Trimethoprim Flashcards
What are common indications for trimethoprim?
First choice for UTI
What is co-trimoxazole commonly used for?
PCP in immunosppressed individuals
How does trimethoprim work?
Inhibits bacterial folate synthesis - slowing growth
What are important adverse side effects of trimethoprim?
- GI upset
- Skin rash
- Hypersensitivity - drug fever, erythema multiforme
- Megaloblastic anaemia
- Leucopenia
- Thrombocytopenia
- Hyperkalaemia
- Plasma creatinine
When is trimethoprim contraindicated for use?
First trimester pregnancy
When should you be cautious with using trimethoprim?
- Folate deficiency
- Renal impairment
- Neonates
- Elderly
- HIV infection
What are important interactions that you should be aware of when using trimethoprim?
- Potassium elevating drugs - aldosterone antagonissts, ACEi, ARBs
- Folate antagnists - methotrexate
- Phenytoin
- Warfarin
What dose of trimethoprim would you give orally to an adult with an acute UTI?
200 mg twice daily
What dose of trimethoprim would you give to prophylactically treat a UTI?
100 mg once daily - to be take at night
What monitoring would you perform for long term trimethoprim treatment?
FBC - for haematological disorder
Why might trimethoprim tend to be less effective for patients with UTI with renal impairment?
Trimethoprim competitively inhibits creatinine secretion by the renal tubules - leads to a small reversible rise in serum creatinine concentration during trimethoprim treatment, without reduction in the glomerular filtration rate. For this reason, trimethoprim tends to be less effective for UTI in patients with renal impairment as it is out-competed by creatinine for secretion into the urinary tract
