What dosage of azithromycin should be used for a second bout of cellulitis?

Not indicated. Azithromycin is not a good choice to treat cellulitis un less you have a penicillin allergy. Augmentin, dicloxacillin and cefalexin are superior. Clindomycin is more effective as well especially if you had a recurrence after first course of azithromycin.