Formulary
Trimethoprim: Indications, Dosing, Side Effects and Interactions
Trimethoprim clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 8 min read
Trimethoprim: Indications, Dosing, Side Effects and Interactions
Trimethoprim clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**Respiratory-tract infections**
- **Child** (By Mouth): 12-17 years 200 mg twice daily.
- **Adult** (By Mouth): 200 mg twice daily.
**Treatment of mild to moderatePneumocystis jirovecii(Pneumocystis carinii) pneumonia in patients who cannot tolerate co-trimoxazole (in combination with dapsone)**
- **Child** (By Mouth): Treatment of mild to moderate Pneumocystis jirovecii ( Pneumocystis carinii ) pneumonia in patients who cannot tolerate co-trimoxazole (in combination with dapsone) 5 mg/kg every 6-8 hours.
- **Adult** (By Mouth): 5 mg/kg every 6-8 hours.
**Acne resistant to other antibacterials**
- **Adult** (By Mouth): 300 mg twice daily.
**Shigellosis,Invasive salmonella infection**
- **Adult** (By Mouth): (consult product literature).
**Acute diverticulitis [in combination with metronidazole]**
- **Adult** (By Mouth): 200 mg twice daily for 5 days then review.
**Acute prostatitis**
- **Adult** (By Mouth): 200 mg twice daily for 14 or 28 days based on clinical assessment.
**Acute pyelonephritis**
- **Child** (By Mouth): 16-17 years 200 mg twice daily for 14 days.
- **Adult** (By Mouth): 200 mg twice daily for 14 days.
**Urinary-tract infection (catheter-associated)**
- **Child** (By Mouth): 16-17 years 200 mg twice daily for 7 days (14 days if upper urinary-tract symptoms are present).
- **Adult** (By Mouth): 200 mg twice daily for 7 days (14 days if upper urinary-tract symptoms are present).
**Lower urinary-tract infection**
- **Child** (By Mouth): 16-17 years 200 mg twice daily for 3 days (7 days in males).
- **Adult** (By Mouth): 200 mg twice daily for 3 days (7 days in males).
**Prophylaxis of recurrent urinary-tract infection in non-pregnant females [using single-dose antibacterial prophylaxis]**
- **Child** (By Mouth): 16-17 years 200 mg for 1 dose, dose to be taken following exposure to a trigger.
- **Adult** (By Mouth): 200 mg for 1 dose, dose to be taken following exposure to a trigger.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis]**
- **Child** (By Mouth): 16-17 years 100 mg once daily, dose to be taken at night, seek specialist advice if considering use for prophylaxis in male patients, or for recurrent upper urinary-tract infection or recurrent complicated lower urinary-tract infection.
- **Adult** (By Mouth): 100 mg once daily, dose to be taken at night, seek specialist advice if considering use for prophylaxis in male patients, or for recurrent upper urinary-tract infection or recurrent complicated lower urinary-tract infection.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis] (initiated under specialist supervision)**
- **Child** (By Mouth): 12-15 years 100 mg once daily, dose to be taken at night.
**Respiratory-tract infections for trimethoprim**
- **Neonate** (By mouth): Initially 3 mg/kg for 1 dose, then 1-2 mg/kg twice daily.
- **Child 4-5 weeks** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg).
- **Child 6 weeks-5 months** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg), alternatively 25 mg twice daily.
- **Child 6 months-5 years** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg), alternatively 50 mg twice daily.
- **Child 6-11 years** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg), alternatively 100 mg twice daily.
- **Child 12-17 years** (By mouth): 200 mg twice daily.
**Treatment of mild to moderate Pneumocystis jirovecii (Pneumocystis carinii) pneumonia in patients who cannot tolerate co-trimoxazole (in combination with dapsone) for trimethoprim**
- **Child** (By mouth): 5 mg/kg every 6-8 hours.
**Shigellosis, Invasive salmonella infection for trimethoprim**
- **Child** (By mouth): (consult product literature).
**Acute pyelonephritis for trimethoprim**
- **Child 16-17 years** (By mouth): 200 mg twice daily for 14 days.
**Urinary-tract infection (catheter-associated) for trimethoprim**
- **Child 3-5 months** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg) for 7-10 days, alternatively 25 mg twice daily for 7-10 days.
- **Child 6 months-5 years** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg) for 7-10 days, alternatively 50 mg twice daily for 7-10 days.
- **Child 6-11 years** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg) for 7-10 days, alternatively 100 mg twice daily for 7-10 days.
- **Child 12-15 years** (By mouth): 200 mg twice daily for 7-10 days.
- **Child 16-17 years** (By mouth): 200 mg twice daily for 7 days (14 days if upper urinary-tract symptoms are present).
**Lower urinary-tract infection for trimethoprim**
- **Neonate** (By mouth): Initially 3 mg/kg for 1 dose, then 1-2 mg/kg twice daily.
- **Child 4-5 weeks** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg).
- **Child 6 weeks-2 months** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg), alternatively 25 mg twice daily.
- **Child 3-5 months** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg) for 3 days, alternatively 25 mg twice daily for 3 days.
