Phase I clinical studies of 7432-S, a new oral cephalosporin: safety and pharmacokinetics

Phase I clinical studies of 7432-S, a new oral cephalosporin, including a randomized placebo-controlled trial were conducted with 40 healthy volunteers. In single-dose studies, 7432-S was orally administered at doses of 25, 50, 100, and 200 mg. The mean plasma levels peaked at 2.1 to 3.0 hours and reached 1.9, 3.6, 5.6, and 11.6 micrograms/ml, respectively. Linear correlation was observed between plasma AUC values and doses given. The half-lives of the plasma levels were 0.88 to 2.26 hours with a mean of 1.53 +/- 0.33 hours. The mean urinary recoveries were 67.5 to 75.2% of the dose within 24 hours. 7432-S was partially metabolized to 7432-S-trans which was excreted in urine at 7.2 to 9.2% of the doses. Study of the meal effect showed that AUC values and peak levels were not altered although the time to the peak levels was slightly prolonged. In multiple-dose studies, 100 mg of 7432-S twice daily for 2 weeks and 200 mg twice daily for 1 week were administered and there was no abnormal accumulation of 7432-S in plasma throughout the study. No significant differences were observed in plasma levels and urinary recoveries between single- and multiple-dose regimens. Clinical symptoms, physical tests, laboratory parameters, and fecal levels of vitamins K1 and K2 were in normal ranges. 7432-S was concluded to be safe and well tolerated.     

Effects of chronic administration of D-003, a mixture of sugar cane wax high molecular acids, in beagle dogs

D-003 is a mixture of high molecular weight aliphatic primary acids purified from sugar cane wax (Saccharum officinarum, L) with cholesterol-lowering and antiplatelet effects. Previous studies, including a 6-month study conducted in rats, have shown no D-003-related toxicity. The present study was undertaken to investigate the effects of D-003 orally administered for 9 months in beagle dogs. The animals were randomly distributed in three groups: a control group receiving the vehicle only and two groups orally administered D-003 (200 and 400 mg/kg). Body weight gain, food consumption and clinical signs were controlled throughout the study. The effects of D-003 on collagen-induced platelet aggregation, bleeding time (BT) and coagulation parameters (prothrombin time and kaolin-activated thromboplastin time) were also investigated. Most blood biochemistry and hematological parameters were assessed at baseline and after 6 and 9 months of treatment, while total cholesterol (TC), triglycerides, platelet aggregation, BT and coagulation parameters were determined at baseline and after 9 months of treatment. At study completion, the animals were sacrificed. D-003 at a dose of 200 and 400 mg/kg significantly reduced TC (p < 0.05), significantly inhibited platelet aggregation and increased BT compared with levels in controls. Data analyses of body weight gain, food consumption, clinical observations, the remaining blood biochemistry and hematology indicators (including coagulation parameters, organ weight ratios and histopathological findings) showed no trends with D-003 doses or significant differences between control animals and treated groups. In conclusion, D-003 administered for 9 months to beagle dogs induced the expected effects with no evidence of drug-related toxicity.     

