[Investigations on the effect of the combination sulfamoxole/trimethoprim on fertility and fetal development in rats and rabbits (author's tranls)].

The chemotherapeutically active combination of N1-(4,5-dimethyl-2-oxazolyl)-sulfanilamide (sulfamoxole) and 2,4-diamino-5-(3,4,5-trimethoxy-benzyl)-pyrimidine (trimethoprim) in a dose ratio of 5:1 (CN 3123, Nevin, Supristol) was investigated, with respect to teratogenicity, effects on fertility and reproduction and influence on peri- and post-natal development. Experiments with the combination and partly with the single substances were done on Sprague-Dawly and Wistar rats and on rabbits (New Zealand White). With regard to the known effects of trimethoprim in this field--fetal malformations typical of those caused by folic acid antagonists--it was to clarify whether or not potentiation phenomena or new toxic effects occur with the combination. The results were as follows: 1. CN 3123 is teratogenically and fetotoxically active when given in very high doses to pregnant rats and rabbits during the critical phase of organogenesis (day 8-15 of pregnancy in rats, day 8-14 in rabbits). There were malformations, decrease in the number of pups and an increase in the number of absorption sites. Litter size and litter weight were reduced. The malformations observed were cleft palates, rarely cleft lips, micrognathies and shortening of limbs. Doses up to 180 mg/kg CN 3123, corresponding to more than tenfold the daily maintenance dose in man, were without any effects on all parameters observed. Toxic effects were observed in Sprague-Dawley rats at a dose level of 420 mg/kg and in Wistar rats with 600 mg/kg, corresponding to the effects seen following 100 mg/kg of trimethoprim alone. Sulfamoxole in the corresponding dose of 500 mg/kg caused no embryotoxic effects in the rat. In rabbits 600 mg/kg CN 3123 induced no malformations but increased fetal loss. Therefore it can be concluded, that the teratogenic and fetotoxic effects seen with high doses of CN 3123 are due to the amount of trimethoprim in the combination. The observed effects with the combination are quantitatively related to those seen with trimethoprim. 2. CN 3123 in high doses which are teratogenic also provoked a reduction of growth of the animals. Food consumption and weight gain were reduced in dams with 420 and 600 mg/kg CN 3123. In this dose range the pup weights and the weight gain of the offspring of dams with continued dosing during lactation were also reduced. Variation rate including retardations was increased. The depressing effect of CN 3123 in high doses on food consumption and weight gain is known from long-term toxicological studies previously described [7]. 3. CN 3123 even with high doses has no effects on the fertility of male and female rats. The number of corpora lutea and implantations and also the pregnancy rate were unaffected when either the female or the male rats used for mating had been treated. There was also no influence on mating activity of the male animals treated. 4. According to the results of the fertility study with treatment of the male rats for a period of ten weeks or more there were no signs of mutagenic effects due to CN 3123.