Anti-Protozoal Agents

Question 1

Name of Anti-protozoal agent

Answer 1

Metronidazole

Question 2

Safe for pregnancy?

Answer 2

No

Question 3

3 Classes of therapeutic agents for amebiasis

Answer 3

1. Luminal Amebicides - Bowel Lumen
2. Systemic Amebicides - Intestinal wall / liver
3. Mixed Amebicides

Question 4

Amebiasis infection - Cause and site of infection?

Answer 4

Entamoeba histolytica in the intestinal tract

Question 5

Metronidazole MOA

Answer 5

• Amoeba have electron transport proteins involved in metabolic electron removal
• Nitro group of metronidazole acts as electron acceptor
• Forms Cytotoxic free radicals
• Cause protein and DNA damage

Question 6

What condition does metronidazole need for MOA?

Answer 6

• Reduction of metronidazole needs strong reducing conditions
• Anaerobic organisms have more reducing potential than aerobic organisms

Question 7

Spectrum activity of Metronidazole

Answer 7

1. Amoebic infections - Entamoeba histolytica, Trichomonas vaginalis, Giardia Lamblia
2. Anaerobes - Bacteroides species and CDAD
3. H Pylori
4. Surgical Prophylaxis

Question 8

Why does Metronidazole target anaerobes?

Answer 8

Due to the stronger reducing conditions in anaerobes that allow for more cytotoxic free radical formation

Question 9

Administration method of Metronidazole

Answer 9

Oral - Rapid and Complete absorption

Question 10

Distribution of Metronidazole

Answer 10

Well distributed throughout body tissues and fluids (vaginal, seminal fluids, saliva, breast milk, CSF)

Question 11

Clearance of Metronidazole

Answer 11

Hepatic metabolism and urine excretion of both parent and metabolites

Question 12

Name 4 Adverse Effects of Metronidazole

Answer 12

1. GI - N/V, epigastric distress, abdominal cramps
2. Metallic taste
3. Oral moniliasis (yeast infection of the mouth)
4. Rare CNS and PNS effect (Convulsive seizures, optic / peripheral neuropathy)

Question 13

Why should we avoid metronidazole use in the first trimester of pregnancy?

Answer 13

• Metronidazole crosses the placental barrier and enters fetal circulation rapidly.
• It is a carcinogen in rodents although not proven in human response
• Avoid unless clearly needed

Question 14

Drug interactions

Answer 14

Warfarin effects may be potentiated

Question 15

What resistant strains are there to metronidazole?

Answer 15

Trichomonads. Usually not a problem for amebiasis