Results from a recent study published in the Journal of Rheumatology revealed that patients with systemic lupus erythematosus (SLE) who have low blood levels of prescribed hydroxychloroquine were more likely to have high disease activity.
Hydroxychloroquine (HCQ) is in a class of drugs called antimalarials and is commonly used to prevent and treat acute attacks of malaria. However, it is also used to treat discoid or systemic lupus erythematosus and rheumatoid arthritis in patients whose symptoms have not improved with other treatments. Patients who are treated with the drug have a positive effect on disease activity along with longterm benefits. However, these effects can be limited by adherence, which can be improved by assessing hydroxychloroquine blood levels.
There are contradictory results concerning blood levels and disease activity, as well as differences in the doses patients should receive. Some experts advocate height-based “ideal body weight” dosing while rheumatologists recommend weight-based dosing. To assess the effect of measurement and counseling on adherence, in the study entitled “Hydroxychloroquine Blood Levels in Systemic Lupus Erythematosus: Clarifying Dosing Controversies and Improving Adherence”, Michelle Petri from the Department of Rheumatology, Johns Hopkins University School of Medicine in Baltimore and colleagues, compared the proportion of patients with hydroxychloroquine levels of 500 ng/ml or higher based on the number of prior assessments.
A total of 686 SLE patients were prescribed with HCQ at a dosing not exceeding 6.5 mg/kg (max 400 mg/day). At each visit, patients were measured for their HCQ levels with a therapeutic range of 500–2000 ng/ml. At baseline, 304 patients had subtherapeutic levels of hydroxychloroquine, of which 88 had 15 ng/mL or lower. Despite weight-based dosing the results showed that 16 patients had supratherapeutic levels.
The results demonstrated that men (71%) were more likely to have therapeutic levels when compared to women (52%). Moreover, SLE patients under 30 or over 60 years of age were more likely to have HCQ levels within the therapeutic range. No differences were associated with income level or education. There was a trend toward lower levels associated with renal failure and blood levels were similar regardless of height and ideal body weight.
No differences were observed based on disease activity using the Physician’s Global Assessment while a statistically significant negative association was observed with hydroxychloroquine levels and the SLE Disease Activity Index (SLEDAI) score. More than half (52%) of patients had vitamin D levels below 40 ng/mL, with lower levels of hydroxychloroquine detected in this patient population. The proportion of SLE patients who had therapeutic levels of hydroxychloroquine increased with each visit from 56% at baseline to 80% in those who underwent three visits or more.
“Our work demonstrates that prior to instituting routine testing, up to 44% of our patients with SLE did not take their most important medication as prescribed,” the researchers wrote, adding, “importantly, our work demonstrates that with repeated measurement and patient counseling, adherence can be significantly improved”.
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