My Son Has Been Prescribed Amoxycilin For Bronchitis And I

my son has been prescribed amoxycilin for bronchitis and i just noticed i still have the Cephalexin, unopened in the fridge from june, which he was also prescribed for bronchitis by a different doctor. my questions are, as it is unopened, is the cephalexin still usable? and which is the better antibiotic for bronchitis?