Antihelminthic drugs

Question 1

how popular are worm infections?

Answer 1

25% world is infection

15% in U.S

Question 2

unique biology of worms

Answer 2

multiple outside of their definitive host in contrast to parasites
-evade immune system-> infections are chronic

Question 3

most common helminth?

Answer 3

ascaris, hook worms, trichuris

Question 4

two phyla of worms

Answer 4

flatworms and roundwarms

Question 5

Flatworms

Answer 5

tapeworm infections:

1. ) beef tapeworm (taenia saginata) global distribution
2. ) Pork tapeworm (taenia solium) bladder worms
3. ) fish tapeworm (diphyllobothruimlatum) robs host vitamine, especially B12

Question 6

tapeworm life cycle

Answer 6

pig or cattle infection-> penetrate intestine and go into muscle-> humans ingest (undercooked or raw)-> development in human small intestine

Question 7

Cysticercosis

Answer 7

autoinfection by ingestion of eggs produced by T. Solium
-after ingestion->oncpsheres hatch in intestine-> invade the intestinal wall-> migrate to striated muscle (or brain, liver)-> develop into cysticerci

Question 8

Flatworms: Dwarf tapeworm

Answer 8

can be transmitted directly between humans

• 3-4cm in length
• found in temperate regions
• children predominantly infected
• infected by ingestion of eggs
• not that serious

Question 9

flatworms: schistosomiasis (bloodflakes)

Answer 9

can live 5-10 years
-headaches, fatigue, fever, GI problems, hepatic fibrosis, bladder cancer, ascites
hematobium
mansoni
japonicum
Caribbean, south america, africa, middle east

Question 10

Praziquantel

Answer 10

highly effective

• disrupts calcium homeostasis
• causes muscular contraction follwed by spastic paralysis
• worms dislodge and die

Question 11

Praziquantel dose

Answer 11

two or three doses

• reduces egg burden in those not cured
• single dose kills 100% of T. saginata, T. solium, and D. latum
• doesn’t kill eggs of T. solium

Question 12

Praziquantel toxicity

Answer 12

mild

• dizziness/drowsiness-avoid driving
• can get a severe reaction to dead/dying worm

Question 13

Hookworms

Answer 13

• found in soil
• associated with poor hygeine
• penetrate through skin or by ingestion
• feed on intestinal tissue and blood
• live up to 15 years
• pulmonary lesions, skin reactions, intestinal ulcerations and anemia

Question 14

Pineworms

Answer 14

temperate regions

• live in GI tract, female migrate to rectum at night
• perianal pruritis
• eggs infect fingers and bed sheets
• eggs remain infective for 3 weeks
• ingestion of eggs starts new infection cycle

Question 15

Ascariasis round worm:

Answer 15

eggs ingested-> larva hatch in small intestine-> penetrate intestinal wall and migrate to lungs-> re-swallowed-> return to small intestine

Question 16

whipeworm

Answer 16

eggs passed in feces, can live for 5 years, 5cm in length
colonic mucosa
abdominal pain, diarrhea, distention

Question 17

Trichinosis

Answer 17

Trichinella spiralis

• undercooked pork
• round replication is in intestines
• progreny throughout body
• diarrhea, abdominal pain, N, muscle pain, edema, weakness

Question 18

Filarial disease: eyeworm

Answer 18

deer flies

• ocular lesions can cause blindness
• africa

Question 19

Filarial disease: onchocerca volvulus

Answer 19

female blackflies

-Africa

Question 20

Benzimidazoles

Answer 20

bind tubulin

• inhibit formation of microtubules-> cap microtubules
• continue to be shortened

Question 21

Benzimidazoles

Answer 21

mebendazole
thiabenazole
albendazole

Question 22

Benzimidazoles kinetics

Answer 22

poorly absorbed in GI tract-> fatty meal can increase absoprtion
-luminal parasites-> empty stomach
-tissue infection-> fatty meal
rapidly metabolized

Question 23

albenazole

Answer 23

drug of choice for cysticercosis

-pineworms, hookworms, ascariasis, trichuriasis and strongyloidiasis

Question 24

Benzimidazoles toxicity?

Answer 24

Albendazole and mebendazole (teratogenic) well tolerated
thiabendazole more toxic
-dizzness, anorexia, N&V, NOT IF PREGNANT

Question 25

diethylcarbamazine

Answer 25

drug of choice for filariasis and loiasis

• microcilariae are rapidly killed
• adults killed more slowly
• well absorbed from GI tract
• well tolerated
• reaction to dying worm-> b/c worms have bacterial endosymboint, can get a systemic inflammatory response-> can be treated with doxycycline

Question 26

Ivermectin

Answer 26

drug of choice for stronglyoidiasis and onchocerciasis

• semisynthetic marcocyclic lactone
• good oral availability

Question 27

Ivermectin MOA

Answer 27

paralyzes microfilariae

• intensifies GABA mediated transmission of signals in peripheral nerves
• allows host cytotoxic cells to adhere
• DOES NOT kill adult worms
• blocks progeny release

Question 28

Ivermectine therapeutic use

Answer 28

single dose
treat onchocerciasis
-used in pets-> lack P-glycoprotein transport so can have neurological symptoms

Question 29

Pyrantel pamoate

Answer 29

Low bioavailability, acts in gut

• treat roundworms and pinworms
• active against adult and immature worms
• not active against migratory worms

Question 30

Pyrantel pamoate MOA

Answer 30

neuromuscular blocking agent
causes release of acetylcholine and inhibiton of cholinesterase
-worms paralyzed and expelled

Question 31

clinical use of Pyrantel pamoate

Answer 31

ascariasis-1 dose

pineworms-> drug of choice

Question 32

tissue nematodes: trichinosis

Answer 32

mebendazole + corticosteroids

Question 33

tissue nematodes: stronglyoidiasis

Answer 33

mebendazole or albendazole

Question 34

tissue nematodes: onchocerciasis

Answer 34

ivermectin

Question 35

tissue nematodes: filariasis

Answer 35

diethyclarbamazine

Question 36

nematode infections: Filariasis

Answer 36

lymphatic dwelling filaria

• wuchereria bancrofti-> tropical regions
• Brugia malayi-> Asia
• Brugia timori-> indonesia
• mosquitoes transmit
• elephantiasis

Question 37

antihelminth medication

Answer 37

diethycarbamazine
ivermectin
mebendazole
praziquantel
pyrantel pamoate

Question 38

thiabendazole is no longer preferred why?

Answer 38

toxicity

Question 39

what is mebendazole used for?

Answer 39

pinworms, hookworms, ascariasis, and trichuriasis