General pharmacology of T-2588, a new oral cephem antibiotic

A new oral cephem antibiotic, T-2588, the pivaloyloxymethyl ester of (+)-(6R, 7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-methoxyiminoacetamido]-3- [(5-methyl-2H-tetrazol-2-yl)methyl]-8-oxo-5-thia-1-azabicyclo[4.2. 0]oct-2-ene-2-carboxylic acid (T-2525), is mainly absorbed from the intestinal tract and biotransformed to T-2525 thereafter. General pharmacological activities of T-2588 were studied and following results were obtained. On the central nervous system, T-2588 did not show any effects at oral doses of 500-2,000 mg/kg and T-2525 produced only a slight elevation of body temperature in rabbits without any other effects at an intravenous dose of 500 mg/kg. On the respiratory and cardiovascular systems, T-2525 caused a slight hypotension and increased both respiratory rate and femoral blood flow, but no changes were observed in heart rate and electrocardiogram in dogs at an intravenous dose of 500 mg/kg. The T-2525 exerted no significant influence on blood pressure response to isoproterenol, acetylcholine or histamine, but showed a slight tendency to decrease pressor response to adrenaline in dogs at intravenous doses of 100-500 mg/kg. For the renal function in rats, T-2588 had no effects on urine volume, electrolytes and PSP excretion at oral doses of 500-2,000 mg/kg. Intravenous administration of T-2525 caused an increase of sodium excretion at 500 mg/kg and dose-dependent increases of PSP excretion at 20-500 mg/kg. Hematological studies revealed that both T-2588 at oral doses of 500-2,000 mg/kg and T-2525 at intravenous doses of 100-500 mg/kg had no effects on bleeding time in mice, blood coagulation and platelet aggregation in rats. The T-2588 exerted no effect on the gastrointestinal system in rats or mice and had no antiinflammatory activity in rats at oral doses of 500-2,000 mg/kg. The T-2525 scarcely affected the motilities of isolated smooth muscle preparations in experimental animals including stomach, ileum, colon, uterus, vas deferens and trachea at a concentration as high as 10(-3) g/ml. The T-2525 increased bile secretion in rats at intravenous doses of 100-500 mg/kg. The T-2525 slightly decreased the twitch tension of musculus gastrocnemius induced by electrical stimulation in rats at an intravenous dose of 500 mg/kg. These results indicate that T-2588 is a pharmacologically inactive antibiotic.     

The hemostatic derangement produced by T-2 toxin in guinea pigs

T-2 toxin produced significant coagulation abnormalities when administered parenterally to Hartley strain guinea pigs. The animals developed depressed activity of all coagulation factors except fibrinogen. Platelet aggregation in whole blood was depressed in response to ADP and collagen. The animals also exhibited an initial rise followed by a fall in hematocrit level, leukocytosis, and a decrease in platelet count. These changes were detectable within hours of toxin administration, reached a maximum at 24 hr, and returned to normal over the next 2 days. Pretreatment of animals with vitamin K1 had no effect on the activity of coagulation factors. The activated partial thromboplastin time of dilutions of plasma from animals given T-2 toxin with plasma from control animals revealed a pattern which pointed to a deficiency of coagulation factors as the principal cause of prolonged clotting times in treated animals. The presence of a weak circulating anticoagulant could not be ruled out. The addition of T-2 to plasma and blood of normal animals in a concentration of 1 microgram/ml had no effect on clotting times or platelet aggregation.     

Safety evaluation and drug development based on biological fate of drugs -efforts made to overcome drug interaction in drug development-

1. Assay methods to detect drug interaction in toxicological samples were established by determining cytochrome P450 content and its activity in liver samples. The O-dealkylation reaction of 7-alkoxycoumarin was indicated to reflect changes in the molecular forms of P450s, and the enzyme induction or inhibition in the toxicological samples was easily detected by using the established methods. 2. During toxicological studies of 450191-S or the sleep inducer rilmazafone, a phenobarbital type-induction of hepatic drug metabolizing enzymes was observed in animals, and the doses required for the induction differed markedly between rats and dogs. Enzyme induction was caused by some specific metabolites of 450191-S, and the plasma concentrations of these metabolites were comparable when the enzyme induction was developed in both animals. 3. A nonsteroidal antiinflammatory compound 480156-S showed a slight or no effect on microsomal drug metabolizing activity in rats. On the other hand, repeated administration of this compound to humans resulted in a marked decrease in the oxidative metabolism of 480156-S, followed by a marked increase in the plasma concentrations of the compound. When volunteers were given 480156-S followed by several drugs, such as tolubutamide, the plasma clearance was delayed remarkably, indicating a severe drug interaction. 4. Cytochrome P450 belonging to the CYP2C family was indicated to participate in the oxidative metabolism of 480156-S in both rat and human liver microsomes. The preincubation of microsomes with 480156-S caused a concentration-dependent inhibition of CYP2C-dependent tolubutamide hydroxylation reaction in both rats and humans. There was a marked species difference in the susceptibility to the inhibitory effect of 480156-S, and the concentration required to inhibit rat CYP2C was almost 10 times higher than that required in humans. 5. The cephem antibiotics having N-methyltetrazolethiol (NMTT) at the 3'-position substituent were demonstrated to inhibit mitochondrial low K(m) aldehyde dehydrogenase (ALDH), and produced disulfiram-like (Antabuse) reaction during alcohol metabolism. Pharmacokinetic studies indicated that NMTT released from the antibiotics in bile duct or intestine cause the inhibitory action followed by the development of disulfiram-like reaction. 6. Attempts had been made to develop new cephem antibiotics lacking the disulfiram-like reaction by changing the chemical structure of 3'-position substituents, and a hydroxyethyltetrazolethiol was found not to inhibit the enzyme. Based on this result, together with the antibacterial activity, we have developed a new oxacephem antibiotic flomoxef (6315-S). Flomoxef showed no disulfiram-like reaction both in rats and human.     

