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Drugs and Medicinal Substances

Trimethoprim

Antiinfective Agents for Systemic Use

Trimethoprim is an antibiotic taken by mouth that is used mainly to treat bladder infections. It is also used for middle ear infections and travellers' diarrhoea, and, combined with sulfamethoxazole or dapsone, it may be given for Pneumocystis pneumonia in people with HIV/AIDS. Its common side effects are nausea, changes in taste and rash, and it can rarely cause blood problems such as too few platelets or white blood cells. It may also make the skin sensitive to sun. The drug works by blocking folate metabolism through dihydrofolate reductase in some bacteria, which prevents them making DNA and RNA and so kills them. It was first used in 1962, appears on the World Health Organization's List of Essential Medicines and is available as a generic medication.

Facts
Classification
Approval Status
Approved 1
ATC Class
J: Antiinfectives for Systemic Use 2
Route of Administration
Oral 1
WHO Essential Medicine
Core List 3
First Approved / Isolated Year
1962 1
Sources
1. Trimethoprim (Wikipedia)
  • Lead section of the English Wikipedia article
    It is available as a generic medication.
  • Lead section of the English Wikipedia article [first-approved-year]
    Trimethoprim was first used in 1962.
  • Lead section of the English Wikipedia article [route-of-administration]
    It is taken orally (swallowed by mouth).
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2. RxNav RxClass, National Library of Medicine: RxClass ATC classes of Trimethoprim
RxNav RxClass, National Library of MedicineRxClass ATC class of the drug (levels 1 to 4); ATC class derived from cited code J01EA (main group J)
Quote, RxClass ATC class of the drug (levels 1 to 4); ATC class derived from cited code J01EA (main group J)
"classId": "J01EA", "className": "Trimethoprim and derivatives", "classType": "ATC1-4"
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3. World Health Organization: The selection and use of essential medicines, 2025: WHO Model List of Essential Medicines, 24th list
World Health OrganizationPDF page 19; section 6.2.1; the entry trimethoprim is in the Core List of the WHO Model List of Essential Medicines, 24th list (2025)
Quote, PDF page 19; section 6.2.1; the entry trimethoprim is in the Core List of the WHO Model List of Essential Medicines, 24th list (2025)
trimethoprim Tablet: 100 mg + 20 mg; 400 mg + 80 mg; 800 mg + 160 mg.
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