Cecal torsion in rodents associated with chronic administration of clinafloxacin

The chronic toxicity of clinafloxacin, a fluoroquinolone antibacterial agent, was evaluated in multiple strains of mice and rats. In 5 separate studies, mice and rats that were orally administered up to 1,000 mg/kg of clinafloxacin from 9 to 104 weeks developed dose-related cecal dilatation and deaths that were attributable to cecal torsion. Cecal rupture was observed in association with torsion. Although cecal dilatation is commonly observed in rodents given antibacterials such as fluoroquinolones, cecal torsion has not been a reported sequelae to dilatation.

Nasal toxicity of CI-959, a novel anti-inflammatory drug, in Wistar rats and Beagle dogs

CI-959, 5-methoxy-3-(1-methylethoxy)-N-1H-tetrazol-5-yl-benzo[b]thio phene-2-carboxamide, an anti-inflammatory agent, was considered for development as a treatment for rhinitis. Two-week topical nasal studies in Wistar rats and Beagle dogs were performed to assess nasal toxicity of CI-959. Rats were given daily doses in the right nostril of 0.05 ml of solutions of varying concentrations (0.5, 2, 10, 20, 30, 60, and 90 mg/ml; doses of 0.08, 0.3, 1.6, 3.2, 4.8, 9.6, and 14.6 mg/kg) of CI-959. Beagle dogs were given daily doses in the right nostril of 0.5 ml of 10, 20, 30, 60, and 90 mg/ml solutions (doses of 0.5, 0.8, 1.2, 2.8, and 3.7 mg/kg) of CI-959. Rats given > or = 60 mg/ml either lost weight or had decreased weight gain. Salivation at dosing was seen in both species. Four sections of nasal cavity were examined from each animal. In rats, 0.5 mg/ml was the "no effect" dose; minimal changes were seen at 2 mg/ ml, and significant changes were dose related in severity at > or = 10 mg/ml in all 4 nasal levels. Degeneration and necrosis of respiratory and olfactory epithelia were minimal to moderate in severity. Adhesions and fibro-osseous proliferation of ethmoturbinates, epithelial hyperplasia, squamous metaplasia, and exudate were also seen. In dogs, 10 mg/ml was the no effect dose; respiratory epithelium was affected at > or =20 mg/ml. Respiratory epithelial degeneration was minimal to mild, with loss of ciliated and goblet cells and thinning of mucosa. Distribution of degeneration increased with increased concentrations. In both species, in accordance with the suggested action of CI-959, infiltration with neutrophils was not significant. CI-959 was locally toxic to nasal cavity respiratory and olfactory epithelia in rats and respiratory epithelium in dogs.

Carcinogenicity of the anticancer topoisomerase inhibitor, amsacrine, in Wistar rats

Amsacrine is an antineoplastic drug used in the treatment of acute adult leukemias. To assess its carcinogenic potential, groups of 50 male and 50 female rats were administered amsacrine by lateral tail vein injection at 0 (vehicle control), 0.25, 1, or 3 mg/kg once daily for 5 days, followed by a 23-day recovery period. This cycle of dosing and recovery was repeated a total of six times. The animals were then maintained without dosing for an 18-month observation period. During the dosing phase, signs of toxicity were limited to the 3 mg/kg animals and included alopecia, diarrhea, injection site lesions, and skin and subcutaneous nodules. Statistically significant reductions in body weight gain and food consumption also occurred at 3 mg/kg during each 5-day dosing period followed by recovery during the latter 3 weeks of each cycle. Except for skin and subcutaneous nodules, signs of toxicity in the 3 mg/kg animals ultimately disappeared during the 18-month observation phase. Survival at study termination for the vehicle control, 0.25, 1, and 3 mg/kg groups was 56, 52, 34, and 0%, respectively, in males, and 64, 48, 54, and 4%, respectively, in females. Mortality was primarily due to bone marrow suppression during the dosing phase, chronic progressive nephropathy, or development of tumors. Incidences of the following tumors were significantly increased in the 3 mg/kg groups of both sexes (Fisher exact test, two-tailed, p < 0.01): all malignancies; all tumors of the small intestine, adenocarcinoma and adenoma of the small intestine, all tumors of the skin, and squamous cell papilloma. Other tumor incidences that were significantly increased in the 3 mg/kg males were thymoma and multiple neoplastic histotypes of the skin and adnexa including basal cell tumor, fibroma, sebaceous gland adenoma, and squamous cell carcinoma. A disproportionate number of the skin tumors were located on the tail, suggesting a localized tissue concentration effect. In the 3 mg/kg females, significantly increased tumor incidences also included all tumors of the mammary gland, adenocarcinoma of the mammary gland, all tumors of the uterine horn, and endometrial stromal polyps of the uterine horn. The 1 mg/kg males had significantly increased incidences of all tumors of the small intestine and skin, adenocarcinoma of the small intestine, and fibroma of the skin. Fibroma of the skin was also significantly increased in the 0.25 mg/kg males. Incidences of all tumors and all benign tumors were significantly increased in the 1 mg/kg females. There were no significantly increased tumor incidences in the 0.25 mg/kg females. The results of this study show that amsacrine is carcinogenic in Wistar rats. Target organs for tumorigenicity include small intestine, skin, mammary gland, thymus, and uterus.

