PlainMeds provides educational information only. This is not medical advice. Always consult your doctor or pharmacist.

metformin vs trimethoprim

Side-by-side comparison of metformin and trimethoprim. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.

minor Known Drug Interaction

Sulfamethoxazole and trimethoprim potentiates the effect of oral hypoglycemics that are metabolized by CYP2C8 (e.g., pioglitazone, repaglinide, and rosiglitazone) or CYP2C9 (e.g., glipizide and glyburide) or eliminated renally via OCT2 (e.g., metformin). Cases of interactions with other OCT2 substrates, memantine and metformin, have also been reported.

Recommendation: Your doctor may need to check your blood sugar more often or adjust your metformin dose.

Drug Class
metformin Biguanide
trimethoprim Dihydrofolate Reductase Inhibitor
Type
metformin Prescription
trimethoprim Prescription
Summary
metformin

No summary available.

trimethoprim

This medicine contains sulfamethoxazole and trimethoprim. It is an antibiotic that fights bacteria in your body.

What It Treats
metformin

Information not available.

trimethoprim

This medicine can treat urinary tract infections, ear infections in children, and bronchitis in adults. It also treats shigellosis, a type of diarrhea. It can also treat or prevent Pneumocystis jiroveci pneumonia, and treat traveler's diarrhea.

How It Works
metformin

Information not available.

trimethoprim

This medicine works by stopping bacteria from making folic acid. Bacteria need folic acid to grow and multiply. By blocking folic acid production, the medicine kills the bacteria.

Common Side Effects
metformin
  • Diarrhea
  • Upper respiratory tract infection (like a cold)
  • Headache
trimethoprim
  • Nausea
  • Vomiting
  • Loss of appetite
  • Skin rash
  • Hives
FAERS Reports
metformin
  • Feeling sick to your stomach 21,946
  • Loose or watery stools 21,887
  • High blood sugar 18,329
  • Feeling tired 17,252
  • Sudden kidney damage 16,440
trimethoprim
  • Nausea 945
  • Diarrhoea 848
  • Headache 835
  • Malaise 815
  • Pyrexia 721
Serious Warnings
metformin

No specific warnings noted.

trimethoprim

Rarely, sulfonamide drugs like this one have caused severe reactions. These include Stevens-Johnson syndrome, toxic epidermal necrolysis, liver damage, and blood problems. Tell your doctor right away if you have a fever, rash, blisters, mouth sores, or signs of infection.

Pregnancy
metformin

No pregnancy information available.

trimethoprim

Tell your doctor if you are pregnant or plan to become pregnant. This medicine may not be safe for your baby. Talk to your doctor about the risks and benefits of taking this medicine while breastfeeding.

How to Read This metformin vs trimethoprim Comparison

metformin is classified in the Biguanide drug class, while trimethoprim sits within the Dihydrofolate Reductase Inhibitor class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are prescription-only, so a licensed provider must authorize use.

Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, metformin has 95,854 submissions while trimethoprim has 4,164. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known minor interaction flagged in FDA labeling, attributed to trimethoprim can stop your kidneys from clearing metformin out of your body as fast as they should.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.

A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between metformin and trimethoprim - always consult your physician or pharmacist first.

Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.