Preclinical toxicology of the anticonvulsant calcium valproate

The oral toxicity of the anticonvulsant calcium valproate with selected comparisons to valproic acid and sodium valproate was evaluated in mice, rats and Beagle dogs. Median lethal doses of the three forms of valproate in rodents ranged from 1100 to 3900 mg/kg. Clinical signs in acute studies and reductions in body weight or body weight gain and food consumption at high doses in rats and dogs during 2-, 13- and 52-week studies were considered to be central nervous system related. In the 13-week study in rats (calcium valproate at 200, 400, 800, 1200 and 1600 mg/kg and sodium valproate at 1200 mg/kg), reduced plasma globulin levels and low white blood cell counts due to suppressed neutrophil maturation were noted at doses of 800 mg/kg and higher. Platelet counts were reduced at 1200 and 1600 mg/kg. Testicular atrophy occurred at 1200 and 1600 mg/kg. In dogs given calcium valproate at 100, 200 and 400 mg/kg for 13 weeks, testicular atrophy was seen at 400 mg/kg and mild hepatocellular changes at all doses. In rats given calcium valproate at 125, 250 and 500 mg/kg for 1 year, reduced plasma protein and globulin levels and a dose-dependent increased incidence and severity of atrophic pancreatitis were noted at 250 and 500 mg/kg. Calcium valproate, given for 1 year to dogs at doses of 50, 100 and 200 mg/kg, was well tolerated. These studies indicated that calcium valproate has a toxicity profile similar to other forms of valproate.     

Preclinical toxicity studies of an adenosine agonist, N-(2,2-diphenylethyl) adenosine

N-(2,2-Diphenylethyl)adenosine (DPEA) has been identified as a potential antipsychotic agent acting via stimulation of adenosine receptors. The projected human therapeutic dose, based on animal studies, is 2-3 mg/kg. DPEA has been tested for potential toxicity in mice, rats, dogs and monkeys. Following single oral doses, median lethal dose values were approximately 10-fold greater in rats than in mice, although similar clinical signs including reduced activity, prostration, and necrosis of the tail were seen in both species. DPEA was well tolerated at daily doses up to 40 mg/kg in rats for 2 weeks. A no observed effect level (NOEL) was not identified in the dog or monkey studies. Reduced activity, dacryorrhea, ptosis, hypothermia, necrosis of the tail, and death occurred in rats given 120 and 160 mg/kg. Pathologic changes consisted of pancreatitis, gastric erosion/ulceration, lymphocyte depletion of the thymus, and pulmonary congestion and hemorrhage at 80 mg/kg or greater. In dogs, sporadic emesis was noted at 12.5 mg/kg and greater, and significant pathologic changes consisted of coronary arteritis associated with myocardial lesions and lymphocyte depletion at 25 and 50 mg/kg, pancreatic acinar necrosis at 50 mg/kg, and renal tubular degeneration at 12.5 mg/kg and greater. Emesis and depression were noted at 25 and 50 mg/kg in monkeys. Renal tubular dilatation and degeneration at 25 and 50 mg/kg were noted in the monkeys. These studies demonstrated that DPEA produced a range of adverse effects in common laboratory animal species.     

Toxic responses to acute, subchronic, and chronic oral administrations of monochlorobenzene to rodents

Acute (single exposure), 14-d repeated exposure, 91-d subchronic, and 103-wk chronic toxicity studies of orally administered (gavage, in corn oil) monochlorobenzene were conducted in male and female Fischer-344 rats and B6C3F1 hybrid mice. A single exposure to 4000 mg/kg was lethal to male and female rats, while a single exposure to a dose as low as 1000 mg/kg was lethal to mice. Fourteen daily exposures to 1000 mg/kg caused death in rats of both sexes, but neither survival nor clinical health were compromised at 500 mg/kg in rats or mice. In the 91-d studies, wherein monochlorobenzene was administered once daily, 5 d/wk, survival was reduced by doses of 500 mg/kg and higher in rats, and by doses of 250 mg/kg and higher in mice. Dose-dependent necrosis of the liver (hepatocytes), degeneration or focal necrosis of the renal proximal tubules, and lymphoid or myeloid depletion of the spleen, bone marrow, and thymus (mild to severe) were produced by doses of 250 mg/kg or greater of monochlorobenzene in both sexes of rats and mice, although the incidences of these lesions varied considerably by sex and species. Consistent changes in the circulating blood components were not observed, but a mild porphyrinuria was detected at the higher doses. No toxic effects were observed at doses of 125 mg/kg or less. In the 2-yr studies, wherein monochlorobenzene was administered once daily, 5 d/wk, doses of 30 or 60 mg/kg in male mice and 60 or 120 mg/kg in female mice and male and female rats did not produce any evidence of toxicity. Doses of 60 or 120 mg/kg caused slight (statistically significant at 120 mg/kg; p less than 0.05) increases in the frequencies of male rats with neoplastic nodules of the liver. Increased tumor frequencies were not observed in female rats or in male or female mice receiving monochlorobenzene.     

