What Causes Muscle Cramps In Legs While Treating Sinus Infections And Bronchitis?

I have been on amoxicillin for a week due to sinus infections and bronchitis. As I did not feel well last week I was not very active and did a lot of sitting. The past couple of days I ve had muscle cramps in both my legs even though I ve been more active and have done a bit of walking. Are these cramps from inactivity last week?