Salicylazosulfapyridine (asulfidine, sulfasalizine, SASP) is classified as a sulfonamide drug. However, it has little antimicrobial effect and is used to treat inflammatory disorders of the gastrointestinal tract. Colonic bacteria metabolize SASP to sulfapyridine and 5-aminosalicylic acid. Numerous case reports and clinical trials document that SASP causes reduced fertility in men and adversely affects sperm count, motility and morphology. Data on female reproductive effects are lacking. SASP also causes hypothyroidism in humans.
SASP was tested according to the NTP's Continuous Breeding Protocol to gain more information on female reproductive effects and to expand the database on the relationship between reproductive toxicity and sperm motility measures. It was also hypothesized that the epididymal effects noted previously might alter circulating levels of acidic epididymal glycoprotein (AEG), a protein produced only by the epididymis, and of interest as a serum marker of epididymal effect.
SASP was administered via gavage to cohabiting rat pairs at 100, 200, and 400 mg/kg/day. Body weights of F0 rats in the 400 mg/kg group were significantly lower than control weights; females were affected more but weights of both sexes were generally within 10% of control values. SASP slightly decreased the number of litters per pair at 400 mg/kg/day by the fifth litter and the treated groups had a mean of 11.4, 10.1 and 9.1 live pups per litter (100, 200 and 400 mg/kg, respectively), vs. 13.2 for controls. Live pup weights were also significantly (8%) decreased at the 400 mg/kg dose level. The crossover mating showed that this was primarily a male effect.
F1 rats were gavaged with parental doses of SASP and were mated at sexual maturity. F2 pup birth weight was decreased at 400 mg/kg. At necropsy, both sexes and generations receiving 400 mg/kg SASP had decreased body weights and increased thyrotropin levels. SASP at all levels increased by 3-fold the incidence of abnormal sperm in males though there were no effects on epididymal sperm density or motility, or on blood levels of acidic epididymal glycoprotein. SASP had no effect on estrual cyclicity or the average estrous cycle length.
Overall, SASP can be classified as a male reproductive toxicant at dose levels that do not affect body weight. It does not appear to adversely affect the reproductive ability of young rats exposed during maturation more than exposed mature animals.
NTIS # PB92-203710