Anti-implantation activity of H2 receptor blockers and meloxicam, a COX-inhibitor, in albino Wistar rats

Objective To evaluate the anti-implantation activity of H-2 receptor blockers ranitidine and famotidine, and Cox-inhibitor meloxicam, alone and in combination, considering the role of histamine and prostaglandins in implantation. Method The drugs were administered orally to female albino Wistar rats at different dose levels for 1 to 7 days, immediately after confirming copulation by observing sperm in the vaginal smear. A laparotomy was done on the 10th day of pregnancy, the implants and corpora lutea were counted, and the pre- and post implantation losses determined. The mast cell stabilising activity was studied using both in vitro and in vivo methods. Results Ranitidine 70 mg/kg (75.41%; p < 0.01), and famotidine 80 mg/kg (74.30%; p < 0.001) showed significant anti-fertility activity. No increase in activity was seen at higher doses. Meloxicam showed significant activity at doses of 3, 4, and 5 mg/kg. The combination of meloxicam (4 mg/kg) with ranitidine (70 mg) and famotidine (80 mg/kg) showed 100% anti-fertility activity. Conclusion Our results indirectly confirm the combined involvement of histamine and prostaglandins in the implantation process. The mast cell stabilising property of H-2 blockers appears to be a possible mechanism for their anti-implantation activity.