Subchronic and chronic safety studies with genistein in dogs.

Genistein is a phytoestrogen that occurs naturally in the diet, especially in soy-based foods. There is widespread interest in phytoestrogens as chemopreventive agents for a variety of diseases and cancers based on epidemiologic evidence. Although soy and its constituents, such as genistein, have been consumed at high levels in several Asian populations without apparent adverse effects, concern has been raised about potential adverse effects due to estrogenic and other activities. The subchronic and chronic safety of genistein were evaluated in the beagle dog including a 4-week study and a 52-week safety study with a 13 week interim sacrifice and a 4 week recovery period. In both studies at doses of 50, 150 and 500 mg/kg/day, genistein was well tolerated. In the 4 week study, except for an increase in uterine weights in female dogs at 500 mg/kg/day, there were no other treatment related findings. In the 52-week study, the primary effects of genistein were observed on the reproductive tract, which included for male dogs: reduced size and/or weight of the testes, epididymus and prostate of 2/2 dogs after 13 weeks of treatment and in 1/4 dogs after 52 weeks of treatment at 500 mg/kg/day. The histological changes observed in the affected dogs at 500 mg/kg/day indicated atrophy of the testes and prostate gland and absent spermatozoa in the epididymus. At the mid-dose of 150 mg/kg/day, although there was a reduction to a lesser extent in testes weight after 13, but not 52 weeks, there were no histopathological changes. In female dogs, the reproductive tract effects included increased uterine weight at 500 mg/kg/day after 13 weeks of treatment, but not after 52 weeks of treatment. There was also a small decrease in ovarian weights at 150 and 500 mg/kg/day after 13 weeks and at 500 mg/kg/day after 52 weeks of treatment. There were no histopathological correlates to the changes in organ weights in female dogs. In the 4-week recovery group dogs, no changes were observed in dogs previously treated for 52 weeks with 500 mg/kg/day of genistein. It is concluded that the administration of genistein to dogs for a period of 4-52 weeks was well tolerated and did not result in systemic toxicity. Effects of genistein on the reproductive tract at very high doses were functional in nature and are of a type that would be expected in view of the relatively weak estrogenic activity of genistein and were considered not adverse effects. In the 4-week study, the no observed adverse effect level (NOAEL) for genistein was considered to be >500 mg/kg/day and the no observed effect level (NOEL) was considered to be 150 mg/kg/day. For the 52-week study, the NOAEL is considered to be >500 mg/kg/day and the NOEL is considered to be 50 mg/kg/day.     

Preclinical toxicology of the GABA uptake inhibitor CI-966

Cl-966 (1-[2-[bis[4-(trifluoromethyl)phenyl]methoxy]]-1,2,5,6-tetr5ahydro-3-pyridinecarboxylic acid, HCl salt) is an anticonvulsant agent that blocks the re-uptake of gammaaminobutyric acid (GABA) into presynaptic nerve terminals and glial cells. The preclinical toxicology of Cl-996 was evaluated in male and female B6C3F1 mice, Wistar rats, and beagle dogs. Doses were administered orally and are expressed as free acid equivalents. Acute (gavage) toxicity was characterized principally by CNS signs (hypoactivity, atasia, tremors, convulsions, and prostration); diarrhea and urine scald; and delayed mortality (2–3 days in mice and 2–11 days in rats) with 14 day median lethal doses of 653 and 825 mg/kg in male and female mice and 1,019 and 830 mg/kg in male and female rats, respectively. In a 4-week rat study in which Cl-966 was given in the diet, the high dose of 500 mg/kg/day was not tolerated, with marked decreases in body weight and food consumption necessitating sacrifice during the second week. The 150 mg/kg/day dose caused reduced body weight gain, lower food consumption, and hyperactivity, while 50 mg/kg/day was clearly a no-effect level. In dogs, Cl-966 was given in gelatin capsules at doses of 2 to 25mg/kg/day in an exploratory study and at 2,6, and 15 mg/kg/day in a 4-week study. Prostration, ataxia, disorientation, and other mainly CNS-related clinical signs occurred at 5 to 25mg/kg. Aspartate and/or alanine aminotransferase activities were elevated at 20 and 25 mg/kg in the exploratory dog study. However, there were no histopathologic findings in either species directly attributable to Cl-966 treatment. Enhanced GABAergic activity was considered to be the cause of most of the clinical signs elicited by Cl-966 in rodents and dogs. Blood Cl-966 levels were dose-dependent, but higher in females than males for both rats and dogs. These results were used to support initial clinical trials of Cl-966 in humans. © 1993 Wiley-Liss, Inc.     

