Toxicological studies on (2'R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic. Its acute toxicity in beagle dogs

(2"R)-4'-O-Tetrahydropyranyladriamycin (THP), a new antitumor antibiotic of anthracycline derivative, was given intravenously to male and female Beagle dogs, followed by observations for 2 weeks. The doses were 0.125, 0.25, 0.5 and 1.0 mg/kg. Observations were performed on mortality, clinical signs, body weight and temperature, food and water consumption, ECG, ophthalmoscopy, testicular measurement, hematology, serum biochemistry, urinalysis, autopsy, histopathology and electron microscopy. The results were as follows. All animals of 1 mg/kg-treated group died but there were no deaths in other groups. All the levels of doses caused vomiting and diarrhea. Furthermore, the highest dose caused bloody diarrhea and decreases in food consumption, motility and body weight, followed by death. These effects may be related to histopathological changes in mucosa of digestive tract. Some changes in water consumption, urine volume and renal histopathology were sporadically observed after treatment, but they were not treatment-related. These results suggest that a treatment with THP does not significantly cause renal disturbance. There were no treatment-related changes in body temperature, ophthalmoscopical observation and testicular measurement. THP produced flattening of T wave and prolongation of QRS interval only at high doses of more than 0.5 mg/kg for males and of 1 mg/kg for females but did not cause any histopathological or electron microscopical changes in hearts. It seems that the abnormalities caused by THP in ECG traces are due to the deterioration of general conditions rather than the direct effect on heart. High doses produce the significant changes in platelet, WBC, Hb, Neutro. (Seg.), Mono., Hb, RBC and Lymph. and further regressive changes in thymus, spleen and bone marrow. These results suggest that THP causes some effects on hemopoietic tissues. The sporadic changes in serum biochemistry and urinalysis were neither related to the treatment nor to the changes in organ weight, autopsy, histopathology and electron microscopy. Therefore, it is likely that THP does not cause toxicological effect on the other tissues and organs except hemopoietic tissues.     

A study of the effect of (2"R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic, on reproduction. II. Its teratogenicity in rats and rabbits

This paper describes the embryotoxicity and teratogenic effects of (2"R)-4'-O-Tetrahydropyranyladriamycin (THP). The drug was administered intravenously to female rats at 0.01, 0.03, 0.1 or 0.3 mg/kg daily from day 7 to day 17 of pregnancy and to female rabbits at 0.01, 0.05 or 0.1 mg/kg daily from day 6 to day 18 of pregnancy. Results were summarized as follows. Rats THP, at the highest dose of 0.3 mg/kg, decreased body weight gains of pregnant females. This dose caused a decrease in body weights of fetuses, tendencies to increase the rate of death of fetuses or of resorption, an increase in the number of lumbar vertebrae and a delayed ossification of forelimbs of fetuses. Other parameters were not affected by THP at any dose levels. At any dose levels, THP did not produce external, visceral or skeletal malformations in the offspring (F1), nor did it affect the development, physiological functions, behavior, mating, fertility or pregnancy of the offspring. However, at the highest dose level, THP decreased the weight of testes of the offspring. The results suggest that the maximum "no effect" dose level of THP to pregnant females and offspring is 0.1 mg/kg/day intravenously. Rabbits The highest dose of THP, 0.1 mg/kg, decreased the consumption of food and water by pregnant females, but at any dose levels, it did not affect their body weight gain. THP did not cause teratological effects such as external malformation or visceral and skeletal anomalies in the fetuses at any dose levels tested. The results suggest that the maximum "no effect" dose of THP is 0.05 mg/kg/day intravenously to pregnant females and above 0.1 mg/kg/day intravenously to fetuses.     

Biological properties of ME2303 (FAD-104), a new anthracycline

ME2303 (FAD-104) is a new anthracycline antibiotic whose structure is characterized by the presence of a 2'-fluoro atom and the lack of a 3'-amino group in the sugar moiety. Its cytocidal activity is superior to or equal to that of adriamycin (ADM). The LD50 value of ME2303 was about 140 mg/kg i.v. in mice and this value was about 7-fold higher than that of ADM. ME2303 was administered intravenously to Golden strain hamsters at doses of 25, 50, 75 and 150 mg/kg and the ECG was examined. From ECG changes, it seems that ME2303 did not show any effect on the heart in acute toxicity. Mutagenicity was recognized as with ADM in the back-mutation test.     

