Hair analysis to monitor adherence to prescribed chronic inhaler drug therapy in patients with asthma or COPD

Background Poor adherence to inhaled drug therapy in individuals with asthma and/or chronic obstructive pulmonary disease (COPD) may be associated with suboptimal therapeutic outcomes. Measurement of drug residues in hair samples has been employed to assess oral medication use over time. Here, we test the feasibility of analyzing hair samples from patients with asthma and/or COPD for assessing adherence to prescribed inhaled medication. Methods: In total, 200 male and female subjects, 18 years of age, with stable asthma and/or COPD who were receiving an acceptable standard of care daily inhaled product consistently, were recruited. Head hair samples were taken during a single visit to the clinical site and grouped by hair color according to the Fischer-Sailer scale. Drug residues were extracted from milled hair samples using solid-phase extraction and analyzed using liquid chromatography tandem mass spectrometry. Results: Inhaled drugs were detected in hair for 72% of subjects from whom it was possible to analyze hair samples (n = 157/200). Most hair samples obtained from subjects receiving formoterol or vilanterol had amounts of drug present that allowed determination of a quantifiable concentration, and demonstrated a dose response. Drugs were detected in all hair colors, with higher concentrations of formoterol observed in darkhaired versus light-haired individuals. Conclusions: This is the first study to demonstrate that inhaled medication can be measured in hair samples from subjects with asthma and/or COPD. The results show that hair drug concentration data could potentially provide a record of historical adherence to inhaled therapeutics.