Anthelmintics: a review.

Helminths infect 25% of the world's population. In the last 50 years specific, safe and effective anthelminitic drug therapy for various parasitic infestations have been developed. The population of the developing countries across the globe suffers not only as a direct result of these infections but due also to co-morbidity such as anemia, malnutrition and reduced immunity status. Earlier anthelmintic drugs suffered from serious drawbacks such as hepatotoxicity and required specific preparation of the patient before treatment such as 12-hour fasting and pre-post purging caused considerable inconvenience to the patient. However, successive discoveries were born out of rationale approach that contributed to the effective, more specific and more easily tolerated drugs i.e. benzimidazoles, piperazine derivatives, avermectins, pyrazinoquinoline, etc. The present approach is to identify the causative parasite on the basis of stool examination and as a result of this approach, different drugs are prescribed for different parasitic infections. Examples include thiabendazole for cutaneous larva migrans, mebendazole for ascariasis, trichiuriasis and hookworm, albendazole for inoperable cases of cystic hydatid disease, DEC for Toxocara induced visceral larva migrans and loiasis, ivermectin for onchocerciasis, praziquantel for schistosomiasis and niridazole for Dracunculus medinensis. The cure rates with these drugs is also high e.g. thiabendazole produces a cure-rate of 98% in cutaneous larva migrans while mebendazole gives cure rate of 76-95% in ascariasis, trichiuriasis and hookworm infestations. A cure rate of 96% is produced by praziquantel in schistosomiasis. Most of these drugs have broad-spectrum anthelmentic effect. The present review aims at evaluating the currently available anthelmintics with respect to their efficacy and adverse effects. Steps to prevent impending helminthic drug resistance are also discussed.