Mirtazapine and Tremors
Yes, mirtazapine can cause tremors as a recognized adverse effect, occurring in approximately 63% of patients taking second-generation antidepressants who experience at least one adverse effect, with tremor being among the commonly reported symptoms. 1
Evidence from FDA Drug Labeling
The FDA-approved prescribing information for mirtazapine explicitly lists tremors as a serious adverse effect, particularly in the context of serotonin syndrome. 2 The drug label warns that tremors, stiff muscles, or muscle twitching are key signs of this potentially life-threatening condition, which requires immediate discontinuation of the medication and emergency medical attention.
Additionally, the FDA label notes that tremor is a symptom of discontinuation syndrome when mirtazapine is stopped abruptly. 2
Clinical Evidence and Epidemiology
A comprehensive literature review identified 35 cases of tremor associated with mirtazapine use across multiple countries, with a mean time from drug initiation to symptom onset of 7.54 days. 3 Importantly, 82.60% of individuals showed improvement within one week of management intervention.
The movement disorder profile associated with mirtazapine includes:
- Tremor (35 cases)
- Restless legs syndrome (69 cases)
- Akathisia (10 cases)
- Other movement disorders 3
Mechanism and Context
Mirtazapine's tremor-inducing potential relates to its complex pharmacological profile as a noradrenergic and specific serotonergic antidepressant (NaSSA). 4 While tremor is listed among common adverse effects alongside sweating, nervousness, and insomnia in SSRI-class medications 5, mirtazapine's unique receptor antagonism (alpha-2, H1, 5-HT2A, 5-HT2C, 5-HT3) contributes to its side effect profile. 3
Important caveat: Drug-drug interactions significantly increase tremor risk. Medications that prolong QTc interval—including domperidone, ondansetron, escitalopram, venlafaxine, sertraline, and notably mirtazapine itself—can compound this adverse effect. 6
Management Algorithm
When tremor develops on mirtazapine:
Assess for serotonin syndrome immediately - Look for accompanying symptoms: agitation, confusion, fast heart rate, dizziness, flushing, stiff muscles, seizures, hallucinations, blood pressure changes, sweating, hyperthermia 2
- If present: STOP mirtazapine immediately and seek emergency care
If isolated tremor without serotonin syndrome:
Do NOT rechallenge with mirtazapine if tremor was significant 3
Review concomitant medications for drug-drug interactions that may be contributing 6
Special Populations
- Elderly patients: May experience more pronounced adverse effects and require lower starting doses 1
- Patients with cardiovascular disease: Exercise additional caution given mirtazapine's association with QTc prolongation when combined with other medications 6
Clinical Pearls
While one small study suggested mirtazapine might theoretically treat essential tremor, the majority of patients (85%) did not benefit, and adverse effects including drowsiness, confusion, gait problems, and paradoxically worsening tremor were common. 7 This contradicts any notion that mirtazapine could be therapeutic for tremor disorders.
The tremor risk must be weighed against mirtazapine's benefits in specific contexts where it excels: appetite stimulation, sleep promotion, and rapid onset of antidepressant effects (particularly valuable in palliative care settings). 8, 9