Effects of 1-S replaced and/or decarboxylated latamoxef on rabbit platelet aggregation in vitro

Latamoxef, 1-S replaced and/or decarboxylated derivatives of latamoxef were examined for their effects on ADP-, collagen- and platelet activating factor (PAF)-induced rabbit platelet aggregation in vitro. The results were compared with those of cefotaxime, cefmetazole, carbenicillin and aspirin. Latamoxef produced a dose-dependent inhibition of platelet aggregation at concentrations over about 4 mM, and the potency was almost similar to that produced by the other beta-lactam antibiotics, although the inhibiting effect of ADP-induced aggregation was more potent for latamoxef, whereas that on collagen-induced aggregation was stronger for cefmetazole and carbenicillin. The inhibitory effect of beta-lactam antibiotics on collagen-induced aggregation was, however, much weaker than that of aspirin. With respect to drug potency, replacement of the oxygen atom in the oxacephem ring with a sulfur atom caused no significant change in ADP-induced aggregation or slightly stronger inhibition of collagen- and PAF-induced aggregations. The decarboxylated derivatives of latamoxef and the 1-S replaced analogue of latamoxef showed slightly weaker inhibition of ADP-induced aggregation, but much stronger inhibition of collagen- and PAF-induced aggregation than the parent compounds. These data suggest that 1) the oxygen atom in the oxacephem ring is not responsible for the inhibitory effect of latamoxef on platelet aggregation and 2) the carboxyl group in the amide side chain had no significant role in this inhibition.     

Effects of S-8527 (1, 1-bis (4'-(1"-carboxy-1"-methylpropoxy) phenyl) cyclohexane), a new hypolipidemic compound, on platelet aggregation, adhesiveness and blood coagulation in rats.

Effects of S-8527 (1,1-bis[4'-(1"-carboxy-1"-methylpropoxy) phenyl] cyclohexane) on platelet aggregation, adhesiveness and blood coagulation were examined in rats. In animals maintained on a semisynthetic diet containing sucrose (62%) as the only carbohydrate source, platelet adhesiveness increased as compared with that in rats fed a normal chow pellet. Under these experimental conditions, oral dose of S-8527 (30-300 mg/kg) for 14 days decreased platelet adhesiveness and ADP-induced platelet aggregation, but did not decrease collagen-induced platelet aggregation. S-8527 also showed a slight but significant increase of R value of thrombelastograph. In rats which were fed a normal chow pellet oral dose of S-8527 for 14 days did not significantly affect the several tests of platelet function and blood coagulation. These results suggest that S-8527 normalizes the platelet function in a hyper-adhesive state, but does not affect the platelet function in a normal state.     

Inhibition of platelet thromboxane synthetase by 1-(3-benzyloxy-1[E]octenyl)imidazole

1-(3-Benzyloxy-1[E]octenyl)imidazole (CBS-645) is a specific inhibitor of thromboxane synthetase. It inhibits the platelet enzyme in human and rabbit at micromolar concentrations. At a dose of 12.5 mg kg-1 in rabbits, CBS-645 displays a prolonged inhibitory effect on the formation of thromboxane (Tx) B2 induced by blood coagulation in vitro. In human volunteers, an oral dose of 50 mg leads to an average 70% inhibition of TxB2 formation. CBS-645 administered at a dose of 25 mg kg-1 p.o. in the rat, significantly increases bleeding time. In another test in which platelet interaction with the vessel wall is involved, i.e. in vivo platelet deposition onto desendothelialized aorta in the rabbit, the drug shows antithrombotic activity after a single oral administration of 5 mg kg-1. CBS-645 could be of interest in the treatment of the various diseases in which the pathological role of thromboxane A2 is suspected.     

