select search filters
briefings
roundups & rapid reactions
Fiona fox's blog
A study in male rhesus monkeys found that long-term administration of the drug commonly known as Ritalin was associated with delay of signs associated with the onset of puberty.
Professor Richard Sharpe, Society for Endocrinology spokesperson and Group Leader at the MRC Centre for Reproductive Health, said:
“Methylphenidate, also known as Ritalin, is one of the most widely prescribed drugs to school-age/adolescent children, in particular to boys. It is highly effective in controlling attention deficit/hyperactivity and related behaviours that can be highly disruptive.
“This study in male rhesus monkeys, which exhibit similar pubertal development to boys, found that chronic administration of methylphenidate delayed pubertal development and the associated increase in testosterone levels; it also delayed descent of the testes into the scrotum. These effects most probably resulted from a central (brain) effect on centres that hormonally control puberty.
“These results suggest that similar effects on onset of puberty are likely in boys if they are treated with methylphenidate in the years leading up to puberty (10-13 years), which is common. Delayed puberty in treated girls might also be anticipated, as similar mechanisms underlie puberty in girls and boys. Earlier studies in rats support both of these conclusions.
“On the positive side, the treatment effects on puberty were fully recoverable, lessening chances of any permanent adverse effects if treatment delays puberty in boys. Also the effect on testis descent is not relevant to boys in whom the testes are normally descended before birth, unlike in rhesus monkeys in which this is delayed until puberty.”
Donald Singer, Professor of Clinical Pharmacology and Therapeutics, The University of Warwick and Member of the British Pharmacological Society, said:
“This experimental study suggests that continued use of methylphenidate hydrochloride (Ritalin) in young animals is associated with a delay in the pace of normal puberty, based on hormonal measurements and rate of testicular growth. Should this be a cause for concern for the use of this drug in humans? The eventual changes expected during puberty still occurred and the authors themselves note that ‘the effects were transient and no permanent deficits were found’, including normal testicular size at the end of the study. They note the need for further studies in humans.
“There are several important criticisms of this study. A major weakness of the study is the absence of a further treatment group given a chemically different behaviour altering treatment. This would have given insight into whether or not the changes observed are simply due to a change in behaviour pattern, as suggested by the observation that effects are transient, rather than to a harmful chemical effect of the treatment. This possible effect of behaviour change alone has been reported elsewhere this week in a study noting that testosterone levels decrease in men who take part in child care. The authors also provide no information on important potential consequences of their findings. For example, it would have been important to know whether or not there was any impact on intellectual or psychological development or on fertility.”
Stephen Tomlin, Royal Pharmaceutical Society (RPS) spokesperson on medicines for children, said:
“This study (whilst under-powered in terms of numbers) is consistent with other similar findings about the effect of methylphenidate (MPH) on neuoendocrine systems such as growth.
“Whilst the findings may cause some concern, some reassurance can be taken in the fact that any delays in puberty and testicular development are transient with no permanent alterations in maturation seen.
“The potential effect appears to be dose related, thus reinforcing good practice, of always using the lowest optimal dose.
“Initiation of MPH should never be taken lightly, however the potential benefit for patients will usually outweigh any detrimental effects.”
‘Pubertal delay in male non-human primates (Macaca mulatta) treated with methylphenidate’ by Donald R Mattison et al., published in Proceedings of the National Academy of Sciences on Monday 19th September 2011.