For the study, Palmer’s team pulled together results from 301 clinical trials testing nine classes of diabetes drugs.
The medications included older standbys such as metformin, insulin, and sulfonylureas such as glipizide (Glucotrol) and glimepiride (Amaryl). Other trials looked at newer, more expensive classes, including thiazolidinediones such as pioglitazone (Actos) and rosiglitazone (Avandia); and DPP inhibitors, such as sitagliptin (Januvia) and saxagliptin (Onglyza).
Many trials tested only a single medication, but over 100 studies used a drug in combination with metformin.
Overall, metformin worked as well, or better than other drugs when it came to reducing blood sugar levels, the review found.
When it came to preventing complications or lengthening people’s lives, no single drug or drug combination stood out.
But the problem, according to Palmer, was a lack of evidence — which is different from proof that all the drugs are equal, she said.
Pantalone agreed. “This [analysis] included many studies that were of short duration,” he said, noting that some ran for only six months.
“I think the important finding was that there was no signal that one therapy may be more harmful than another from a cardiovascular standpoint,” Pantalone said.
That’s important, he explained, because the U.S. Food and Drug Administration has only required diabetes drugs to undergo cardiovascular safety testing since 2008. So older medications never went through that process.
Plus, Pantalone said, there is evidence from recent trials that two newer diabetes drugs can, in fact, curb the risk of death from heart disease or stroke. Those drugs are an injectable medication called liraglutide (Victoza) and an oral medication called empagliflozin (Jardiance).
However, metformin remains the recommended first-line drug. It not only lowers blood sugar, Pantalone said, but also carries a low risk of hypoglycemia (potentially dangerous drops in blood sugar).
If another drug needs to be added, Pantalone said, the decision should be based on a person’s overall health and the side effects of the different medications.
Some drugs, like insulin and sulfonylureas, are more likely to cause hypoglycemia, for instance. Others can cause weight gain, Pantalone said.
Whatever medication is used, he stressed, lifestyle changes for people with type 2 diabetes remain key.
“Lifestyle modification, through diet changes and regular exercise, is a critical component to any treatment regimen,” Pantalone said.
The study was published July 19 in the Journal of the American Medical Association.