Cardiovascular actions of a new dihydropyridine calcium antagonist, 8363-S: comparison with nifedipine and nicardipine in awake, unsedated dogs

The systemic and coronary hemodynamic actions of a new dihydropyridine, 8363-S, were compared with nifedipine and nicardipine in conscious, instrumented dogs following intravenous and oral administration. All agents produced similar reductions in arterial and ventricular pressures and increases in heart rate, dP/dt, and coronary blood flow velocity, following intravenous infusion. Following oral administration, all agents had qualitatively similar actions; however, there was a marked difference in potency. 8363-S was found to be most potent in that 0.25 mg/kg produced equivalent or larger changes from control than 0.5 mg/kg nifedipine or 1.0 mg/kg nicardipine. Furthermore, 8363-S had a longer duration of action following oral administration. The results suggest that important differences in bioavailability exist amongst dihydropyridines which may have important therapeutic implications.     

Therapeutic efficacy of ceftibuten in chronic respiratory tract infections

We evaluated the therapeutic efficacy of ceftibuten (CETB, 7432-S), a new cephem antibiotic for oral use, in chronic respiratory tract infections. A daily dose of 400 mg (b.i.d.: 15 cases) or 600 mg (t.i.d.: 5 cases) of CETB was given orally for 3-14 days (mean: 10.6 days) to 20 patients: 9 with infected bronchiectasis, 3 with infection supervened on pulmonary emphysema, 3 with acute pneumonia (supervened on bronchiectasis in 2 of 3 cases), 2 with infected bronchial asthma, 1 each with infection supervened on old pulmonary tuberculosis, chronic bronchitis and pulmonary fibrosis. The clinical effects were excellent in 3, good in 11, fair in 3 and poor in 3. Eighteen strains were identified as causative organisms. Eight of 15 strains for which bacteriological responses were evaluable were eradicated by the use of CETB. Eosinophilia in 2 patients and an elevation of S-GPT value was observed in 1 patient. These adverse reactions disappeared after the completion of the therapy. From the above results, we conclude that CETB is one of the most useful antibiotics for oral use as a first choice in chronic respiratory tract infections.     

Influence of fenflumizole on platelet aggregation in man

Summary The anti-aggregatory effect of fenflumizole, a new non-steroidal anti-inflammatory imidazole derivative is described in a study in 6 healthy male volunteers, mean age 33 years. Arachidonic acid (AA), ADP, collagen aggregation, coagulation and fibrinolysis parameters were examined before, during and after treatment with oral fenflumizole first 50 mg b.i.d. for 4.5 d and then 200 mg/d for 5 days. During treatment the threshold concentration for collagen aggregation demonstrated hypo-aggregability in all subjects. No significant change was noted in ADP aggregation. AA-induced aggregation showed an increased threshold concentration during and for 7 days after fenflumizole administration. No significant change was seen in bleeding time, fibrinolysis or coagulation parameters. No side effects were observed during or after treatment. It is concluded that fenflumizole is a potent inhibitor of platelet aggregation ex vivo.     

