MONDAY, Sept. 19 (HealthDay News) -- The widely used attention-deficit/hyperactivity disorder (ADHD) medication methylphenidate -- best known as Ritalin -- appears to be tied to delayed puberty in male monkeys.
But, researchers cautioned that the finding needs to be replicated before parents should concern themselves about similar effects in boys.
Male primates given methylphenidate over a 40-month span experienced "impaired testicular descent" and smaller-sized testicles, as well as lower testosterone levels, all of which resolved over the course of the study.
"To our knowledge, it's the first observation in primates to suggest an alteration in testicular function," said study author Dr. Donald Mattison, a medical officer at the National Institute of Child Health and Human Development, part of the U.S. National Institutes of Health.
"We believe they're interesting observations, but substantially more work needs to be done . . . to make sure they're repeatable," Mattison said. "It's really too early to say there are clinical implications."
The study is published in this week's online issue of the Proceedings of the National Academy of Sciences.
The most commonly diagnosed behavioral disorder in childhood, ADHD affects between 3 percent and 5 percent of school-age kids, mostly boys. Ritalin and other forms of methylphenidate have long been the most widely used drugs to treat ADHD, which involves issues of inattentiveness, overactivity and impulsivity. Other brand name versions of methylphenidate include Concerta, Metadate and Methylin.
According to Mattison, the young rhesus monkeys in the study were given either a low dose or high dose of methylphenidate, with the low dose designed to match typical blood levels of the drug observed in human ADHD patients. The high dose was intended to produce blood levels five to 10 times higher than used
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