A 2011 German study involving 5,432 patients with RA also found that those treated with biologics had a signification reduction in fatigue at 3 and 6 months.

TNF Inhibitors (Tumor necrosis factor inhibitors)
What they do for RA:
 TNF-inhibitors block the effects of TNF, a pro-inflammatory protein.  
Known Risks:
TNF-inhibitors increase the risk for infections, and may increase the risk for lymphoma (cancer of the lymph nodes.)  
Potential Benefits:
 A 2011 study at the Center for Health Research at Geisinger Medical Center in Danville, Pennsylvania, involving 1881 people with RA, found that TNF-inhibitors were associated with a 51 percent reduced risk of diabetes  compared to those who had never taken the drugs.

According to the Centers for Disease Control (CDC), 52 percent of people with diabetes also have arthritis.

“The association may be because TNF-a  and other pro-inflammatory [proteins] play a central role in the [development] of both RA and insulin resistance,” says study author Androniki Bili, MD, MPH, a rheumatologist at CDC.  “Insulin resistance, or lowered response to insulin, may predispose someone to diabetes, she says: “So, decreased insulin resistance may lead to decreased risk of diabetes.”

TNF-inhibitors also lead to less use of steroids, another risk factor for diabetes, she says.

It’s not clear how long someone would need to take TNF-inhibitors to see an association with lowered diabetes risk, says Bili.

“Diabetes is a major risk factor for cardiovascular disease, and RA is also associated with a high risk of cardiovascular disease,” says Bili: “Medications that can control disease activity and reduce the risk of developing diabetes are highly desirable.”

Hydroxychloroquine (Plaquenil)
What it does for RA:
Hydroxychloroquine is a disease-modifying anti-rheumatic drug (DMARD) that decreases RA pain and swelling, and may prevent disease progression.
Known risks:  The most common side effects are nausea and diarrhea, which often improve over time or when the drug is taken with food.
Potential benefits: The drug may reduce the risk of diabetes.  According to a 2011 study at Geisinger Health System involved 1127 newly diagnosed RA patients who did not have diabetes.  After 23 to 26 months, of 48 people who developed diabetes, only three had been taking hydroxychloroquine.  The lowered risk of diabetes may be because the drug lowers blood sugar levels.