inhibitor of leukotriene biosynthesis, were investigated in healthy male Japanese volunteers. Single oral doses of 50, 125, 250 and 500 mg and multiple oral doses of 125 mg twice daily for 9.5 days and 250 mg once daily for 10 days were administered. 2. After the single-dose administration following overnight fasting, Cmax and AUC of MK-0591 in plasma increased in a dose-dependent manner, while elimination half-life remained constant (11.2-13.2 h) irrespective of dose. Food intake decreased Cmax and AUC by 71% and 68%, respectively, at a dose of 250 mg. With respect to multiple-dose administration before meals, there were no significant differences in the pharmacokinetic parameters between the first and last days, indicating a lack of significant accumulation of MK-0591 in plasma. Urinary recovery as the unchanged form was negligible throughout the study. 3. Ionophore-stimulated production of leukotriene B4 (LTB4) in blood ex vivo was inhibited significantly from 1 h until 12 to 48 h after single-dose administration as compared with predose value. In parallel, the urinary excretion of endogenous leukotriene E4 (LTE4) was significantly decreased from 4 to 8 h until 48 to 72 h after drug administration. Reduction of ionophore-stimulated LTB4 biosynthesis and urinary excretion of LTE4 following single administration of MK-0591 was statistically significant as compared with placebo group, and the duration of inhibition of LTB4 biosynthesis was dose-related.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of a parenteral carbapenem, biapenem, in patients with end-stage renal disease and influence of haemodialysis

The effects of haemodialysis on the pharmacokinetics of a carbapenem, biapenem, were evaluated in five patients with end-stage renal disease, who received 1 h iv infusions of 300 mg biapenem on both the days on and off 4 h haemodialysis. With haemodialysis, plasma biapenem exhibited two elimination phases, one during and the other after haemodialysis with half-lives of 1.16 +/- 0.12 and 3.33 +/- 0. 91 h, respectively. Ninety percent of biapenem was removed from blood to dialysate. Without haemodialysis, plasma biapenem was mono-exponentially eliminated with a half-life of 4.35 +/- 1.30 h.

Isorhamnetin Promotes 53BP1 Recruitment through the Enhancement of ATM Phosphorylation and Protects Mice from Radiation Gastrointestinal Syndrome

Flavonoids are a subclass of polyphenols which are attractive, due to possessing various physiological activities, including a radioprotective effect. Tumor suppressor p53 is a primary regulator in the radiation response and is involved in the pathogenesis of radiation injuries. In this study, we revealed that isorhamnetin inhibited radiation cell death, and investigated its action mechanism focusing on DNA damage response. Although isorhamnetin moderated p53 activity, it promoted phosphorylation of ataxia telangiectasia mutated (ATM) and enhanced 53BP1 recruitment in irradiated cells. The radioprotective effect of isorhamnetin was not observed in the presence of ATM inhibitor, indicating that its protective effect was dependent on ATM. Furthermore, isorhamnetin-treated mice survived gastrointestinal death caused by a lethal dose of abdominal irradiation. These findings suggested that isorhamnetin enhances the ATM-dependent DNA repair process, which is presumably associated with the suppressive effect against GI syndrome.