Early Effects of CI-924 on hepatic peroxisome proliferation, microsomal enzyme induction, PCNA, and apoptosis in B6C3F1 mice and Wistar rats

 The lipid lowering agent 5,5′{[1, 1′-biphenyl]-2,5-diylbis(oxy)}bis[2, 2-dimethylpentanoic acid] (CI-924) is a peroxisome proliferator in rats and mice, but increased the incidence of hepatic tumors in mice only. Male and female B6C3F1 mice and albino Wistar rats were treated with CI-924 at doses of 0, 25 and 75 mg/kg for 1, 3, 7 and 28 days. Our aim was to identify species differences potentially related to tumorigenicity and to establish the time course of early events related to or associated with peroxisome proliferation. After 24 h of exposure to CI-924 in the diet there were increases in carnitine acyl transferase and CYP4A1 activity in mice at 25 and 75 mg/kg. In rats, carnitine acyl transferase activity was increased after 24 h and CYP4A1 activity increased after 3 days at 75 mg/kg. Acyl CoA oxidase activity was increased at both doses in male and female rats and mice by 3 days. In general the changes in enzyme activity were of greater magnitude in rats. In contrast to the rapid peroxisome proliferation, increases in the amount of PCNA were observed in CI-924 treated rats and mice at later times after administration and only at 75 mg/kg. PCNA was increased to a similar extent in both rats and mice, while apoptosis was decreased at both doses of CI-924 after 3 days in female rats, 7 days in male rats, and was largely unchanged in mice. It was concluded that the sequence of peroxisome proliferation was generally similar in rats and mice. Early changes in cell proliferation and programmed cell death were not directly correlated with subsequent CI-924-induced hepatotumorigenicity. Received: 21 May 1996 / Accepted: 20 August 1996     

Toxicological investigations with the benzodiazepine antagonist flumazenil

The benzodiazepine antagonist ethyl 8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4] benzodiazepine-3-carboxylate (flumazenil, Ro 15-1788, Anexate) was investigated in a series of toxicological studies. In a single intravenous injection study in male and female mice and rats, the highest non-lethal (maximum tolerated) doses were found to be between 62.5 and 125 mg/kg (the amounts of flumazenil present in the aqueous ampoules available for intravenous injection in man are 0.5 and 1.0 mg). In intravenous studies of 4 weeks duration, 10 mg/kg/d were systemically well tolerated in dogs and rats. In 13-week oral studies, 80 mg/kg/d were very well tolerated in dogs (capsule administration) and, after 125 mg/kg/d (by feed-admix) in rats, no untoward compound-related findings apart from a 10-15% increase of the liver weights in females were made. In reproductive toxicity studies, flumazenil revealed no drug-related embryotoxic or teratogenic effect and no adverse effects upon fertility of dosed animals themselves or on the peri- and postnatal development of their offspring. There was no indication for mutagenic potential of flumazenil in vitro concerning induction of gene mutations or clastogenic effects. An in vivo DNA repair test using germ cells of male mice did not yield DNA-damaging activities. From all these toxicological investigations it can be concluded that the risk in man given therapeutic doses or even intentional or accidental overdoses of flumazenil is extremely small.     

Toxicological properties of closantel

The acute, subacute and chronic toxicity studies in laboratory animals showed that closantel is a well tolerated substance. At multiples of the clinical dose, overdosing might result in central nervous system effects and death. Repeated oral dosing was without effects up to 40 mg/kg in rats and dogs except for focal swelling of the epididymis in male rats at 40 mg/kg due to formation of spermatic granulomas. In sheep repeated dosing at 10 and 40 mg/kg orally and at 5 and 20 mg/kg intramuscularly every four weeks during 40 weeks demonstrated an acceptable safety margin in this target species. Reproduction studies including a three-generation study in rats showed that fertility was not affected except slightly in male rats at 40 mg/kg whereas an embryotoxic or teratogenic potential in rats and rabbits was absent. Peri- and postnatal parameters in rats were not affected. In target animals, reproduction was extensively studied in bulls, rams and ewes showing no risk of closantel for reproduction parameters. A mutagenic potential was found to be absent in a Salmonella Ames test, a sex-linked recessive lethal test in Drosophila melanogaster and a dominant lethal test in male and female mice. In 400 mice and 400 rats closantel was shown not to be carcinogenic. Tolerance studies in sheep and cattle demonstrated that oral and parenteral clinical doses were very well tolerated and devoid of serious side-effects.     

