What is trimethoprim?

Trimethoprim is a synthetic antibacterial available in tablet form for oral administration. Each scored white tablet contains 100 mg trimethoprim. Trimethoprim is 5-[(3,4,5-trimethoxyphenyl)methyl]-2,4-pyrimidinediamine. It is a white to light yellow, odorless, bitter compound with a molecular weight of 290.32 and the molecular formula C 14 H 18 N 4 O 3 . The structural formula is: Inactive Ingredients Colloidal silicon dioxide, lactose monohydrate, magnesium stearate, microcrystalline cellulose, pregelatinized starch, sodium starch glycolate, and purified water. C:\Users\LdeepthI\Desktop\tri-strctre.jpg

What kind of drug is trimethoprim?

The FDA classifies trimethoprim as a dihydrofolate reductase inhibitor antibacterial. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

Can you take trimethoprim 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 trimethoprim 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 trimethoprim sold under?

We track 5 trimethoprim-containing products in the U.S.: Trimethoprim, Primsol, Proloprim, Trimpex and Trimpex 200. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

What forms does trimethoprim come in?

Across the brands we track, trimethoprim is currently marketed as tablet and solution, 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 trimethoprim?

Yes. Our catalog lists 1 generic trimethoprim 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 trimethoprim been recalled?

The FDA's Enforcement database lists at least 5 recall records whose product description mentions trimethoprim. 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.

Trimethoprim: uses, dosing, side effects & brands

Trimethoprim is a dihydrofolate reductase inhibitor antibacterial sold in the U.S. under 5 brand and generic names, for bronchitis, escherichia coli infections and klebsiella infections. 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) sourcesHow we research

Key facts

Drug class: Dihydrofolate Reductase Inhibitor Antibacterial
Treats: Bronchitis, Escherichia Coli Infections and Klebsiella Infections
Available as: Tablet · Solution
Sold as: 5 products — Trimethoprim, Primsol and Proloprim, and others
Prescription?: Prescription only
Generic available?: Yes
Typical price: about $36 for a 30-count supply

How trimethoprim is dosed

From the FDA label for Trimethoprim (application ANDA071259). Other trimethoprim products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.

The usual oral adult dosage is 100 mg of trimethoprim every 12 hours or 200 mg of trimethoprim every 24 hours, each for 10 days. The use of trimethoprim in patients with a creatinine clearance of less than 15 mL/min is not recommended. For patients with a creatinine clearance of 15 to 30 mL/min, the dose should be 50 mg every 12 hours.

Trimethoprim side effects

The adverse effects encountered most often with trimethoprim were rash and pruritus. Dermatologic Rash, pruritus, and phototoxic skin eruptions. At the recommended dosage regimens of 100 mg b.i.d. or 200 mg q.d., each for 10 days, the incidence of rash is 2.9% to 6.7%. In clinical studies which employed high doses of trimethoprim, an elevated incidence of rash was noted. These rashes were maculopapular, morbilliform, pruritic, and generally mild to moderate, appearing 7 to 14 days after the initiation of therapy. Hypersensitivity Rare reports of exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis (Lyell Syndrome), and anaphylaxis have been received. Gastrointestinal Epigastric distress, nausea, vomiting, and glossitis. Elevation of serum transaminase and bilirubin has been noted, but the significance of this finding is unknown. Cholestatic jaundice has been rarely reported. Hematologic Thrombocytopenia, leukopenia, neutropenia, megaloblastic anemia, and methemoglobinemia. Metabolic Hyperkalemia, hyponatremia. Neurologic Aseptic meningitis has been rarely reported. Miscellaneous Fever, and increases in BUN and serum creatinine levels.

Who shouldn’t take trimethoprim

Trimethoprim is contraindicated in individuals hypersensitive to trimethoprim and in those with documented megaloblastic anemia due to folate deficiency.

Trimethoprim drug interactions

Trimethoprim may inhibit the hepatic metabolism of phenytoin. Trimethoprim, given at a common clinical dosage, increased the phenytoin half-life by 51% and decreased the phenytoin metabolic clearance rate by 30%. When administering these drugs concurrently, one should be alert for possible excessive phenytoin effect.

Every trimethoprim product we track (5)

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

Trimethoprim products
#	Drug	Rating	Type	Form	Generic?	Typical price
1	Trimethoprim	46/100	Prescription	Tablet	Generic	$36	View →
2	Primsol	Not yet rated	Prescription	Solution	Generic	$36

What trimethoprim pills look like

Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.

Trimethoprim pill imprints
Imprint	Strength	Colour	Shape	Maker
IP;271	400 mg / 80 mg	white	round	—
IP;272	800 mg / 160 mg	white	oval	—
H;48	400 mg / 80 mg	white	round	—
H;49	800 mg / 160 mg	white	oval	—
H;49	800 mg / 160 mg	white	oval	—

Combination products containing trimethoprim

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.

Trimethoprim recalls

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

Frequently asked questions

What is trimethoprim?: Trimethoprim is a synthetic antibacterial available in tablet form for oral administration. Each scored white tablet contains 100 mg trimethoprim. Trimethoprim is 5-[(3,4,5-trimethoxyphenyl)methyl]-2,4-pyrimidinediamine. It is a white to light yellow, odorless, bitter compound with a molecular weight of 290.32 and the molecular formula C 14 H 18 N 4 O 3 . The structural formula is: Inactive Ingredients Colloidal silicon dioxide, lactose monohydrate, magnesium stearate, microcrystalline cellulose, pregelatinized starch, sodium starch glycolate, and purified water. C:\Users\LdeepthI\Desktop\tri-strctre.jpg
What kind of drug is trimethoprim?: The FDA classifies trimethoprim as a dihydrofolate reductase inhibitor antibacterial. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take trimethoprim 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 trimethoprim 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 trimethoprim sold under?: We track 5 trimethoprim-containing products in the U.S.: Trimethoprim, Primsol, Proloprim, Trimpex and Trimpex 200. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does trimethoprim come in?: Across the brands we track, trimethoprim is currently marketed as tablet and solution, 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 trimethoprim?

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.