Virtually all the important helminth infections in humans can be treated with one of five anthelmintics currently in use: albendazole, mebendazole, diethylcarbamazine, iver-mectin and praziquantel (de Silva et al., 1997). These drugs are vital not only for the treatment of individual infections but are also useful in controlling transmission of the more common infections. This article reviews briefly the pharmacology of these five drugs, and then discusses current issues in the use of anthelmintics in the treatment and/or control of soil-transmitted nematode infections, filariasis, onchocerciasis, schistosomiasis (and other trematode infections), neurocysticercosis and hy-datidosis.
Mebendazole and albendazole are most effective against intestinal nematodes, but are contraindicated during the first trimester of pregnancy. The efficacy of prolonged therapy with these two drugs for treatment of larval cestode infections has not yet been established. Diethylcarbamazine is widely used to treat and control lymphatic filariasis, but adverse effects related to death of microfilariae or damage to adult worms may be marked. While ivermectin has been used in the treatment of patients with onchocerciasis, it is also undergoing investigation for use against lymphatic filariae. Praziquantel, used to treat schistosome infections, is also effective in other trematode infections and adult cestode infections (de Silva etal., 1997).
Ivermectin is the drug of choice for onchocerciasis. A small study demonstrated no increased incidence of birth defects when it was given inadvertently to pregnant women (Pacque et al., 1990).
Intestinal protozoan disease diagnosed in pregnant women is mostly controlled by symptomatic treatment. Specific therapy can be delayed until after delivery. Only severe cases, i.e. continued diarrhea leading to malnutrition of either mother or fetus, require an immediate speci fic drug therapy, which might be harmful to the fetus due to toxic and teratogenic potentials. Vertical transmission of intestinal protozoa has not been described. Invasive protozoan infections can be lethal to the mother, making immediate drug therapy mandatory, even if the potentials of fetotoxicity or teratogenicity are known. Vertical transmission occurs independent of maternal symptoms, causing clinical disease in the child either directly after birth or during the first months of life. Knowledge of endemic regions and of the maternal travel history is essential for early diagnosis and treatment of protozoan disease in pregnancy and of congenital protozoan infections (Bialek and Knobloch, 1999).
Prevention is the key concept, owing to the potential adverse effects resulting from the parasite or its treatment. it requires a basic knowledge of the life cycle of the parasite.
Parasitic infection during pregnancy is common. With most parasites, primary prevention is very effective in avoiding infestation. With the exceptions of malaria, toxoplasmosis and African trypanosomiasis, when infection does occur treatment decisions should be based on the impact of the infection on the patient and her fetus on an individual basis. When treatment is indicated, selection of medications with the least potential to harm the mother, and more particularly the developing fetus, is essential (Tietze and Jones, 1991).
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