Can Lithium Cause Tremors?
Yes, tremor is a well-established and common side effect of lithium therapy that occurs even at therapeutic serum levels, not just in toxicity. 1
Tremor as a Side Effect of Lithium
Tremor is explicitly listed by the FDA as a clinical sign that patients and families should be warned about when starting lithium therapy. 1 The FDA label specifically instructs that patients must discontinue lithium and contact their physician if tremor occurs alongside other signs like diarrhea, vomiting, mild ataxia, drowsiness, or muscular weakness. 1
Classification and Characteristics
- Lithium tremor is classified as a postural tremor, specifically an exaggerated physiologic tremor that occurs with therapeutic lithium use. 2
- The tremor is described as irregular and nonrhythmic, affecting the distal extremities with variable intensity and frequency. 3
- Incidence ranges widely from 4% to 65% depending on how tremor is defined and reported in different studies. 4
Tremor in Toxicity vs. Therapeutic Levels
- Tremor is an early/mild sign of lithium toxicity, appearing alongside nausea, diarrhea, and polyuria-polydipsia. 5
- However, tremor also occurs at therapeutic serum levels and is not exclusively a toxicity phenomenon. 1, 2
- The FDA emphasizes that lithium toxicity is closely related to serum concentrations and can occur at doses close to therapeutic levels, with toxicity risk beginning at 1.5 mEq/L. 6
Important Clinical Considerations
Patients with pre-existing tremor or cerebellar disease warrant special caution, as baseline tremor may lower the threshold for developing more severe movement abnormalities including myoclonus, even at therapeutic lithium levels. 7
- Tremor often decreases with time on lithium in many patients, though it can persist. 4
- Combined therapy with antidepressants (particularly serotonergic agents like paroxetine) significantly increases tremor activity, with the greatest increments occurring approximately 3 weeks after initiating combination treatment. 8
Monitoring Recommendations
- Patients should be evaluated for lithium tremor on a regular basis during ongoing therapy. 4
- Serum lithium concentrations should be checked twice per week during the acute phase until levels and clinical condition stabilize. 6
- Once stable, lithium levels, renal and thyroid function should be monitored every 3-6 months. 9
Management Options When Tremor Occurs
If disabling tremor develops, treatment options include:
- Adjusting the lithium dose or changing the preparation of lithium. 4
- Beta-blocking drugs (particularly propranolol 30-40 mg daily in divided doses) remain effective with long-term administration. 3
- Reducing or eliminating other medications that may contribute, especially NSAIDs which increase lithium levels. 1
- Alternative pharmacologic options include primidone, fatty acids, or potassium supplementation. 4
Critical Warning
Severe tremor may indicate lithium toxicity and requires immediate evaluation of serum lithium levels and assessment for precipitating factors such as dehydration, medication interactions (especially NSAIDs), or renal impairment. 5, 1