RESUMEN
Ribavirin (1-beta-D-ribofuranosyl-1, 2, 4-triazole-3-Carboxamide) is a potent inhibitor of inosine monophosphate dehydrogenase, used widely as an antiviral drug. Although it has been reported as a teratogen, its effect on spermatogenesis is not known. Male Wistar rats were segregated into 24 groups of 5 in each. Six groups were treated with water, 6 groups with 20 mg/kg, another 6 groups with 100 mg/kg and remaining 6 groups with 200 mg/kg for 5 days at intervals of 24 h (i.p.). Animals were anaesthetized at 14, 28, 35, 42, 70 and 105 days following the last exposure, laparatomy was conducted, epididymis was removed, minced in 1 ml phosphate buffered saline (PBS, pH 7.2), filtered and stained with 1% aqueous eosin Y. An aliquot was taken in haemocytometer, diluted in PBS and charged into Neubauer's chamber. Spermatozoa were counted in 8 squares except the central, and multiplied by 5 x 10(4). Data were analysed by Mann-Whitney "U" test. Ribavirin significantly decreased the sperm count in a dose and time dependent pattern and showed a recovery by day 105 except at 200 mg/kg. Ribavirin is reversibly cytotoxic to germ cells and decreases the production of spermatozoa.