The Food and Drug Administration approved guanfacine (Intuniv) for treatment of attention-deficit/hyperactivity disorder for children and adolescents aged 6-17 years.
The extended-release form of the drug is a selective alpha-2A adrenergic receptor agonist and was first approved for the treatment of hypertension in 2002, and for ADHD in 2007. But its use was limited by its short half-life. The once-daily version will be available in four dosages: 1 mg, 2 mg, 3 mg, and 4 mg.
Unlike many other drugs for ADHD, Intuniv is not a controlled substance. According to manufacturer Shire Pharmaceuticals, Intuniv “has no known potential for abuse or dependence.” The company said that it expected the drug to be available in November.
The FDA sent Shire an “approvable” letter in January 2008, but in early August, the company was told by the agency that it still was not in agreement on the final labeling for the extended-release form of guanfacine.
With approval, Shire said that Intuniv's labeling will contraindicate use in patients with a history of hypersensitivity to guanfacine or any of its active ingredients. Because hypotension, bradycardia, and syncope were all observed in clinical trials, the drug should be used with caution in patients who have experienced any of those conditions previously, or who may be predisposed to syncope, or who are taking antihypertensives.
Labeling will also note that sedation and somnolence were observed in trials.
The mechanism of action is unknown, but, according to statement from Shire, the drug seems to stimulate the postsynaptic alpha-2A receptors, which are “thought to strengthen working memory, reduce susceptibility to distraction, improve attention regulation, improve behavioral inhibition, and enhance impulse control.”