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Oral formulations of trimethoprim

Drugs List

  • trimethoprim 100mg tablets
  • trimethoprim 200mg tablets
  • trimethoprim 50mg/5ml oral suspension sugar-free
  • Therapeutic Indications


    Antibiotic sensitive infections
    Prophylaxis of recurrent urinary tract infections
    Respiratory tract infections - upper and lower
    Urinary tract infection

    Unlicensed Uses

    Acne vulgaris
    Mild-mod Pneumocystis jiroveci pneumonia in pts intolerant of cotrimoxazole

    Acne resistant to other antibacterials (prolonged treatment with trimethoprim may depress haemopoiesis, it should be initiated by specialists).

    Mild to moderate pneumocystis pneumonia where co-trimoxazole is not tolerated or is inappropriate, dapsone may be given with trimethoprim.



    Acute infections
    200mg twice daily.
    Treatment period ranges between 3 to 14 days, depending on nature and severity of infection. The first dose can be doubled.

    Long term treatment and prophylactic therapy
    100mg at night.

    Antibacterial resistant acne (unlicensed)
    300mg twice daily. Prolonged treatment with trimethoprim may depress haemopoiesis.

    Mild to moderate pneumocystis pneumonia where co-trimoxazole is not tolerated or is inappropriate (unlicensed)
    5mg/kg every 6 to 8 hours. Given with dapsone.


    Not all brands are recommended in all age groups.

    Acute infections:
    The following dosages are based on 8mg/kg bodyweight daily.
    Children aged over 12 years: 200mg twice daily.
    Children aged 6 to 12 years: 100mg twice daily.
    Children aged 6 months to 6 years: 50mg twice daily.
    Children aged 6 weeks to 6 months: 25mg twice daily.

    The following alternative dosing schedule may be suitable:

    The following dosages are based on 4mg/kg bodyweight daily.
    Children aged 6 to 12 years: 100mg twice daily.
    Children aged 6 months to 5 years: 50mg twice daily.
    Children aged 6 weeks to 5 months: 25mg twice daily.
    Children aged 4 to 5 weeks: 4mg/kg twice daily.

    Long term treatment and prophylactic therapy:
    The following dosages are based on 2mg/kg bodyweight daily.
    Children 12 to 18 years: 100mg at night.
    Children 6 to 12 years: 50mg at night.
    Children 6 months to 6 years: 25mg at night.
    Children 6 weeks to 5 months: 12.5mg at night.
    Children 4 to 6 weeks (unlicensed): 2mg/kg at night.

    Mild to moderate pneumocystis pneumonia where co-trimoxazole is not tolerated or is inappropriate (unlicensed):
    Trimethoprim 5mg/kg every 6 to 8 hours may be given with dapsone.


    Use in children aged under 6 weeks is unlicensed.

    Acute infections:
    3mg/kg as a single dose, then 1mg/kg to 2mg/kg twice daily.

    Long term treatment and prophylactic therapy:
    2mg/kg once daily at night.

    Patients with Renal Impairment

    Use with caution in patients with renal impairment to avoid accumulation. Regular haematological examination is required with long term therapy.

    Trimethoprim is removed by dialysis. Do not administer to dialysis patients unless plasma concentrations can be estimated regularly.

    The Renal Drug Handbook suggests short term folic acid supplements may be used in CKD 4 to 5.

    The manufacturers of the solid formulations suggest the following:
    Creatinine clearance over 0.45ml/second
    Dose as usual.

    Creatinine clearance 0.25 to 0.45ml/second
    Day one to three: Dose as usual.
    Day four and onwards: Use half usual dose for age.

    Creatinine clearance under 0.25ml/second
    Half the usual dose.

    The manufacturer of the liquid formulation suggests the following regimen in renal impairment for treatment of infection in adults. Similar reductions should be made in children:
    Creatinine clearance over 25ml/minute
    200mg twice daily.
    From day four onwards, monitor serum trimethoprim.

    Creatinine clearance 10 to 25ml/minute
    Day one: 200mg twice daily.
    Day two and onwards: 100mg twice daily.
    From day four onwards, monitor serum trimethoprim.

    Creatinine clearance under 10ml/minute
    Day one: 200mg twice daily.
    Day two and onwards: 50 to 100mg twice daily. Monitor serum trimethoprim.


