Antiparasitic Drugs

Lumen & Tissue Protozoacides - Gut & Glory Guys

• Nitroimidazoles (Metronidazole, Tinidazole):
  • Targets: Giardia, Entamoeba (invasive), Trichomonas. 📌 "GET on the Metro!"
  • MOA: Prodrugs; form free radicals → DNA damage in anaerobes.
  • SE: Metallic taste, disulfiram-like reaction with alcohol, neurotoxicity.
  • Use: Trichomoniasis (single 2g dose), Giardiasis, Amoebic dysentery/abscess.
• Lumenal Amebicides (E. histolytica cysts):
  • Diloxanide furoate (DOC: asymptomatic carriers).
  • Iodoquinol (SE: Optic neuritis).
  • Paromomycin (Aminoglycoside; Giardia in pregnancy, Cryptosporidiosis).
• Nitazoxanide:
  • Broad-spectrum: Giardia, Cryptosporidium, E. histolytica.
  • MOA: Inhibits PFOR enzyme pathway.

⭐ Metronidazole: DOC for symptomatic amebiasis; combine with lumenal agent for E. histolytica.

Hemoflagellate & Sporozoa Slayers - Blood & Tissue Terminators

• Leishmaniasis:
  • Pentavalent Antimonials (SSG): Cardiotox.
  • Amphotericin B (Visceral): Nephrotoxic. Kala-azar gold std.
  • Miltefosine: Oral; teratogenic.
• Trypanosomiasis:
  • African (Sleeping Sickness):
    • Early: Suramin (East), Pentamidine (West; hypoglycemia).
    • Late (CNS): Melarsoprol (arsenical, encephalopathy!), Eflornithine (West).
    • 📌 "Early birds get SuP (Suramin/Pentamidine), Late comers get MEl (Melarsoprol/Eflornithine)."
  • American (Chagas): Nifurtimox, Benznidazole. (Chronic: low efficacy)
• Toxoplasmosis:
  • Pyrimethamine + Sulfadiazine + Folinic acid (myelosuppression rescue).

  ⭐ Sulfadiazine (Toxo regimen) causes crystalluria; hydrate.

• Babesiosis:
  • Atovaquone + Azithromycin.
  • Severe: Quinine + Clindamycin.

Antimalarial Agents - Malaria Mashers

Targets: Blood schizonts (active infection), Liver schizonts (incl. hypnozoites for relapse), Gametocytes (transmission). Key drugs:

• Blood Schizonticides:
  • Artemisinins (Artesunate, Artemether): Rapid acting. Backbone of ACT. For uncomplicated & severe falciparum.

    ⭐ ACT (Artemisinin Combination Therapy) is 1st line for uncomplicated P. falciparum.

  • Chloroquine: For sensitive P. falciparum, P. vivax/ovale/malariae. SE: Retinopathy (long-term).
  • Quinine/Quinidine: For severe/resistant malaria. SE: Cinchonism, hypoglycemia.
  • Mefloquine: Prophylaxis, treatment. SE: Neuropsychiatric.
• Tissue Schizonticides (Liver Stage):
  • Primaquine: Eradicates hypnozoites (P. vivax/ovale). Gametocidal. ⚠️ Test G6PD (hemolysis).
• Prophylaxis:
  • Mefloquine
  • Doxycycline
  • Atovaquone-Proguanil (Malarone)

Anthelminthic Drugs - Worm Whackers

• Benzimidazoles (Albendazole, Mebendazole)
  • MOA: Inhibit β-tubulin polymerization. 📌 "Bend the Worms".
  • Spectrum: Broad (nematodes, some cestodes & trematodes).
  • Albendazole: Systemic; better with fatty meal. Mebendazole: Intraluminal; poor absorption.
  • SE: GI upset, ↑LFTs, bone marrow suppression (prolonged use).
• Praziquantel
  • MOA: ↑Ca²⁺ influx → spastic paralysis.
  • Spectrum: Trematodes (Schistosoma), Cestodes (Taenia).
  • SE: Dizziness, headache, GI upset.
• Ivermectin
  • MOA: Glutamate-gated Cl⁻ channel activator → flaccid paralysis.
  • Spectrum: Nematodes (Onchocerca, Strongyloides), ectoparasites.
  • SE: Mazzotti reaction (in onchocerciasis).
• Pyrantel Pamoate
  • MOA: Neuromuscular blocker → spastic paralysis.
  • Spectrum: Pinworm, roundworm, hookworm.
• Diethylcarbamazine (DEC)
  • MOA: Alters surface membrane → immune attack.
  • Spectrum: Filariasis (Wuchereria, Brugia), Loa loa.
  • SE: Mazzotti reaction.

⭐ Praziquantel is the drug of choice for schistosomiasis and neurocysticercosis.

High‑Yield Points - ⚡ Biggest Takeaways

• Metronidazole: DOC for amoebiasis, giardiasis, trichomoniasis; damages DNA.
• Albendazole/Mebendazole: Treat nematodes, hydatid, neurocysticercosis by inhibiting microtubule synthesis.
• Praziquantel: DOC for schistosomiasis, tapeworms, flukes; causes parasite paralysis via Ca²⁺ influx.
• Chloroquine: For sensitive malaria (inhibits heme polymerase); risk of retinopathy.
• Artemisinin Combination Therapies (ACTs): First-line for uncomplicated P. falciparum malaria.
• Ivermectin: DOC for onchocerciasis, strongyloidiasis; activates glutamate-gated Cl⁻ channels.
• Liposomal Amphotericin B: For visceral leishmaniasis; liposomal form reduces nephrotoxicity.