Antiparasitics: antihelminthic drugs

Question 1

Helminth infections - worms have a unique biology. Why?

Answer 1

They multiply outside of their definitive host in contrast to other parasites

They evade the immune system - infections are chronic (last for lifetime of host)

Question 2

Flatworms aka

Answer 2

tapeworms

Question 3

Taenia saginata (beef tapeworms) are transmitted by

Answer 3

eating undercooked meat

Question 4

Taenia solum (pork tapeworms) are transmitted by? what organ do they affect?

Answer 4

eating undercooked pork

affects bladder

Question 5

Diphyllobothrium latum (fish tapeworm) is transmitted by? what do they do to the host?

Answer 5

eating undercooked fish

they rob the host of nutrients, especially vitamin B12

Question 6

cysticerosis

• caused by?
• how do they cause infection?

Answer 6

caused by auto infection by ingesting the eggs produced by T. solum

after ingestion, oncospheres hatch in the intestine, invade the intestinal wall, and migrate to striated mm (and brain, liver, and other tissues). Develop into cysticerci. Can cause serious infection in the brain.

Question 7

dwarf tapeworm (hymenolepis nana)

• special b/c its the ..
• who does it mainly affect?

Answer 7

most common cestode infection

mainly affects children

Question 8

What are the three species of schistosomiasis (bloodflukes)?

What causes the symptoms we see?

Answer 8

Schistosoma hematobium
Schistosoma mansoni
Schistosoma japonicum

symptoms are cause by immune reactions to the eggs

Question 9

What drug is used to treat cestodes and trematodes?

Answer 9

Praziquantel

Question 10

What is the mechanisms of action of praziquantel?

Answer 10

• disrupts Ca homeostatsis
• causes mm contraction followed by spastic paralysis
• immune response likely involved
• worms dislodge and die

Question 11

Praziquantel is the drug of choice for

Answer 11

all forms of schistosomiasis

Question 12

What problems do we see with praziquantel treatments?

Answer 12

1. severe immune reaction to the worm after it has been killed
2. increased abortion rates in rats - so avoid if prego
3. may cause dizziness/drowsiness - avoid driving

Question 13

Hookworms are found where?
How do we become affected with them?
What do they feed on?
What are the consequences of hookworm infections?

Answer 13

Found in soil

They can penetrate the skin or can be orally digested

They feed on intestinal tissue and blood

Cause

1. pulmonary lesions
2. skin reactions
3. intestinal ulceration
4. anemia

Question 14

Enterobiasis - life cycle?

Answer 14

• Live in GI tract
• Female migrate to rectum at night to deposit eggs
• Causes perianal pruritis
• Eggs infect fingers and bed sheets (remain infective for 3 weeks)
• Ingesting of eggs starts new infection cycle

Question 15

Ascariasis aka

Answer 15

roundworms

Question 16

Ascariasis - life cycle?

Answer 16

• Eggs are ingested
• larva hatch in small intestine
• penetrate intestinal wall and are transported to lungs
• after ~ 10 days, pass out through lungs to trachea and are re-swallowed
• return to small intestine

Question 17

Whipworm infections (trichuriasis)

• caused by ..?
• causes (effects of infection)..?

Answer 17

Caused by ingesting eggs in contemned food or liquids

Causes irritation and inflammation of colonic mucosa, abdominal pain, diarrhea, and distention

Question 18

Trichinosis

• associated with ..?
• causes ..?

Answer 18

associated with undercooked pork

causes diarrhea, abd pain, nausea and mm pain, edema, and weakness

Question 19

Filariasis

• where in the body do we find it?
• what does it cause?

Answer 19

its lymphatic dwelling

causes elephantiasis

Question 20

eyeworm (loa loa)

Answer 20

transmitted by deed flies

ocular lesions can cause blindness

Question 21

river blindness (onchocerca volvulus)

Answer 21

transmitted by female blackflies

causes blindness?

Question 22

Benzimidazoles mechanism of action

Answer 22

• bind to tubulin
• inhibit formation of microtubules
• can bind to mammalian tubulin

Question 23

Pharmacokinetics of benzimidazoles

Answer 23

• poorly absorbed in GI - eating a fatty meal increases absorption
  
  • – can take advantage of this - if infection in intestine, take on empty stomach; if infection in tissue, take with fatty meal to increase absorption

-rapidly metabolized in the liver

Question 24

Toxcity of thiabendazole

• side effects?
• should not be used when?

Answer 24

• dizziness, anorexia, nausea, vomiting

- should not be used in pregnant women

Question 25

mebendaolze is …?

Answer 25

teratogenic

-not used in pregnant women

Question 26

Therapeutic uses of albendazole

Answer 26

drug of choice for cysticercosis

also used for pinworms, hookworms, ascarasos, trichuriasis, and strongyloidiasis

Question 27

Therpeutic uses of mebendazole

Answer 27

used for pinworms, hookworms, ascariasis, and trichuriasis

Question 28

Diethylcarbamazine is the drug of choice for …?

What adverse effects do we see with treatment here?

Answer 28

Filariasis and loiasis

Dying worms can cause severe infection
— may lead to systemic inflammation from release of bacterial endosymbiont

Question 29

Ivermectin is the drug of choice for?

Answer 29

Strongyloidiasis and onchocerciasis

Question 30

Ivermectin mechanism of action?

Answer 30

• paralyzes microfilariae
• intensifies GABA mediated transmission of signals in peripheral nerves
• allows host cytotoxic cells to adhere
• does not kill adult worm; blocks release of progeny

Question 31

Ivermectin therapeutic uses?

Answer 31

• primarily used to treat onchocerciasis

- single dose

Question 32

Pyrantel pamoate is a

• bioavailability?
• effective against?

Answer 32

broad-spectrum antihelminth that is available over the counter

bioavailability is very low

highly effective against pinworms and ascaris; moderately effective against hookworm

Question 33

Pyrantel pamoate mechanism of action?

Answer 33

neuromuscular blocking agent

causes release of Ach and inhibition of cholinesterase

worms are paralyzed and expelled

Question 34

How do we treat trichinosis?

Answer 34

mebendazole + coritcosteroids

Question 35

How do we treat strongyloidiasis?

Answer 35

mebendazole or albendazole

Question 36

How do we treat onchocericiasis

Answer 36

ivermectin

Question 37

How do we treat filariasis?

Answer 37

diethylcarbamazine

Question 38

Most important human parasitic helminth infections can be treated with one of the following drugs

Answer 38

1. diethylcarbamazine
2. ivermectine
3. mebendazole or albendazole
4. praziquantel
5. pyrantel pamoate