Metformin

Diabetes drug Metformin safe for patients with kidney disease:

review
Although metformin, the popular type 2 diabetes medication, is usually not prescribed for people with kidney disease, a new analysis shows the drug may be safer for these patients than once thought.
Metformin has been used in the United States for two decades to help lower blood sugar levels among people with type 2 diabetes. The U.S. Food and Drug Administration cautions that people with kidney disease should not take the drug because it could increase their risk for a potentially serious condition called lactic acidosis. This is when lactic acid builds up in the bloodstream after oxygen levels in the body are depleted.

After reviewing published research to evaluate the risks associated with metformin among people with mild to moderate kidney disease, a team of researchers led by Dr. Silvio Inzucchi, a professor of medicine at Yale University, found these patients were at no greater risk for lactic acidosis than people who were not taking the drug.
"What we found is that there is essentially zero evidence that this is risky," Inzucchi, who is also medical director of the Yale Diabetes Center, said in a university news release. "The drug could be used safely, so long as kidney function is stable and not severely impaired," he said.
Despite warnings, many doctors are already prescribing metformin to patients with kidney disease, the study published in the Dec. 24/31 issue of the Journal of the American Medical Association revealed.
"Many in the field know that metformin can be used cautiously in patients who have mild to moderate kidney problems," Inzucchi said. "Most specialists do this all the time."
Still, the researchers said their findings are significant because many doctors stop prescribing metformin once their patients get older and their kidney function starts to decline.
"What invariably happens next is their diabetes goes out of control," Inzucchi said. "Other drugs may be substituted, but they are usually not generic products like metformin, and so [they're] more expensive and may also have more side effects."
The study authors pointed out their research didn't involve patients with severe kidney disease. They also added that patients with kidney disease would need to be more closely monitored if they were taking metformin. The dosage of the drug may also need to be adjusted, depending on patients' level of kidney function. 
Source: Drugs.com