Comprehensive medication guide to Sulfamethoxazole/Trimethoprim including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$0–$10 copay for generic TMP-SMX on most commercial and Medicare Part D plans; Tier 1 on the vast majority of formularies, no prior authorization required for standard indications.
Estimated Cash Pricing
$22–$35 retail for a standard 14-tablet DS course without insurance; as low as $2.10–$2.80 with GoodRx or SingleCare coupons at most major pharmacies.
Medfinder Findability Score
88/100
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Sulfamethoxazole/trimethoprim (TMP-SMX) is a combination antibiotic that has been FDA-approved since 1973. It combines two drugs that work synergistically: sulfamethoxazole (a sulfonamide) and trimethoprim (an antifolate). Together, they block two consecutive steps in bacterial folate synthesis, disrupting DNA production and killing or stopping bacterial growth.
Sold under brand names Bactrim, Bactrim DS, Septra, Septra DS, and Sulfatrim, TMP-SMX is prescribed for urinary tract infections (UTIs), ear infections (pediatric), traveler's diarrhea, shigellosis, Pneumocystis jirovecii pneumonia (PCP), and community-acquired MRSA skin infections. It is available as tablets (single-strength and double-strength), an oral suspension, and an intravenous formulation.
TMP-SMX is not a controlled substance. It is manufactured by multiple generic pharmaceutical companies, making it one of the most affordable antibiotics in the United States. It is available only by prescription.
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TMP-SMX kills or stops bacteria by blocking two consecutive steps in the folate synthesis pathway — a chain of chemical reactions that bacteria need to make DNA. Sulfamethoxazole blocks the enzyme dihydropteroate synthase (DHPS), preventing bacteria from converting PABA into dihydrofolate. Trimethoprim then blocks dihydrofolate reductase (DHFR), preventing conversion of dihydrofolate into the active tetrahydrofolate.
Without functional folate, bacteria cannot synthesize purines, amino acids, or ultimately DNA and proteins required for cell division. Each drug alone is primarily bacteriostatic (slows growth), but the combination creates a synergistic effect that can be bactericidal — especially in the urinary tract where drug concentrations are highest.
Human cells are largely unaffected because humans absorb folate from food (no DHPS enzyme) and trimethoprim binds human DHFR approximately 50,000 times less tightly than bacterial DHFR. TMP-SMX has no activity against viruses, which do not use the folate synthesis pathway.
80 mg / 400 mg — tablet (single-strength, SS)
Standard single-strength tablet; two SS equal one DS tablet
160 mg / 800 mg — tablet (double-strength, DS)
Most commonly prescribed adult form; taken twice daily for most infections
40 mg / 200 mg per 5 mL — oral suspension
Pediatric liquid form (Sulfatrim); dosed by weight for children 2 months and older
80 mg / 400 mg per 5 mL — IV solution
Hospital use only; for severe PCP, hospitalized UTIs, or when oral administration not feasible
As of 2026, sulfamethoxazole/trimethoprim tablets (both SS and DS) are not in shortage and are generally widely available at pharmacies nationwide. The drug is manufactured by multiple generic companies. However, the oral suspension (Sulfatrim) can be intermittently difficult to find at individual pharmacies, particularly during fall and winter when pediatric infection prescriptions spike.
While chain pharmacies usually carry DS tablets, independent pharmacies, grocery-store pharmacies, and hospital outpatient pharmacies may have better stock of less common formulations. If your usual pharmacy is out, call ahead before driving — or let medfinder do the calling for you.
Use medfinder to find which pharmacies near you have sulfamethoxazole/trimethoprim in stock right now. Enter your medication details and location, and medfinder contacts pharmacies on your behalf — no hold music, no wasted trips.
Sulfamethoxazole/trimethoprim is not a controlled substance and has no DEA scheduling or special prescribing requirements. Any licensed prescriber in the United States can write a prescription for it.
Primary care physicians (PCPs) and internal medicine doctors
Nurse practitioners (NPs) and physician assistants (PAs)
Pediatricians (for children 2 months and older)
Urologists (for UTIs and urinary conditions)
Infectious disease specialists (for complex infections, PCP, MRSA)
Emergency medicine physicians and urgent care providers
TMP-SMX is widely available via telehealth for common indications such as uncomplicated UTIs. Platforms like Teladoc, MDLive, Amazon Clinic, and UTI-specific telehealth services can evaluate and prescribe the same day. For immunocompromised patients requiring PCP prophylaxis, specialist oversight (HIV provider, oncologist, transplant team) is recommended.
