Macrolide antibiotics, such as erythromycin, are an effective treatment for DPB when taken regularly over an extended period of time.[16][17] Clarithromycin or roxithromycin are also commonly used.[18] The successful results of macrolides in DPB and similar lung diseases stems from managing certain symptoms through immunomodulation (adjusting the immune response),[17] which can be achieved by taking the antibiotics in low doses. Treatment consists of daily oral administration of erythromycin[7] for two to three years, an extended period that has been shown to dramatically improve the effects of DPB. This is apparent when an individual undergoing treatment for DPB, among a number of disease-related remission criteria, has a normal neutrophil count detected in BAL fluid, and blood gas (an arterial blood test that measures the amount of oxygen and carbon dioxide in the blood) readings show that free oxygen in the blood is within the normal range.[16][17][19] Allowing a temporary break from erythromycin therapy in these instances has been suggested, to reduce the formation of macrolide-resistant P. aeruginosa.[16] However, DPB symptoms usually return, and treatment would need to be resumed.