What is trimethoprime?
Trimethoprim is an antibiotic used for treating urinary tract infections. It selectively inhibits a bacterial enzyme and thereby acts bacteriostatic to bactericidal.
The drug concentrates in urine and reaches high concentrations there. With uncomplicated bladder inflammation, a 3-day therapy is usually sufficient.
Trimethoprim can also be used in combination with sulfamethoxazole (Cotrimoxazole), but trimethoprim alone is sufficient for urinary tract infections.
Active Ingredients & Mechanism of Action
Active ingredient: Trimethoprim
Trimethoprim inhibits bacterial folic acid synthesis:
Active mechanism:
- inhibits the enzyme dihydrofolate reductase (DHFR)
- Blocks the synthesis of tetrahydrofolic acid
- Without tetrahydrofolic acid, bacteria cannot produce DNA components
- Bacteria growth is inhibited
Selectivity: Trimethoprim inhibits bacterial DHFR about 50,000 times stronger than human DHFR. It therefore acts specifically against bacteria.
Activity spectrum:
- E. coli (the most common pathogen of urinary tract infections)
- Clebsiella
- Proteus mirabilis
- Staphylococcus saprophyticus
- Enterobacter
Who is it suitable for?
Trimethoprim is suitable for:
- Uncomplicated urinary tract infections (cystitis)
- Prophylaxis in recurring urinary path infections
Advantages:
- Easy dosage (2x daily)
- Short treatment time (3 days)
- Good compatibility
- Value
Not suitable for:
- Kidney pelvic inflammation
- Complicated urinary path infections
- Pregnancy
- Folic acid deficiency
- Heavy kidney failure
Available Dosages
Acute bladder inflammation:
- 200 mg 2x daily for 3 days OR
- 300 mg 1x daily (retard form) for 3 days
Prophylaxis:
- 100 mg in the evening for several months
Available starches:
- Tablets 100 mg, 200 mg
- Retard tablets 300 mg
For renal insufficiency: Dose reduction required.
How to Take
Intake:
- With or after eating
- With plenty of water
- Both daily doses at a distance of about 12 hours
Language:
- 3 days in acute bladder inflammation
- Use the entire package
- Do not break prematurely
Prophylaxis:
- Evening before bedtime
- possible for several months
- Under medical control
**
- Drink a lot during treatment
- symptoms usually improve after 1-2 days
- In case of deterioration or fever visit doctor
Contraindications
**Trimethoprim must not be taken at:* *
- hypersensitivity to trimethoprim
- Pregnancy (especially 1st trimester – folic acid antagonist)
- Still time
- Heavy liver failure
- Megaloblastic anemia due to folic acid deficiency
- Blood disorders
Preview at:
- Kidney insufficiency (dose adjustment)
- Folic acid deficiency
- Older patients
- Potassium preparations (hyperkaliemia risk)
Possible Side Effects
Acid (1-10%):
- nausea
- Break.
- diarrhea
- Skin rash
- Itching
Occasionally:
- Headaches
- Blood-image changes
- Increased potassium in the blood
Selten:
- Megaloblastic anemia (for longer use)
- Heavy skin reactions
- liver damage
** For short-term use (3 days), severe side effects are rare.
Interactions
Reactions:
- Methotrexate – increased toxicity (both inhibit folic acid metabolism)
- ACE inhibitors, potassium-saving diuretics – hyperkaliemia risk
- Warfarin – increased bleeding
- Phenytoin – Increased Mirror
Preview at:
- Folic acid antagonists
- Drugs that affect the blood count
Recommendation: When taking methotrexate or potassium: inform doctor.
Frequently Asked Questions
Similar Medications
Is trimethoprime right for you?
A licensed doctor will review your information and issue a prescription if suitable. Discreet and secure.
Important Notice
This information does not replace medical advice. If you have questions about your health or the suitability of this medication, please consult a doctor. Read the package leaflet before use.