Antiparasitic Agents

Antimalarials - Malaria Mayhem Meds

• Goal: Eradicate parasites from blood (clinical cure) & liver (radical cure).
• **Classification (Simplified):
  • Blood Schizonticides: Act on erythrocytic forms. E.g., Chloroquine, Artemisinins, Quinine, Mefloquine.
  • Tissue Schizonticides: Act on liver stages (hypnozoites). E.g., Primaquine.
  • Gametocytocidals: Kill sexual forms. E.g., Primaquine.
• Key Drugs & Actions:
  • Chloroquine: Inhibits heme polymerase. For sensitive P. vivax/ovale/malariae. Resistance in P. falciparum (PfCRT gene).
  • Artemisinins (Artesunate, Artemether): Endoperoxide; free radical damage. Rapid action. DOC for severe malaria (IV Artesunate) & uncomplicated P. falciparum (as ACTs).
  • Primaquine: Radical cure for P. vivax/ovale. ⚠️ Test for G6PD deficiency (risk of hemolysis).
  • Mefloquine: Prophylaxis & treatment. Neuropsychiatric side effects.
  • Atovaquone-Proguanil (Malarone®): Prophylaxis & treatment.
• 📌 All Clinicians Treat with ACTs for uncomplicated Falciparum.

⭐ Artemisinin-based Combination Therapy (ACT) is the WHO-recommended first-line treatment for uncomplicated P. falciparum malaria to combat resistance and improve efficacy.

Other Antiprotozoals - Protozoa Purge Pills

• Metronidazole & Tinidazole:
  • MOA: Free radical damage in anaerobes.
  • Uses: Amoebiasis, Giardiasis, Trichomoniasis, anaerobic infections. 📌 GET Anaerobes on the Metro (Giardia, Entamoeba, Trichomonas).
  • AE: Disulfiram-like effect with alcohol, metallic taste, neurotoxicity (rare).
• Luminal Amoebicides: (For asymptomatic E. histolytica cyst passers)
  • Diloxanide furoate (DOC), Iodoquinol (AE: optic neuritis), Paromomycin.
• Nitazoxanide:
  • Broad spectrum: Giardia, Cryptosporidium. MOA: Inhibits PFOR enzyme.
• Leishmaniasis:
  • Sodium Stibogluconate: AE: Cardiotoxicity (QT prolongation), pancreatitis.
  • Amphotericin B (liposomal): DOC for Visceral Leishmaniasis (Kala-azar).
  • Miltefosine: Oral, teratogenic.
• African Trypanosomiasis (Sleeping Sickness):
  • Hemolymphatic stage: Suramin, Pentamidine.
  • CNS stage: Melarsoprol (arsenical; AE: encephalopathy), Eflornithine.
• American Trypanosomiasis (Chagas Disease):
  • Nifurtimox, Benznidazole.
• Pentamidine:
  • Uses: Pneumocystis jirovecii pneumonia (PJP), Leishmaniasis, African Trypanosomiasis (early West African).
  • AE: Pancreatitis, dysglycemia, nephrotoxicity.

⭐ Metronidazole is ineffective against luminal amoebic cysts; requires a luminal agent like Diloxanide furoate for eradication of infection and to prevent carrier state development or relapse after tissue amoebicide therapy for invasive disease.

Anthelmintics - Worm Wipeout Weapons

• Benzimidazoles (BZDs): Albendazole, Mebendazole
  • Mech: Inhibit parasite β-tubulin → disrupt microtubule polymerization.
  • Uses: Broad-spectrum - Ascaris, hookworm, whipworm (Trichuris), pinworm (Enterobius).
  • Albendazole: Hydatid disease, neurocysticercosis. Fatty meal ↑ absorption.
• Praziquantel (PZQ):
  • Mech: ↑ Ca²⁺ influx → tetanic muscle contraction & paralysis.
  • Uses: Trematodes (Schistosomiasis, Clonorchiasis), Cestodes (Taeniasis, Diphyllobothriasis).

  ⭐ Praziquantel is the drug of choice for infections caused by all Schistosoma species.

• Ivermectin:
  • Mech: Activates glutamate-gated Cl⁻ channels → flaccid paralysis.
  • Uses: Onchocerciasis (DOC), Strongyloidiasis, Filariasis (microfilaricidal for W. bancrofti, B. malayi).
• Pyrantel Pamoate:
  • Mech: Depolarizing neuromuscular blocker (nicotinic agonist) → spastic paralysis.
  • Uses: Pinworm, Ascaris, Hookworm (alternative).
• Diethylcarbamazine (DEC):
  • Mech: Alters parasite surface membrane → enhances host immune destruction; inhibits arachidonic acid metabolism.
  • Uses: Lymphatic filariasis (W. bancrofti, B. malayi - DOC for adult worms & microfilariae), Loiasis (DOC), Tropical Pulmonary Eosinophilia.
  • ⚠️ Mazzotti reaction (from dying microfilariae).

High‑Yield Points - ⚡ Biggest Takeaways

• Metronidazole: DOC for amebiasis, giardiasis, trichomoniasis; disulfiram-like reaction with alcohol.
• Albendazole/Mebendazole: Inhibit microtubule synthesis; Albendazole for neurocysticercosis, hydatid disease.
• Praziquantel: DOC for schistosomiasis & most cestodes; increases Ca²⁺ permeability.
• Chloroquine: For malaria prophylaxis & sensitive strains; risk of retinopathy (chronic use).
• ACTs (Artemisinin Combination Therapies): First-line for uncomplicated P. falciparum malaria.
• Ivermectin: DOC for onchocerciasis, strongyloidiasis; acts on glutamate-gated Cl⁻ channels.
• DEC (Diethylcarbamazine): DOC for lymphatic filariasis, loiasis; can cause Mazzotti reaction.