葛根素对凝血功能的影响

目的:通过研究不同剂量葛根素对凝出血时间、血小板聚集以及血流变学的作用,探讨其对凝血功能方面的影响及作用机制。方法:分别将3种不同剂量的葛根素药液灌胃给予正常小鼠,测凝血时间和出血时间;剂量转换后再将3种不同剂量的葛根素药液灌胃给予正常大鼠测定血小板聚集率和血液流变学指标。结果:不同剂量葛根素组可显著延长出、凝血时间;明显抑制血小板聚集率;能显著降低高、中、低切变率下的全血黏度。结论:葛根素有较强的抗凝血作用,其抗凝作用与其抑制血小板聚集作用和改善血流变有关。     

Clinical studies of ceftibuten in the field of urology

We studied clinical effects and safety of ceftibuten (7432-S, CETB), a new oral cephem antibiotic, against chronic complicated urinary tract infections in 9 cases and bacterial prostatitis in 10 cases. CETB was administered at a daily dose of 400-600 mg divided into twice or 3 times for a duration of 1-4 weeks. The overall clinical effect was 83.3% according to the criteria of UTI Committees (excellent: 4 cases, moderate: 1, poor: 1) in evaluated 6 cases, and the efficacy rate was 77.8% in the bacterial prostatitis cases according to physicians' evaluation (good: 7 cases, fair: 2, unknown: 1). There was 1 case of nausea, vomiting and lightly diarrhea on the third day after treatment but those tendencies all disappeared after stopping administration. So, we concluded that CETB was a useful agent for chronic complicated UTI and bacterial prostatitis with a daily dose level of 400-600 mg except in severe cases.     

Blood coagulation tests in toxicological studies--review of methods and their significance for drug safety assessment

In general toxicological studies, prothrombin time and activated partial thromboplastin time are routinely measured to assess blood coagulation. Special (problem-driven) tests for blood coagulation are of significance to detect abnormalities and investigate the mechanism of toxicity in detail. In this review, we compiled widely scattered information on blood coagulation testing from different fields in the biological area, and reviewed the methods available and their significance in toxicological studies. The relevant literature cited here reports large species differences in platelet aggregation, coagulation factors or fibrinolysis, and technical limitations. However, the following tests are basically applicable to laboratory animals; (1) assays for individual coagulation factors and protein induced by vitamin K absence or antagonists (PIVKA) to investigate coagulation factor abnormalities; (2) platelet aggregation-, platelet adhesion-, platelet release-tests and von Willebrand factor assay to screen and/or investigate platelet dysfunction; (3) fibrin/fibrinogen degradation products (FDP), D-dimer and thromboelastogram to detect fibrinolitic abnormalities, and assays for plasminogen, plasmin and their activator/inhibitor to investigate fibrinolysis in detail; and (4) bleeding-time to grossly evaluate blood coagulation capability in vivo. An appropriate battery of these tests provides significant information for risk assessment of drugs.     

Effect of change of hepatic drug-metabolizing activity on plasma concentrations of major metabolites of the new sleep inducer 450191-S, a 1H-1,2,4-triazolyl benzophenone derivative

Plasma concentrations of the major metabolites of 450191-S, a new sleep inducer which is a 1H-1,2,4-triazolyl benzophenone derivative, were determined in rats. Under the HPLC conditions employed, several major metabolites were detected in plasma, and thus the plasma concentration-time profiles for these metabolites were checked in rats in various states. When the animals were pretreated with high doses of 450191-S (200 or 600 mg/kg for 5 or 3 days, respectively) to induce hepatic drug-metabolizing enzymes, plasma concentrations of the metabolites after oral administration of a dose of 200 mg/kg of 450191-S decreased markedly depending on the induced enzyme activity. Pretreatment of rats with phenobarbital also caused decreased plasma levels of metabolites, which were almost the same as those in 450191-S-pretreatment. On the other hand, administration of beta-naphthoflavone to rats led to higher plasma levels of metabolites, and slower elimination compared with those in the control and 450191-S- or phenobarbital-pretreated rats. These results indicate that plasma levels of metabolites are regulated by the drug-metabolizing enzymes in the liver. It also suggests the participation of some specific forms of cytochrome P-450 in the biotransformation of 450191-S and its metabolites.     

Clinical studies of ceftibuten in the field of obstetrics and gynecology

Clinical studies on ceftibuten (CETB, 7432-S) were carried out in the field of obstetrics and gynecology. A total of 6 patients comprising 1 case of endometritis, 3 of bartholin's abscess, 1 of adnexitis and 1 of vulvar abscess was given 200-300 mg of CETB divided into 2 or 3 equal oral doses daily for 5 days. The clinical efficacy rate was 83 percent. Neither adverse reactions nor abnormal laboratory values were observed in any of the cases. From the results, it was concluded that CETB was an useful antibiotic in the field of obstetrics and gynecology.     

