Serum and Saliva Theophylline Levels in Adult Outpatients with Asthma and Chronic Obstructive Pulmonary Disease (COPD): A Cross-Sectional Study

Due to a narrow therapeutic range, measurment of theophylline serum levels is highly recommended in patients with a long-term theophylline therapy. In this regard, since blood sampling is an invasive method, exploring alternative methods using other biological fluids in particular saliva samples are targeted. This study was designed to determine any relationship between serum and saliva levels of theophylline in patients with asthma and COPD, whom have been under xanthine–therapy for an extended period of time. Also, any relationship between serum or saliva levels of theophylline with possible explanatory factors was investigated. Adult (?18 years) outpatients with a history of theophylline use (for at least 1 month) entered this study. Serum and stimulated saliva samples obtained 1 h before the morning dose and were measured using a high performance liquid chromatography (HPLC) method. To stimulate saliva production, patients chewed a piece of parafilm for 5 min before sampling. Relevant demographic information, medical and medication histories of the patients were also recorded. Collected data were entered into the SPSS (Statistical Package for Social Scientists, version 11.5) software and analyzed using the appropriate statistical tests (p