Background Hydroxychloroquine (HCQ) and chloroquine, referred to as antimalarial agents (AMA), are cornerstone drugs in systemic lupus erythematosus (SLE), which inhibit type I interferon release via toll-like receptor binding and increasing the pH in plasmacytoid dendritic cell lysosomes [1]. AMA use has established benefits in SLE, such as improved prognosis and decelerated accrual of organ damage. Use of HCQ is safe for most patients and serious side-effects are uncommon, even during pregnancy. Medical therapy to prevent repeated disease flares is of essential weight in the treatment of SLE. However, it is well-known that non-adherence to prescription of AMA is a considerable problem [2].

Objectives The aim of this cross-sectional study was to investigate the frequency of AMA prescription, and evaluate factors associated with ongoing use and discontinuation of AMA in a Swedish SLE population.

Methods We retrieved data from the Clinical Lupus Register in North-Eastern Gothia (Swedish acronym: KLURING), a longitudinal research and quality registry, including all prevalent and incident cases of SLE in the Östergötland County from 2008 onwards. All included subjects fulfilled the validated 1982 American College of Rheumatology (ACR) and/or the 2012 Systemic Lupus International Collaborating Clinics (SLICC) classification criteria and had been diagnosed from 1963 onwards. Factors associated with ongoing use and discontinuation of AMA were investigated using logistic regression analysis, Mann-Whitney U test and chi-square test.

Results A total of 328 subjects were included in the analysis. The mean age at diagnosis was 40.0 years (range: 3–85; standard deviation [SD]: 17.7) and 85.7% were females. The mean SLICC/ACR damage index (SDI) score at last visit was 2.0 (range: 0—11; SD: 2.5). In total, 92.4% had used AMA at some point during their disease course (“ever” users; Table 1). Data from the last available visit indicated that 73.2% were currently prescribed AMA, exclusively HCQ, yielding a daily mean HCQ dose of 228.0 mg (range: 100—400; SD: 71.0). Among individuals who had discontinued AMA, 25.9% had developed a contraindication, mostly on ophthalmological basis (33.3%). Less common reasons were cardiac conditions (19.0%) and renal failure (9.5%). Subjective side-effects were also common; the most frequently reported were gastrointestinal symptoms (n=20/37). Most common patient-related factor associated with discontinuation was intentional non-adherence (e.g., low motivation; 8/11). Patients who had discontinued AMA showed a higher SDI score at the last visit (mean: 2.9; SD: 2.8; mean follow-up: 20.0 years) compared with patients on AMA (mean: 1.4; SD: 1.8; p=0.001; mean follow-up: 15.3 years). Those who fulfilled the immunological disorder ACR criterion (ACR-10) were more likely to continue on AMA (p=0.003). No significant differences were found regarding gender or smoking status.

Conclusion The vast majority of patients in KLURING had been exposed to AMA, and approximately 25% discontinued AMA therapy during follow-up. The main reason for discontinuation were therapy-related factors, such as contraindications and experience of side-effects. Above 50% of the reported side-effects that led to discontinuation were gastrointestinal symptoms. The group of discontinued AMA users accrued more damage over time.

References

1. Crow MK, Rönnblom L. Type I interferons in host defence and inflammatory diseases. Lupus Sci Med 2019;6:e000336
2. Costedoat-Chalumeau N, Houssiau F, Izmirly P, et al. A Prospective International Study on Adherence to Treatment in 305 Patients With Flaring SLE: Assessment by Drug Levels and Self-Administered Questionnaires. Clin Pharmacol Ther 2018;103:1074-1082

Acknowledgements: NIL.

Disclosure of Interests Tomas Walhelm: None declared, Lina Wirestam: None declared, Yvonne Enman: None declared, Ioannis Parodis Grant/research support from: Amgen, AstraZeneca, Aurinia Pharmaceuticals, Elli Lilly and Company, Gilead Sciences, GlaxoSmithKline, Janssen Pharmaceuticals, Novartis, Otsuka Pharmaceutical, and F. Hoffmann-La Roche AG., christoffer Sjöwall: None declared.

Keywords: Disease-modifying drug (DMARDs), Systemic lupus erythematosus

DOI: 10.1136/annrheumdis-2023-eular.3518