8.7

Question 1

Where does Trimethoprim work?

Answer 1

Inhibits Dihydrofolate reductase.

inhibits purine, pyrimidine, & amino acid synthesis

Question 2

What are the clinical applications of Trimethoprim?

Answer 2

• UTI’s
• Bacterial prostatitis
• Bacterial vaginitis

Question 3

What are the adverse effects of Trimethoprim?

Answer 3

• Antifolate effects (contraindicated in pregnancy)

* Skin rash, pruritus

Question 4

What is the drug of choice for PCP

Answer 4

Cotrimoxazole

Question 5

What are the clinical applications of Cotrimoxazole?

Answer 5

• Uncomplicated UTI’s (drug of choice)
• PCP (drug of choice)
• Nocardiosis (drug of choice)
• Toxoplasmosis (alternative drug)
• Respiratory, ear, sinus infections (H.influenzae,
M.catarrhalis)

Question 6

What are the adverse effects of Cotrimoxazole?

Answer 6

• Dermatologic (common)
• GI
• Hematologic (hemolytic anemia)
• AIDS patients = higher incidence
• Contraindicated in pregnancy (esp. 1st trimester)

Question 7

What does Metronidazole mainly affect?

Answer 7

Activity against anaerobic bacteria (including bacteroides & Clostridium)

(below diaphram)

Question 8

What is needed for Metronidazole to be effective?

Answer 8

Aerobic conditions bc undergoes reductive bioactivation of nitro group by ferrodoxin.

Question 9

What are the clinical applications of Metronidazole?

Answer 9

• C.difficile infections (drug of choice)
• Anaerobic or mixed intra-abdominal infections
• Vaginitis (trichomonas & bacterial vaginosis, G.vaginalis)
• Brain abscesses
• H.pylori eradication (in combination)

Question 10

What are the adverse effects of Metronidazole?

Answer 10

• GI irritation, stomatitis, peripheral neuropathy (prolonged use)
• Headache, dark coloration of urine
• Leukopenia, dizziness, ataxia (rarer)
• Opportunistic fungal infections
• Disulfiram-like effect (avoid alcohol)
• Use generally not advised in 1st trimester

Question 11

Which drug is a urinary antiseptic?

Answer 11

Nitrofurantoin

Question 12

What are the adverse effects of Nirofurantoin?

Answer 12

• Anorexia, nausea & vomiting.

* Neuropathies, hemolytic anemia (G6PD deficient patients)

Question 13

What are the contraindications of Nitrofurantoin?

Answer 13

• Significant renal insufficiency
• Pregnancy at term (38-42 weeks)
• Infants <1 month (risk of hemolytic anemia)