Nonclinical Toxicology Studies with Zidovudine: Acute, Subacute, and Chronic Toxicity in Rodents, Dogs, and Monkeys

In single dose acute toxicity studies in CD-1 mice and CD rats,the median lethal dose (MLD) for zidovudlne (ZDV) was >750mg/kg after iv dosing and >3000 mg/kg after po administration(recommended human dose is 100 mg every 4 hr while awake). Becauseof the short half-life in rats (0.8 hr), dogs (1.0 hr), andmonkeys (0.8 hr), the daily dose of ZDV in most studies wasgiven in two equal portions approximately 6 hr apart. Intravenousadministration of ZDV was well tolerated in beagle dogs at doselevels up to 42.5 mg/kg bid for 2 weeks and in CD rats at doselevels up to 75 mg/kg bid for 4 weeks. In a 2-week dose range-findingstudy in beagle dogs, cytostatic effects were noted at po doselevels of 62.5 to 250 mg/kg bid in certain tissues with rapidcell replication rates. In contrast, in 3-to 12-month oral toxicitystudies in CD rats and cynomolgus monkeys, the principal toxicologicfinding was reversible macrocytic normochromic anemia whichoccurred at 225–250 mg/kg bid in rats and 17.5–150mg/kg bid in monkeys. In the 12-month rat study, RBC was decreasedat 25 and 75 mg/kg bid. In the 12-month monkey study WBC wasslightly decreased at 150 mg/kg bid.     

Effects of Cl-949, a Novel Antiallergy Compound, on Host Resistance in Mice

Effects of CI-949, a Novel Antiallergy Compound, on Host Resistancein Mice. BLEAVINS, M. R., MARTIN, R. A., DE LA IGLESIA, F. A.,MUNSON, A. E., MCCAY, J. A., FOUANT, M. M., AND WHITE, K. L.,JR. (1991). Fundam. Appl. Toxicol. 17, 723–732. The effectof CI-949, a novel inhibitor of allergic mediator release, onimmune function was assessed with holistic mouse models of immunocompetence.Resistance to the bacterial pathogens Listeria monocytogenesand Streptococcus pneumoniae and the B16F10 melanoma cell linewas used to evaluate the potential of CI-949 to affect immunefunction. CI-949 treatment of female B₆C₃F₁, mice increasedpulmonary tumor burden at 100 mg/kg/day in the B16F10 melanomamodel, with a no effect level of at least 50 mg/kg/day. A correlationwas seen between decreased clearance of the B16F10 cells andincreased tumor burden. However, CI-949 produced this effectonly at the maximum tolerated dose. No effect of the drug wasseen in the S. pneumoniae model. Host resistance to L. monocytogeneswas increased after CI-949 administration, with the no adverseeffect level in this model being at least equivalent to thetop dose of 100 mg/kg/day. Therefore, the immune system doesnot appear to be adversely affected or to be a specific targetfor CI-949 even at an overtly toxic.     

Toxicological Properties of Closantel

ABSTRACT

The acute, subacute and chronic toxicity studies in laboratory animals showed that closantel is a well tolerated substance. At multiples of the clinical dose, overdosing might result in central nervous system effects and death. Repeated oral dosing was without effects up to 40 mg/kg in rats and dogs except for focal swelling of the epididymis in male rats at 40 mg/kg due to formation of spermatic granulomas. In sheep repeated dosing at 10 and 40 mg/kg orally and at 5 and 20 mg/kg intramuscularly every four weeks during 40 weeks demonstrated an acceptable safety margin in this target species.

Reproduction studies including a three-generation study in rats showed that fertility was not affected except slightly in male rats at 40 mg/kg whereas an embryotoxic or teratogenic potential in rats and rabbits was absent. Peri- and postnatal parameters in rats were not affected. In target animals, reproduction was extensively studied in bulls, rams and ewes showing no risk of closantel for reproduction parameters.