A study on the effect of (2"R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic, on reproduction. I. Its effect on the fertility of rats

The effect of a new antitumor antibiotic on the fertility was studied using SD rats. (2"R)-4'-O-Tetrahydropyranyladriamycin (THP) was administered to each rat at 0.01, 0.03 or 0.1 mg/kg daily. Males were given the drug intravenously for 63 days prior to mating and during the mating period; females were given the drug intravenously from 14 days prior to mating until day 7 of pregnancy. All the pregnant rats were sacrificed on day 20 of pregnancy, followed by external, visceral and skeletal observations of their fetuses. Results were summarized as follows. THP, at 0.1 mg/kg, suppressed body weight gain in females during the late period of pregnancy but did not affect body weight gain in males. THP, at 0.1 mg/kg, increased the numbers of dead fetuses and of resorptions. It caused no external, visceral or skeletal anomalies at any dose levels. The results suggest that, in rats, the maximum "no effect" dose of THP is 0.03 mg/kg/day intravenously regarding fertility and fetal development.     

A study on the effect of (2"R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic, on reproduction. III. Its effects on perinatal and postnatal rats

This paper describes effects of (2"R)-4'-O-tetrahydropyranyladriamycin hydrochloride (THP) on perinatal and postnatal rats. The drug was administered intravenously to female rats at 0.01, 0.03 or 0.1 mg/kg daily from day 17 of pregnancy to 21 days after delivery. Results were described below. At any dose levels tested, THP did not affect the body weight gain, food and water consumption by pregnant rats, and length of gestation period or delivery rate. However, at the highest dose level, THP decreased spleen weight. THP, at any dose levels, did not have toxic effect on development, physiological functions, behavior, mating, fertility or pregnancy of the first generation offspring (F1). At the highest dose of 0.1 mg/kg, however, THP produced delayed ossification of sacrococcygeal vertebra in the second generation fetuses (F2). The results suggest that the maximum "no effect" dose of THP to pregnant rats and offsprings is 0.03 mg/kg/day intravenously.     

延胡索乙素对大鼠实验性心肌缺血的保护作用

目的 研究延胡乙素（dl-THP)对大鼠实验性心肌缺血的保护作用。方法 观察dl-THP对垂体后叶素（pit)所致大鼠心电图急性缺血性改变的预防作用以及对异丙肾上腺素（Iso)引起心肌损伤大鼠的保护作用。结果 dl-THP对垂体后叶素所致心电图改变有明显预防作用。能对抗Iso所致ECG的ST段升高。显著抑制心肌组织中磷酸肌激酶（CPK）、乳酸脱氢酶（LDH）的释放,降低血清CPK和LDH水平,保护心肌组织超氧化物歧化酶（SOD）活性,减少丙二醛（MDA）生成。结论 dl-THP对实验性心肌缺血有明显的保护作用。     

Effects of dizocilpine (MK-801) on flash-evoked potentials, body temperature, and locomotor activity of hooded rats