Toxicological comparison of a muscarinic agonist given to rats by gavage or in the diet

Corneal opacities and urinary tract sepsis were previously observed by the authors in rats given muscarinic agonists mixed in the diet or by gavage. To explain the differential toxicity generated by each means of administration, toxicokinetics of the muscarinic agonist CI-979 were investigated. In addition, the muscarinic antagonist scopolamine was co-administered with CI-979 to evaluate the relationship of these effects to pharmacological mechanism of action of CI-979. Female rats were given CI-979 daily by gavage at 0, 1, 10 and 30 mg/kg body weight or in the diet at 0, 1, 10 and 50 mg/kg body weight for up to 14 days. Dose-related clinical signs of muscarinic stimulation, such as sialorrhoea and dacryorrhoea, were observed predominantly in rats given 10 and 30 mg/kg body weight CI-979 by gavage, and corresponded with the high plasma drug concentrations. In contrast, hydronephrosis, pyelonephritis, and inflammation and necrosis of the kidney, urinary bladder, urethra and urinary papilla were linked to sustained, albeit lower plasma drug concentrations attained by dietary administration of CI-979 at 10 and 50 mg/kg body weight. Comparable incidences of corneal opacities were induced by both means of administration, but lesions appeared more rapidly and were generally of greater severity when CI-979 was given in the diet. The induction of corneal lesions, as well as urinary sepsis, may not relate simply to maximum plasma concentrations or to areas under the curve per se, but rather may arise when plasma drug concentrations are sustained. Corneal opacification and development of urinary tract pathology were inhibited by scopolamine, suggesting that these effects were related to the muscarinic mechanism of action of CI-979.

In vitro and in vivo activities of clinafloxacin, CI-990 (PD 131112), and PD 138312 versus enterococci

Certain new fluoroquinolones have high activity against enterococci. Against Enterococcus faecalis (n = 18), MICs at which 90% of the isolates were inhibited were as follows (in micrograms per milliliter): clinafloxacin, 0.125; CI-990, 0.5; and PD 138312, 0.25 (compared with 1 microgram/ml for ciprofloxacin and 2 micrograms/ml for ofloxacin). Strains producing beta-lactamase or that were vancomycin resistant or resistant to high-level gentamicin were not quinolone cross-resistant. The drugs were bactericidal and were unaffected by 50% human serum. Oral efficacies (in milligrams per kilogram of body weight for 50% protective doses) in lethal mouse infections with quinolone-susceptible strains were 4.3 to 24 for clinafloxacin, 7.2 to 39 for CI-990, 7.2 to 76 for PD 138312, and 41 to > 100 for ciprofloxacin; when the drugs were given subcutaneously, the order was similar and values ranged from 1.1 to 12.5. Clinafloxacin, CI-990, and PD 138312 may have therapeutic potential in systemic enterococcal infections in humans.