A mutagenic potential was found to be absent in a Salmonella Ames test, a sex-linked recessive lethal test in Drosophila melanogaster and a dominant lethal test in male and female mice. In 400 mice and 400 rats closantel was shown not to be carcinogenic. Tolerance studies in sheep and cattle demonstrated that oral and parenteral clinical doses were very well tolerated and devoid of serious side-effects.     

Pre-clinical toxicity studies on the new nitroimidazole 1-methylsulphonyl-3-(1-methyl-5-nitroimidazole-2-yl)-2- imidazolidinone

Administration of 1-methylsulphonyl-3-(1-methyl-5-nitro-2-imidazole-yl)-2-imidazolidinone (Go 10213) at a dose of 5000 mg/kg to rat, mouse, guinea pig and rabbit and 3000 mg/kg to dog did not induce any toxic symptoms or mortality. Repeated daily gavaging with doses ranging from 50-3000 mg/kg/day were tolerated by rats for 2 weeks. No mortality was noticed in treated animals. Reduction in weight gain was observed in male rats on 2000 mg/kg per day and females on 1000 mg/kg per day. No toxic changes were noticed in dogs treated with 200 mg/kg per day for 2 weeks. One monkey treated with 75 mg/kg per day for 4 weeks tolerated the compound without exhibiting any toxic effects. No drug induced alterations were noticed in rats gavaged with 60 and 200 mg/kg per day for 4 weeks. Rats treated with a daily dose of 600 mg/kg showed reduction in body weight gain and atrophy of testes and these changes were reversible after stopping of medication. Dogs medicated with 30 and 100 mg/kg per day tolerated the drug for 4 weeks. Except slight ataxia in a few dogs treated with 100 mg/kg per day, no other drug induced toxic effects were noticed. Neurological symptoms were noticed in all dogs on high dose of 200 mg/kg. Three animals out of six were sacrificed in extremis in this dose. After discontinuation of Go 10213 all dogs on 100 and 200 mg/kg per day recovered normal gait in about a week. No definitive drug induced changes were noticed in laboratory investigations, gross and histopathological examinations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Respiratory and cardiovascular toxicity studies of a novel antiprion compound, GN8, in rats and dogs

Prion diseases, also known as transmissible spongiform encephalopathies, are fatal neurodegenerative disorders for which no effective curative or prophylactic method has been established. Recently, we discovered a novel antiprion compound, GN8. Administration of GN8 was found to prolong the survival of prion-infected mice. The aim of this study was to characterize the toxicological and pharmacological features of GN8 in rats and dogs treated via a single intravenous injection. Minimum lethal doses of GN8 were estimated to be approximately 60 and 40 mg/kg in rats and dogs, respectively. In the respiratory toxicity experiments, GN8 was administered to rats at doses of 0, 15.6, and 46.9 mg/kg, and rats were observed for consciousness, behavior, autonomic nervous symptoms, and body weights. GN8 was found to have little adverse effect on the rat respiratory system at a dose of 46.9 mg/kg. In the cardiovascular toxicity experiments, GN8 was administered to dogs at doses of 0, 7.8, and 31.3 mg/kg, and dogs were observed similarly. Although GN8 was found to have a slight effect on the cardiovascular system at a dose of 31.3 mg/kg, we did not find severe adverse effects of GN8 at doses sufficient for antiprion activity. This study would serve as a stepping stone to a clinical application of GN8 as an antiprion agent.     

Respiratory and cardiovascular toxicity studies of a novel antiprion compound,GN8, in rats and dogs

Prion diseases, also known as transmissible spongiform encephalopathies, are fatal neurodegenerative disorders for which no effective curative or prophylactic method has been established. Recently, we discovered a novel antiprion compound, GN8. Administration of GN8 was found to prolong the survival of prion-infected mice. The aim of this study was to characterize the toxicological and pharmacological features of GN8 in rats and dogs treated via a single intravenous injection. Minimum lethal doses of GN8 were estimated to be approximately 60 and 40?mg/kg in rats and dogs, respectively. In the respiratory toxicity experiments, GN8 was administered to rats at doses of 0, 15.6, and 46.9?mg/kg, and rats were observed for consciousness, behavior, autonomic nervous symptoms, and body weights. GN8 was found to have little adverse effect on the rat respiratory system at a dose of 46.9?mg/kg. In the cardiovascular toxicity experiments, GN8 was administered to dogs at doses of 0, 7.8, and 31.3?mg/kg, and dogs were observed similarly. Although GN8 was found to have a slight effect on the cardiovascular system at a dose of 31.3?mg/kg, we did not find severe adverse effects of GN8 at doses sufficient for antiprion activity. This study would serve as a stepping stone to a clinical application of GN8 as an antiprion agent.     

