Drug Interaction Report

MONITOR: Limited data suggest that aminosalicylic acid may decrease the gastrointestinal absorption of vitamin B12. Coadministration of aminosalicylic acid 5 g orally has been reported to reduce the absorption of vitamin B12 by 55%. Clinically significant erythrocyte abnormalities have been reported; however, the body (primarily the liver) usually has a copious supply of vitamin B12 that can sustain a person for several years in the absence of adequate intake.

MANAGEMENT: Due to the potential for reduced vitamin B12 absorption, the manufacturer recommends that maintenance vitamin B12 be considered in patients on aminosalicylic acid therapy for longer than one month. As for the treatment of B12 deficiency-related anemia, non-oral routes of administration (e.g., parenteral, intranasal, sublingual) are generally preferred, which would bypass the potential interaction.