NEW YORK (Reuters Health) – When patients with rheumatic illnesses and concomitant diabetes are treated with hydroxychloroquine, their HbA1c levels drop significantly. Methotrexate, however, does not have the same effect, according to findings reported in an August 18th online issue of Arthritis & Rheumatism.

Dr. Daniel H. Solomon, at Brigham and Women’s Hospital in Boston, Massachusetts and colleagues note that patients with rheumatic diseases such as rheumatoid arthritis or systemic lupus erythematosus are at substantially elevated risk of insulin resistance, which often precedes diabetes.

“It has been known for a long time that hydroxychloroquine can lower blood glucose levels in diabetic patients but this has never been systematically examined in rheumatic disease patients before,” Dr. Solomon pointed out in an email.

To see if this effect of hydroxychloroquine, an approved disease modifying anti-rheumatic drug (DMARD), is apparent in patients with rheumatic diseases, and whether a more potent DMARD like methotrexate affects HbA1c, the researchers identified 82 diabetic adults being treated for a rheumatologic condition with hydroxychloroquine (N = 45) or methotrexate (N = 37).

Before treatment, the mean HbA1c values were 7.71% and 7.38% in the two groups, respectively. The reduction in HbA1c from baseline to the lowest value within 12 months after starting treatment was significantly greater in the hydroxychloroquine group (0.66%) than in the methotrexate group (0.11%).

“In adjusted analyses this drop in HbA1c among hydroxychloroquine users was 0.54% greater than that in methotrexate users (p = 0.041),” Dr. Solomon and colleagues report.

“Hydroxychloroquine is a weak hypoglycemic agent compared with other typical oral anti-diabetic drugs,” Dr. Solomon noted. “However, it is important to note that it can lower blood glucose. Rheumatologists should be aware of this when starting hydroxychloroquine in diabetics and non-diabetics,” he advised.

The authors conclude, “These findings add to an existing literature suggesting beneficial effects of hydroxychloroquine on insulin and glucose metabolism, perhaps distinct from methotrexate. Comprehensive, larger, and prospective studies are clearly warranted to determine the potential role of hydroxychloroquine in mitigating cardiovascular morbidities in patients with systemic rheumatic diseases.”

Reference:

Changes in glycated hemoglobin after initiation of hydroxychloroquine or methotrexate in diabetic patients with rheumatologic diseases


Arthritis Rheum 2010.