The present study examined the effects of Dizocilpine (MK-801; a noncompetitive N-methyl-D-aspartate receptor antagonist) on flash-evoked potentials recorded from both the visual cortex (VC) and superior colliculus (SC) of chronically implanted hooded rats. The potentials were recorded at 5, 20, and 35 min following i.p. injections of saline, and of 0.1, 0.3, and 1.0 mg/kg MK-801 on separate days. The amplitude of VC component P1 was unaltered following drug treatment. N1 was increased in amplitude by the 0.1-, 0.3-, and 1.0-mg/kg doses, while two other negative peaks in the VC emerged, beginning with the 0.1-mg/kg dose, to complicate the waveform. One negative peak developed between N1 and P2, while the other effectively split peak P2 (forming P2A and P2B). P2A was depressed at all doses, while P2B was depressed at 0.1 mg/kg but augmented at the 1.0-mg/kg dose. N2 was elevated by the 0.3- and 1.0-mg/kg doses, while P3 was increased in amplitude by all doses. N3 was transiently enhanced by the 0.3-mg/kg dose. SC amplitudes were less affected, with P3 and N4 reduced in amplitude by the 0.3- and 1.0-mg/ kg doses. The latencies of most components in both structures were decreased, often with all doses, but generally at the later recording times. A second experiment demonstrated significant MK-801-induced hyperthermia at all of the above doses, although a higher dose of 3.0 mg/kg MK-801 caused hypothermia. The reduction in component latencies may, therefore, result at least in part from a drug-induced hyperthermia. A third experiment demonstrated MK-801-induced changes in locomotor activity in rats in an open field. The effects were both dose and time dependent. The 0.3-mg/kg dose of MK-801 produced significant increases in the number of line crossings from 20-60 min in comparison to the saline condition. Increases in the number of line crossings with the 1.0-mg/kg dose peaked at 15 min, and then gradually declined. It is unlikely, however, that these changes in movement can account for the effects of MK-801 on evoked potentials. In conclusion, the results show that blockade of the ion channel associated with the NMDA receptor produces profound changes in the activity of the neural pathways that are reflected in the middle components of the flash-evoked potential recorded from the VC.     

Pharmacological manipulations of sucrose consumption in the Syrian hamster

Nondeprived, male Syrian hamsters (Mesocricetus auratus) were adapted to a daily schedule of 2-hr access to a 10% sucrose solution. Two benzodiazepines, midazolam (1.0-10 mg/kg) and flurazepam (1.0-10 mg/kg), produced dose-dependent increases in sucrose consumption. In contrast, the alpha 2-adrenergic agonist, clonidine (0.01-0.3 mg/kg), had no effect on sucrose intake. Neither d-fenfluramine nor d-amphetamine affected sucrose ingestion in the hamsters, except at a large dose (10 mg/kg). Nevertheless, significant, dose-dependent reductions in sucrose consumption were observed after the administration of either opiate antagonists (naltrexone; nalmefene) or selective dopamine D2 receptor agonists (N-0437; quinpirole). The results are compared and contrasted with previously reported data for rats.     

Antitumor efficacy of AG3340 associated with maintenance of minimum effective plasma concentrations and not total daily dose, exposure or peak plasma concentrations

Oral administration of AG3340, a novel metalloprotease (MMP) inhibitor, suppresses the growth of human colon adenocarcinoma (COLO-320DM) tumors in vivo (Proc Am Assoc Cancer Res 39: 2059, 1998). In this report, we tested the hypothesis that the growth inhibition of these tumors is associated with maintaining minimum effective plasma concentrations of AG3340. Nude mice were given a total oral daily dose of 25 or 200 mg/kg; 6.25 mg/kg was given four times per day (QID) (25 mg/kg/day), and 100 mg/kg was given in two daily doses (BID) (200 mg/kg/day). Peak plasma concentrations (Cmax) of 83 +/- 43 (mean +/- SD) and 1998 +/- 642 ng/ml were detected 30 min after a single dose with 6.25 mg/kg and 100 mg/kg AG3340, respectively. AUC(0-24 h) values estimated from dosing with 25 and 200 mg/kg/day AG3340 were 672 and 10882 ng*h/ml, respectively. Importantly, both regimen inhibited tumor growth equivalently (74 to 82%). Efficacy was also compared at a total daily dose of 25 mg/kg by giving AG3340: QID (6.25 mg/kg per dose), BID (12.5 mg/kg per dose), and once daily (25 mg/kg per dose). The Cmax of these regimens was 83 +/- 43, 287 +/- 175 and 462 +/- 495 ng/ml, respectively. AG3340 did not inhibit tumor growth with the latter two regimens. The efficacy of 6.25 mg/kg QID (25 mg/kg/day) was superior to the efficacy of 25 mg/kg BID (50 mg/kg/day), substantiating the independence of efficacy from the total daily dose and Cmax. Expectedly, peak to trough fluctuations were significantly smaller with the QID regimen than with BID and QD dosing. After 24 h, the trough was greater than 1 ng/ml with QID dosing but was less than 1 ng/ml after QD and BID dosing. These results suggest that the antitumor efficacy of AG3340 was associated with maintaining minimum effective plasma concentrations of AG3340 and demonstrate that the antitumor efficacy of AG3340 was independent of the total daily dose, peak plasma concentration, and drug exposure in this tumor model.     

