Do oxycodone, gabapentin, baclofen, or hydroxyzine cause involuntary muscle twitching (myoclonus or fasciculations)?

Medication-Induced Twitching: Direct Answer

Yes, gabapentin, baclofen, and oxycodone can all cause involuntary muscle twitching (myoclonus), while hydroxyzine is not typically associated with this adverse effect.

Gabapentin

Gabapentin is strongly associated with myoclonus and should be considered a likely culprit when twitching develops. 1

• Gabapentin has level A evidence (highest quality) for causing drug-induced myoclonus 1
• In one case series, 13 of 104 patients (12.5%) developed myoclonus while taking gabapentin for epilepsy 2
• The myoclonus can be multifocal (affecting multiple body areas) or focal (localized to one area) 2
• Critically, gabapentin-induced myoclonus can occur even with normal kidney function, low doses, and short treatment duration 3
• The twitching typically persists as long as gabapentin is continued but resolves rapidly after discontinuation 2
• Gabapentin can also cause negative myoclonus (sudden brief interruption of muscle contraction causing jerky movements) 3
• In one study, 21 patients developed negative myoclonus from gabapentin or pregabalin, with 18 having completely normal kidney function 3

Baclofen

Baclofen is not directly associated with causing myoclonus or twitching based on the available evidence. 4

• The evidence reviewed discusses baclofen primarily in the context of alcohol dependence treatment, not movement disorders 4
• No guideline or research evidence in the provided materials links baclofen to twitching or myoclonus as an adverse effect

Oxycodone

Opioids including oxycodone are associated with myoclonus, particularly at higher doses or with prolonged use. 1

• Pure opioid agonists including morphine and fentanyl have level A evidence for causing drug-induced myoclonus 1
• While oxycodone specifically wasn't highlighted in the myoclonus systematic review, it belongs to the same pure opioid agonist class that demonstrates this adverse effect 1
• Common opioid side effects include sedation and dizziness, which occur in approximately 50% of patients, though myoclonus is less frequently reported 4

Hydroxyzine

Hydroxyzine is not associated with causing myoclonus or muscle twitching based on available evidence.

• No evidence in the provided materials links hydroxyzine to twitching or involuntary movements
• Hydroxyzine is an antihistamine that can exacerbate restless legs syndrome but is not directly linked to tremor or myoclonus 5

Clinical Management Approach

If twitching develops while on these medications:

1. Identify the temporal relationship: Determine which medication was started or dose-increased closest to symptom onset 2
2. Prioritize gabapentin as the most likely cause if the patient is taking it, regardless of dose or kidney function 3
3. Consider dose reduction first rather than immediate discontinuation, as lower doses may be tolerated without myoclonus 2
4. Discontinue the suspected medication if symptoms are bothersome or interfere with function 2
5. Expect rapid resolution within days of stopping gabapentin-induced myoclonus 2

Important Caveats

• Gabapentin-induced myoclonus is often subtle and can be easily overlooked unless specifically assessed 2
• The myoclonus may not significantly interfere with daily activities in most cases, so discontinuation isn't always necessary 2
• Renal impairment increases risk but is not required for gabapentin to cause myoclonus 3
• Multiple medications can contribute simultaneously, particularly in patients on polypharmacy 2