Anthelmintics

Question 1

What is the MOA of Mebendazole & Albendazole?

Answer 1

Bind to b-tubulin of the microtubule, inhibit polymerization & cause loss of function
Also block glucose uptake

Question 2

What is the MOA of Pyrantel pamoate?

Answer 2

Depolarizing neuromuscular blocking agent → inhibits cholinesterases & causes spastic paralysis in the worm

Question 3

What is the MOA of Ivermectin?

Answer 3

Binds to glutamate-gated chloride ion channels in muscle & nerve → paralyzes the worm which results in death

Question 4

What are the drugs of choice for treating intestinal nematodes?

Answer 4

Mebendazole & Pyrantel

Question 5

What are the drugs of choice for treating tissue nematodes?

Answer 5

Mebendazole, Albendazole & Ivermectin

Question 6

What are important instructions when taking Ivermectin PO?

Answer 6

MUST BE taken with full glass of water on empty stomach 1 hour BEFORE meal

Question 7

How are Albendazole, Mebendazole, & Pyrantel absorbed?

Answer 7

poor absorption with limited serum concentration

Question 8

What are instructions to give a patient when taking albendazole PO?

Answer 8

Bioavailability enhanced if consumed with a fatty meal; swallow whole with small amount of water

Question 9

What are instructions to give a patient when taking Mebendazole PO?

Answer 9

Should be taken with high fatty meal; can be crushed or chewed

Question 10

Describe Albendazole’s metabolism & excretion:

Answer 10

-Rapidly converted by the liver to primary metabolite (albendazole sulfoxide)
-Almost exclusive biliary excretion

Question 11

Describe Mebendazole’s metabolism & excretion:

Answer 11

-extensively metabolized by liver
-95% in feces and remainder by kidney

Question 12

Describe Ivermectin metabolism & excretion:

Answer 12

Metabolized by CYP450
Excretion: almost exclusively in feces in ~12 days

Question 13

Describe Pyrantel metabolism & excretion:

Answer 13

Metabolism: limited
Excretion: 50% unchanged in feces, less than 7% in urine

Question 14

The four drugs listed in this chapter should be used with caution in:

Answer 14

Patients with hepatic and kidney impairment

Question 15

What is the consensus for the use of these drugs in pregnancy?

Answer 15

albendazole, mebendazole and, pyrantel should only be used in pregnancy (2nd or 3rd trimester) if benefit outweighs the risk

Question 16

What is the consensus for the use of these drugs in children?

Answer 16

-Mebendazole, Albendazole, & Pyrantel NOT recommended for children younger than 2 years
-Ivermectin CONTRAINDICATED in children weighing less than 15kg

Question 17

ADR’s for Albendazole:

Answer 17

Report signs of neutropenia

Question 18

What drug should NOT be used when taking Albendazole?

Answer 18

cimetidine

Question 19

These two drugs are associated with transient elevation of LFT’s:

Answer 19

Albendazole & Mebendazole

Question 20

ADR for Ivermectin:

Answer 20

Mazzotti reaction in SOME patients using ivermectin for Onchocerca volvulus

Question 21

What is a Mazzotti reaction?

Answer 21

fever, headache, dizziness, somnolence, weakness, rash, pruritus, diarrhea, joint pain/muscle spasms, hypotension, tachycardia, lymphadenitis, and peripheral edema)

Question 22

When taking albendazole, avoid coadministration with

Answer 22

dexamethasone

Question 23

When taking Mebendazole, avoid concomitant use of:

Answer 23

carbamazepine & phenytoin

Question 24

Pinworms, Whipworms & hookworms can be treated with:

Answer 24

pyrantel , albendazole & mebendazole

Question 25

roundworms can be treated with:

Answer 25

albendazole, mebendazole & Ivermectin

Question 26

Treatment for threadworm:

Answer 26

1st line: ivermectin
Alternative: albendazole