Researchers from the Norwegian Institute of Public Health have shown that methadone, which has been used to treat heroin addicts for nearly 50 years, affects the brain and impairs the attention of experimental animals.
In general, opioids such as heroin and morphine are known to weaken intellectual functions such as learning, memory and attention.
"It is therefore tempting to assume that methadone has similar effects," says researcher Jannike M. Andersen at the NIPH's Division of Forensic Toxicology and Drug Abuse.
In a new study, Andersen and colleagues treated rats daily with methadone for three weeks and studied the rats' attention. The researchers measured how long the rats examined a new object introduced into their cage. The results show that the treatment clearly reduced the attention of the animals. This was true both when the rats had methadone in the body and, more importantly - a day after the last treatment, when the methadone had been excreted.
"The fact that the attention is impaired even after the drug was no longer present in the body suggests that methadone causes changes in brain cells," says Andersen.