The old and inexpensive antimalarial drug hydroxychloroquine may protect people with rheumatoid arthritis (RA) from another serious health threat – diabetes, according to two new studies presented at the American College of Rheumatology Annual Scientific Meeting in San Francisco.

In one study, people with RA who took hydroxychloroquine – a medication developed to treat malaria that is currently used to treat some autoimmune diseases – were 53 percent less likely to develop diabetes. These findings were presented by Androniki Bili, MD, MPH, of Geisinger Health System, Danville, Penn.

“We should revisit this antimalarial drug because, in addition to the disease-modifying effects, it may prevent the development of diabetes in this high risk group of patients,” she says. People with RA are at risk of diabetes because of steroid use, sedentary lifestyle and chronic inflammation.

The second, Arthritis Foundation-funded study found that people with RA who took the antimalarial drug hydroxychloroquine alone for their RA were 33 percent less likely to develop diabetes than were people who took methotrexate alone.

Lead researcher Daniel Solomon, MD, MPH, of Brigham and Women’s Hospital and Harvard Medical School in Boston, said the jury is out on exactly how this antimalarial drug reduces diabetes risk among people with RA. “It may allow the hormone insulin to hang around longer, which could improve insulin sensitivity or reduce insulin resistance, but no one really knows yet.”

Insulin helps the body use glucose, or blood sugar. Cells need glucose for energy. If a body is resistant to the effects of insulin, the pancreas overcompensates and secretes additional insulin. The cells may resist the high levels of insulin, and glucose, in turn, builds up in the blood, resulting in high blood glucose or type 2 diabetes.

“These are suggestive studies that would warrant follow-up through clinical trials to determine the real effect on insulin resistance in patients with RA,” researcher Solomon says.

Whether or not antimalarial drugs have a role in staving off diabetes among people without rheumatoid arthritis is also not known. “These drugs are not anti-diabetic in the true sense, but there have been some trials on blood sugar and glycosylated hemoglobin (hemoglobin A1c) and they do seem to lower blood sugar by a little bit,” Solomon says. They are not [potential anti-diabetic drugs], but in the setting where someone may get a benefit for other reasons as well, they may be kind of a two-fer.”

The two studies bolster older findings published in Journal of the American Medical Association, which showed that the risk of new-onset diabetes dropped by 77 percent in RA patients who had taken hydroxychloroquine for more than four years. The analysis is based on data from the ARAMIS (Arthritis, Rheumatism, and Aging Medical Information System) longitudinal, multicenter, observational study begun in 1976 and sponsored by the Arthritis Foundation of Western Pennsylvania, the National Arthritis Foundation, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the Intramural Research Program at NIAMS, and the National Institutes of Health.