Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Co-trimoxazole combines two antibiotics that block successive steps of bacterial folate production: sulfamethoxazole and trimethoprim. It is used for urinary tract infections, some chest and skin infections including MRSA, and to treat and prevent Pneumocystis pneumonia in people with weakened immunity. It is sold as Bactrim and Septra, among other names.
The US FDA lists NAT2 for co-trimoxazole: slow acetylators clear sulfamethoxazole more slowly, which older studies linked to more hypersensitivity reactions. Its rare severe skin reactions have been linked to immune-system gene versions, such as HLA-B*13:01, HLA-B*15:02 and HLA-B*38:02, and to HLA-C variants, in different populations. In G6PD deficiency, sulfonamides can cause haemolysis. There is no CPIC or DPWG guideline.
Clinical guidelines that name a gene for Bactrim. They sort people into groups by the gene copies they carry.
US FDA: NAT2. Poor Metabolizer. Data that Indicate a Potential Impact on Safety or Response.
Every published finding on gene variants and Bactrim. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
HLA-B HLA-B*13:01, HLA-B*15:02, HLA-B*38:02: Level 2A · replicated. Toxicity: Stevens-Johnson Syndrome, Toxic Epidermal Necrolysis. 2.
HLA-C HLA-C*06:02, HLA-C*07:27, HLA-C*08:01: Level 2B · replicated. Toxicity: Stevens-Johnson Syndrome, Toxic Epidermal Necrolysis. 2.
NAT2 NAT2*4, NAT2*5, NAT2*6, NAT2*7, NAT2*14, NAT2*16: Level 3. Toxicity: adverse events, Hypersensitivity, Severe Cutaneous Adverse Reactions. 6.
NAT2 rs1799931: Level 3. Toxicity: adverse events, Hypersensitivity. 2.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Sulfamethoxazole (Sulfonamides)
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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