Antihelminthic Drugs

Question 1

The helminth life cycle is strongly dependent on the following factors:

Answer 1

1. Neuromuscular coordination for worm feeding movements and for maintaining a
   favourable location within the host.
2. Carbohydrate metabolism as the source of energy, with glucose as the primary
   substrate.
3. Microtubular integrity – egg laying and hatching, larval development, glucose
   transport, and enzyme activity and secretion are hindered when microtubules are
   modified.

Question 2

BENZIMIDAZOLES include

Answer 2

mebendazole, thiabendazole and albendazole.

Question 3

Mebendazole is extensively absorbed when administered orally. True or false?

Answer 3

False. Little of an oral dose (10%) is
absorbed by the body, therefore it is relatively free of toxic effects.

Question 4

Albendazole given orally is rapidly absorbed. True or false?

Answer 4

True

Question 5

BENZIMIDAZOLES are teratogenic. True or false?

Answer 5

True

Question 6

Pyrantel pamoate MOA

Answer 6

• Acts as a depolarizing neuromuscular blocking agent.
• Causes spastic paralysis.
• Paralyzed worm is expelled from the host’s intestinal tract.
• It has some anticholinesterase activity

Question 7

Pyrantel pamoate indication

Answer 7

Used along with mebendazole, it is effective in treatment of infections caused by
roundworms, pinworms and hookworms.

Question 8

Ivermectin is a drug derived from

Answer 8

avermectins, a group of natural substances
derived from actinomycete

Question 9

Ivermectin is contraindicated in

Answer 9

Patients with meningitis (compromised BBB) and in pregnancy.

Question 10

Praziquantel MOA

Answer 10

Increases permeability of helminth cell to calcium → contraction of musculature →
paralysis and death of worm.

Question 11

Praziquantel distributes into the CSF. True or false?

Answer 11

True

Question 12

Drug of first choice for all spp. of Schistosomes and is effective in cysticercosis.

Answer 12

Praziquantel

Question 13

Drug of choice for most cestode (tapeworm) infections

Answer 13

Niclosamide

Question 14

Niclosamide MOA

Answer 14

• Inhibition of parasites mitochondrial anaerobic phosphorylation of ADP which
  produces usable energy in the form of ATP.
• Also blocks glucose uptake by intestinal tapeworms.

Question 15

How is Niclosamide administered by for T. Solium

Answer 15

Given in a single dose after a light meal, followed by a purgative 2
hours later (to prevent cysticercosis).

Question 16

Piperazine MOA

Answer 16

Reversibly inhibits neuromuscular transmission in the worm, acting possibly like
GABA on GABA-gated chloride channels → worms paralyzed and expelled alive.

Question 17

Piperazine indications

Answer 17

Treatment of infections with common roundworm (Ascaris vermicularis) and
threadworm/pinworm (Enterobius vermicularis).

Question 18

DEC is a derivative of

Answer 18

Piperazine derivative

Question 19

Levamisole MOA

Answer 19

Nicotinic-like action (stimulate and then block NMJ) → paralysed worm expelled
with faeces by normal peristalsis.

Question 20

Levamisole indication

Answer 20

Treatment of infection with common roundworm (Ascaris lumbricoides)

Question 21

Oxamniquine MOA

Answer 21

Inhibits DNA, RNA and protein synthesis. Parasite may have a unique enzyme capable of esterifying oxamniquine to form a
reactive metabolite which alkylates helminth DNA.

Question 22

Oxamniquine indications

Answer 22

• Active against S. mansoni (mature and immature forms).

Question 23

Metriphonate MOA

Answer 23

Paralytic action related to inhibition of parasite cholinesterase.

Question 24

Metriphonate is a pro drug. True or false?

Answer 24

True

Question 25

Metriphonate indications

Answer 25

Effective against S. haematobium but not S. mansoni (possibly due to difference in drug accessibility (S. mansoni resides in mesenteric veins whereas S. haematobium live within veins surrounding the bladder).

Question 26

Suramin MOA

Answer 26

Inhibits numerous enzymes of filarial helminthes (most notably lactate dehydrogenase, malate dehydrogenase, dihydrofolate reductase and various protein kinases). It is a large polyanion that complexes proteins readily.

Question 27

Only antihelmithic to be given parenterally (IV) is…

Answer 27

Suramin

Question 28

Drug of choice against Onchocerca volvulus is

Answer 28

Suramin

Question 29

Metronidazole MOA

Answer 29

Inhibits nucleic acid synthesis by disrupting DNA of microbial cells.