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 or pharmacist.
Important Safety Information
This service operates under German pharmaceutical law (HWG). For risks and side effects, read the package leaflet and consult your doctor or pharmacist. All medications are dispensed from a licensed pharmacy in Germany.