Stability of Formoterol concentration in Scalp Hair of patients using maintenance Formoterol Therapy for Asthma or COPD (INCTFISH)

Esther Sportel^1*Kay Wagelaar¹Marjolein Brusse^2,3Job Van Der Palen^2,4Ilonka Van Veen⁵Mireille Wessels⁶Job Van Boven^6,7Daan Touw^6,8Kris Movig¹

• ¹Department of Clinical Pharmacy, Medisch Spectrum Twente, Enschede, Netherlands
• ²Department of Epidemiology, Medisch Spectrum Twente, Enschede, Netherlands
• ³Section Cognition, Data and Education, Universiteit Twente, Enschede, Netherlands
• ⁴Health Technology and Services Research, Universiteit Twente, Enschede, Netherlands
• ⁵Department of Clinical Pulmonology, Medisch Spectrum Twente, Enschede, Netherlands
• ⁶Department of Clinical Pharmacy and Pharmacology, Universitair Medisch Centrum Groningen, Groningen, Netherlands
• ⁷Universitair Medisch Centrum Groningen Groningen Research Institute for Asthma and COPD, Groningen, Netherlands
• ⁸Rijksuniversiteit Groningen Groningen Research Institute of Pharmacy, Groningen, Netherlands

Introduction Hair testing provides a non-invasive, objective method with a long (retrospective) surveillance window for assessing medication adherence. Previous studies have developed a method to analyze formoterol in hair and suggest a possible dose-response relationship. The INCTFISH study aims to assess the stability of formoterol concentrations in hair in patients using formoterol for asthma or COPD maintenance therapy. Methods In total, 13 subjects ≥ 18 years of age, with asthma or COPD, who demonstrated stable to intermediate adherence and medication possession ratio, were included in this pilot study. To study the stability of formoterol, two hair segments located at one and three centimeters from the patient’s scalp were collected, corresponding to a time frame of approximately three months. Scalp hair samples were taken during a study visit and analyzed using Liquid Chromatography-Tandem Mass Spectrometry. Results Inhaled formoterol was detected in most hair samples with all hair colors in a concentration range of 0.73-7.6 ng/g. The intraclass correlation between segment one and two was excellent (ICC=0.97). Discussion The pilot study reveals a strong correlation between formoterol concentrations in segment one and two, indicating that drug levels remain stable in hair over a period of at least three months. While the study does not yet provide sufficient evidence to establish the utility of hair testing for monitoring formoterol adherence, it provides important directions for future research.