title: Prolongation of gestation in the rat and hamster by naproxen.
abstract: Administration of naproxen by once or twice daily subcutaneous injection, or orally in the drinking water, was found not to routinely prevent parturition in either the rat or the hamster. However, the duration of labor was prolonged and associated with poor pup viability. The prolonged labor and fetal mortality were thought to be due to suppression of myometrial activity after onset of labor and caused by the episodic administration regimens. Thus fetal deaths could result from asphysia due to suppression of uterine contractions, after partial or total placental separation had occurred. Naproxen was, therefore, administered on a more continuous basis by subcutaneous implantation of pellets in rat and hamster, or orally every four hours in the rat. Either of these regimens was then able to postpone parturition beyond the range of deliveries in control animals. In such naproxen treated rats there was no sign of placetal detachment, even out to day 25 of pregnancy. Fetal viability was preserved and fetuses continued to gain weight. These observations are consistent with a true prolongation of gestation by naproxen rather than merely an interference with the process of labor.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002784:Cholesterol / Q000494:pharmacology; D006224:Cricetinae; D004343:Drug Implants; D005260:Female; D007279:Injections, Subcutaneous; D008647:Mesocricetus; D009288:Naproxen / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D051381:Rats; D013045:Species Specificity; D013997:Time Factors
chemical_list: D004343:Drug Implants; D009288:Naproxen; D002784:Cholesterol