Assessment of Hydroxychloroquine Blood Levels in Sjögren’s Disease Patients: Drug Adherence and Clinical Associations

Hydroxychloroquine (HCQ) has been used to treat Sjögren’s disease (SjD) patients. However, there are no studies evaluating drug adherence through HCQ blood levels, pharmacy refill (PR) and medication adherence questionnaires. The relationship of HCQ blood levels with glandular/extraglandular disease parameters was also poorly assessed. This cross-sectional observational study included 74 adult SjD patients, who were receiving a stable HCQ dose (4-5.5 mg/kg/day, actual weight) for at least 3 months before study inclusion. HCQ blood levels were quantified by high-performance liquid chromatography coupled to mass spectrometry. Adherence was assessed by PR and Medida de Adesão aos Tratamentos (MAT) questionnaire. The following parameters were evaluated: Xerostomia Inventory, Ocular Surface Disease Index, EULAR (European League Against Rheumatism) Sjögren’s Syndrome Disease Activity Index, EULAR Sjögren’s Syndrome Patient Reported Index, Schirmer’s I test and non-stimulated/stimulated salivary flow rates. HCQ blood levels were 775.3(25.0–2,568.6)ng/mL. Eleven patients (14.9