Antitumor efficacy of AG3340 associated with maintenance of minimum effective plasma concentrations and not total daily dose, exposure or peak plasma concentrations

Oral administration of AG3340, a novel metalloprotease (MMP) inhibitor, suppresses the growth of human colon adenocarcinoma (COLO-320DM) tumors in vivo (Proc Am Assoc Cancer Res 39: 2059, 1998). In this report, we tested the hypothesis that the growth inhibition of these tumors is associated with maintaining minimum effective plasma concentrations of AG3340. Nude mice were given a total oral daily dose of 25 or 200 mg/kg; 6.25 mg/kg was given four times per day (QID) (25 mg/kg/day), and 100 mg/kg was given in two daily doses (BID) (200 mg/kg/day). Peak plasma concentrations (C_max) of 83 ± 43 (mean ± SD) and 1998 ± 642 ng/ml were detected 30 min after a single dose with 6.25 mg/kg and 100 mg/kg AG3340, respectively. AUC_{(0-24 h)} values estimated from dosing with 25 and 200 mg/kg/day AG3340 were 672 and 10882 ng^*h/ml, respectively. Importantly, both regimen inhibited tumor growth equivalently (74 to 82%). Efficacy was also compared at a total daily dose of 25 mg/kg by giving AG3340: QID (6.25 mg/kg per dose), BID (12.5 mg/kg per dose), and once daily (25 mg/kg per dose). The C_max of these regimens was 83 ± 43, 287 ± 175 and 462 ± 495 ng/ml, respectively. AG3340 did not inhibit tumor growth with the latter two regimens. The efficacy of 6.25 mg/kg QID (25 mg/kg/day) was superior to the efficacy of 25 mg/kg BID (50 mg/kg/day), substantiating the independence of efficacy from the total daily dose and C_max. Expectedly, peak to trough fluctuations were significantly smaller with the QID regimen than with BID and QD dosing. After 24 h, the trough was greater than 1 ng/ml with QID dosing but was less than 1 ng/ml after QD and BID dosing. These results suggest that the antitumor efficacy of AG3340 was associated with maintaining minimum effective plasma concentrations of AG3340 and demonstrate that the antitumor efficacy of AG3340 was independent of the total daily dose, peak plasma concentration, and drug exposure in this tumor model.     

Electroencephalographic properties of zaleplon, a non-benzodiazepine sedative/hypnotic, in rats

The encephalographic (EEG) properties of zaleplon were investigated in comparison with those of other sedative hypnotics in conscious rats with chronically implanted electrodes. The oral administration of zaleplon (0.25-1.0 mg/kg), triazolam (0.0625-0.25 mg/kg), zopiclone (1.0-4.0 mg/kg), brotizolam (0.0625-0.25 mg/kg), and nitrazepam (0.125-0.5 mg/kg) lengthened the total sleep in a dose-dependent manner. On distribution of sleep-wakefulness stages, zaleplon, in particular, increased the slow wave deep sleep (SWDS), whereas triazolam, brotizolam, and nitrazepam increased the slow wave light sleep (SWLS) in a dose-dependent manner. Zopiclone significantly increased the SWDS at a dose of 2 mg/kg and both the SWLS and the SWDS at a dose of 4 mg/kg. All tested hypnotics caused no influence on fast wave sleep (FWS) at doses tested. The appearance of the sleep-inducing activity of zaleplon was more rapid than those of any compounds tested, and zaleplon significantly increased the relative EEG power density in the delta frequency band over that of triazolam at 20 and 30 min after the administration in the spectral analysis. Therefore, the present findings suggest that the non-benzodiazepine zaleplon can be expected to exhibit high practical potential as a hypnotic and is characterized by an increase in SWDS with rapid onset of hypnotic action.     

