Burley Garcia|What is gabapentin? Here's why it's so controversial.

Many of the prescription drugs that are Burley Garciacommonly abused or misused are brands most people have heard of. Painkillers, also known as opioids, are the most frequently abused ones, per data from the New York State Department of Health. These include morphine, codeine, oxycodone and hydrocodone, with brand names OxyContin, Vicodin and Lortab. Depressants that are used to treat anxiety and sleep disorders include brands like Valium and Xanax and are also commonly abused. Ditto for stimulants that treat ADHD such as Ritalin, Dexedrine and Adderall. 

Dr. Holly Geyer, an addiction medicine specialist and the lead physician of the Mayo Clinic opioid stewardship program in Arizona, explains that in an effort to help combat opioid-related drug abuse, many doctors have been turning to a class of drugs that isn't classified as a controlled substance: gabapentinoids. This has contributed to a drug called gabapentin becoming the sixth-most prescribed medication in the United States. 

As a result of this, and somewhat ironically, "we are now seeing emerging patterns of abuse with gabapentin across the country," Geyer says, adding that such abuse can occur with gabapentin alone, "or in combination with other drugs of abuse, such as opioids."

Here's who gabapentin was originally approved for, what it's used for today and why it's becoming a drug of increasing concern for abuse and misuse. 

What's the latest health trend?! Sign up for USA TODAY's Everyone's Talking newsletter to find out.

What is gabapentin? 

Gabapentin is a prescription medication that was approved by the U.S. Food and Drug Administration in 1993 as a treatment for epilepsy. It works by binding to a type of calcium channel in nerve cells, "which is thought to modify how the nerve functions," explains Dr. Tom Lombardi, medical director of neurosciences for Intermountain Health in Salt Lake City.

In this capacity, the drug can help control specific types of nerve pain and treat seizure disorders, "as it acts on the nervous system to help reduce nerve transmission," says Geyer.

It's typically administered as an oral medication, is usually taken two to three times daily by mouth and is available in pill or liquid form, says Andrea Tedeschi, a neuroscientist at The Ohio State University College of Medicine and co-author of gabapentin-related research. It's available "as both a brand name product and a lower-cost generic," he says. Brand names include Neurontin, Horizant and Gralise. 

What are gabapentin side effects?

While gabapentin can be helpful in a number of circumstances, some of the common side effects associated with taking the drug as directed include drowsiness, dizziness, headache, dry mouth, weight gain, swelling of the hands, feet or ankles, back or joint pain and flu-like symptoms such as nausea, fever and body aches, per Harvard Medical School.

Rare but serious side effects include rash, itching, yellowing of the skin, swelling of the face and throat, problems speaking, difficulty swallowing and changes in memory, personality or ability to concentrate.

The more you know:Left untreated, heartburn can turn into this more serious digestive disease: GERD

What is gabapentin used for? 

When used as directed, gabapentin is known to have numerous uses and benefits. It has been FDA-approved to help control and treat seizures and to diminish a specific type of nerve pain called post-herpetic neuralgia that often follows a shingles' diagnosis. 

In addition to these FDA-approved uses, Tedeschi says gabapentin is also sometimes prescribed off-label by providers for a variety of other medical conditions. (Off-label use means evidence exists that a drug is helpful in treating conditions other than those for which it has been FDA approved.)

Known off-label uses where doctors prescribe gabapentin include as a treatment for hot flashes, restless leg syndrome, mood disorders, anxiety, and to diminish nerve pain related to diabetes or the neck and back pain associated with conditions such as sciatica.

Among the reasons it's so popular are that "it's a generic medication, so it is relatively inexpensive," says Lombardi. It also offers "excellent pain control for many medical conditions driven by damaged nerves," says Geyer. 

In case you missed:Yes, dietary choices can contribute to diabetes risk: What foods to avoid

What is the controversy with gabapentin?

Despite its FDA approval and proven benefits, gabapentin is often misused. Though not considered addictive, "in some patients, the drug can cause a ‘high,’ which increases its abuse potential," notes Geyer. 

It's also known to enhance the psychological effect of opioids, says Tedeschi, and can thereby contribute to their continued abuse – even to the point of being associated with drug overdose deaths, notes Harvard Medical School. Because of such factors, "several states have taken the step of listing gabapentin as a schedule V controlled substance," says Lombardi. 

Its abuse can occur by taking a prescribed version of the drug differently than is directed, and, like other illicit substances, "can also be purchased without a prescription on the dark web," says Geyer.

She says that for most people, gabapentin is a safe drug to take, "however, its potential for abuse is increasingly being recognized." She says it's impossible to predict who may be susceptible to abuse the drug, but a history of addiction to other drugs may be a risk factor. "Patients should be counseled on this potential side effect when starting the medication," she cautions, "and be encouraged to speak up if they have concerns."