Drug interactions
Folic acid + Sulfamethoxazole
Severity: Minor
Folic acid and Sulfamethoxazole: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Sulfamethoxazole, usually with trimethoprim, interferes with bacterial folate synthesis and trimethoprim also inhibits human dihydrofolate reductase, which may contribute to folate deficiency. Folic acid does not usually impair antibacterial effect in standard use but may reduce efficacy in some infections such as Pneumocystis pneumonia.
What this interaction means in plain words
Folic acid and Sulfamethoxazole have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Antifolate effect of the sulfonamide-trimethoprim combination; folic acid may bypass or counteract this in some settings.
What to do
Avoid routine folic acid with high-dose treatment of Pneumocystis infection unless deficiency is documented. Consider folinic acid when marrow suppression occurs.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Folic acid
- Ethotoin + Folic acid Moderate
- Folic acid + Fosphenytoin Moderate
- Folic acid + Glucarpidase Moderate
- Folic acid + Methotrexate Moderate
- Folic acid + Pafolacianine Moderate
- Folic acid + Phenobarbital Moderate
Frequently asked questions
Can I take Folic acid with Sulfamethoxazole?
MediHelp rates the interaction as minor. Folic acid and Sulfamethoxazole have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Sulfamethoxazole, usually with trimethoprim, interferes with bacterial folate synthesis and trimethoprim also inhibits human dihydrofolate reductase, which may contribute to folate deficiency. Folic acid does not usually impair antibacterial effect in standard use but may reduce efficacy in some infections such as Pneumocystis pneumonia.
How serious is the interaction between Folic acid and Sulfamethoxazole?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid routine folic acid with high-dose treatment of Pneumocystis infection unless deficiency is documented. Consider folinic acid when marrow suppression occurs.
What other medicines interact with Folic acid?
MediHelp also lists interactions of Folic acid with, for example, Ethotoin, Fosphenytoin, Glucarpidase. The full list is on the Folic acid page.
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