Dose-Dependent Pharmacokinetics of a New Oral Cephalosporin,Cefixime, in the Dog

Cefixime (CL 284,635; FK 027) is a new third-generation oral cephalosporin. To study dose-dependent pharmacokinetics of cefixime in dogs, two balanced four-way crossover studies were conducted. In the first study, oral doses of 50, 100, and 200 mg/kg and an intravenous dose of 50 mg/kg cefixime were administered. In the second study, oral doses of 6.25, 12.5, and 25 mg/kg and an intravenous dose of 12.5 mg/kg cefixime were administered to the same dogs. A period of 1 month separated the two studies. When the two intravenous doses were compared (i.e., 12.5 and 50 mg/kg), a twofold increase in clearance and volume of distribution was observed after the higher dose. The oral systemic bioavailability in the dose range 6.25–50 mg/kg was 55%. It decreased to 44% at 100 mg/kg and 27% at 200 mg/kg. The average peak serum concentrations ranged from 15.8 µg/ml at 6.25 mg/kg to 119 µg/ml at 200 mg/kg. Within this concentration range, the fraction of free drug in serum (unbound to proteins) increased from 7 to 25%. This concentration-dependent protein binding was primarily responsible for changes in total clearance, volume of distribution, and bioavailability of the drug in dogs.     

Effect of scopolamine on the hippocampal theta rhythm during an eight-arm radial maze task in rats

The changes in the hippocampal theta rhythm during an impairment of reference and working memory of radial maze task induced by scopolamine administration were studied. Intraperitoneal injection of scopolamine at doses of 0.5 and 1.0 mg/kg caused a significant increase in the number of total, reference memory and working memory errors. On the other hand, scopolamine significantly increased the hippocampal theta power (5-12 Hz) at doses (0.5 and 1.0 mg/kg) that caused an impairment of reference and working memory. A significant increase in the peak frequency of the hippocampal theta rhythm was also observed with scopolamine, even at a dose of 0.2 mg/kg. At doses of 0.2, 0.5 and 1.0 mg/kg, scopolamine caused a decrease in the locomotor activity during the radial maze task. From these results, it may be concluded that an increase in amplitude of the hippocampal theta rhythm induced by scopolamine is closely associated with memory/learning function of the eight-arm radial maze.     

Effect of rat pretreatment with aqueous solutions of stevioside and bile acids on the action of certain cardioactive drugs.

The interaction of aqueous solutions of stevioside and bile acids with cardioactive drugs was studied in rats by registering changes in their electrocardiograms (ECG). Wistar rats of both sexes received daily doses of 20 mg/kg (i.p.) of an aqueous solution of stevioside or physiological solution (controls), then were narcotized with urethane and connected to the ECG apparatus for the first recording. The jugular vein was prepared and connected to an infusion pump to administer one of the drugs: adrenaline (0.1 mg/ml), verapamil (2.5 mg/ml) or metoprolol (1 mg/ml) to rats in both groups, while recording their ECGs. In the second part of the study, the animals were treated in the same way but instead of the stevioside solution received a single dose of 4 mg/kg of monoketocholic acid methyl ester (ME) or sodium salt of the same bile acid (MKHNa), 30 minutes before cardioactive drug infusion. The infusion rate of cardioactive drugs was 0.2 ml/min, except for verapamil (0.1 ml/min). The events observed on ECG recordings were the first myocardial reaction to drug infusion, the second longer-lasting reaction (observed as more extended extrasystoles, decrease in intensity of the QRS complex, or changes in heart rate frequency), and toxicity effect. In the control animals, adrenaline induced a decrease in heart rate frequency at a dose of 0.094 mg/kg, while with stevioside-pretreated rats this effect appeared significantly earlier (at a dose of 0.018 mg/kg). No toxic effect of adrenaline was observed, either in control or stevioside-pretreated group. Bile acids caused no changes in myocardial reaction to adrenaline. Only in the group of animals that received MKHNa, a significant decrease in the QRS complex was observed. Finally, the infusion of stevioside to intact animals at doses of 45 and 55 mg/kg caused no significant changes in the ECG patterns. The myocardial reaction to metoprolol remained unchanged in rats of all groups when compared with controls except for a mild decrease in heart rate frequency. Stevioside induced/produced a significant increase in myocardial sensitivity to verapamil, but no toxic effect was observed in any of the cases. A similar conclusion also holds for the interaction with MKHNa, whereas ME caused an increase in the toxicity of verapamil.     

