Drug - Intuniv™ (guanfacine HCl) [Shire]
Therapeutic area - ADHD
No approvals will be granted for use in children under the age of 3.
A once-daily, extended-release formulation of guanfacine hydrochloride (HCl) in a matrix tablet. Guanfacine is a known antihypertensive agent. The mechanism of action in ADHD is not known. Intuniv is dosed once daily and often tiitrated from 1mg/day. Tablets should not be crushed, chewed or broken.
Immediate-release guanfacine and Intuniv cannot be substituted on a mg for mg basis as Intuniv provides about 50% of the dose provided by immediate release guanfacine. [Intuniv bioavailability is 46%, whereas the bioavailability of immediate release guanfacine is 80%.]
The half-life (T1/2) of the two formulations is similarly long.
Pharmacokinetic Parameters in Adults
|Parameter||Intuniv 1 mg QD||guanfacine 1 mg QD|
|Cmax (ng/mL)||1.0 ± 0.3||2.5 ± 0.6|
|AUC0-∞ (ng.h/mL)||32 ± 9||56 ± 15|
|tmax (h)||6.0 (4.0 – 8.0)||3.0 (1.5-4.0)|
|t½ (h)||18 ± 4||16 ± 3|
Somnolence and fatigue are the most commonly reported adverse events (up to 45% incidence). Potential for additive somnolence effects when used with antipsychotics.
Treatment with Intuniv can cause decreases in blood pressure and heart rate.
Measure heart rate and blood pressure prior to initiation of therapy, following dose increases.
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