Praziquantel, the drug of choice for the treatment of all types of schistosomiasis, was first released under a patent by Bayer (Leverkusen, Germany) in 1979 and at that time underwent the mandatory toxicology testing. However, despite few data to suggest a potentially adverse outcome, this drug was never tested on pregnant or lactating women prior to its release. This resulted in the drug being listed as a pregnancy category B drug, which is presumed safe based on animal studies, but one for which caution should be used when given to pregnant women. With regard to lactating women, the advice was to cease breast feeding for 72 hours following treatment to eliminate potential toxicity to the infant. This has resulted operationally in the exclusion of most pregnant and lactating women from national treatment campaigns and even the exclusion of adolescent girls from mass deworming programmes. As a result, the majority of women of childbearing age living in endemic countries have been left untreated or their treatment has been significantly delayed because they may be pregnant or lactating for a great part of their lives.

In an upcoming issue of Acta Tropica, the risk benefit of this issue is discussed in detail (1). In addition, a WHO informal consultation was convened with representation from the pharmaceutical industry, WHO, public health officials and international experts (2). Three main areas of evidence were reviewed: (i) experimental animal studies; (ii) human toxicology data; and (iii) a risk/benefit analysis of the detrimental impact of the disease versus the theoretical toxicity of the drug on the mother and her child.

The evidence was conclusive. Praziquantel may be considered the safest of all anthelminthic drugs and forms the backbone for all programmes to control schistosomiasis. The risks from praziquantel to either pregnant women or unborn or nursing children are exceedingly small - if they exist at all. In contrast, little doubt exists that both the mother and her unborn child suffer morbid sequels from schistosomiasis, some of which are irreversible. Moreover, the fact that pathology can develop more rapidly in pregnant women than previously thought, means that treatment delays are likely to result in even more serious outcomes (2).

Both the article and the WHO informal consultation concluded that not only should pregnant and lactating women be treated, but that some effort should be made to ensure inclusion of this vulnerable group in any national deworming efforts. This is an important change of policy and one with significant implications for deworming programmes (3).

References

1. Olds, G.R. Administration of praziquantel to pregnant and lactating women. Special Issue: Action starts now to control disease due to schistosomiasis and soil-transmitted helminthiasis. Acta Tropica, (In press.)

2. World Health Organization. Report of the WHO Informal Consultation on the use of praziquantel during pregnancy/lactation and albendazole/mebendazole in children under 24 months. Geneva, 8-9 April 2002. Geneva, WHO Document (in press).

3. Savioli, L., Crompton, D.W.T., Neira, M. Use of anthelminthic drugs during pregnancy. American Journal of Obstetrics and Gynecology, 188: 5-6 (2003).