Subchronic toxicity of pentostatin in Wistar rats

Pentostatin, an adenosine deaminase inhibitor, has been approved for the treatment of refractory hairy cell leukemia. In a preclinical toxicity study, Wistar rats were administered 0, 1, 10, 25, and 50 mg/kg (0, 6, 60, 150, and 300 mg/m2, respectively) pentostatin intravenously once a week for 26 wk (1.5-75-fold above the therapeutic dose in humans). Lymphoplasmacytic thyroiditis was present in 20% of females given 25 mg/kg and in 20 and 47% of males and females given 50 mg/kg, respectively. Thyroiditis was still present 4 wk following drug withdrawal. Thyroiditis was characterized by glandular enlargement, follicular epithelial hyperplasia and degeneration, colloid depletion, and interstitial infiltrates of lymphocytes and plasma cells. Drug-related changes in other tissues included lymphoid depletion of T-cell regions of thymus, spleen, and lymph nodes; bronchiolization of alveolar ducts with accumulation of mucus and foamy macrophages; testicular atrophy with sperm granulomas; dermoepidermal lymphocytic infiltrates with ulceration and alopecia; and hepatocytomegaly.

Leucovorin protection against repeated daily dose toxicity of trimetrexate in rats

Repeated high doses of trimetrexate (TMX), a potent non-classical antifolate, have been administered as an experimental treatment for life-threatening Pneumocystis carinii infections in man. This therapy includes the coadministration of leucovorin, a reduced folate cofactor, to prevent antifolate toxicity in the host. The purpose of this investigation was to assess possible toxicologic sequelae of this combination regimen in an animal model. TMX at daily oral doses of 25, 35, and 45 mg/kg produced dose-related myelosuppression, thymic lymphoid depletion, seminiferous tubular atrophy, and degenerative lesions of the gastrointestinal tract. Mortality observed with TMX alone occurred earlier at higher doses and was specifically associated with severe degenerative enteropathy of the cecum. Oral leucovorin doses of 1, 5, 20, or 50 mg/kg administered twice daily, at the time of TMX administration and 6 hr later, protected against TMX lethality and target organ toxicity in a dose-related manner. Leucovorin was only partially protective against TMX-induced macrocytic anemia and the degree of protection was not dose-related. Leucovorin protection against cecal enteropathy was associated with increased DNA synthetic rates and higher mitotic activity of cecal epithelium than those in rats administered TMX alone. Importantly, the combination of daily administration of high dose TMX for 4 weeks with protective coadministration of leucovorin did not result in target organ toxicities that differed from TMX alone.

Granular basal cell tumor in a Wistar rat

A granular cell variant of a cutaneous basal cell tumor in a Wistar rat is described. The tumor resembles the variant as described in man and dogs. The granular basal cells contain cytoplasmic PAS positive granules, and immunostained positively with HMW cytokeratins. Ultrastructurally, the cytoplasmic granules were secondary lysosomes.

Proliferative bone lesions in rats given anticancer compounds

Proliferative endosteal lesions were observed in metaphysis and diaphysis of femur and sternebra of Wistar (CRL:[WI]BR) rats administered 3 chemically-distinct anticancer compounds with dissimilar mechanisms of action: trimetrexate glucuronate, an antifolate; pentostatin, an adenosine deaminase inhibitor; and CI-980, a mitotic inhibitor. Islands of woven bone, often circumscribed by conspicuous myelostromal proliferation, were seen on Days 8-28 in rats given trimetrexate glucuronate daily by gavage, and on Day 4 but not Day 29 in rats given a single intravenous dose of pentostatin. Intravenous administration of CI-980 for 1 or 5 days resulted in marrow necrosis, marked centripetal new bone formation, and myelostromal proliferation on Days 4 and 8, respectively. These lesions were not present at the termination of these latter studies (Days 29 and 35, respectively). In conclusion, anticancer compounds induced local bone marrow injury and the release of local inflammatory mediators which may have provided the stimulus for bone formation and myelostromal proliferation.

Effect of l-dopa or bromocriptine on feeding and motor behavior of rats with lesions in the globus pallidus

Rats were lesioned bilaterally in the globus pallidus (GP) with anodal current or 6-OHDA, and were observed in various motor tests 10 min daily for 3 weeks. Body weight, home cage water and food intakes were recorded daily under two different food accessibility conditions. The lesions produced adipsia, aphagia, loss of body weight and motor impairments which could not be reversed by either l-dopa or bromocriptine. Animals could be made to recover, however, by making food easily accessible and palatable. The results do not support a "metabolic" role for the GP but support the idea that aphagia, adipsia and mortality is due to motoric impairments produced by the lesion.