Sulfamethoxazole: uses, dosing, side effects & brands

Sulfamethoxazole is a medicine sold in the U.S. under 3 brand and generic names. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.

By the pharmaranks editorial teamReviewed against the FDA (openFDA label, NDC Directory & Enforcement) sourcesUpdated Jul 24, 2026How we research

Key facts

Available as: Tablet · Suspension
Sold as: 3 products — Gantanol, Gantanol-Ds and Sulfamethoxazole
Prescription?: Prescription only
Generic available?: Yes
Half-life: about 10 hours

Every sulfamethoxazole product we track (3)

Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.

Sulfamethoxazole products
#	Drug	Rating	Type	Form	Generic?	Pharmacy pays
1	Gantanol	Not yet rated	Prescription	Tablet	No data	—	View →
2	Gantanol-Ds	Not yet rated	Prescription	Tablet	No data	—	View →
3	Sulfamethoxazole	Not yet rated	Prescription	Tablet	No data	—	View →

Combination products containing sulfamethoxazole

A combination is a different drug — different dosing, different warnings. It is listed here so you can find it, not so you can substitute it.

Sulfamethoxazole recalls

From the FDA Enforcement database. A recall covers specific lots — not the drug as a whole.

Sulfamethoxazole and breastfeeding

From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.

With healthy, fullterm infants it appears acceptable to use sulfamethoxazole during breastfeeding after the newborn period. The time of greatest risk for hemolysis in fullterm newborns without glucose-6-phosphate dehydrogenase (G6PD) deficiency might be as short as 8 days after birth. Until further data are accumulated, alternate agents should probably be used in jaundiced, ill, stressed or premature infants, because of the risk of bilirubin displacement and kernicterus. Sulfamethoxazole should be avoided while breastfeeding a G6PD deficient infant.

Full LactMed record for sulfamethoxazole: levels in milk, effects in breastfed infants, and the drugs it would consider instead

National Institute of Child Health and Human Development, record revised November 15, 2024. LactMed states its information is not a substitute for professional judgement.

What people report to the FDA about sulfamethoxazole

The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 65,792 reports naming sulfamethoxazole, and the FDA flagged 90% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:

pyrexia6,938 reports
rash5,718 reports
fatigue5,452 reports
dyspnoea5,192 reports
pruritus4,278 reports
diarrhoea4,276 reports
infection4,148 reports
nausea4,109 reports

Read these as a signal, not a rate. A report does not mean sulfamethoxazole caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.

Source: openFDA drug/event (FAERS), retrieved July 26, 2026.

How long sulfamethoxazole stays in your system

The elimination half-life of sulfamethoxazole is about 10 hours. The FDA label states the mean serum half-life of sulfamethoxazole is 10 hours (co-formulated with trimethoprim, whose half-life is 8 to 10 hours). Half-life is prolonged in patients with severely impaired renal function, requiring dosage adjustment; the elderly, who often have reduced kidney function, may also clear it more slowly. Sulfamethoxazole is not a prodrug; it is partly metabolized to an inactive N-acetylated metabolite that does not outlast the parent. Half-life is not the same as a drug-test detection window — the drug can remain detectable longer than a single half-life implies.

DailyMed - Sulfamethoxazole and Trimethoprim Tablet (FDA label) ↗

Half-life is how long the body takes to clear half a dose. It is not the same as how long a drug test can detect it, and it varies with age, kidney and liver function.

Related calculators

How long it stays in your system →

Frequently asked questions

How long does sulfamethoxazole stay in your system?

The elimination half-life of sulfamethoxazole is about 10 hours — that is how long the body takes to clear half of a dose. The FDA label states the mean serum half-life of sulfamethoxazole is 10 hours (co-formulated with trimethoprim, whose half-life is 8 to 10 hours). Half-life is prolonged in patients with severely impaired renal function, requiring dosage adjustment; the elderly, who often have reduced kidney function, may also clear it more slowly. Sulfamethoxazole is not a prodrug; it is partly metabolized to an inactive N-acetylated metabolite that does not outlast the parent. Half-life is not the same as a drug-test detection window — the drug can remain detectable longer than a single half-life implies. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

Can you take sulfamethoxazole with other medicines?

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run sulfamethoxazole against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

What brand names is sulfamethoxazole sold under?

We track 3 sulfamethoxazole-containing products in the U.S.: Gantanol, Gantanol-Ds and Sulfamethoxazole. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

What forms does sulfamethoxazole come in?

Across the brands we track, sulfamethoxazole is currently marketed as tablet and suspension, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Is there a generic sulfamethoxazole?

Yes. Our catalog lists 1 generic sulfamethoxazole product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

Has sulfamethoxazole been recalled?

The FDA's Enforcement database lists at least 5 recall records whose product description mentions sulfamethoxazole. The most recent: Sulfamethoxazole and Trimethoprim (Sep 2, 2025). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

Cite this page

APA: pharmaranks. (2026, July 24). Sulfamethoxazole: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/sulfamethoxazole
MLA: “Sulfamethoxazole: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/sulfamethoxazole.

We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.

Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.

Read the full FDA label for sulfamethoxazole on DailyMed (NIH) ↗.