Shakti N. Upadhyay, Charu Kaushic, and G.P. Talwar. 1990. Antifertility effects of neem (Azadirachta indica) oil by single intrauterine administration: a novel method for contraception. Proceedings of the Royal Society of London Series B: Biological Sciences 242:175-179.
A novel use of neem (Azadirachta indica) oil, a traditional plant product, for long-term and reversible blocking of fertility after a single intrauterine application is described. Female Wistar rats of proven fertility were given a single dose (100 µl) of neem oil by intrauterine route; control animals received the same volume of peanut oil. Whereas all control animals became pregnant and delivered normal litters, the rats treated with neem oil remained infertile for variable periods ranging from 107 to 180 days even after repeated matings with males of proven fertility. The block in fertility was, however, reversible, as half of the animals regained fertility and delivered normal litters by five months after treatment, without any apparent teratogenic effects. Unilateral administration of neem oil in the uterus blocked pregnancy only on the side of application, whereas the contralateral uterine horn treated with peanut oil had normally developing foetuses; no sign of implantation or foetal resorption was noted in the neem-oil-treated horn. The ovaries on both sides had 4-6 corpora lutea, indicating no effect of treatment on ovarian functions. The animals treated with neem oil showed a significant leukocytic infiltration in the uterine epithelium between days 3 and 5 post coitum, i.e., during the pre-implantation period. Intrauterine application of neem oil appears to induce a pre-implantation block in fertility; the possible mechanisms of the antifertility action are discussed.
Gp. Capt. K.C. Sinha and Lt. Col. S.S. Riar. 1985. Neem oil—an ideal contraceptive. Biological Memoirs 10(1 and 2):107-114.
Neem oil in vitro proved to be a strong spermicidal agent. Rhesus monkey and human spermatozoa became totally immotile within 30 seconds of contact with the undiluted oil.
In vivo studies in rats (20), rabbits (8), rhesus monkeys (14), and human volunteers (10) proved that neem oil applied intravaginally before sexual intercourse prevented pregnancy in all the species.
Neem oil has also been found to have anti-implantation/abortifacient effect in rats and rabbits if applied intravaginally on day 2 to day 7 of expected pregnancy. The minimum effective dose is 25 µl for rats. One month after the stoppage of neem oil application there was complete reversibility in fertility in these animals. It had no deleterious effect on the subsequent pregnancies and the offsprings.