What evidence supports the use of ketamine as a maintenance treatment for bipolar disorder?

Ketamine for Maintenance Treatment in Bipolar Disorder

Ketamine should NOT be used as a standard maintenance treatment for bipolar disorder, as there is no FDA approval, no guideline support, and emerging evidence suggests significant risk of affective switching during long-term use, despite promising acute antidepressant effects.

Current Regulatory and Guideline Status

The FDA has not approved ketamine for any phase of bipolar disorder treatment 1. Established guidelines for bipolar disorder maintenance therapy recommend lithium, lamotrigine, or olanzapine as FDA-approved options 2. Ketamine is conspicuously absent from all bipolar disorder treatment algorithms and guidelines.

Evidence for Acute vs. Maintenance Use

Acute Treatment Data

The most recent high-quality evidence comes from the 2026 Ket-BD randomized controlled trial 3, which demonstrated that 4 ketamine infusions over 2 weeks produced significant antidepressant effects in treatment-resistant bipolar depression (TRBD) compared to midazolam (7.3-point greater MADRS reduction, Cohen d = 0.7, p = .003). This acute efficacy is supported by multiple real-world studies showing rapid symptom improvement 4, 5, 6.

Critical Maintenance Safety Concerns

The evidence reveals a concerning pattern of affective switching during maintenance treatment:

• In the 2024 Yale real-world cohort 7, while NO patients experienced mania/hypomania during acute treatment (twice-weekly dosing), 28.9% (13/45) developed hypomanic or manic symptoms during the maintenance phase, equating to 1 event per 2.7 patient-years
• One severe manic episode required hospitalization 7
• The 2025 maintenance study 4 reported only 1 case (4%) of affective switching in TRBD patients, but this represents limited long-term data

Efficacy During Maintenance

The 2025 real-world study 4 showed that depression and suicidality improvements persisted during maintenance infusions over "several weeks and months" in 25 TRBD patients who initially responded. However, this study lacks:

• A control group
• Standardized maintenance protocols
• Long-term safety data beyond months
• Clear stopping rules 8

Clinical Algorithm for Decision-Making

If considering ketamine for TRBD:

1. Acute Phase Only (Weeks 1-4):

   • Use only after ≥2 failed evidence-based treatments 3
   • Require concurrent mood stabilizer or antipsychotic 3
   • Administer 0.5-0.75 mg/kg IV over 40 minutes, twice weekly for 2-4 weeks 4, 5, 3
   • Monitor closely for dissociative symptoms and vital signs 1

2. Transition Planning (Week 4):

   • If response achieved, transition to FDA-approved maintenance agents (lithium, lamotrigine, olanzapine) 2
   • Do NOT automatically continue ketamine maintenance

3. Maintenance Consideration (Beyond Week 4):

   • Only if patient achieved response but cannot tolerate or failed all FDA-approved maintenance options
   • Reduce frequency substantially (e.g., weekly to every 2-4 weeks) 4
   • Mandatory monitoring at every visit for hypomanic/manic symptoms (increased energy, decreased sleep need, pressured speech, impulsivity) 7
   • Establish clear stopping criteria if any mood elevation emerges 8

Critical Pitfalls to Avoid

1. Assuming acute safety predicts maintenance safety: The switch risk emerges specifically during maintenance, not acute treatment 7

2. Inadequate mood stabilizer coverage: Never use ketamine monotherapy; always maintain therapeutic doses of lithium, valproate, or antipsychotics 3

3. Missing early hypomanic symptoms: The 28.9% switch rate during maintenance 7 demands vigilant monitoring at every encounter

4. Ignoring abuse potential: The FDA label explicitly warns of ketamine dependence, withdrawal syndromes, and abuse liability 1—particularly concerning in long-term use

5. Lack of exit strategy: Without defined maintenance protocols or stopping rules 8, patients may continue indefinitely without evidence of sustained benefit-risk ratio

Evidence Quality Assessment

The strongest evidence (2026 RCT) 3 only evaluated 2 weeks of treatment. The maintenance data comes from observational studies 4, 7 with significant methodological limitations: no control groups, variable dosing protocols, short follow-up periods, and small bipolar-specific samples. The 28.9% affective switch rate during maintenance 7 represents the most clinically significant safety signal and should guide conservative prescribing.

Bottom Line

Use ketamine only for acute treatment-resistant bipolar depression (2-4 weeks maximum) with concurrent mood stabilizers, then transition to FDA-approved maintenance therapies. If maintenance ketamine is considered as a last resort, implement intensive monitoring for mood elevation and establish predetermined discontinuation criteria. The risk-benefit ratio for long-term ketamine maintenance in bipolar disorder remains unfavorable given the substantial switch risk 7 and absence of controlled long-term data.