VAGINAL DELIVERY OF NEW FORMULATIONS OF NONOXYNOL-9 COPRECIPITATED WITH POLYVINYLPYRROLIDONE IN RABBITS - COMPARISONS BETWEEN 2 FORMULATIONDELIVERY SYSTEMS

The objective of this study was to assess the efficacy of two formulat ion delivery systems (FDS) in preventing the onset of pregnancy in rab bits. Nonoxynol-9 (N-9) was coprecipitated with polyvinylpyrrolidone ( PVP), which yields PVP/N-9, and prepared as capsules or tablets. Semen specimens were collected (from eight male rabbits), pooled, and used for in vitro spermicidal assessment or artificial insemination (AI). i n vitro spermicidal assessment was performed by introducing and mixing the FDS containing PVP or PVP/N-9 with 1.0 mt of semen, followed by i ncubation at 37 degrees C for 6 h. Semen samples were taken at various time intervals to determine killing of spermatozoa and dissolution of the FDS. The efficacy of the FDS in preventing the onset of pregnancy was assessed by inserting the FDS vaginally. The does were artificial ly inseminated at 0, 0.5, and 6 h after insertion of the FDS vaginally . The number of pregnant does and newborn rabbits was recorded. In the in vitro spermicidal trial, semen specimens exposed to both FDS conta ining PVP/N-9 were killed within 10 to 15 min of incubation. Tablets c ontaining PVP only or PVP/N-9 dissolved completely after 3 h of incuba tion. However, capsules did not dissolve completely by 6 h of incubati on. The results obtained in the in vivo trial showed that both FDS exh ibited some variations in preventing the onset of pregnancy over the v arious time intervals following the insertion of tablets or capsules a nd AI. The tablet seemed to be a more efficient delivery system than t he capsule, yielding significantly lower pregnancy rates at all three time intervals assessed. The tablet FDS, as applied in this study, was found to be the most efficient mode of delivery of the tested spermic idal formulations. (C) 1997 Elsevier Science Inc. All rights reserved.