Prenatal Multivitamin and Trimethoprim Interaction
Drug interaction information between Prenatal Multivitamin and Trimethoprim.
Prenatal Multivitamin and Trimethoprim have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Prenatal Multivitamin and Trimethoprim. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Trimethoprim can lower the amount of folate, an important B-vitamin, in your blood. This can make the folate in your prenatal vitamin less effective.
What To Do
Your doctor should use caution when prescribing these together and may need to monitor your vitamin levels.
FDA Label Information
• L-dopa, triamterene, colchicine, and trimethoprim may decrease plasma folate levels. Caution should be exercised with the concomitant use of folinic acid and trimethoprim- sulfamethoxazole for the acute treatment of Pneumocystis carinii pneumonia in patients with HIV infection as it is associated with increased rates of treatment failure and mortality in a placebo-controlled study.
Prenatal Multivitamin Also Interacts With
- Phenytoin moderate
- Metformin minor
- Fluoxetine minor
- Ibuprofen minor
- Potassium Chloride minor
Trimethoprim Also Interacts With
- Theophylline major
- Spironolactone moderate
- Spironolactone (Acne) moderate
- Metformin minor
- Glipizide minor
Frequently Asked Questions
Can I take Prenatal Multivitamin and Trimethoprim together?
This is a moderate interaction. Your doctor should use caution when prescribing these together and may need to monitor your vitamin levels.
How serious is the interaction between Prenatal Multivitamin and Trimethoprim?
This interaction is classified as "moderate" severity by the FDA. Moderate interactions may worsen your condition or change how your medications work.
Why do Prenatal Multivitamin and Trimethoprim interact?
Trimethoprim can lower the amount of folate, an important B-vitamin, in your blood. This can make the folate in your prenatal vitamin less effective.
Understanding the Prenatal Multivitamin and Trimethoprim Interaction
FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Prenatal Multivitamin belongs to the Prenatal Vitamin class and Trimethoprim belongs to the Dihydrofolate Reductase Inhibitor class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Trimethoprim can lower the amount of folate, an important B-vitamin, in your blood. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Prenatal Multivitamin has 23 total documented interactions on file in this dataset, and Trimethoprim has 22. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Your doctor should use caution when prescribing these together and may need to monitor your vitamin levels. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Prenatal Multivitamin or Trimethoprim based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.