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PH8.9 | PH8.9 | Anthelmintic Drugs — SDL Guide — SDL Guide (Part 3)

Self-Assessment: Anthelmintic Drug Selection

Apply your knowledge to these scenarios:

Scenario A: A 32-year-old pregnant woman (12 weeks gestation) living in a tribal district is found to have hookworm infection (Hb 7g/dL, stool shows hookworm eggs). She needs anthelmintic treatment. What is the appropriate drug?

Discussion: In the first trimester, albendazole should be avoided due to teratogenicity (FDA Category C with animal teratogenicity data). Mebendazole (100mg BD × 3 days) or pyrantel pamoate (10mg/kg × 3 days) are the safer alternatives — both have very poor systemic absorption, minimising fetal exposure. Iron supplementation is simultaneously essential. Note: WHO's position has evolved — for women in the second and third trimesters, albendazole has been used in MDA programmes with reassuring safety data. However, for the first trimester, pyrantel or mebendazole remain the preferred choices for clinical practice.

Scenario B: A 40-year-old HIV-positive man on ART (CD4 count 80 cells/μL) presents with recurrent abdominal pain and diarrhoea. Stool examination shows Strongyloides larvae (rhabditiform larvae). His physician considers giving albendazole. Is this appropriate?

Discussion: Albendazole is NOT the drug of choice for strongyloides. Ivermectin 200mcg/kg/day × 2 days is the preferred treatment — cure rates with ivermectin are consistently superior to albendazole (which has variable activity vs Strongyloides). In this HIV-positive, immunocompromised patient with CD4 of 80, there is a serious risk of hyperinfection syndrome (autoinfection accelerates → massive worm burden → intestinal perforation → bacteraemia from enteric organisms tracked by larvae through the gut wall). Ivermectin must be given promptly; monthly suppressive ivermectin may be considered until CD4 improves. Albendazole can be used if ivermectin is unavailable, but must be given for at least 7 days.

Scenario C: A 50-year-old returning from Kenya on holiday develops diarrhoea with blood and mucus, abdominal pain, and haematuria 6 weeks later. A urine examination shows Schistosoma haematobium eggs (with terminal spine). He has no allergies. What is the treatment?

Discussion: Schistosoma haematobium (urinary schistosomiasis) — treatment is praziquantel 40mg/kg in 2 divided doses on a single day (20mg/kg given twice, 4–6 hours apart). This is the WHO-standard treatment for all schistosome species. Check for treatment response at 4–8 weeks (repeat urine exam — egg counts should dramatically reduce; a small number of eggs may persist transiently as dead eggs pass through). Re-treatment with a second course is given if significant egg counts persist. Ensure concurrent treatment for any intestinal parasites co-acquired during travel. Niclosamide has NO activity against schistosomiasis (trematode, not cestode mechanism).