FILE - Cough syrup containing dextromethorphan is displayed at a pharmacy in Edmond, Okla.
FILE - Cough syrup containing dextromethorphan is displayed at a pharmacy in Edmond, Okla.

An active ingredient in common cough medicine has been shown to reduce blood sugar levels in both humans and mice, indicating that it could someday be used to treat diabetes.

The ingredient, dextromethorphan, is in many syrups and tablets that suppress coughs. It also lowers blood sugar levels in both Type 1 and Type 2 diabetes by protecting insulin-producing beta cells. It is not, however, a cure for diabetes.

Eckhard Lammert, a professor of physiology and director of the Diabetes Center in Dusseldorf, Germany, and colleagues found that dextromethorphan lowers blood sugar levels in mice.

"We also did a single-dose clinical trial with 20 individuals with Type 2 diabetes, and could see in these individuals that dextromethorphan is able to lower blood glucose levels similar to what we see in mice,” he said.

Insulin is a hormone that helps cells absorb glucose for fuel. If beta cells do not produce enough insulin, dangerous and destructive levels of sugar can build up in the blood, leading to serious complications, including blindness and kidney failure.

Type 1 diabetes is caused by a misdirected immune system, destroying insulin-producing beta cells. It affects roughly 10 percent of all diabetics.

Much more common, and a growing health problem worldwide, is Type 2 or adult-onset diabetes. People with this condition have insulin-resistance; the cells of their bodies become unable to absorb the amount of sugar in their blood.

Lammert said dextromethorphan reduces blood sugar levels by around 10 percent.

It’s tempting to buy cough medicine and give it a try. Lammert said, however, that the use of dextromethorphan is experimental, and he discouraged the use of cough medicine by people trying to treat their diabetes.

“This is something we don’t want to see," he said, noting that the data gathered thus far were limited. "They make us optimistic, but they are not sufficient for anyone to self-medicate.”

Eventually, Lammert said, dextromethorphan may be used as an add-on to standard diabetes medicine, such as metformin.  

The study was published in the journal Nature Medicine.