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According to the Centers for Disease Control, between 21 and 29 percent of patients who are prescribed opioids for chronic pain misuse them, and 8 to 12 percent become addicted. Even worse, each day more than 115 people in the U.S. die after overdosing on opioids.

Faced with these daunting statistics, the National Institutes of Health is trying to better understand just how opioids affect brain function and why they are so addictive. They are looking at the chemical messenger dopamine, which carries signals between brain cells, and may affect addiction.

Heavy use of opioids like heroin, OxyContin and Vicodin, may decrease the amount of dopamine available to the brain. Researchers want to study if decreased dopamine decreases self-control and increases impulsiveness.

Volunteers sought

The study is recruiting people age 18 to 65 who use opiates daily or almost daily. Half the study participants will receive a drug called methylphenidate (brand name Ritalin), which works in the treatment of attention deficit hyperactivity disorder by increasing levels of dopamine in the brain. The other half will receive a placebo.

The study will take place at the NIH Clinical Center in Bethesda, Md., and includes up to four study visits.

Participants will first be screened with a physical exam and give blood and urine samples. They will answer questions about their medical, psychiatric, and alcohol and drug use history.

To measure brain activity, participants will have two to three positron emission tomography (PET) scans, in which they will lie on a bed that slides in and out of the donut-shaped scanner.

They will also will have magnetic resonance imaging (MRI) scans, where they will lie on a table that slides into a cylinder in a strong magnetic field. They may do tasks on a computer screen while inside the scanner.

Participants will be randomly divided into two groups. Both will get the scans, but one will take methylphenidate an hour before the scan, while the other group will get a placebo with no active ingredient.

During the study, participants will have their breath and urine tested each day. They will also take tests of memory, attention and thinking, and wear an activity monitor for one week.

Can continue opioid use

Those in the study can be either receiving treatment or not undergoing treatment for their opiate use. However, they cannot have a serious medical condition, such as HIV, diabetes or cardiovascular disease, including uncontrolled high blood pressure. They also cannot have a psychiatric condition, such as schizophrenia, that requires medication or hospitalization.

To ensure participants can undergo scans, they cannot have a variety of implants, including pacemakers, brain stimulators and dental implants. They also must weigh less than 400 pounds.

Participants will be compensated for time and travel.

For more information or to volunteer, call the NIH Clinical Center Office of Patient Recruitment at 800-411-1222 and refer to study number 17-AA-0114, or visit https://go.usa.gov/xnvcz.