Patients undergoing total and reverse shoulder arthroplasty for primary glenohumeral arthritis will be invited to participate in this study if patients meet inclusion and exclusion criteria. Patients will be randomized to receive either standard perioperative antibiotics with cefazolin or to the treatment group to receive doxycycline in addition to cefazolin. Patients will then undergo routine surgical treatment. 3 cultures from the superficial tissue, dermis, and glenohumeral joint will be taken and cultured for 14 days to detect any bacterial growth.