TRIMETHOPRIM

Question 1

Drug class

Answer 1

trimethoprim

Question 2

How does it work? (3)

Answer 2

1. bacteria use folate for DNA synthesis
2. Trimethoprim inhibits bacterial folate synthesis
3. this consequently slows bacterial growth - bacteriostatic

Question 3

What type of bacteria does trimethoprim work against?

Answer 3

1. gram positive and gram negative bacteria

e. g. E.coli (gram -ve bac)

Question 4

What is the problem with trimethoprim?

Answer 4

bacterial resistance

Question 5

Indications

Answer 5

1. UTIs

Question 6

What is the combination of trimethoprim and sulfamethoxazole used for?

Answer 6

Pneumocystitis pneumonia in the immunocompromised

Question 7

Contra-indications (6)

Answer 7

1. 1st trimester of pregnancy
2. patients with folate def
3. renal impairment
4. elderly
5. neonates
6. HIV

Question 8

Why can not trimethoprim be used in the 1st trimester of pregnancy?

Answer 8

• fetal abnormalities such as CVS or oral clefts

- due to folate antagonist

Question 9

Side effects (5)

Answer 9

1. GI upset

• nausea
• vom
• sore mouth

2. Skin rash
3. severe hypersensitivity reaction
4. haematological disorders
5. hyperkaelemia

Question 10

Interactions (4)

Answer 10

1. potassium elevating drugs

• aldosterone antagonists
• ACEIs
• ARBs

2. Folate antagonists
   - methotrexate
3. Drugs increasing folate metabolism
   - phenytoin
4. Enhances the anticoagulant effects of warfarin
   - kills the normal gut flora that synthesises vit K

Question 11

Eliminations

Answer 11

urine