Pharm of GI - Fitspatrick

Question 1

Drugs to treat nematodes (Enterobius, filarias, trichurias, hookworms, ascaris)

Answer 1

albendazole and mebendazole

Question 2

Drugs to treat cestodes

Answer 2

Albendazole, mebendazole and praziquandtel

Question 3

Drug to treat trematodes

Answer 3

Praziquantel

Question 4

what is the MOA of Benzimidazole (Me- and Albendazole)

Answer 4

binds to parasite beta tubulin, disrupt microtubule polymerization and microtubule dependent process

Question 5

what PK properties of mebendazole makes it a good drug?

Answer 5

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.

Question 6

PK differences between mebendazole and albendazole

Answer 6

Albendazole PK is same as mebendazole except albendazole has modest absorption

Question 7

what is the active metabolite of albendazole?

Answer 7

Albendazole sulfoxide – good distribution affects tissue dwelling helminths, hydatid cysts

Question 8

Thiabendazole is only used for

Answer 8

cutaneous use only for things like larval migrans. it has systemic toxicity thus limited use

Question 9

which particular worms are best against albendazole?

Answer 9

• Necator americanus an ancylostoma duodenale - HOOKWORM

- toxocara spp larval migrans

Question 10

which worms are best against Mebendazole

Answer 10

• Enterobius vermincularis - Pinworm
• Ascaris lumbricoides
• Trichuris trichiura - whipworm

Question 11

what AE are associated with al and medendazole?

Answer 11

Embyotoxic and teratogenic. Pregnancy category C

Question 12

Pyrantels are effective against which worms?

Answer 12

hookworm, pinworm and roundworm, but NOT good for trichuris trichiura

Question 13

what is the MOA of pyrantel?

Answer 13

• pyrantel is depolarizing neuromuscular blocking agent. It causes persistent activation of nicotinic acetylcholine receptor and spastic paralysis of worm

Question 14

Pyrantal bioavailability and safety

Answer 14

• poorly absorbed from GI tract

- use with caution in pregnant women and kids <2

Question 15

what drug is used against strongloidyiasi (thread worm) and onchoceriasis - river blindness

Answer 15

Ivermectin

Question 16

what is the MOA of ivermectin?

Answer 16

• 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.

Question 17

Ivermectin is contraindicated in what kind of patients/

Answer 17

Pt with disrupted BBB such as meningitis, trypanosomiasis

Question 18

Drug of choice for adult form of tapeworms infection (taenia solium/saginata, diphyllobothrium latum)

Answer 18

Praziquantel

Question 19

drug of choice for larval form of tape worm (cysticerocosis, echinococus granulosus, cystic hydatid disease)

Answer 19

Albendazole

Question 20

Praziquantel is contraindicated for treatment of which cysticercosis disease

Answer 20

Ocular cysticercosis since destruction of the organism in the eye may damage the eye

Question 21

Drug of choice for all forms of schistosomiasis

Answer 21

Praziquantel. Effective as single dose or 3 doses in a single day

Question 22

MOA of praziquantel

Answer 22

interferes with Ca homeostasis and causes flaccid paralysis in adult flukes

Question 23

Is host immune response needed in order for praziquantel to work?

Answer 23

Yes. praziquantel causes antigens within the parasites to be exposed to action of host antibodies

Question 24

MOA of metronidazole

Answer 24

bug’s mode of energy source is disrupted. Most’s energy metabolism (pyruvate-ferrodoxin oxidoreductase (PFOR) complex activates metronidazole

Question 25

Drug of choice for amebiasis

Answer 25

Metronidazole

Question 26

Drug of choice for Giardiasis

Answer 26

tinidazole

Question 27

AE of metronidazole and tinidazole

Answer 27

• Metallic taste

- Disuldiram-like reaction

Question 28

How should amebiasis that is symptomatic or cause invasive colitis be treated?

Answer 28

Metronidazole followed by luminal amebicide such as paromomycin, diiodohydroxyquin. Asymptomatic people treated with intraluminal agents only (paromomicin)

Question 29

Drug of choice of colonization of intestine with E histolytica

Answer 29

Paromomicin (aminoglycoside)

Question 30

management of C diff: abx acquired, if recurs after treatment, if acquired from ICU

Answer 30

• Initial choice: Metronidazole
• If recurs then Vanco
• If ICU acquired: fidaxomicin is first choice