Adult exposure to diethylstilbestrol induces spermatogenic cell apoptosis in vivo through increased oxidative stress in male hamster

Effects of diethylstilbestrol (DES), an endocrine disrupting chemical, on abnormal spermatogenesis were studied in adult hamster using daily subcutaneous injection of 0.01, 0.1 and 1.0mg/kg body weight for 1 week. Testicular weight and seminiferous tubular area gradually decreased as dosage increased to 1.0mg/kg DES. Germ cells were rarefied and showed irregular distribution in seminiferous tubules. Apoptosis was pronounced among spermatocytes and spermatids at the 1.0mg/kg dose level. Antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and total antioxide capacity (T-AOC) markedly decreased and malondialdehyde (MDA) concentration significantly increased in the testes. These results suggest that DES (1.0mg/kg) induces testicular oxidative stress and spermatogenic apoptosis in adult male hamsters to extend findings shown for prenatal and/or neonatal exposure.     

Effect of (2"R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic, on the bone marrow function of rabbits. (2) Repeated intravenous injections

(2'R)-4'-O-Tetrahydropyranyladriamycin-HCl (THP), a new antitumor antibiotic, was intravenously injected to New Zealand White rabbits at a dose of 2.5 mg/kg every 2 weeks for 6 weeks (3 courses) or at a dose of 0.5 mg/kg/day daily for the first 5 days of a 2-week course for 6 weeks (3 courses). The total dose was 7.5 mg/kg in both dosing schedules. The peripheral leucocyte and erythrocyte counts decreased. The leucocyte count decreased to 57% of the initial count on Day 3 in the first course and then increased gradually. The decrease was smaller in the divided dosing schedule than the single dosing. The nucleated cells, especially immatured myelocytes and erythroids reduced remarkably. Subsequently the matured myelocyte ratio in bone marrow cell constituents increased and the M/E ratio increased. These changes were observed on Day 3 and reverted by Day 9 in each course. The divided dosing schedule resulted in a higher nadir. All the changes in the peripheral blood and the bone marrow reverted even after the 3 course-treatment.     

Pharmacokinetics of (-)-epicatechin-3-O-gallate,an active component of Onpi-to,in rats

(-)-Epicatechin-3-O-gallate (ECG), a component of Rhei Rhizoma, is one of the active components of Onpi-to, a herbal medicine composed of five crude drugs (Rhei Rhizome, Glycyrrhizae Radix, Ginseng Radix, Zingiberis Rhizoma and Aconiti Tuber), which has been used in patients with chronic renal failure. Pharmacokinetics of ECG was investigated in male rats employing an HPLC-electrochemical detection method. 1. Following oral administration of ECG, ECG plasma levels revealed curves characterized by peaks at 0.065, 0.063 and 0.085 h corresponding to dosages of 12.5, 25.0 and 50.0 mg/kg at mean concentrations of 49.62, 212.89 and 464.04 ng/ml, respectively. Plasma levels subsequently declined bi-exponentially. ECG demonstrated nonlinear pharmacokinetics in terms of C(max) and AUC(0-inf). 2. The absolute bioavailability values (F) were 1.02, 1.47 and 3.30% at doses of 12.5, 25.0, and 50.0 mg/kg, respectively. 3. Following intravenous injection of ECG, plasma levels of ECG decreased with the gamma-elimination half-life (t(1/2gamma)) of 4.03 h. 4. Following oral administration of ECG, urinary levels of ECG were lower than the quantitation limit. Moreover, cumulative excretion of the metabolites, delta-(3,4-dihydroxyphenyl)-gamma-valerolactone and delta-(3-methoxy-4-hydroxyphenyl)-gamma-valerolactone, was 2.45 and 0.23% of dose, respectively, up to 30 h after dosing.     

Physiologically based pharmacokinetics of KNI-272, a tripeptide HIV-1 protease inhibitor.

