I suffer from generalised Myasthenia Gravis.  My medication is Mestinon and azathioprine (immune-suppressant).  Today I went to a walk-in clinic with cystitus and was prescribed Keflex (anti-biotic).  I am just checking whether it is okay to take as I dont want to take anything that sends me into crisis.
Good Evening ! Cephalosporin group Antibiotics wiz. Keflex etc. are safer in MG.  My sincere advise to you that if any Infective conditions you will have in the future you can discuss with your treating physician for culture & antibiotic sensitivity test before starting any antibiotics. Hope this will help you. Regards.