Thiamine, riboflavin, pyridoxine, niacinamide and ascorbic acid in Multivitamin & Multimineral [A-Z junior infusion preparation] have been reported to reduce how well Erythromycin works as an antibiotic.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.