Warfarin: Vitamin K, a component of multiple vitamins injection (pediatric), antagonizes the anticoagulant action of warfarin. In patients who are co-administered warfarin and multiple vitamins injection (pediatric), blood levels of prothrombin/INR should be monitored to determine if dose of warfarin needs to be adjusted [see Warnings and Precautions (5.4)].
Antibiotics: Thiamine, riboflavin, pyridoxine, niacinamide, and ascorbic acid decrease antibiotic activities of erythromycin, kanamycin, streptomycin, doxycycline, and lincomycin.
Bleomycin: Ascorbic acid and riboflavin inactivate bleomycin in vitro, thus the activity of bleomycin may be reduced.
Levodopa: Pyridoxine may increase the metabolism of levodopa (decrease blood levels of levodopa) and decrease its efficacy.
Phenytoin: Folic acid may increase phenytoin metabolism and lower the serum concentration of phenytoin resulting in increased seizure activity.
Methotrexate: Folic acid may decrease a patient’s response to methotrexate therapy.