The influence of pentoxifylline (Trental) on the antifertility effect of intrauterine devices in rats.

OBJECTIVE: To test the hypothesis that the inflammatory response stimulated by intrauterine devices (IUDs) plays a role in the antifertility action of IUDs. We treated rats with pentoxifylline (Trental; Hoechst-Roussel Pharmaceuticals, Inc., Somerville, NJ) and evaluated its effect on the anti-implantation action of IUDs. The number of embryos in treated compared with untreated rats was determined. DESIGN: Breeder female Sprague-Dawley rats (Harlan Sprague Dawley, Indianapolis, IN) were randomized into one of five test groups (n = 20 per group). A monofilament nylon IUD was inserted transcervically into one horn of the bicornuate uterus in two groups. The IUD-bearing groups received either intraperitoneal (IP) injections of pentoxifylline (45 mg/kg per every 12 hours) or normal saline (NS). The two non-IUD-bearing groups received IP injections of pentoxifylline or NS. The non-IUD group was not injected. All injections were administered daily for 21 days and the animals then mated. Successful mating was determined by the presence of spermatozoa in vaginal washings. The injections of pentoxifylline or NS were continued until day 12 of pregnancy when the rats were killed. The total number of embryos in each uterine horn was determined. SETTING: University research laboratory. RESULTS: Embryo numbers (1.0 +/- 0.6 [mean +/- SEM]) were reduced in the IUD horn compared with the contralateral non-IUD horn (6.4 +/- 1.0) and with the uterine horns from each of the four other test groups. The number of embryos were increased in the IUD horn (3.5 +/- 0.9) of the pentoxifylline-treated rats. CONCLUSION: Pentoxifylline appeared to reduce the contraceptive effectiveness of the IUDs in this model.