The effects of dose on the pharmacokinetic characteristics of KNI-272 were evaluated in rats after intravenous (iv) administration. The plasma kinetics of KNI-272 were dose-independent within a dose range of 1.0 to 10.0 mg/kg. However, when the dose was increased to 50.0 mg/kg, the area under the plasma concentration-time curve (AUC)/dose significantly increased and the total plasma clearance (Cl(tot)) significantly decreased, possibly due to saturation of hepatic metabolism. On the other hand, the terminal elimination half-life (t(1/2,lambda(z))) was independent of dose. Using biochemical and physiological parameters obtained from in vitro and in vivo studies, we developed a physiologically based pharmacokinetic (PBPK) model for KNI-272 in rats in which concentration-dependent nonlinear hepatic metabolism (Michaelis-Menten type metabolism) was considered. Using this PBPK model, plasma KNI-272 concentration-time profiles were simulated. From these profiles it was demonstrated that the terminal elimination phase was proportional to the dose at lower doses. However, as the dose increased to 50.0 mg/kg, the simulated plasma concentrations at the terminal elimination phase increased more than the increase of dose in the same way as the observed data. Accordingly, the dose-dependent plasma kinetics observed after a 50.0 mg/kg dose was considered to be attributable in part to concentration-dependent hepatic metabolism in rats.     

Effects of the combination of new quinolones and a nonsteroidal anti-inflammatory drug, fenbufen, on the EEG of rabbits]

A combination of fenbufen, a non-steroidal anti-inflammatory drug and the new quinolone produces a central stimulating action. To confirm the action, we used 6 kinds of new quinolones: enoxacin, norfloxacin, ofloxacin, ciprofloxacin, lomefloxacin and tosufloxacin in this experiment. The convulsive effects of these drugs were tested on the EEG recorded from the neocortex and subcortical regions of the rabbits. Animals treated with fenbufen (50-200 mg/kg, p.o.) tended to have a high amplitude slow wave in their EEG. Rabbits treated with the new quinolones at the dose of 100 mg/kg, p.o., with the exception of tosufloxacin, also tended to show a high amplitude slow wave in their EEG. Each new quinolone given 30 min after fenbufen (50 mg/kg, p.o.) elicited characteristic spikes on the EEG. Then, high-frequency-spikes and epileptiform seizure waves appeared for a long experimental period with this combination. The combination of fenbufen and tosufloxacin (100-400 mg/kg, p.o.) caused no changes in EEG and behavior. The spike and epileptiform wave could be suppressed only temporarily with diazepam (1-4 mg/kg, i.v.). These results suggest that combined use of fenbufen and one of the new quinolones, except for tosufloxacin, produces the seizure. Not only GABA but also several other mechanisms in the central nervous system may be involved in the convulsion.     

Acetylcholinesterase inhibition by (+)physostigmine and efficacy against lethality induced by soman

The optical isomer (+)Physostigmine [(+)Phy] is a very weak anticholinesterase. In a recent report, pretreatment with (+)Phy, at a dose which failed to inhibit acetylcholinesterase (AChE), and atropine provided efficacy against a lethal dose of sarin (SYNAPSE:2, 139, 1988). It was of interest to see whether (+)Phy could protect against soman at a dose which caused only marginal inhibition of the whole blood (WB) AChE in guinea pigs (GPs). (-)Phy (0.15 mg/kg, im) and (+)Phy (10.0 mg/kg, im) produced nearly 70% inhibition of WB AChE at 30 min whereas (+)Phy (0.15 mg/kg, im) caused only marginal inhibition. Groups of guinea pigs (20/group) were dosed, im, with (-)Phy (0.15 mg/kg), (+)Phy (0.15 mg/kg), (+)Phy (10.0 mg/kg) or vehicle (0.5 ml/kg) respectively in one thigh while the mild anticholinergic trihexyphenidyl (THP), 2.0 mg/kg, was injected into the other thigh of 10 animals from each of the respective groups. Thirty min after pretreatment, all animals were challenged with soman (60 micrograms/kg, sc; 2 LD50s); this dose of soman is lethal in unprotected animals. (-)Phy or (+)Phy (10 mg/kg) alone protected nearly 50% from soman lethality, and in combination with THP, all animals survived. In contrast, (+)Phy (0.15 mg/kg; alone or together with THP) was completely ineffective against a 2 LD50 challenge of soman. These data support the hypothesis that protection against soman-induced lethality is related to the degree of carbamylation of the AChE just prior to challenge.