Comparisons of the depressor, inotropic and renal effects of milrinone and CI-930 to different pure vasodilators and diuretics in conscious instrumented dogs.

The cardiovascular and renal effects of graded i.v. dosages of two low Km cAMP cGMP-inhibitable (cGi) phosphodiesterase (PDE) inhibitors: CI-930 and milrinone (both 10-300 micrograms/kg), and three pure vasodilators: fenoldopam (0.1-3 micrograms/kg), Na nitroprusside (3-100 micrograms/kg) and hydralazine (0.1-3 mg/kg), were compared in conscious dogs. Mean arterial pressure was decreased by CI-930 at 0.3 mg/kg, milrinone at doses greater than or equal to 0.1 mg/kg (both by approximately -17 mmHg [max. change]), nitroprusside at doses greater than or equal to 0.01 mg/kg (-60 +/- 5 mmHg, [mean +/- SEM, max. change]), fenoldopam at doses greater than or equal to 0.001 mg/kg, and hydralazine at all doses (both by approximately -26 mmHg). Heart rate was increased by milrinone and CI-930 at dosages greater than or equal to 0.03 mg/kg (both by approximately 57 beats/min), nitroprusside and hydralazine at all dosages (54 +/- 18 and 91 +/- 18 beats/min, respectively) and fenoldopam at 3 micrograms/kg (21 +/- 2 beats/min). The cGi PDE inhibitors at 0.01-0.3 mg/kg and the pure vasodilators (except fenoldopam) at all dosages increased dP/dt (approximately 1500 and 900 mmHg/s, respectively). Milrinone (greater than or equal to 0.1 mg/kg), CI-930 (greater than or equal to 0.03 mg/kg), nitroprusside (greater than or equal to 0.01 mg/kg) and hydralazine (0.3-1 mg/kg) decreased left ventricular end diastolic pressure (all by approximately -4 mmHg). None of the agents adversely affected urinary volume, Na+ and K+ excretion rates. In conclusion, all agents (except fenoldopam) induced positive inotropic and chronotropic effects, and preload and afterload reduction. The cardiac effects of the pure vasodilators may be reflexly induced, whereas those of the cGi PDE inhibitors may be primarily due to inhibition of cardiac cGi PDE.     

Toxicological studies on cefuroxime sodium.

The intravenous LD50 of cefuroxime sodium for mice was 10.4 g/kg. The maximum dosage administered in other acute toxicity tests was well tolerated by mice (10 g/kg, subcutaneous), by rats (4 g/kg, intravenous, 5 g/kg, subcutaneous) and by cats, dogs and monkeys (2 g/kg, intramuscularly). Cefuroxime sodium was administered subcutaneously (s.c.) or intramuscularly (i.m.) for 3 months to rats (100, 300 or 900 mg/kg/day) followed by a recovery period, and also for 6 months to rats and dogs (50, 150 or 450 mg/kg/day) and for 1 month to monkeys (150 or 450 mg/kg/day). In all these tests there were no serious toxic effects. Minor haematological changes were attributable in part if not entirely to haemorrhage and tissue reaction at the site of injection of large doses. In rats large doses caused some increase in urine volume and electrolyte excretion, and slightly aggravated an age related nephropathy. Administration to rats intravenously (i.v.) for1 month of up to 400 mg/kg/day had no toxic effects. In reproduction studies on mice and rabbits there were no adverse effects on fertility, organogenesis or the rearing of young.     

Preclinical toxicity of a new oral anticancer drug, CI-994 (Acetyldinaline), in rats and dogs

CI-994 (acetyldinaline) is an orally active anticancer drug currently in Phase 1 clinical trials. To assess int preclinical toxicity, CI-994 was administered orally as suspensions to Wistar rats (10/sex/dose) and in capsules to beagle dogs (3/sex/dose) once daily for two weeks. Doses were 1.5,5, and 15 mg/kg for rats (9,30, and 90 mg/m², respectively), and 0.5, 2, and 5 mg/kg for dogs (10,40 and 100 mg/m², respectively) systemic exposure was dose-proportional based on toxicokinetic analysis in dogs. Severe clinical signs and mortality occurred at the highest dose in both species beginning on Day 10. Neutropenia, lymphocytopenia, thrombocytopenia, lymphoid depletion, bone marrow hypocellularity, and testicular degeneration were observed in both species, primarily at the mid- and high-dosed. Despite cotinued treatment, neutrophil counts in dogs returned to control levels in Week 2. Othere microscopic findings in rats included splenic hematopoietic depletion at all doses and epithelial cell necrosis in various tissues at 15 mg/kg. Additional bone marrow changes in dogs involved myeloid and megakaryocyte hyperplasia at 2 mg/kg and abnomal myeloid and megakaryocyte maturation at 2 and 5 mg/kg. Except for the testicular efficts in both species, all chages were reversible within a 4- week (rat) or 9- week (dog) recovery period. The results of these studies show that target organ effects of CI-944 principally involve tissues with rapidly dividing cell populations and that bone marrow suppression is the dose-limiting toxicity. CI-944 also seems to interfere with the release and/or maturation of cells in the bone marrow.     

