Possible Interaction: Folic Acid and Trimethoprim, Sulfamethoxazole Drug Combination

“ Cotrimoxazole (CTX) inhibits folic acid synthesis which is important for the survival of many bacteria, protozoa, and fungi and has been used to prevent several opportunistic infections among HIV/AIDS patients.”

“For example, cotrimoxazole (trimethoprim-sulfamethoxazole) inhibits folic acid metabolism through direct binding to dihydrofolate reductase, an enzyme which is also inhibited by methotrexate.”

“Accordingly, folic acid can reverse the action of TMP-SMX.”

“It should be remembered that many of the best-selling vitamin supplements in the United States (compared with many of the European products) contain substantial amounts of folic acid that will probably interfere with the action of TMP-SMX.”

“Patients receiving TMP-SMX should be questioned about their use of vitamins and should be advised not to use supplements containing folic acid.”

“ Trimethoprim-sulfamethoxazole is a well-known antibiotic that inhibits folic acid synthesis, a topic of renewed interest.”

“ Folic acid co-administration with co-trimoxazole partially reversed the decrease in sperm quality and structural abnormalities of high doses of co-trimoxazole (60 and 120 mg/kg/daily) (p<0.001).”

“ Folic acid co-administration with co-trimoxazole reversed partially all these parameters compared to the co-trimoxazole group (P<0.001).”