Fertility studies antifertility effects

The male rat has a large reserve of spermatozoa and it is difficult to detect antifertility effects by using pregnancy as an endpoint. This is because the ejaculate in rats contains over 1000-fold the number of sperm that will produce maximum fertility, in man the multiple is only 2-A times and some studies have suggested that in certain Western populations, average human sperm counts appear to have declined over the past 50 years.The rat s testes are also relatively about 40 times the size of man s, if antifertility effects are observed, it can be helpful to measure various sperm parameters (seminology) to help characterise effects. 

The routine developmental toxicity study for vaccines includes dosing of the females before mating and may thus be capable of detecting antifertility effects in the female. There are no requirements to assess effects on male fertility. 

Mohan, J., Panda, J. N., Singh, U. S., and Moudgal, R. P. (1989). Studies on antifertility effects of gossypol acetic acid in domestic cocks. ]. Reprod. Fertil. 85, 73-78. 

A retrospective assessment of the potential antifertility influence of ethylene dibromide was conducted by studying the reproductive perfonnance of men exposed to ethylene dibromide in the workplace. Data were obtained from four chemical plants manufacturing ethylene dibromide located in the southern part of the United States (Arkansas and Texas). Exposures in the plants ranged from less than 0.5 ppm to 5 ppm [3.8-38 mg/m- ]. Evaluations were made exclusively on the basis of the men s reproductive histories of live births to their wives, subsequent to their occupational exposure. The mmiber of live births was compared with the expected mmiber derived from national fertility tables. One of the four plants studied showed a significant decrease in fertility however, when data from the four plants were combined, there was no significant effect of ethylene dibroniide exposure on reproductive performance (Wong et al., 1979). 

Information on the safety of andrographis during pregnancy is limited. Conflicting results on effects on fertility and pregnancy have been reported in animal studies, with some studies indicating no adverse effects on fertility in mice (Dhammaupakorn and Chaichantipyuth 1989 Shamsuzzoha et al. 1978,1979) and other studies indicating antifertility or abortifacient activity (Chen and Chen 2004 But 1988 Zoha et al. 1989). 

The compound gossypol has been shown to have antifertility activity in men at doses of 0.3 mg/kg. Doses in clinical trials generally range between 7.5 and 15 mg daily. After clinical trials, approximately 60% of men regained fertility by 16 weeks after the end of the trial, whereas azoospermia (lack of sperm in the semen) persisted in about 19% of men (Coutinho 2002). Human studies have indicated that gossypol has no significant effects on hormone levels (De Smet 1993 Qian and Wang 1984). 

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