Long Term ADHD Drugs Appear Safe

Ritalin appears safe to use for extended time periods

(RxWiki News) Between five and seven percent of adolescents in the US are diagnosed with attention deficit hyperactivity disorder (ADHD). However, little is known about the long-term effects of drugs used to treat ADHD.

A new study on monkeys suggests that long-term usage of some ADHD medication is safe.

The study tested methylphenidate (MPH), better known as Ritalin, on rhesus monkeys. Further research is necessary, however.

The animal study does not directly indicate, however, that long-term usage of the medication is safe for humans.

"Ask your psychiatrist about long term use of any medications."

The study was conducted by Kathryn E. Gill, a graduate student at Wake Forest Baptist Medical Center.

"We know that the drugs used to treat ADHD are very effective, but there have always been concerns about the long-lasting effects of these drugs," said Linda Porrino, PhD, professor and chair of the Department of Physiology and Pharmacology at Wake Forest. "We didn't know whether taking these drugs over a long period could harm brain development in some way or possibly lead to abuse of drugs later in adolescence."

The team gave eight rhesus monkeys a daily dose of MPH for one year. Another eight monkeys were monitored but not given medication. All 16 primates had body weight and growth measurements taken and brain scans conducted before and after the treatment period.

The researchers used a brain scan technology called positron emission tomography in order to monitor activity in brain receptors related to ADHD.

After the treatment period all the primates were given the opportunity to use cocaine for several months. This test was set up to determine if those with long-term MPH use were more susceptible to drug addiction.

The study found no significant differences in weight gain, brain development or vulnerability to drug addiction. The researchers believe that the results could relate to human adolescents.

"After one year of drug therapy, we found no long-lasting effects on the neurochemistry of the brain, no changes in the structure of the developing brain. There was also no increase in the susceptibility for drug abuse later in adolescence," Porrino said. "We were very careful to give the drugs in the same doses that would be given to children.”

While the results of the study look promising, it should be noted that animal studies do not directly translate to humans and that these results do not necessarily indicate that MPH is safe for long-term usage.

The study was published July 18, 2012, in the journal Neuropsychopharmacology and was funded by the National Institute of Drug Abuse of the National Institutes of Health. Study medication was provided by UCB SA, Belgium.

Review Date: 
July 24, 2012