Co-trimoxazole

Medication sulfonamide antibiotic combination antibiotic

Aka: sulfamethoxazole + trimethoprim, Bactrim, Septrin

Brands seen in Singapore: Apo-Sulfatrim, Suprim, Mortin, Trimaxazole, Co-Trimexazole

Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.

How to use

What it’s for

Prescribed for bacterial infections — your doctor decides

When to take

HealthHub: the whole course, even once you feel better

Take with

HealthHub: with or without food · a meal eases nausea

Pros & cons

Pros

HealthHub: two antibiotics blocking two growth steps
FDA: one ds tablet every 12 hours for most adult uses
SG register: tablets, paediatric tablets, suspension

Cons

FDA: nausea, vomiting, appetite loss and rash lead
FDA: rare fatal skin, blood, liver and lung reactions
HealthHub: sun sensitivity; thrush can follow a course

Sources

HSA — Listing of Registered Therapeutic Products (open dataset on data.gov.sg; same register as HSA Infosearch) · read 2026-08-27
what it says
“Forensicclassification = 'Prescription Only' for all 10 sulphamethoxazole+trimethoprim products: SIN00435P APO-SULFATRIM, SIN00508P APO-SULFATRIM PEDIATRIC, SIN02308P SUPRIM B.P. 480, SIN01417P SUPRIM SUSPENSION, SIN10251P MORTIN, SIN10250P MORTIN-DS, SIN00407P TRIMAXAZOLE, SIN00583P CO-TRIMEXAZOLE, SIN00960P B.S., SIN02183P DBL injection.”
MOH National Drug Formulary — APO-SULFATRIM TABLET [SIN00435P], SG product information (last updated 28 July 2026) · read 2026-08-27
what it says
“SULPHAMETHOXAZOLE - 400 MG TRIMETHOPRIM - 80 MG … Forensic Classification: PRESCRIPTION ONLY MEDICINES … Prescription-only Medicines with Exemptions for Supply without Prescription: NA”
HealthHub (MOH Singapore / Pharmaceutical Society of Singapore) — Co-trimoxazole medication information leaflet (reviewed 20 Oct 2021) · read 2026-08-27
what it says
“an antibiotic made up of two different antibiotics … blocking two essential steps in the growth of bacteria … may be taken with or without food … more sensitive to the sun … may cause a fungal infection called thrush.”
FDA / openFDA drug label — BACTRIM and BACTRIM DS (sulfamethoxazole and trimethoprim) tablets, prescribing information (Sun Pharmaceutical, effective 30 Dec 2024) · read 2026-08-27
what it says
“The usual adult dosage in the treatment of urinary tract infections is 1 BACTRIM DS (double strength) tablet or 2 BACTRIM tablets every 12 hours … The total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim.”

Report a correction View as JSON

Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.

In Singapore

Classification
HSA register

prescription-only

This is the Singapore classification, taken from the HSA register. Dosing stays with the label and your pharmacist or doctor — this page never tells you how much to take.

What the label says

The US bactrim label states 'The usual adult dosage in the treatment of urinary tract infections is 1 BACTRIM DS (double strength) tablet or 2 BACTRIM tablets every 12 hours for 10 to 14 days', and for paediatric prophylaxis sets an explicit ceiling — 'The total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim'; higher weight-based regimens (75–100 mg/kg sulfamethoxazole a day) exist for pneumocystis pneumonia only; no SG label with a dosing section was found; as directed on the label or by your doctor

Who should check first

Talk to a doctor or pharmacist before taking this if any of these apply to you.

Sulfa allergy, or rash after a sulfa drug: HealthHub says tell your professional
G6pd deficiency: FDA label: haemolysis may occur, often dose-related
Pregnancy: FDA warns of a possible rise in birth defects
Kidney or liver problems, folate deficiency, asthma: FDA says avoid

Documented interactions

With medicines and supplements

Warfarin: FDA: prothrombin time may lengthen — the label says monitor pt and INR^4,3
Phenytoin: FDA: phenytoin half-life rose 39% — the label says monitor levels^4,3
Methotrexate: FDA: avoid concurrent use — free methotrexate levels can rise^4,3
Ace inhibitors, arbs, spironolactone: HealthHub: these raise potassium, as co-trimoxazole can^3,4
Thiazide diuretics in older people: FDA: avoid concurrent use — more thrombocytopenia with purpura reported⁴

Only combinations someone has written down appear here. A pair that is missing is unrecorded, not cleared.