Abstract: Purpose: To observe the effect of metadoxine on male reproductivetoxicity on rats. Methods: Male Sprague-Dawley rats were administrated orally with metadoxine at 0, 500, 1 000, and 2 000 mg / kg once daily for 2 weeks. Half of the animals were sacrificed 24 h after the end of treatment and the others were examined with a 3-week interval time. The organ ratio of testis, epididymidis, and other androgen dependent tissues were measured. Sperm count, mortality, activity, morphology were also analyzed. Results: There were not any significant changes in all the parameters examined in 500 mg / kg group either at the end of treatment or 3 weeks after treatment. Twenty-four hours after the end of treatment, no significant abnormalities were observed except that the organ ratio of prepuse gland slightly but significantly decreased in 1 000 and 2 000 mg / kg compared with the control (P<0.05). Three weeks after treatment, however, the ratios of cremaster muscle / prostate gland and epididymidis / body weight decreased, and the frequency of sperm abnormality increased significantly in 1 000 mg / kg group. Dramatic decline in organ ratios of testis, epididymidis, and prepuse gland, and the ratio of cremaster muscle / prostate gland, sperm count, the percentage of survival and activity of sperm were observed in 2 000 mg / kg group. Conclusion: Male reproductive toxicities were induced by exposure with metadoxine at 1 000 mg / kg or higher for two weeks in Sprague-Dawley rats, and the damages seen to be progressive.

Key words: metadoxine, male reproductive toxicity, rats, sperm