Sulfamethoxazole
Sulfamethoxazole 100GM of
What is Sulfamethoxazole?
Sulfamethoxazole is a sulfonamide antibiotic that is commonly used in combination with trimethoprim to treat a wide range of bacterial infections, including urinary tract infections, bronchitis, and specific types of pneumonia. It works by inhibiting the production of dihydrofolic acid, a form of folic acid that bacteria require to produce essential proteins and DNA, thereby stopping bacterial growth.Side Effects
- Nausea
- Vomiting
- Diarrhea
Warnings
- May cause severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Avoid prolonged exposure to sunlight and wear sunscreen due to increased risk of sunburn
- May cause a drop in blood cell count (e.g., leukopenia, thrombocytopenia)
- May precipitate in kidney tubules when urine is acidic; adequate hydration is important
- Risk of hypersensitivity reactions especially in patients with a history of allergy to sulfa drugs
Prescription savings · · · ·
What is Sulfamethoxazole ?
Sulfamethoxazole is a sulfonamide antibiotic that is commonly used in combination with trimethoprim to treat a wide range of bacterial infections, including urinary tract infections, bronchitis, and specific types of pneumonia. It works by inhibiting the production of dihydrofolic acid, a form of folic acid that bacteria require to produce essential proteins and DNA, thereby stopping bacterial growth.- Nausea
- Vomiting
- Diarrhea
- Rash
- Dizziness
- Headache
- Fever
- May cause severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Avoid prolonged exposure to sunlight and wear sunscreen due to increased risk of sunburn
- May cause a drop in blood cell count (e.g., leukopenia, thrombocytopenia)
- May precipitate in kidney tubules when urine is acidic; adequate hydration is important
- Risk of hypersensitivity reactions especially in patients with a history of allergy to sulfa drugs
- Should not be used in infants younger than 2 months old due to the risk of kernicterus
- Possible interaction with warfarin, increasing risk of bleeding
Sulfamethoxazole Coupons & Prices
Sulfamethoxazole 100GM of
If you're comparing a sulfamethoxazole coupon before you fill this prescription, it helps to know what you're actually shopping for: sulfamethoxazole is almost always dispensed as sulfamethoxazole and trimethoprim (co-trimoxazole, SMX-TMP), the combination antibiotic sold under brand names like Bactrim and Septra, and it has long been available as a generic. Because this generic is stocked at essentially every pharmacy but priced differently from one to the next, it's worth checking before you fill rather than assuming your usual pharmacy has the best price; Rx.com compares pricing across 60,000+ pharmacies so you can see today's price at the ZIP code you enter above before you commit to a location.
What is sulfamethoxazole and how does it work?
Sulfamethoxazole is a sulfonamide antibiotic that is almost never prescribed alone. It's combined with trimethoprim, a dihydrofolate reductase inhibitor, in a fixed-dose product commonly known by brand names such as Bactrim, Bactrim DS, Septra, Septra DS, and Sulfatrim. The two ingredients block bacteria at two different steps of the same folate-production pathway, which is why the combination is bactericidal (kills bacteria) even though each drug alone is only bacteriostatic.
This combination is FDA-approved to treat urinary tract infections, acute ear infections (otitis media) in children, flare-ups of chronic bronchitis in adults, traveler's diarrhea in adults, and both treatment and prevention of Pneumocystis jirovecii pneumonia (PJP), including in people with HIV or other immunocompromising conditions. It's also used off-label by some clinicians for MRSA skin and soft-tissue infections and as prophylaxis in certain other immunocompromised patients; talk with your provider about whether an off-label use applies to your situation.
Cost and how to find the best price
A generic version of sulfamethoxazole-trimethoprim is FDA-approved and widely substitutable, so most patients are not tied to the Bactrim or Septra brand name at the pharmacy counter. That doesn't mean every pharmacy charges the same amount, though — cash prices for this generic can vary noticeably from one pharmacy to another, and from one day to the next. Rather than guessing, enter your ZIP above to see today's price at pharmacies near you and compare before you fill.
There is no manufacturer savings card associated with this generic antibiotic, so pharmacy-to-pharmacy comparison, rather than a coupon from the drug maker, is the main lever for finding a better price. If your prescriber has written for the brand name Bactrim or Septra specifically, ask your pharmacist whether the generic is an appropriate substitute for your prescription.
Alternatives and related antibiotics
Sulfamethoxazole is one of the two active ingredients in the combination; you can look up trimethoprim separately, or the combined brand product Bactrim, for more on how the combination is used. Depending on the type of infection and any sulfa allergy, your provider may consider a different class of antibiotic instead, such as ciprofloxacin, nitrofurantoin, amoxicillin, or doxycycline — each covers a different range of bacteria, so the right choice depends on the specific infection being treated.
Because these drugs aren't interchangeable for every infection, don't switch between them on your own; your prescriber selects the antibiotic based on the type and location of infection and local resistance patterns.
Safety information
Sulfamethoxazole-trimethoprim carries a boxed warning: rare but fatal reactions have occurred, including Stevens-Johnson syndrome, toxic epidermal necrolysis, severe liver injury (fulminant hepatic necrosis), agranulocytosis, aplastic anemia, and other blood disorders. It should not be used by people with a sulfa allergy, in pregnancy at term or while nursing an infant under 2 months old, or in significant liver or kidney impairment; it's also not recommended in the third trimester of pregnancy or in infants under 2 months due to a risk of kernicterus.
Tell your provider about all other medications you take — this drug can increase the effects of warfarin, methotrexate, and phenytoin, and combining it with ACE inhibitors or ARBs raises the risk of high potassium (hyperkalemia). People with G6PD deficiency should use it with caution because of a risk of hemolytic anemia. This is general information, not medical advice — talk with your provider or pharmacist about your specific health history before starting or stopping this medication.
This Sulfamethoxazole information was written and reviewed against authoritative U.S. medical sources — MedlinePlus (U.S. National Library of Medicine), DailyMed, and FDA prescribing information — and checked for accuracy. It is provided for education and is not a substitute for professional medical advice.
Verify the official label: Sulfamethoxazole on DailyMed (FDA)
Reviewed against FDA labeling · Last reviewed July 2026
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Medical disclaimer: This information is provided for general educational purposes only and is not medical advice. It is not a substitute for professional diagnosis or treatment. Always consult a licensed physician, pharmacist, or other qualified healthcare provider before starting, stopping, or changing any medication or treatment. Never disregard professional medical advice or delay seeking it because of something you read here. If you think you may have a medical emergency, call your doctor or 911 immediately.