Ketamine is not safe for everyone. People with uncontrolled high blood pressure, aneurysms, active psychosis, or a history of schizophrenia are among those who should avoid ketamine therapy. The list extends further depending on your specific health profile, psychiatric history, and what medications you currently take.
Whether you’re considering ketamine infusions for depression, the FDA-approved nasal spray form for treatment-resistant depression, or another therapeutic use, certain conditions create risks serious enough to rule it out entirely.
Cardiovascular Conditions
Ketamine raises blood pressure and heart rate. For most people this is temporary and manageable, but for anyone with an underlying cardiovascular problem, that spike can be dangerous. The conditions that rule out ketamine include uncontrolled hypertension, aortic dissection, aneurysms (in the aorta, brain, or peripheral arteries), arteriovenous malformations, significant heart valve disease, and advanced heart failure.
The FDA-approved nasal spray lists aneurysmal vascular disease as its only absolute contraindication, meaning it is the one condition where the drug must never be given regardless of circumstances.
For blood pressure specifically, most clinics will check your readings before each session. An international consensus panel recommends that patients with a baseline blood pressure above 140/90 should not proceed with treatment. During an infusion, if blood pressure climbs above 160/100, the infusion is typically paused until it drops back down. If you have a history of heart attack or are at significant risk for one, ketamine is generally not an option.
Psychotic Disorders
Ketamine produces dissociative and perceptual changes by design. In someone with schizophrenia or a history of psychotic episodes, these effects can worsen the underlying condition. People with active psychotic symptoms and those with a past history of psychosis are routinely excluded from ketamine treatment, both in clinical trials and in practice.
This applies to psychotic features associated with any diagnosis, not just schizophrenia. If you’ve experienced hallucinations, delusions, or breaks from reality in the past, most providers will consider you ineligible. The concern is theoretical rather than proven in large studies, since these patients have been excluded so consistently that there’s little data on what would actually happen. But the risk is considered too high to test casually.
Active Substance Use
Ketamine itself carries potential for abuse and misuse. The FDA-approved nasal spray is only available through a restricted program specifically because of this risk, requiring patients to be monitored in a healthcare setting for at least two hours after each dose.
Most ketamine clinics screen for active substance abuse, including alcohol, cannabis, and non-prescribed medications. A current substance use disorder is a common exclusion criterion. This doesn’t necessarily mean a distant history of substance use will disqualify you, but active use typically will. Providers want to ensure that introducing a drug with abuse potential doesn’t create a new problem or complicate an existing one.
Medications That Interact With Ketamine
Several commonly prescribed psychiatric medications can interfere with ketamine or create safety concerns when combined with it.
- Benzodiazepines (used for anxiety and sleep) have been repeatedly shown to reduce the duration of ketamine’s antidepressant effect. Higher doses appear to blunt the therapeutic benefit more significantly. If you take a benzodiazepine regularly, your provider may ask you to hold the dose before treatment or may reconsider whether ketamine is the right approach.
- Lamotrigine (a mood stabilizer) may also weaken ketamine’s effects, though findings are mixed.
- MAOIs (an older class of antidepressants) combined with ketamine could theoretically increase blood pressure and heart rate beyond safe levels, or trigger serotonin syndrome, a potentially life-threatening reaction caused by excess serotonin activity.
- Antipsychotics such as risperidone, haloperidol, and clozapine have shown various interactions with ketamine. Clozapine in particular blunted some of ketamine’s effects in patients with schizophrenia, though these patients would typically be excluded from treatment anyway.
Your provider should review all current medications, including opioids and benzodiazepines, before starting treatment. The issue isn’t always danger. Sometimes the interaction simply means ketamine won’t work as well, making it a waste of time and money.
Pregnancy
Ketamine for therapeutic purposes like depression is generally avoided during pregnancy, though the picture is more nuanced than a blanket ban. When ketamine is used as anesthesia during delivery, the amount that passes into breast milk is very low. Studies measuring the drug in breast milk found the relative infant dose was under 1%, which is well below the threshold of concern. Available data suggest that ketamine used for anesthesia in nursing mothers does not appear to affect the breastfed infant.
That said, the manufacturer recommends limiting ketamine use in nursing mothers to anesthesia only, not for ongoing psychiatric treatment. If you’re pregnant or breastfeeding and considering ketamine for depression, the risk-benefit calculation is different from a one-time anesthetic dose.
Allergic Reactions
Ketamine is contraindicated in anyone who has previously had a hypersensitivity reaction to it. Though rare, anaphylaxis and angioedema (severe swelling under the skin) have been reported. If you’ve received ketamine before and had an allergic response of any kind, you should not receive it again.
Children and Older Adults
The FDA-approved nasal spray is not approved for pediatric patients, and the boxed warning specifically notes an increased risk of suicidal thoughts and behaviors in young people taking antidepressants. Most clinical trials for ketamine as a depression treatment have focused on adults between 18 and 65, leaving less data for people outside that range.
A systematic review looking at both adolescents and adults over 60 found that ketamine appeared safe and well-tolerated in these groups, but the evidence base is thinner. Older adults are more likely to have the cardiovascular conditions that make ketamine risky, so extra screening is important even if age alone isn’t a disqualifier.
Eye Pressure Concerns
For decades, ketamine was assumed to raise pressure inside the eye, making it potentially dangerous for people with glaucoma or eye injuries. This belief originated from studies in the 1960s and 1970s, some of which used unusually high doses or studied children who already had glaucoma. More recent research has challenged this assumption. A study measuring intraocular pressure during ketamine sedation at standard doses (up to 4 mg/kg) found no clinically meaningful elevation. None of the patients reached the threshold of 22 mmHg that would signal concern. While some providers still list glaucoma as a precaution, the evidence supporting it as a true contraindication is weak.
Elevated Intracranial Pressure
A similar story has played out with brain pressure. Ketamine was long avoided in patients with traumatic brain injuries out of concern that it would raise intracranial pressure and reduce blood flow to damaged brain tissue. This belief, rooted in older studies, has been largely overturned. A review of seven papers found that none reported adverse events related to elevated intracranial pressure or increased mortality after ketamine use in brain injury patients. Multiple studies found no difference in intracranial pressure between patients receiving ketamine and control groups. Some research even showed a slight decrease in pressure. Current evidence suggests ketamine is safe in this population, particularly when patients are on mechanical ventilation with well-controlled carbon dioxide levels.