Anti- helminthic agents

Question 1

Main mechanisms of action

Answer 1

• incapacitating the parasite by paralysis - by preventing muscular contraction
• altering metabolic processes - by affecting micro-tubule function
• drug must be able to penetrate the tough exterior cuticle of the worm or gain access to its alimentary tract in sufficient concentrations

Question 2

Drugs used to kill Roundworms (nematodes)

Answer 2

Albendazole
Mebendazole
Ivermectin

Question 3

Albendazole

• pharmacokinetics
• mechanism of action
• clinical uses

Answer 3

• oral, rapidly undergo first pass metabolism in the liver and metabolites are excreted in the urine
• inhibit microtubule synthesis –> decrease glucose uptake
• ascariasis
• pinworm (threadworm)
• cysticercosis

Question 4

Albendazole

• adverse effects
• contraindications and cautions

Answer 4

• mild and transient epigastric distress, diarrhea, headache, nausea
• in long term –>. well tolerated

-blood count and liver function should be monitored during long-term therapy

Question 5

Mebendazole

• pharmacokinetics
• mechanism of action
• clinical uses

Answer 5

• less than 10% is orally absorbed
• inhibit microtubule synthesis –> decrease glucose uptake
• ascariasis
• pinworm infections
• trichiniasis

Question 6

Mebendazole

• adverse effects
• contraindications and cautions

Answer 6

• nearly free of adverse effects
• mild nausea, vomiting, diarrhea, abdominal pain
• pregnancy
• should be used with caution in children younger than 2 years old
• should be used with caution in patients with cirrhosis

Question 7

Ivermectin

• pharmacokinetics
• mechanism of action
• clinical uses

Answer 7

-oral, excretion almost exclusively in the feces

• intensifies GABA-mediated transmission of signals in peripheral nerves = paralysis of the helminth
• in onchocerciasis –> blocks the release of microfilariae
• onchocerciasis
• strongyloidiasis
• filarial infection

Question 8

Ivermectin

• adverse effects
• contraindications and cautions

Answer 8

• in strongyloidiasis is infrequent
• in onchocerciasis –> fever, headache, dizziness, somnolence, weakness
• avoid concomitant use with other drugs that enhance GABA activity
• should not be used during pregnancy

Question 9

Drugs used to kill flukes and tapeworms

-names

Answer 9

Praziquantel

Question 10

Praziquantel

• pharmacokinetics
• mechanism of action
• clinical uses

Answer 10

• oral bioavailability is 80%
• excretion is mainly in via kidneys and bile

-increase the permeability of cell membranes to calcium resulting in paralysis

• Schistosomiasis
• Taeniasis
• Neurocysticercosis

Question 11

Praziquantel

• adverse effects
• contraindications and cautions

Answer 11

• some probably due to the release of proteins from dying the worms rather than direct toxicity
• in neurocysticercosis, neurologic abnormalities may be exacerbated by inflammatory reactions around dying parasites

-in ocular cysticercosis

Question 12

Metronidazole

Answer 12

Anti-protozoal drug - amoebiasis and trichomoniasis

Anti-bacterial drug - anaerobes (C-difficle, bacteroides)

Question 13

Main drug used to treat Trichomoniasis

Answer 13

Metronidazole

Question 14

Metronidazole

-mechanism of action (4)

Answer 14

• bactericidal
• selectively absorbed by anaerobic bacteria and sensitive protozoa
• produce products toxic to anaerobic cells –> selective accumulation in anaerobes
• metabolities are taken up into bacterial DNA
• relatively little effect on human cells or aerobic bacteria

Question 15

Metronidazole

• pharmacokinetics
• unwanted effects

Answer 15

• well absorbed after oral administration
• metabolized in the liver
• nausea, diarrhea, stomatitis, peripheral neuropathy
• should be avoided with alcohol