NTP toxicology and carcinogensis Studies of 2,4-hexadienal (89% trans,trans isomer, CAS No. 142-83-6; 11% cis,trans isomer) (Gavage Studies)

2,4-Hexadienal, a colorless to yellow liquid with a pungent "green" or citrus odor, is used as a food additive for flavor enhancement, as a fragrance agent, as a starting material or intermediate in synthetic reactions in the chemical and pharmaceutical industries, as a fumigant, and as a corrosion inhibitor for steel. 2,4-Hexadienal was nominated for study by the National Cancer Institute because of the potential for carcinogenicity based on its alpha,beta-unsaturated aldehyde structure and the potential link between exposure to lipid peroxidation products in the diet and human malignancies. The commercial product is a mixture containing chiefly trans,trans-2,4-hexadienal in equilibrium with cis,trans-2,4-hexadienal. Male and female F344/N rats and B6C3F1 mice received 2,4-hexadienal (89% trans,trans; 11% cis,trans) in corn oil by gavage for 16 days, 14 weeks, or 2 years. Tissues and plasma from dosed rats were examined for malondialdehyde and glutathione concentrations, and DNA adducts were characterized in liver and forestomach samples from dosed rats and mice. Genetic toxicology studies were conducted in Salmonella typhimurium, rat and mouse bone marrow cells, and mouse peripheral blood erythrocytes. 16-DAY STUDY IN RATS: Groups of five male and five female rats were administered 0, 3, 9, 27, 80, or 240 mg 2,4-hexadienal/kg body weight in corn oil by gavage, 5 days per week, for 16 days. Three male and three female 240 mg/kg rats died before the end of the study. Mean body weight gains of 240 mg/kg rats were significantly less than those of the vehicle controls. Clinical findings included diarrhea, ataxia, lethargy, and nasal/eye discharge in males, and lethargy, paleness, and abnormal breathing in females in the 240 mg/kg groups. Liver weights of 240 mg/kg females were significantly greater than those of the vehicle controls. Gross and microscopic lesions indicative of forestomach necrosis and ulceration were present in most 240 mg/kg rats, and forestomach epithelial hyperplasia was microscopically evident in most 80 mg/kg rats. 16-DAY STUDY IN MICE: Groups of five male and five female mice were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 3, 9, 27, 80, or 240 mg/kg, 5 days per week, for 16 days. Chemical-related deaths occurred in one male and one female in the 240 mg/kg groups. Female mice in the 240 mg/kg group lost weight during the study. Gross and microscopic lesions indicative of forestomach necrosis and ulceration were present in all 240 mg/kg mice, and forestomach epithelial hyperplasia and hyperkeratosis were microscopically evident in 80 mg/kg mice. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 7.5, 15, 30, 60, or 120 mg/kg, 5 days per week, for 14 weeks. All rats survived to the end of the study. Mean body weights of 30, 60, and 120 mg/kg males were significantly less than those of the vehicle controls. The only clinical finding attributed to 2,4-hexadienal administration was hypersalivation in 30 and 120 mg/kg males and females. The incidences of forestomach hyperplasia and nasal olfactory atrophy or necrosis were significantly increased in 120 mg/kg rats. Nasal lesions occurred in most 120 mg/kg male rats. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 7.5, 15, 30, 60, or 120 mg/kg, 5 days per week, for 14 weeks. No deaths were attributed to administration of 2,4-hexadienal. Mean body weights of males and females were similar to those of the vehicle controls throughout the study. Clinical findings included salivation and anal wetness in males and females. Kidney weights of 60 and 120 mg/kg males and liver weights of 60 mg/kg males and females were significantly greater than those of the vehicle controls. The incidences of forestomach hyperplasia and/or nasal olfactory atrophy or necrosis were significantly increased in 120 mg/kg mice. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 2,4-hexministered 2,4-hexadienal in corn oil by gavage at doses of 0, 22.5, 45, or 90 mg/kg, 5 days per week, for up to 105 weeks. Survival of all dosed groups of rats was similar to that of the vehicle control groups. The mean body weights of 90 mg/kg males were generally less than those of the vehicle controls throughout the study. The incidences of squamous cell papilloma of the forestomach occurred with positive trends in male and female rats. This neoplasm was found in 58% of males and 34% of females in the 90 mg/kg groups. In the forestomach of male rats, papilloma multiplicity was increased in the 90 mg/kg group, and squamous cell carcinomas were found in one 45 mg/kg male and two 90 mg/kg males. Epithelial hyperplasia of the forestomach occurred in most 45 and 90 mg/kg rats. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 2,4-hexadienal in corn oil by gavage at doses of 0, 30, 60, or 120 mg/kg, 5 days per week, for up to 105 weeks. Survival of dosed mice was similar to that of the vehicle controls. The mean body weights of all dosed groups were generally similar to those of the vehicle controls throughout the study. The incidences of squamous cell papilloma of the forestomach occurred with positive trends in male and female mice; squamous cell carcinomas were present in 120 mg/kg males and females. Epithelial hyperplasia of the forestomach occurred in many 120 mg/kg mice. Two 120 mg/kg males had uncommon squamous cell carcinoma of the oral cavity (tongue). GENETIC TOXICOLOGY: 2,4-Hexadienal was mutagenic in S. typhimurium strain TA100 with and without induced hamster or rat liver enzymes; no mutagenic activity was detected with strains TA1535 or TA98, with or without S9. Results of bone marrow tests in male rats and male mice given intraperitoneal injections of 2,4-hexadienal showed a small increase in the induction of micronucleated erythrocytes. However, neither test was repeated, and the test results were judged to be inconclusive. Results of peripheral blood micronucleus tests in male and female mice treated with 2,4-hexadienal by gavage for 14 weeks were negative. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was clear evidence of carcinogenic activity* of 2,4-hexadienal in male and female F344/N rats and male and female B6C3F1 mice based on increased incidences of squamous cell neoplasms of the forestomach. The occurrence of squamous cell carcinoma of the oral cavity (tongue) in male B6C3F1 mice may have been related to the administration of 2,4-hexadienal. Hyperplasia of the forestomach in male and female rats and mice was associated with administration of 2,4-hexadienal. Synonyms: Hexa-2,4-dienal; 2,4-hexadienal; 2,4-hexadien-1-al; 2,4-Hx; 1,3-pentadiene-1-carboxaldehyde; 2-propylene acrolein; sorbaldehyde; sorbic aldehyde     

