Are sedating indiawomandating
Seems like a no-brainer to substitute the generic, right?
Well, the manufacturer of Intuniv warns against substituting the cheaper, generic, immediate-release guanfacine for its product.
This is not an unusual pharmacokinetic difference when comparing an extended-release to an immediate-release formulation and, oftentimes, this relates to lower rates of adverse effects seen with an extended- release formulation.
Interestingly, rates of somnolence in patients taking GXR as monotherapy compared to patients taking immediate-release guanfacine appear similar when comparing reported frequencies in the package inserts (not head-to-head studies unfortunately, but the best we have for comparison).
Price and Pharmacokinetics The majority of the controlled trial data with guanfacine in ADHD is with the brand name only GXR (Intuniv).
The dosing recommendation for Intuniv is to start at 1 mg/day and to increase by 1 mg/day weekly to a maximum of 4 mg/day.
The company bases this on the differing pharmacokinetic properties.
From data in adults, the extended-release formulation of guanfacine is reported to have a peak serum level that is about 60% lower and occurs three hours later than that with immediate-release.
Guanfacine, a drug originally used to treat hypertension, has been reformulated and now has new life as a medication to treat ADHD in children.
An alpha-2A agonist, this medication was initially marketed as Tenex (now available as a generic) for treating hypertension.
Unfortunately, there have been no published trials comparing guanfacine to other approved medications for ADHD although a search of clinical trial registries finds two unpublished head-to-head studies, one versus methylphenidate (NCT00429273) and the other versus ato- moxetine (NCT01244490).