A survey of clarithromycin monotherapy and long-term administration of ethambutol for patients with MAC lung disease in Japan: A retrospective cohort study using the database of health insurance claims.

BACKGROUND: The number of patients with nontuberculous mycobacteriosis (NTM) has increased exponentially in recent years. In Japan, approximately 88.8% of patients with NTM suffer from Mycobacterium avium-intracellulare complex (MAC) lung disease. Incidence of MAC lung disease is increasing in particularly among the middle-aged and elderly women owing to a rapid increase in nontuberculous mycobacterial infections. General treatment for MAC lung disease is chemotherapy. The type of chemotherapy recommended by specialists to prevent the development of a drug-resistant strain of the bacteria consists of a combination of clarithromycin (CAM), rifampicin, and ethambutol (EB). CAM monotherapy is contraindicated by specialists owing to its high potential to induce drug-resistant bacterial strains in patients with MAC lung disease. In addition, administering EB at doses not less than 1000 mg d-1 is not recommended to avoid adverse drug reactions. However, it is unclear how much such treatment cases exist in real world clinical settings. This is because no long-term investigation has been carried out. MATERIALS AND METHODS: This study investigated treatment with these drugs from 2005 to 2017, by studying 1135 patients with MAC lung disease based on health insurance claims database. RESULTS: Results showed that approximately 9.2% (101 cases) were prescribed long-term CAM monotherapy for 3 months or longer and approximately 3.6% (18 cases) were prescribed high doses of EB. CONCLUSION: CAM monotherapy over a long period of time is potentially detrimental to some patients. Better awareness of the types of treatments and their potential negative effects will be beneficial to clinical practitioners.