When Ketamine Is Not Appropriate: Medical and Psychiatric Contraindications

Ketamine can be a powerful treatment for depression, PTSD, anxiety, trauma, and chronic pain. Particularly for individuals who have not responded to traditional medications. When used responsibly, many patients experience relief, clarity, and renewed emotional flexibility.

However, ketamine is not appropriate for every situation or every patient. Safe, ethical ketamine treatment requires recognizing when to prescribe, and just as importantly, when not to.

This guide explains the medical and psychiatric scenarios where I would not prescribe ketamine, and why those boundaries exist.

1. Psychosis or History of Schizophrenia

Ketamine temporarily alters perception and internal-external boundaries. For individuals with a history of psychosis or schizophrenia, ketamine can destabilize them and cause worsening hallucinations, paranoia, or disorganized thinking.

2. Bipolar Disorder Without a Mood Stabilizer

Ketamine can lift bipolar depression, but without a mood stabilizer, it may trigger:

• Mania

• Agitation

• Mixed states (which carry exceptionally high suicide risk)

Bipolar patients must be on a mood stabilizer such as lithium, lamotrigine, or valproate. If there has been recent mania, ketamine is delayed until stable.

3. Acute Suicidality With Immediate Safety Risk

Ketamine often reduces suicidal thinking, but outpatient ketamine requires that the patient can stay safe between sessions.

If there is:

• Active intent

• A plan or accessible means

• Inability to contract for safety

→ Hospital-based or intensive support is the safer first step.

Once safety stabilizes, outpatient ketamine may become appropriate.

4. Uncontrolled Hypertension or Cardiovascular Instability

Ketamine temporarily increases heart rate and blood pressure.

Ketamine is not appropriate for patients with:

• Severe uncontrolled hypertension

• Recent heart attack or cardiac event

• Uncontrolled arrhythmias

Blood pressure and heart must be stabilized first.

5. Moderate to Severe Liver Dysfunction

Ketamine is processed in the liver.
When liver function is compromised, ketamine may accumulate unpredictably.

• Mild impairment → Possible with caution

• Moderate/severe impairment → Contraindicated

6. Active Substance Use Disorder

For patients actively misusing alcohol, stimulants, opioids, or dissociatives, ketamine may:

• Reinforce addictive patterns

• Intensify emotional dysregulation

• Increase relapse vulnerability

Stabilization comes first, then ketamine can be reconsidered safely.

7. Seeking Ketamine Only for “The Experience”

Ketamine is not prescribed for:

• Curiosity or novelty

• A psychedelic “trip”

• Recreational or spiritual tourism

Medical ketamine is a treatment with clinical goals, not a sensation-seeking experience.

A clear medical indication is required.

8. Pregnancy or Breastfeeding

Out of caution and due to possible transfer to the fetus or breastmilk, ketamine is avoided during pregnancy and breastfeeding unless the situation is urgent and medically necessary.

9. Lack of a Safe Home Environment or Peer Supervisor During Treatment

Ketamine temporarily alters awareness, coordination, and sensory interpretation. During the dissociated phase, patients must not be alone.

Ketamine is not prescribed when a patient does not have:

• A quiet, stable, and safe home environment

• A peer supervisor physically present during dosing

• The ability to rest after treatment

• Emotional support between sessions

What the Peer Supervisor Does

A peer supervisor is a calm, trusted adult who stays in the room during the ketamine experience to ensure:

Safety - Prevent walking, falling, or unsafe movements during dissociation

Reassurance - Offer gentle grounding if the patient is confused or anxious
Monitoring - Observe for distress and contact the clinician if needed

Grounding Support - Help the patient return to baseline after the experience

They do not guide the experience or provide therapy — they ensure physical and emotional safety.

When support is in place, ketamine sessions are safer, smoother, and more deeply therapeutic.

10. Medication Conflicts

Some medications reduce ketamine’s therapeutic effect or increase cardiovascular risk.

Benzodiazepines (Xanax, Klonopin, Ativan) — Can blunt ketamine’s antidepressant effects, concurrent use can increase risk of sedation and respiratory depression

High-dose stimulants — Can raise heart rate and blood pressure too high

Clozapine — Sedation and blood pressure instability risk

Recent MAOIs — Risk of hypertensive reaction

These do not always prevent treatment, but they require careful evaluation and planning.

11. Lack of Psychological Support or Integration Resources

Ketamine brings emotional material to the surface. Patients need space and support to process what arises.

If a patient has:

• No therapist

• No support network

• No openness to reflection

We build support first, then reconsider ketamine.

12. Allergy or Hypersensitivity to Ketamine

Rare, but an absolute contraindication.

Conclusion

Ketamine can be transformative, but only in the right clinical context. Safe care means recognizing when ketamine helps, and when the priority is stabilization first. When the foundation is in place, emotional support, safe environment, medication stability, readiness for integration, then ketamine becomes not only safe, but profoundly effective.