Emergent Dyskinesia with Tenex (Guanfacine) and Strattera (Atomoxetine)
Yes, emergent dyskinesia can occur when combining Tenex (guanfacine) and Strattera (atomoxetine), though this is a rare adverse event that has been documented specifically with atomoxetine when combined with other psychoactive medications including clonidine (a closely related alpha-2 agonist to guanfacine). 1
Evidence for Dyskinesia Risk
The most relevant evidence comes from a case series documenting dyskinesias specifically with atomoxetine combinations:
- A 9-year-old patient taking clonidine and dextroamphetamine developed psychosis, abnormal involuntary movements, and insomnia when atomoxetine was added. 1
- The acute dyskinetic symptoms did not respond to diphenhydramine but resolved after atomoxetine and other medications were discontinued. 1
- The authors concluded that clinicians should be aware of emergent dyskinesias when combining atomoxetine with dopaminergic, noradrenergic, or serotonergic medications. 1
Mechanism and Risk Factors
The proposed mechanisms for this adverse reaction include:
- Excess synaptic norepinephrine or dopamine from the drug combination 1
- Poor metabolizer status (CYP2D6 polymorphism/deficiency) leading to elevated atomoxetine levels 1
- Drug-drug interactions causing elevated drug concentrations 1
- Approximately 7% of the population are poor metabolizers of atomoxetine, experiencing significantly higher plasma levels and longer half-lives, which increases adverse effect risk. 2
Clinical Monitoring Requirements
When using this combination, specific monitoring is essential:
- Obtain baseline cardiovascular assessment including detailed personal and family cardiac history, baseline heart rate and blood pressure 3
- Consider baseline ECG if cardiac risk factors are present 3
- Titrate atomoxetine cautiously in the presence of clonidine/guanfacine, starting at 40 mg daily and adjusting every 7-14 days 3
- Monitor closely for emergent movement disorders, behavioral changes, and unusual symptoms, especially during the first few months of treatment or at times of dose changes 2
Important Caveats
While dyskinesias are documented with atomoxetine combinations, the overall incidence appears rare:
- Atomoxetine is generally well tolerated with common adverse events being headache, abdominal pain, decreased appetite, vomiting, somnolence, and nausea—not typically dyskinesias 4
- The majority of adverse events with atomoxetine are mild or moderate, with very low incidence of serious adverse events 4
- Interestingly, clonidine has historically been used as a treatment for tardive dyskinesia and related movement disorders, with 75% of patients showing at least moderate improvement in older studies. 5, 6
Practical Management
If dyskinesias emerge:
- Discontinue atomoxetine immediately and consider discontinuing guanfacine as well 1
- Do not expect diphenhydramine to be effective for these movement disorders. 1
- Symptoms should resolve after medication discontinuation, though the timeframe varies. 1
- Consider CYP2D6 genotyping if available to identify poor metabolizer status before restarting any similar regimen. 2, 4