Morphological characteristics of the internal organs of experimental animals after administration of different doses of chanerol]

Experiments were conducted with rats and dogs to study the influence of different hanerol doses on the condition of anumber of internal organs. The drug was introduced in a single dose: to rats in the form of a 0.1% solution in amounts of 6, 8, 10, 13, 20 and 30 mg/kg and to dogs as a 0.1% solution in doses of 24 mg/kg. Doses of 20 and 30 mg/kg for rats and 24 mg/kg for dogs proved intolerable and animals perished in consequence of circulatory disturbances (blood effusion, thrombosis of capillaries in the lungs, spleen, suprarenals and in organs of the gastro-intestinal tract). On application of doses amounting to 6 and 13 mg/kg in rats and 6-12 in dogs the animals remained alive, although the lungs, testes and the spleen were found to be afflicted with thrombosis of individual capillaries and there was demonstrable the the development of pneumosclerotic foci, atrophy of spermatogenic epithelium and slight splenic infarctions.     

Reproductive, acute and subacute toxicity studies with nefopam in laboratory animals.

Nefopam hydrochloride, a compound with non-narcotic analgesic activity, was evaluated for its acute and subacute toxicity in mice, rats, and dogs. Potential teratogenic effects in mice and rabbits and its effect on general reproduction and postnatal development in rats were also studied. The LD50 by various routes of administration showed that in all three species oral LD50 values (80–178 mg/kg) were greater than im LD50 values (30–57 mg/kg) which were higher than iv LD50 values (20–45 mg/kg). A comparative oral acute toxicity study did indicate a strain difference in rats. Repeated daily administration of nefopam hydrochloride to rats and dogs at doses up to 10 mg/kg/day parenterally and 80 mg/kg/day orally revealed no toxic effects except for mild tissue irritation at injection sites and slight weight loss in some dogs receiving the high dose. Reproduction studies did not reveal any effects on fertility, lactation, or pup development and viability.