wals2050

Hello. I am new to this forum. I have been giving my 7 yr old a mag supp. for the last week in addition to B complex. My son has an ear infection and was prescribed amoxicillin for the next 10 days. Can someone tell me if there is a negative interaction between mag and the antibiotic. Does it mess up his stomach? What else does it do? Thank you for your help. I am so new to this.