DPP4 and nasopharyngitis: Hence, potential hazards associated with DPP-4 inhibitors are prolongation of action of other peptide hormones, neuropeptides and chemokines metabolized by the protease and their (DPP-4 inhibitors) interaction with DPP-4 related proteases.[31] Some researchers have reported that DPP-4 inhibitors have an increased risk of infection (for nasopharyngitis and urinary tract infection) and headache.[33]