From the Guidelines
The best time to take guanfacine XR is typically once daily in the evening or at bedtime. This recommendation is based on the fact that drowsiness is a common side effect of guanfacine, and taking it before sleep can minimize its impact on daily activities 1. Taking guanfacine XR at the same time each day helps maintain consistent blood levels of the medication. The medication should be swallowed whole with water and can be taken with or without food, though taking it consistently with respect to meals helps maintain steady absorption.
Some key points to consider when taking guanfacine XR include:
- Do not crush, chew, or break the tablet as this would disrupt the extended-release mechanism and could lead to too much medication being released at once.
- If you miss a dose, take it as soon as you remember, but if it's almost time for your next dose, skip the missed dose and continue with your regular schedule.
- Never take a double dose to make up for a missed one.
- The extended-release formulation is designed to provide steady medication levels throughout the 24-hour period, which helps control symptoms consistently while minimizing side effects 1.
It's worth noting that guanfacine XR is approved as an adjunctive therapy to stimulant medications, which can help increase treatment effects and/or decrease adverse effects of stimulants, such as sleep disturbances and cardiovascular effects 1. However, the primary consideration for the timing of guanfacine XR administration should be to minimize its sedative effects and optimize its therapeutic benefits.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION The recommended initial dose of guanfacine tablets, USP when given alone or in combination with another antihypertensive drug is 1 mg daily given at bedtime to minimize somnolence The best time to take guanfacine XR is at bedtime to minimize somnolence 2.
From the Research
Administration Time of Guanfacine XR
The optimal time to take guanfacine XR is not strictly defined, but studies suggest that it can be effective when taken either in the morning or evening.
- A study published in the Journal of child and adolescent psychopharmacology in 2014 found that guanfacine extended release (GXR) was effective in reducing ADHD symptoms regardless of whether it was administered in the morning or evening 3.
- Another study published in the Journal of attention disorders in 2017 also found that adjunctive GXR was associated with improvements in morning and evening ADHD symptoms, whether taken in the morning or evening 4.
Efficacy of Guanfacine XR
Guanfacine XR has been shown to be effective in treating ADHD symptoms in both children and adults.
- A systematic review and meta-analysis published in the Journal of child and adolescent psychopharmacology in 2023 found that guanfacine was significantly more effective in treating ADHD compared to placebo, with a risk ratio of 1.78 5.
- A study published in The Journal of clinical psychiatry in 2020 found that guanfacine extended-release improved ADHD symptoms in Japanese adults with ADHD, with significant improvements in ADHD-RS-IV total score reduction and CGI-I scores 6.
Mechanism of Action
Guanfacine's mechanism of action involves the selective activation of norepinephrine α2A-adrenoceptors in the prefrontal cortex, which strengthens network connectivity and enhances PFC neuronal firing.
- A study published in Neurobiology of learning and memory in 2020 found that guanfacine acts within the PFC to inhibit cAMP-PKA-K+ channel signaling, thus strengthening network connectivity and improving PFC cognitive functions 7.