Switching from Guanfacine to Strattera: Tapering Recommendations
You should taper guanfacine by 1 mg every 3-7 days before or during the switch to atomoxetine (Strattera) to prevent rebound hypertension, even though the patient has only been on 1 mg for 4 weeks. 1, 2
Why Tapering is Necessary
Guanfacine must be tapered rather than abruptly discontinued because rebound hypertension has been observed after sudden cessation of alpha-2 agonists like guanfacine and clonidine. 1, 2 This recommendation applies regardless of:
- Duration of treatment (your patient's 4 weeks is sufficient to warrant tapering) 2
- Dose level (even 1 mg requires tapering) 2
- The reason for discontinuation (switching medications does not eliminate the risk) 1, 2
The FDA drug label explicitly warns that "abrupt cessation of therapy with orally active central α2-adrenergic agonists may be associated with increases in plasma and urinary catecholamines, symptoms of nervousness and anxiety, and less commonly, increases in blood pressure to levels significantly greater than those prior to therapy." 3
Practical Tapering Protocol
For a patient on guanfacine 1 mg daily, use this straightforward approach:
- Days 1-4: Reduce to 0.5 mg daily (half tablet if using immediate-release, or discuss liquid formulation with pharmacy if using extended-release) 2
- Day 5 onward: Discontinue guanfacine completely 2
You can start atomoxetine on Day 1 of the taper (when reducing guanfacine to 0.5 mg), as there are no significant drug interactions between these medications and atomoxetine requires several weeks to reach therapeutic effect anyway. 1, 4
Monitoring During the Switch
Measure blood pressure and heart rate at baseline (before starting the taper) and monitor throughout the tapering process to detect any signs of rebound hypertension. 1, 2 Watch specifically for:
- Systolic blood pressure increases >10-15 mmHg above baseline 2
- Tachycardia (heart rate increases) 2
- Symptoms of nervousness, anxiety, or headache 3, 5
Evidence Regarding Rebound Risk
The evidence shows that guanfacine's rebound hypertension risk is lower than clonidine's but still clinically significant enough to warrant tapering. 6, 7, 5 Studies demonstrate:
- Withdrawal symptoms with guanfacine are generally mild compared to clonidine 6
- Blood pressure typically returns to baseline over 2-4 days after discontinuation, with occasional transient increases above baseline 7, 5
- One small study in healthy young adults showed no significant rebound with abrupt cessation of guanfacine ER up to 4 mg, but this was in a controlled research setting with healthy volunteers, not real-world clinical practice 8
Despite the lower risk compared to clonidine, consensus guidelines from the American Academy of Pediatrics, American College of Cardiology, and FDA all recommend tapering guanfacine to avoid rebound hypertension. 1, 2, 3
Atomoxetine Initiation
Atomoxetine does not require tapering when starting or stopping, so you can begin it immediately during the guanfacine taper. 1 Start atomoxetine at the standard initial dose:
- 0.5 mg/kg/day for 3-7 days, then increase to target dose of 1.2 mg/kg/day (maximum 100 mg/day) 4
- Expect 2-4 weeks before observing clinical benefits from atomoxetine, similar to guanfacine's delayed onset 1, 4
Common Pitfall to Avoid
Do not abruptly stop guanfacine just because the dose is low (1 mg) or the duration is short (4 weeks). The FDA black box warning and all major guidelines emphasize that tapering is required for all alpha-2 agonists regardless of dose or duration. 1, 2, 3 The consequences of rebound hypertension—though uncommon—can include hypertensive crisis, particularly in patients with underlying cardiovascular risk factors. 2, 3