Status of platelet functions in volunteers of various blood groups: effect of aspirin

Platelet functions (platelet aggregation and adhesiveness) were studied in volunteers of different blood groups. The platelet aggregation time was found to be significantly (P less than 0.01) more in blood group O as compared A, B and AB blood groups. Similarly, platelet adhesive index was higher in A, B and AB blood groups when compared to that of blood group O. The administration of a single dose of aspirin (4 mg/kg, po) increased the platelet aggregation time and reduced the platelet adhesive index in all the blood groups.     

Plumbago zeylanica action on blood coagulation profile with and without blood volume reduction

Plumbago zeylanica (PZ) is extensively used in Indian systems of medicine for its medicinal properties. The structure of its active principle is similar to that of vitamin K. Its effect on blood coagulation profile after chronic administration has not been reported so far. The PZ extract (2 mg/kg body weight) and napthoquinone (2 mg/kg body weight) given to individual groups were screened for its effect on bleeding time (BT), clotting time (CT), prothrombin time (PT), platelet count and platelet adhesion in albino rats after 1-day, 15-day and 31-day treatment. There was no change in the platelet count in the treated groups when compared to the control levels. But the platelet adhesion was significantly decreased after PZ and also napthaquinone-treated animals in both with and without blood volume reduction after 15th as well as 31st day. Since the napthoquinone-treated group also showed similar response the changes observed after PZ treatment may be due to this component. Even at a lower dosage level (2 mg/kg body weight), the chronic PZ administration prolongs the bleeding time by altering platelet adhesiveness and the coagulation.     

Effect of a new sleep inducer, 1H-1,2,4-triazolyl benzophenone derivative 450191-S on rat liver drug-metabolizing enzyme system

The effect of a new sleep inducer, 450191-S, on the hepatic drug-metabolizing enzyme system was examined using rats and compared with those of nitrazepam and phenobarbital. Cytochrome P-450-dependent 7-alkoxycoumarin O-dealkylation activity determined using liver homogenate and isolated microsomes increased after successive oral administrations of 450191-S, and induction of the enzyme system was observed by administration of 150 approximately 200 mg/kg of the drug for at least 3 approximately 5 days. Normal activity was recovered with withdrawal of the drug for 3 approximately 5 days after induction of the hepatic enzyme system. Administration of higher amounts of 450191-S (200 approximately 600 mg/kg/day) for 3 days caused remarkable increases in the O-dealkylase and UDPGA-glucuronyltransferase activities and cytochrome P-450 and b5 contents. Similar changes in the hepatic enzyme system were observed with administration of nitrazepam (200 approximately 600 mg/kg for 3 days, p.o.) or phenobarbital (10 approximately 40 mg/kg for 3 days, i.p.). We concluded that the inducing activity of 450191-S is almost the same as that of nitrazepam, but weaker than that of phenobarbital. When the hepatic enzyme system was induced by the administration of either 450191-S or phenobarbital, the pentobarbital-induced sleeping time was shortened with increasing doses of the drugs. On the other hand, sleeping time was prolonged by the administration of another type of inducer, beta-naphthoflavone. The results suggest that the inductive pattern of 450191-S is similar to that of phenobarbital.     

Effect of etersalate on human platelet responsiveness. A study in healthy volunteers

Ex vivo antiplatelet properties of 2-(p-acetamido-phenoxy)ethyl-o-acetoxybenzoate (etersalate, Daital) and its effects on serum thromboxane A2 (TXA2) levels and prostaglandin I2 (PGI2) generation were studied in human volunteers at two levels of oral dosing. Etersalate inhibited at the lower dosage platelet function and decreased TXA2 levels, but PGI2 generation from rat aortic rings was stimulated when incubated with plasma from etersalate-treated donors. Blood coagulation parameters remained within normal values. It is suggested that etersalate administration could act on platelet arachidonate metabolism at a different level than that of the cyclooxygenase pathway.