Antiparasitic medications

Anti-protozoals - Protozoa Punishers

• Metronidazole/Tinidazole: Forms toxic free radicals that damage DNA.
  • Uses: 📌 Giardia, Entamoeba histolytica, Trichomonas vaginalis (GET on the Metro!). Also for anaerobic bacteria (Bacteroides, C. diff).
  • ⚠️ Avoid alcohol (disulfiram-like reaction).
• Nitazoxanide: Inhibits pyruvate-ferredoxin oxidoreductase pathway.
  • Uses: Cryptosporidium, Giardia.
• Paromomycin: Aminoglycoside antibiotic effective against luminal parasites.
  • Uses: Luminal amebiasis, cryptosporidiosis in pregnancy.
• Nifurtimox: Used for Chagas disease (Trypanosoma cruzi).
• Suramin/Melarsoprol: For African trypanosomiasis (T. brucei).

⭐ Metronidazole can cause a severe disulfiram-like reaction (flushing, tachycardia, nausea) when consumed with alcohol due to inhibition of acetaldehyde dehydrogenase.

Anti-helminthics - Worm Wranglers

• Benzimidazoles (Mebendazole, Albendazole)
  • MOA: Inhibit microtubule polymerization by binding to β-tubulin. 📌 Bendazoles bend the cytoskeleton.
  • Use: Broad-spectrum against nematodes (roundworms, pinworms, hookworms).
• Ivermectin
  • MOA: Activates glutamate-gated Cl⁻ channels → hyperpolarization & paralysis.
  • Use: Strongyloidiasis, Onchocerciasis (River Blindness).
• Praziquantel
  • MOA: Increases Ca²⁺ permeability → tetanic contraction & paralysis.
  • Use: Trematodes (flukes like Schistosoma), Cestodes (tapeworms like Taenia).
• Pyrantel Pamoate
  • MOA: Depolarizing neuromuscular blocker → spastic paralysis.
  • Use: Pinworm, hookworm, roundworm.

⭐ For neurocysticercosis (a CNS infection with Taenia solium larvae), Albendazole is a key treatment, often co-administered with corticosteroids to reduce inflammation from dying cysts.

Anti-malarials - Malaria Mashers

• Chloroquine: Blocks plasmodium heme polymerase. For sensitive species (P. falciparum in some regions, P. malariae).
  • ⚠️ Resistance is common.
• Artemisinins (e.g., Artesunate, Artemether): Generate free radicals. For severe malaria.
  • 📌 Artesunate for Artery-clogging severe malaria.
• Atovaquone-Proguanil: Disrupts mitochondrial electron transport (Atovaquone) & inhibits dihydrofolate reductase (Proguanil).
  • Used for treatment & prophylaxis.
• Mefloquine: Unknown mechanism. Used for prophylaxis.
  • ⚠️ Mefloquine Madness: potent neuropsychiatric side effects.
• Primaquine/Tafenoquine: Kills hypnozoites (dormant liver forms) of P. vivax & P. ovale.
  • 💡 Must screen for G6PD deficiency before use.

⭐ G6PD Deficiency & Primaquine: Primaquine is an oxidant drug that can cause severe hemolytic anemia in patients with G6PD deficiency. Always test for G6PD deficiency before initiating treatment for P. vivax/ovale hypnozoites.

High‑Yield Points - ⚡ Biggest Takeaways

• Metronidazole: Treats key protozoa (Giardia, Entamoeba, Trichomonas) by forming toxic free radicals. Causes a disulfiram-like reaction with alcohol.
• Benzimidazoles (e.g., albendazole): Broad-spectrum anti-helminthic that inhibits microtubule synthesis.
• Praziquantel: Treats tapeworms (cestodes) and flukes (trematodes) by increasing calcium influx, causing spastic paralysis.
• Ivermectin: Effective for Onchocerciasis and Strongyloidiasis; paralyzes nematodes by activating chloride channels.
• Antimalarials: Chloroquine blocks heme polymerase, while artemisinins produce free radicals.