Pharm of GI - Fitspatrick Flashcards
Drugs to treat nematodes (Enterobius, filarias, trichurias, hookworms, ascaris)
albendazole and mebendazole
Drugs to treat cestodes
Albendazole, mebendazole and praziquandtel
Drug to treat trematodes
Praziquantel
what is the MOA of Benzimidazole (Me- and Albendazole)
binds to parasite beta tubulin, disrupt microtubule polymerization and microtubule dependent process
what PK properties of mebendazole makes it a good drug?
Poor solubility = poor absorption, plus efficeint metabolism, plus protein binding = low systemic exposure making it safe and effective: sing dose is enough in kids >2 and adults.
PK differences between mebendazole and albendazole
Albendazole PK is same as mebendazole except albendazole has modest absorption
what is the active metabolite of albendazole?
Albendazole sulfoxide – good distribution affects tissue dwelling helminths, hydatid cysts
Thiabendazole is only used for
cutaneous use only for things like larval migrans. it has systemic toxicity thus limited use
which particular worms are best against albendazole?
- Necator americanus an ancylostoma duodenale - HOOKWORM
- toxocara spp larval migrans
which worms are best against Mebendazole
- Enterobius vermincularis - Pinworm
- Ascaris lumbricoides
- Trichuris trichiura - whipworm
what AE are associated with al and medendazole?
Embyotoxic and teratogenic. Pregnancy category C
Pyrantels are effective against which worms?
hookworm, pinworm and roundworm, but NOT good for trichuris trichiura
what is the MOA of pyrantel?
- pyrantel is depolarizing neuromuscular blocking agent. It causes persistent activation of nicotinic acetylcholine receptor and spastic paralysis of worm
Pyrantal bioavailability and safety
- poorly absorbed from GI tract
- use with caution in pregnant women and kids <2
what drug is used against strongloidyiasi (thread worm) and onchoceriasis - river blindness
Ivermectin
what is the MOA of ivermectin?
- glutamate gated Cl channel play a fundamental roles in nematodes and insects. ivermectin paralyzes body wall and pharyngeal muscle in nematodes but has NO such impact in mammals, as it cannot cross BBB into CNS where GAB-gated Cl channels are located.
Ivermectin is contraindicated in what kind of patients/
Pt with disrupted BBB such as meningitis, trypanosomiasis
Drug of choice for adult form of tapeworms infection (taenia solium/saginata, diphyllobothrium latum)
Praziquantel
drug of choice for larval form of tape worm (cysticerocosis, echinococus granulosus, cystic hydatid disease)
Albendazole
Praziquantel is contraindicated for treatment of which cysticercosis disease
Ocular cysticercosis since destruction of the organism in the eye may damage the eye
Drug of choice for all forms of schistosomiasis
Praziquantel. Effective as single dose or 3 doses in a single day
MOA of praziquantel
interferes with Ca homeostasis and causes flaccid paralysis in adult flukes
Is host immune response needed in order for praziquantel to work?
Yes. praziquantel causes antigens within the parasites to be exposed to action of host antibodies
MOA of metronidazole
bug’s mode of energy source is disrupted. Most’s energy metabolism (pyruvate-ferrodoxin oxidoreductase (PFOR) complex activates metronidazole
Drug of choice for amebiasis
Metronidazole
Drug of choice for Giardiasis
tinidazole
AE of metronidazole and tinidazole
- Metallic taste
- Disuldiram-like reaction
How should amebiasis that is symptomatic or cause invasive colitis be treated?
Metronidazole followed by luminal amebicide such as paromomycin, diiodohydroxyquin. Asymptomatic people treated with intraluminal agents only (paromomicin)
Drug of choice of colonization of intestine with E histolytica
Paromomicin (aminoglycoside)
management of C diff: abx acquired, if recurs after treatment, if acquired from ICU
- Initial choice: Metronidazole
- If recurs then Vanco
- If ICU acquired: fidaxomicin is first choice
