Antihelminths Flashcards
Metronidazole
Distribution: Tissue antiparasitic. Low concentration in intestine, high oral bioavalability.
Drug of choice for Giardia
MOA: Free radical damage –> DNA strand breaks.
Toxicity: Disulfiram, Normal GI flora
Tinidazole
Distribution: Tissue antiparasitic. Low concentration in intestine, high oral bioavalability.
Drug of choice for Giardia. Tissue amebicide.
MOA: Free radical damage –> DNA strand breaks.
Toxicity: Disulfiram, Normal GI flora
Nitazoxanide
MOA: Interferes w/ pyruvate ferredoxin oxidoreductase. Essential to anaerobic metabolism and specific to helminths.
Distribution: Rapidly metabolized to tizoxanide. Moderately absorbed (33%). Primarily luminal.
Effectiveness goes down in immunocompromised host in treating Cryptosporidium. Use w/ antiretrovirals and antiperistaltics agents/oral rehydration.
Iodoquinol
Mechanism: unknown
Toxicity: Loss of visual acuity. Use w/ caution in patients w/ thyroid disease (IODOquinol), it interferes w/ certain thyroid tests.
Distribution: only 10% absorbed –> luminal
Luminal Amebicide
Paromomycin
Mechanism: Aminoglycoside –> targets 30s ribosomal subunit (buy AT 30)
Toxicity: Diarrhea, GI effects, loss of normal flora (avoids systemic affects of normal aminoglycosides due to lack of absorbtion)
Luminal amebicide
TMP-SMX
Broad spectrum, many bacteria, but also effective against apicomplexans including toxoplasma (double dip w/ aids ppx for pcp), cytoisopora, and cyclospora.
Albendazole
Broad spectrum esp. in tissues
Rx for roundworms and tapeworms
Distribution - limited oral absorbtion, albendazole is better absorbed
MOA: Binds to parasite B-tubulin and inhibits formation of microtubules (death can take several days; some helminths may require more than one dose).
Toxicity: (not very toxic –> mass drug campaigns). Systemic effects = liver/bone marrow (rare). Abdominal pain, nausea, dizziness, headache
Embryotoxic and teratogenic in rats
Safe in children when warranted.
Mebendazole
Broad spectrum esp. in tissues
Rx for nematodes/roundworms and cestodes/tapeworms
Distribution - limited oral absorbtion, albendazole is better absorbed
MOA: Binds to parasite B-tubulin and inhibits formation of microtubules (death can take several days; some helminths may require more than one dose).
Toxicity: (not very toxic –> mass drug campaigns). Systemic effects = liver/bone marrow (rare). Abdominal pain, nausea, dizziness, headache
Embryotoxic and teratogenic in rats
Safe in children when warranted.
Pyrantel pamoate
MOA: selectively opens a restricted subgroup of nematode AchR –> depol –> muscle spasm –> parasite is swept away.
Toxicity: Causes N/V and diarrhea
Poorly absorbed
Levamisole
MOA: selectively opens a restricted subgroup of nematode AchR –> depol –> muscle spasm –> parasite is swept away.
Toxicity: Causes N/V and diarrhea
Poorly absorbed
Ivermectin
MOA: Binds to glutamate-gated chloried channels in invertebrate nerve and muscle cells, causing deactivation of channel: worm paralysis and death by starvation.
Resistance = efflux transporters
Toxicity: Generally well tolerated. Itching, swollen lymph glands and rarely dizziness. Inflammatory reactions due to the death of worms.
Specificity: channel only in CNS of humans and drug doesn’t cross BBB
Spectrum: Nematodes: Ascaris, Strongyloides (only rx), and Onchoerca (IVERmectin for rIVER blindness)
Praziquantel
MOA: increased permeability of the parasite to divalent cations leading to contraction of musculature.
Toxicity: Low; dizziness and nausea
Spectrum: Cestodes (tapeworms) and trematodes (only option)