- **Child 6 months-5 years** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg) for 3 days, alternatively 50 mg twice daily for 3 days.
- **Child 6-11 years** (By mouth): 4 mg/kg twice daily (max. per dose 200 mg) for 3 days, alternatively 100 mg twice daily for 3 days.
- **Child 12-15 years** (By mouth): 200 mg twice daily for 3 days.
- **Child 16-17 years** (By mouth): 200 mg twice daily for 3 days (7 days in males).
**Prophylaxis of recurrent urinary-tract infection in non-pregnant females [using single-dose antibacterial prophylaxis] for trimethoprim**
- **Child 16-17 years** (By mouth): 200 mg for 1 dose, dose to be taken following exposure to a trigger.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis] for trimethoprim**
- **Child 16-17 years** (By mouth): 100 mg once daily, dose to be taken at night, seek specialist advice if considering use for prophylaxis in male patients, or for recurrent upper urinary-tract infection or recurrent complicated lower urinary-tract infection.
**Prophylaxis of recurrent urinary-tract infection [using daily antibacterial prophylaxis] (initiated under specialist supervision) for trimethoprim**
- **Neonate** (By mouth): 2 mg/kg once daily, dose to be taken at night.
- **Child 4-5 weeks** (By mouth): 2 mg/kg once daily, dose to be taken at night.
- **Child 6 weeks-5 months** (By mouth): 2 mg/kg once daily, dose to be taken at night, alternatively 12.5 mg once daily, dose to be taken at night.
- **Child 6 months-5 years** (By mouth): 2 mg/kg once daily (max. per dose 100 mg), dose to be taken at night, alternatively 25 mg once daily, dose to be taken at night.
- **Child 6-11 years** (By mouth): 2 mg/kg once daily (max. per dose 100 mg), dose to be taken at night, alternatively 50 mg once daily, dose to be taken at night.
- **Child 12-15 years** (By mouth): 100 mg once daily, dose to be taken at night.
Cautions
Acute porphyrias ; elderly (in adults); predisposition to folate deficiency
Contraindications
Blood dyscrasias
Side effects
Common or very common Diarrhoea; electrolyte imbalance; fungal overgrowth; headache; nausea; skin reactions; vomiting Rare or very rare Agranulocytosis; angioedema; anxiety; appetite decreased; arthralgia; behaviour abnormal; bone marrow disorders; confusion; constipation; cough; depression; dizziness; dyspnoea; eosinophilia; erythema nodosum; fever; haemolysis; haemolytic anaemia; haemorrhage; hallucination; hepatic disorders; hypoglycaemia; lethargy; leucopenia; meningitis aseptic; movement disorders; myalgia; neutropenia; oral disorders; pancreatitis; paraesthesia; peripheral neuritis; photosensitivity reaction; pseudomembranous enterocolitis; renal impairment; seizure; severe cutaneous adverse reactions (SCARs); sleep disorders; syncope; systemic lupus erythematosus (SLE); thrombocytopenia; tinnitus; tremor; uveitis; vasculitis; vertigo; wheezing Frequency not known Gastrointestinal disorder; megaloblastic anaemia; methaemoglobinaemia
Interactions
**Severe interactions:**
- Azathioprine: There are conflicting clinical reports of interactions between azathioprine and trimethoprim-sulfamethoxazole, resulting in serious haematological abnormalities.
**Other interactions (24):**
- Interaction with laboratory tests : Trimethoprim may interfere with the estimation of serum/plasma creatinine when the alkaline picrate reaction is used.
- Zidovudine: in some situations, concomitant treatment with zidovudine may increase the risk of haematological adverse reactions to co-trimoxazole.
- Cyclosporin: reversible deterioration in renal function has been observed in patients treated with co-trimoxazole and ciclosporin following renal transplantation.
- Rifampicin: concurrent use of rifampicin and Co-Trimoxazole results in a shortening of the plasma half-life of trimethoprim after a period of about one week.
- When trimethoprim is administered simultaneously with drugs that form cations at physiological pH, and are also partly excreted by active renal secretion (e.g.
- Diuretics (thiazides): in elderly patients concurrently receiving diuretics, mainly thiazides, there appears to be an increased risk of thrombocytopenia with or without purpura.
Pregnancy
Teratogenic risk in first trimester (folate antagonist). Manufacturers advise avoid during pregnancy.
Breast feeding
Present in milk-short-term use not known to be harmful.
Renal impairment
Manufacturer advises caution in impairment. Dose adjustments In adults: Manufacturer advises dose reduction to half normal dose after 3 days if eGFR 15-30 mL/minute/1.73 m 2 . Manufacturer advises dose reduction to half normal dose if eGFR less than 15 mL/minute/1.73 m 2 . In children: Manufacturer advises dose reduction to half normal dose after 3 days if estimated glomerular filtration rate 15-30 mL/minute/1.73 m 2 . Manufacturer advises dose reduction to half normal dose if estimated glomerular filtration rate less than 15 mL/minute/1.73 m 2 .
Medicinal forms
Solution,Tablet,Suspension
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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