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New medicine for ADHD: guanfacine


The medicinal treatment of ADHD has expanded rapidly. Methylphenidate, dexamphetamine and atomoxetine have been authorised for the treatment of children and adolescents with ADHD, but should, according to the prevailing guidelines, only be prescribed when, after appropriate professional diagnostics, non-medicinal treatment proves inadequate. Guanfacine has recently been added to the repertory, with the additional condition for authorisation that central stimulating agents should have proved ineffective or unsuitable. According to recent research sponsored by the manufacturer, guanfacine has proved to be effective, although the study found remarkably high percentages of placebo responders and patients reporting side-effects. Guanfacine has not been tested among the patients for whom it is intended to be used in the Netherlands, proof of its superiority over other agents is lacking as no comparative studies with other drugs have been undertaken, and there are ongoing concerns over side-effects, so Ge-Bu’s drug rating at this stage is ‘+/-’.

The ‘+/-’ drug rating implies that the product is of doubtful value for the treatment of the disorder or that its added value can as yet not be adequately evaluated based on currently available research findings.

  • Guanfacine is a selective α2A-adrenergic receptor agonist, which has been registered for the treatment of ADHD among children and adolescents when treatment with stimulants proves ineffective or unsuitable.
  • The efficacy of guanfacine has so far not been studied among the patients for whom the drug was authorised in the Netherlands.
  • Although the efficacy of guanfacine has proved to be statistically significantly greater than that of placebo, the number of placebo responders was also large.
  • A six-months’ withdrawal study found that even if treatment with guanfacine is continued, about half of the patients terminate their treatment due to lack of efficacy.
  • The efficacy of guanfacine has not been compared with that of methylphenidate or other medicinal therapies.
  • A multi-year study found that the number of patients reporting side-effects during the use of guanfacine was large (82.7%).
  • Based on the registration guidelines, there is no place for guanfacine as a therapy of first choice for ADHD.
  • Since there has been no appropriate study comparing this drug with existing treatments, and guanfacine has not been studied among the population for whom it was authorised, Ge-Bu’s drug rating can at this stage only be ‘+/’. 

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Authors

  • dr L.M.L. Stolk