Switching to Intuniv (Guanfacine Extended-Release) Before Adding Stimulants
For this 11-year-old with ADHD and DMDD on Tenex 1mg BID with persistent hyperactivity and SSRI-induced hypomania, switch to Intuniv (guanfacine extended-release) rather than continuing Tenex (immediate-release guanfacine), as the extended-release formulation provides superior 24-hour symptom coverage, better tolerability with once-daily evening dosing, and is the only FDA-approved guanfacine formulation specifically indicated for ADHD. 1
Why Intuniv Over Tenex
Intuniv provides "around-the-clock" symptom control with once-daily dosing, unlike immediate-release Tenex which requires multiple daily doses and creates peak-trough fluctuations that may worsen behavioral symptoms. 1 The extended-release formulation delivers more stable plasma levels throughout the day, reducing the sedation peaks and symptom rebound that occur with immediate-release formulations. 1
Evening administration of Intuniv is strongly preferred because somnolence and fatigue are the most common adverse effects (occurring in 36-38.6% of patients), and evening dosing minimizes daytime sedation that could interfere with school performance. 1, 2 This timing strategy allows the sedative effects to occur during sleep while maintaining therapeutic coverage during school hours. 1
Specific Conversion and Dosing Strategy
Convert from Tenex 1mg BID (2mg total daily) to Intuniv 2mg once daily in the evening, as the total daily dose equivalence remains the same but the pharmacokinetic profile differs significantly. 1 Start Intuniv the evening after the last Tenex dose—no cross-tapering is required since both are guanfacine formulations working through the same alpha-2A adrenergic receptor mechanism. 1
Titrate Intuniv by 1mg weekly based on response and tolerability, with a target range of 0.05-0.12 mg/kg/day or maximum 7mg/day. 1 For an 11-year-old, the typical weight-adjusted target dose would be 3-4mg daily, though some patients require up to 6-7mg for optimal effect. 1
Expect 2-4 weeks before observing clinical benefits from Intuniv, unlike stimulants which work immediately—this delayed onset is critical for setting appropriate family expectations. 1, 3 The therapeutic effects build gradually as prefrontal cortical network connections strengthen through sustained alpha-2A receptor activity. 3
Why This Matters for DMDD and Hyperactivity
Guanfacine is particularly appropriate when ADHD co-occurs with disruptive mood dysregulation disorder or oppositional symptoms, as it addresses both hyperactivity and emotional dysregulation through prefrontal cortex modulation. 1 The medication enhances top-down regulatory control of attention, emotion, and behavior—exactly what this patient needs given the DMDD diagnosis. 1
The history of SSRI-induced hypomania makes stimulants a reasonable next step only after optimizing non-stimulant therapy, as stimulants carry lower risk of mood destabilization than SSRIs in patients with mood dysregulation. 4 However, maximizing guanfacine efficacy first provides the safest approach before introducing stimulant medication. 1
Critical Monitoring Requirements
Obtain baseline blood pressure and heart rate before switching to Intuniv, then monitor these cardiovascular parameters at each dose adjustment (weekly during titration) and periodically during maintenance therapy. 1 Guanfacine causes modest decreases in blood pressure (1-4 mmHg) and heart rate (1-2 bpm), which are generally mild but require monitoring. 1
Monitor ADHD symptoms systematically at each dose adjustment using parent and teacher reports, specifically tracking hyperactivity, impulsivity, and emotional dysregulation across home and school settings. 1 Use standardized rating scales like the ADHD-RS-IV to objectively measure treatment response. 5
Screen for excessive somnolence during the first 3 weeks of treatment, as sedative adverse events peak during week 3 and decrease thereafter. 5 If daytime sedation persists beyond 3-4 weeks, consider dose reduction rather than abandoning the medication. 1
When to Add Stimulants
If hyperactivity remains inadequately controlled after 6-8 weeks on optimized Intuniv dosing (typically 3-4mg for this age/weight), add a long-acting stimulant as adjunctive therapy rather than switching away from guanfacine. 1 Extended-release guanfacine and extended-release clonidine are the only two medications with FDA approval and sufficient evidence for adjunctive use with stimulants. 1
The combination of Intuniv plus stimulant allows for lower stimulant dosages while maintaining efficacy and potentially reducing stimulant-related adverse effects, which is particularly valuable given the DMDD diagnosis and mood instability concerns. 1 Start with methylphenidate extended-release 18mg or lisdexamfetamine 20-30mg as first-line stimulant options. 4
Critical Safety Warnings
Never abruptly discontinue Intuniv—it must be tapered by 1mg every 3-7 days to avoid rebound hypertension. 1 This is essential patient/family education before starting treatment. 1
Common adverse effects beyond somnolence include headache (20.5-28.5%), fatigue (15.2-20.1%), and constipation (5-16%), which are typically mild to moderate, transient, and dose-related. 1, 2 These effects generally improve after the first 3-4 weeks of treatment. 5
Contact the provider immediately if the patient experiences chest pain, very slow heart rate, irregular heartbeat, or accidentally misses multiple doses—do not restart at full dose without medical guidance. 1
Why Not Continue Tenex
Continuing immediate-release Tenex at higher doses (e.g., increasing to 1.5mg BID or 2mg BID) is inferior to switching to Intuniv because: (1) the immediate-release formulation lacks FDA approval for ADHD treatment, (2) multiple daily doses reduce adherence in children, (3) peak-trough fluctuations worsen behavioral symptoms and side effects, and (4) all clinical trial evidence supporting guanfacine efficacy in ADHD used the extended-release formulation. 1, 2
The current Tenex regimen has already failed to control hyperactivity adequately—simply increasing the dose of an inferior formulation is not the evidence-based approach. 1 The extended-release formulation provides fundamentally different pharmacokinetics that translate to superior clinical outcomes. 1, 5