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Sperm analyses are often incorporated into reproductive toxicity studies in rats. Due to the relative ease of collecting multiple samples throughout a study, semen analysis in non-rodents such as dogs offers the opportunity to assess potential development of functional effects of compounds on male reproduction over time. In the present study, semen parameters were evaluated in beagle dogs during and at termination of a chronic toxicity study with the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, atorvastatin. Male dogs received 0, 10, 40, or 120 mg/kg orally in gelatin capsules for up to 104 weeks (n = 10/group). After 52 weeks of dosing, 3 dogs/group were euthanized, and 2/group were withdrawn from treatment for a 12-week reversal period and euthanized at Week 64. The remaining 5/group continued treatment until Week 104. Semen was collected from all animals for 3 consecutive weeks prior to termination of the 52-week animals (Weeks 50, 51, 52) for analysis of sperm parameters, using manual methods of evaluation. Semen was collected from the remaining animals at Weeks 64, 78, 91, and 104, and was analyzed. At necropsy, testes, epididymides, and prostates were weighed and evaluated histologically, and epididymal sperm counts were determined. Serum cholesterol was decreased 25--60% at all doses during the study. There were no drug-related differences in semen volume and color, total sperm count, and sperm concentration, morphology, progressiveness, and percent motility during treatment with atorvastatin. There were also no effects on reproductive organ weights or histopathology, and no effects on epididymal sperm count. Thus, incorporation of semen analyses into this study allowed the evaluation of potential male reproductive effects in dogs at multiple time points during the study. Statistical power calculations demonstrated acceptable statistical power (> 80%) for semen sperm count, concentration, morphology, and motility with group sizes of 8--10 animals, and for semen sperm count and concentration or epididymal sperm count with group sizes of 3--5 animals, using the methodology described in this paper.

The chronic toxicity of atorvastatin (AT), an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, was evaluated in beagle dogs. Dogs were treated with 0, 10, 40, or 120 mg/kg of AT daily. Treatment lengths were 52 wk, 52 wk followed by 12 wk without drug, or 104 wk. Decreases in cholesterol levels were dose related and stable throughout the treatment period. Increases in alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase were transient and dose related in severity at > or = 40 mg/kg. Two dogs administered 120 mg/kg of AT daily were sacrificed moribund during the first 9 wk of treatment. Hepatic lesions were reversible with or without continued treatment and dose related in severity and distribution. Hepatic microgranulomas and hepatocellular degeneration were seen at the 120-mg/kg dose in dogs sacrificed before 53 wk. Before 53 wk, hepatocellular lipofuscin deposits were increased in dogs given > or = 40 mg/kg of AT daily but were similar to controls after 12 wk without drug and after 104 wk of continuous treatment. Bile stasis occurred in dogs given > or = 40 mg/kg of AT daily at all time points but was less severe after reversal and at week 104 compared with week 52.

Purpose: Atorvastatin (Lipitor) was developed as an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase for treatment of serum lipid disorders. Other reductase inhibitors (RIs) induce cataracts in dogs exposed to relatively high levels of the drugs for extended periods of time. The purpose of these studies was to assess the cataractogenic potential of atorvastatin, when administered for up to 2 years in beagle dogs., Methods: Atorvastatin was administered at doses up to 150 mg/kg/day in 2-week, 13-week or 104-week studies. A 52-week interim sacrifice and a reversal group in which dosing was terminated at week 52 and the dogs sacrificed at week 64, was included in the 104-week study., Results: Serum cholesterol was significantly lowered in all studies. No clinical or histologic evidence of drug-induced cataracts was found in any study. Lens biochemical analyses in the 13-week study revealed no statistically significant changes in lenticular weight, reduced or oxidized glutathione content, adenosine nucleotide content, glucose-6-phosphate dehydrogenase activity or phosphofructokinase activity in any treatment group. Modest (11-17%) and transient decreases in lens protein, potassium and glucose content were noted in the 13-week study and at week 52 (glucose only) in the 104-week study, at the doses > or = 40 mg/kg., Conclusions: These studies demonstrated that, in spite of marked reduction in serum cholesterol, atorvastatin was not cataractogenic in dogs at any tested dose. We conclude that atorvastatin differs from other RIs in this regard.

While HMG-CoA reductase inhibitors such as fluvastatin, lovastatin, pravastatin and simvastatin demonstrate lack of in vitro and in vivo mutagenicity and clastogenicity in bacterial and mammalian cells, long term rodent carcinogenicity studies resulted in an increased incidence in neoplasms at high doses. These effects may be attributable to an exaggeration of the desired biochemical effect of the drug and/or a tumor promoting effect. The genotoxicity of atorvastatin, a newly developed HMG-CoA reductase inhibitor, was evaluated in a variety of test systems. In bacterial mutagenicity tests, the E. coli tester strain WP2(uvrA) and S. typhimurium strains TA98, TA100, TA1535, TA1537, and TA1538 were exposed to concentrations of atorvastatin as high as 5000 micrograms/plate both in the absence (S9-) and presence (S9+) of metabolic activation. Atorvastatin was not mutagenic in either E. coli or S. typhimurium. Chinese hamster lung V79 cell cultures were exposed to atorvastatin at concentrations of 50-300 micrograms/ml (S9-) and 100-300 micrograms/ml (S9+) and structural chromosome aberrations were assessed. Mutation at the hgprt locus was assessed at concentrations of 100-300 micrograms/ml (S9-) and 150-275 micrograms/ml (S9+). Atorvastatin was neither mutagenic nor clastogenic in the absence or presence of S9. The lack of in vitro genotoxicity was corroborated in vivo in a mouse micronucleus study in which single oral doses of atorvastatin were administered to male and female CD-1 mice at 1, 2500, or 5000 mg/kg. No biologically significant increases in the frequency of micronucleated polychromatic erythrocytes in bone marrow at 24, 48, or 72 h postdosing were observed. Thus, atorvastatin, as with the other tested HMG-CoA reductase inhibitors, is not genotoxic.