No. Sulfamethoxazole/trimethoprim is not a controlled substance. It is not scheduled by the DEA and has no special prescribing restrictions. Any licensed healthcare provider — including primary care physicians, nurse practitioners, physician assistants, pediatricians, and telehealth providers — can prescribe it for appropriate indications.
Because TMP-SMX is not controlled, prescriptions can be transferred freely between pharmacies without restriction. Refills for chronic indications (such as PCP prophylaxis or UTI suppression) can be filled at any pharmacy, including mail-order pharmacies. Patients can also receive telehealth prescriptions for common indications.
Most patients tolerate short courses of TMP-SMX well. Common side effects include:
Nausea and vomiting (take with food and water to minimize)
Diarrhea
Rash (report any rash to your provider immediately — can be a warning sign)
Photosensitivity (increased sun sensitivity — use sunscreen)
Headache
Loss of appetite
Serious side effects requiring immediate medical attention:
Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN) — blistering/peeling skin, mouth sores, fever
DRESS Syndrome (widespread rash, fever, organ involvement) — can occur 2–8 weeks after starting
Anaphylaxis (throat swelling, difficulty breathing)
Blood disorders: agranulocytosis, aplastic anemia, thrombocytopenia
Hyperkalemia (dangerously high potassium) — especially with ACE inhibitors or ARBs
Hepatotoxicity (jaundice, dark urine, severe abdominal pain)
C. difficile-associated diarrhea (severe/bloody diarrhea during or after treatment)
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Nitrofurantoin (Macrobid)
First-line alternative for uncomplicated UTIs; effective, few drug interactions, safe with sulfa allergy
Ciprofloxacin (Cipro)
Fluoroquinolone for UTIs and more serious infections; reserve for complicated cases due to adverse effects
Doxycycline
Alternative for MRSA skin infections and respiratory infections; avoid in pregnancy and children under 8
Amoxicillin-clavulanate (Augmentin)
Broad-spectrum option for UTIs, respiratory, and skin infections in penicillin-tolerant patients
Dapsone
First-line PCP prophylaxis alternative for patients who cannot tolerate TMP-SMX; check G6PD status first
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Warfarin
majorTMP-SMX significantly potentiates anticoagulant effect via CYP2C9 inhibition and protein binding displacement. Monitor INR closely; anticipate 50-100% increase.
Methotrexate
majorReduces methotrexate renal clearance by ~40% and adds anti-folate effects. Avoid combination; risk of cytopenia, mucositis, hepatotoxicity.
Dofetilide (Tikosyn)
majorContraindicated. TMP-SMX inhibits dofetilide elimination, causing dangerous QTc prolongation and risk of Torsades de Pointes.
ACE inhibitors / ARBs
majorCombination can cause clinically significant hyperkalemia, especially in elderly or renally impaired patients. Monitor potassium.
Sulfonylureas (glipizide, glyburide)
majorTMP-SMX potentiates hypoglycemic effect. Monitor blood glucose carefully in diabetic patients.
Phenytoin
moderateSMX inhibits CYP2C9 metabolism of phenytoin; serum levels may rise. Monitor for phenytoin toxicity.
Digoxin
moderateTMP-SMX can raise digoxin levels. Monitor serum digoxin levels, especially in elderly patients.
Amiodarone
majorBoth drugs prolong QTc interval. Increased arrhythmia risk with combination.
Leucovorin (for PCP treatment)
majorContraindicated during TMP-SMX PCP treatment — associated with increased treatment failure and mortality.
Sulfamethoxazole/trimethoprim remains one of the most versatile, cost-effective antibiotics available more than 50 years after its FDA approval. It treats a uniquely broad range of infections — from everyday UTIs to life-threatening PCP in immunocompromised patients — at a cost of just a few dollars per course. As of 2026, there is no active national shortage of TMP-SMX tablets.
The drug does carry a notable interaction profile — with warfarin, methotrexate, potassium-altering drugs, and others — and has serious (though rare) side effects including Stevens-Johnson Syndrome and blood dyscrasias. Patients should take it exactly as prescribed, complete the full course, use sun protection, and report any rash immediately.
If you've been prescribed TMP-SMX and need help finding it at a pharmacy near you, medfinder calls pharmacies on your behalf and texts you which ones have your medication in stock — saving you the time and frustration of calling each pharmacy yourself.
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