Can lithium cause akathisia?

Lithium Can Cause Akathisia, Though It Is Rare

Yes, lithium can cause akathisia, but this is an uncommon side effect that is not typically emphasized in standard monitoring protocols for lithium therapy. While akathisia is well-established as a side effect of antipsychotic medications, lithium-induced akathisia represents a rare but documented adverse effect that clinicians should recognize 1, 2.

Evidence from FDA Labeling and Clinical Guidelines

The FDA drug label for lithium lists "restlessness" among its adverse reactions under the neuromuscular and central nervous system categories, though it does not explicitly use the term "akathisia" 1. The label describes various neurological side effects including tremor, muscle hyperirritability, ataxia, and psychomotor symptoms that can occur independent of serum lithium levels.

Importantly, the major clinical guidelines for bipolar disorder management in children and adolescents do not specifically mention akathisia as a lithium side effect 3. These guidelines focus primarily on lithium's more common adverse effects including:

• Tremor and polyuria
• Thyroid dysfunction
• Renal effects
• Weight gain
• Gastrointestinal symptoms

Clinical Case Evidence

The strongest evidence for lithium-induced akathisia comes from case reports. A 2021 case report documented a 49-year-old woman who developed akathisia shortly after starting lithium carbonate 600 mg/day for mood stabilization 2. Critically, her akathisia was treatment-resistant—it did not respond to reducing risperidone dose, propranolol, or lorazepam (the standard treatments for akathisia). The akathisia only resolved when lithium was discontinued and replaced with valproic acid 2.

An earlier 1995 case report described lithium-induced akathisia that responded to low-dose mianserin (15 mg/day), suggesting a serotonergic mechanism since lithium activates serotonergic neurotransmission 4.

Distinguishing Lithium-Induced Akathisia from Antipsychotic-Induced Akathisia

This distinction is clinically crucial because:

Akathisia from antipsychotics is well-characterized in guidelines as "a subjective feeling of restlessness frequently manifest as pacing or physical agitation, commonly seen in patients treated with antipsychotics" 5. It typically:

• Occurs within the first few days of antipsychotic therapy 6
• Responds to dose reduction, beta-blockers, or benzodiazepines 5
• Is often misinterpreted as psychotic agitation or anxiety 5

Lithium-induced akathisia appears to:

• Be much rarer
• Potentially be treatment-resistant to standard akathisia interventions 2
• Require lithium discontinuation for resolution 2

Clinical Management Algorithm

If akathisia develops in a patient on lithium:

1. First, determine if the patient is also on antipsychotics (common in bipolar disorder treatment). Many patients receive combination therapy with lithium plus antipsychotics 3.

2. If on antipsychotics: The akathisia is most likely antipsychotic-induced. Try standard treatments:

   • Reduce antipsychotic dose if clinically feasible
   • Add propranolol (beta-blocker) or benzodiazepines 5
   • Consider switching to a lower-potency antipsychotic

3. If on lithium monotherapy or if akathisia persists despite antipsychotic management:

   • Consider lithium as the causative agent 2
   • Check lithium level (though akathisia can occur at therapeutic levels)
   • Be aware that standard akathisia treatments may not work 2
   • Consider switching to an alternative mood stabilizer (valproate, lamotrigine) 2

4. Monitor closely after any medication change as discontinuing lithium carries significant relapse risk—over 90% of non-compliant adolescents relapsed in one study 3.

Critical Clinical Pitfall

The most important pitfall is misattributing akathisia to psychotic agitation or anxiety rather than recognizing it as a medication side effect 5. This is particularly problematic because:

• It may lead to inappropriate dose increases of antipsychotics
• It is a common reason for medication non-compliance 5
• Patients may have difficulty articulating the subjective restlessness, especially younger patients 5

When lithium is the cause, standard akathisia treatments may fail, and clinicians must consider the rare possibility of lithium-induced akathisia and be prepared to switch mood stabilizers 2.

Monitoring Recommendations

While routine monitoring for lithium focuses on renal function, thyroid function, and lithium levels every 3-6 months 3, clinicians should specifically ask about subjective restlessness and observe for pacing or motor agitation at each visit, recognizing this as a potential lithium side effect even though it is not emphasized in standard guidelines.