Trimethoprim Flashcards
What is the mechanism of action of trimethoprim?
Inhibits dihydrofolate reductase, an enzyme that converts dihydrofolic acid (DHF) to tetrahydrofolic acid (THF), disrupting the bacterial synthesis pathway
Is trimethoprim broad or narrow spectrum?
Broad
What is trimethoprim effective against?
Gram +ve and gram -ve bacteria
What is the route of delivery of trimethoprim?
PO
What are the indications for trimethoprim?
- Urinary tract infection
- Acute and chronic bronchitis
- Pneumocystitis jiroveci pneumonia
What are the contraindications to trimethoprim?
- Blood dyscrasia
- Pregnancy in first trimester
What might trimethoprim interact with?
- Warfarin
- ACEi and angiotensin receptor antagonists
- Amiodarone
- Azathioprine
- Mercaptopurine
- Methotrexate
- Diuretics
- Amphotericin
- Aciclovir
What might happen if trimethoprim is given with warfarin?
Increased anticoagulant effect
What might happen if trimethoprim is given with ACEi or angiotensin receptor antagonists?
Increased risk of hyperkalaemia
What might happen if trimethoprim is given with amiodarone?
Increased risk of arrhythmias
What might happen if trimethoprim is given with azathioprine, mercaptopurine, or methotrexate?
Increased risk of haematological toxicity
What might happen if trimethoprim is given with diuretics, amphotericin, or acyclovir?
Increased risk of nephrotoxicity
What monitoring is required with trimethoprim?
Monitor FBC during long-term treatment
Why should FBC be monitored during long term treatment with trimethoprim?
To detect and treat any blood disorders that occur
What are the rare side effects of trimethoprim?
- Anaphylaxis and allergic reactions
- Angioedema
- Erythema multiforme and toxic epidermal necrolysis
- Photosensitivity
What are the other side effects (frequency not known) of trimethoprim?
- Aseptic meningitis
- Hyperkalaemia
- Reduction in haematopoiesis
- Nausea
- Rashes
- Uveitis
What patient counselling is required with trimethoprim?
- Complete antibiotic course
- Not for use in pregnancy
- When to seek help
Why should trimethoprim not be used in pregnancy?
Can cause fetal abnormalities
When should the patient be advised to seek help with trimethoprim?
If they notice bleeding, bruising, rashes, fever, or sore throats whilst on trimethoprim