    Children under 4 months
    Haematological disorder

    Precautions and Warnings

    Children under 6 weeks
    Predisposition to folate deficiency
    Folate deficiency
    Glucose-galactose malabsorption syndrome
    Hereditary fructose intolerance
    Lactose intolerance
    Renal dialysis
    Renal impairment
    Severe hepatic impairment

    Folate supplementation may be necessary in some patients
    Not all available products are licensed for all age groups
    Presentations with sorbitol unsuitable in hereditary fructose intolerance
    Some formulations contain lactose
    Perform blood counts on prolonged use of this treatment
    Advise patient to report unexplained fever, sore throat, bruising, bleeding
    May affect results of some laboratory tests

    Caution in patients with, or predisposed to, folate deficiency (e.g. elderly patients). Consider administration of a folate supplement. Although an effect on folic acid metabolism is possible, interference with haematopoiesis rarely occurs at the recommended dose. If any such change is seen, folinic acid should reverse the effect. Elderly people may be more susceptible and a lower dose may be advisable.

    Consider monitoring serum electrolytes in patients at risk for hyperkalaemia. Elderly patients or those taking high doses may be more susceptible to hyperkalaemia and hyponatraemia.

    Pregnancy and Lactation


    Use trimethoprim with caution in pregnancy.

    The manufacturer does not recommend the use of trimethoprim during pregnancy.

    In the guidance published within Clinical Knowledge Summaries (CKS), when indicated, trimethoprim is suggested as one of a number of second line drugs for the treatment of symptomatic urinary tract infection (UTI) or asymptomatic bacteriuria, when other alternatives are not suitable. There may be teratogenic risk in the first trimester. CKS note that trimethoprim should be avoided in women who are folate deficient, taking a folate antagonist or who have been treated with trimethoprim in the last year. Schaefer considers trimethoprim an appropriate second line agent. Briggs suggests folic acid supplementation, at least 0.4 mg/day, may reduce the risk of congenital defects.

    Trimethoprim is a folate antagonist, which raises concerns that its use during pregnancy may limit the availability of folic acid to the developing foetus. Human and animal data suggest that there may be risks associated with the use of trimethoprim in pregnancy, some reports and studies suggesting that use in the first trimester may result in structural defects.


    Use trimethoprim with caution in breastfeeding.

    The manufacturers suggests although trimethoprim is excreted in breast milk this is not a contraindication to its short term use.

    Schaefer suggests breastfeeding can continue during trimethoprim therapy. Hale suggests as trimethoprim is a folate antagonist, its long term use should be avoided in breastfeeding mothers or the infant should be considered for supplementation with folic acid.

    Side Effects

    Allergic reaction
    Altered liver enzymes values
    Anaphylactic reaction
    Aseptic meningitis
    Blood dyscrasias
    Cholestatic jaundice
    Decreased haemopoiesis
    Erythema multiforme
    Exfoliative dermatitis
    Folate deficiency
    Gastro-intestinal disturbances
    Increase in blood urea nitrogen
    Megaloblastic anaemia
    Serum creatinine increased
    Sore mouth
    Stevens-Johnson syndrome
    Toxic epidermal necrolysis


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: November 2016

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.

    Medications and Mothers' Milk, Sixteenth Edition (2014) Hale, T and Rowe, H, Hale Publishing, Plano, Texas.

    Summary of Product Characteristics: Trimethoprim 100 mg tablets. Kent Pharmaceuticals Ltd. Revised August 2013.
    Summary of Product Characteristics: Trimethoprim 50 mg/5ml Suspension. Pinewood Healthcare. Revised April 2011.
    Summary of Product Characteristics: Trimogal tablets. Ennogen Pharma Limited. Revised July 2019.

    The Renal Drug Handbook. Fourth Edition (2014) ed. Ashley, C and Dunleavy, A, Radcliffe Publishing Ltd, London.

    Clinical Knowledge Summaries - Urinary Tract Infection (lower) - women. Revised December 2019.
    Available at:

    NICE - Evidence Services
    Available at:
    Last accessed: 09 June 2017

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Trimethoprim Last revised: 31 October 2018
    Last accessed: 19 May 2020

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