Why we fast before a ketamine session

An IV ketamine infusion is not general anesthesia, but it sits in the same procedural neighborhood. You receive a sedating medication through an IV. You are monitored by a CRNA. Your level of consciousness shifts during the infusion. For that reason, we apply the same preoperative fasting logic that anesthesia teams use everywhere—not because we expect a problem, but because the consequence of vomiting under sedation is serious enough that the entire field has standardized around prevention.

The core concern is aspiration. If the stomach is full and a patient becomes nauseated under sedation, gastric contents can be inhaled into the lungs. That is uncommon at our dose ranges, but it is preventable, and the prevention is straightforward: do not eat before your appointment. Ketamine is FDA-approved as an anesthetic; its use for depression, PTSD, and chronic pain is off-label, but the safety practices that surround it are the same anesthesia practices used in every operating room in the country.

Patients sometimes ask whether the rules really apply to a 40-minute infusion at 0.5 mg/kg. The honest answer is that the rules were written for a margin of safety, and we honor them across the board. Marla Peterson, CRNA oversees every infusion in our clinic and follows the same intake checks she would for an OR case.

The ASA fasting guideline: 8 hours solids, 2 hours clear liquids

The American Society of Anesthesiologists Task Force on Preoperative Fasting published its current guidelines in Anesthesiology in 2017, with a 2023 update. The framework is simple and worth memorizing if you are a regular ketamine patient.

For our patients, the practical rule we communicate is 8 hours for solids, 2 hours for clear liquids. That builds in a buffer above the 6-hour solids minimum and removes the guesswork about whether last night's pasta counts as light or heavy. If your appointment is at 10:00 a.m., stop solids by 2:00 a.m.—in practice, that means finish dinner the night before and skip breakfast. Clear liquids are fine until 8:00 a.m.

Our intake team will give you the exact times for your specific appointment. If you make a mistake and eat too close to your session, tell us. We may reschedule or adjust the protocol; what we do not do is improvise around an unknown stomach.

What counts as a clear liquid (and what doesn't)

The clear liquid category is more specific than people assume. The ASA defines it as a liquid you can see through that contains no fat, no pulp, and no solid particles. The common ones:

The most common mistake is the morning latte. A splash of cream or oat milk turns coffee into a "solid" for fasting purposes, which means an 8-hour wait, not a 2-hour one. If you cannot do black coffee, switch to tea or skip it. If you absolutely must have your usual latte, finish it before bed the night prior.

Chewing gum is a gray area in the literature; we ask patients to avoid it within 2 hours of the appointment. Hard candy and lozenges count as solids. Smoking and vaping nicotine are not part of the fasting rules but are worth mentioning to the CRNA because nicotine affects heart rate and blood pressure, both of which we monitor during the infusion.

Medications that are usually fine: most antidepressants

The largest piece of medication anxiety we hear from new patients is, "Do I need to stop my antidepressant?" In almost every case, the answer is no.

Andrade's 2017 narrative review in the Journal of Clinical Psychiatry (part 5 of the Ketamine for Depression series) addressed this question directly. The review concluded that most conventional antidepressants—SSRIs, SNRIs, tricyclics, mirtazapine, bupropion—can be safely combined with ketamine at the doses used for psychiatric treatment. There is no robust evidence that taking your morning Zoloft, Lexapro, Effexor, Wellbutrin, or Cymbalta will cause harm or block the response.

A 2021 review by Veraart and colleagues in the International Journal of Neuropsychopharmacology looked specifically at pharmacodynamic interactions between ketamine and psychiatric medications. The authors confirmed Andrade's framework and added nuance for two specific classes that do appear to interact meaningfully—benzodiazepines and lamotrigine, which we cover in the next section.

Our default position: take your morning medications as you normally would. We confirm this on a case-by-case basis during the consult, and we coordinate with your prescribing provider when there is anything unusual in your regimen. Never stop or change a psychiatric medication on your own; the discontinuation effects can be worse than the medication.

Medications that affect the experience: benzodiazepines and lamotrigine

Two psychiatric medication classes have enough evidence behind them that we discuss them specifically.

Benzodiazepines. Andrade 2017 and Veraart 2021 both flagged that concurrent benzodiazepines may diminish the antidepressant benefit of ketamine. The mechanism is plausible—benzos enhance GABA, ketamine's downstream effect involves a glutamate surge that GABA enhancement may dampen—and the clinical signal is consistent across studies. Patients on standing daily Klonopin, Xanax, or Ativan tend to show smaller improvements than patients who are not.

What we do with that information varies. Sometimes we ask a patient to coordinate with their prescriber about timing the benzodiazepine dose later in the day, well after the infusion. Sometimes the daily dose is essential for functioning and we proceed without changes. We never ask a patient to abruptly stop a benzodiazepine; that comes with its own risks, including seizure. The conversation is between you, your prescriber, and our CRNA.

Lamotrigine. Lamotrigine is a sodium channel modulator used for bipolar disorder and some seizure conditions. Veraart's 2021 review noted that it can blunt the dissociative experience during a ketamine infusion. That is not necessarily a clinical problem—some patients find a milder experience preferable—but it is something we want to know in advance so that the infusion is calibrated correctly.

Stimulants, mood stabilizers like lithium and valproate, antipsychotics, and sleep medications all have their own considerations. None of them is an automatic disqualifier. All of them belong on your medication list when you arrive.

CYP3A4 and CYP2B6: why the CRNA asks about specific drugs

Ketamine is metabolized in the liver primarily through two cytochrome P450 enzymes: CYP3A4 and CYP2B6. Drugs that induce these enzymes speed up ketamine clearance and lower its plasma levels. Drugs that inhibit these enzymes do the opposite—ketamine sticks around longer at higher concentrations. Andrade's 2017 review explicitly called out this category as the one with the clearest pharmacokinetic relevance.

Common CYP3A4 inducers (lower ketamine levels):

Common CYP3A4 inhibitors (raise ketamine levels):

None of these means you cannot have a ketamine infusion. It means the CRNA needs to know so that the dose, the monitoring, and the timeline can be adjusted. This is exactly the kind of information that is invisible from a one-line "I take a few things" answer at intake. Bring the actual list.

Supplements, OTC, and the things people forget to mention

The category that catches most patients off guard is supplements and over-the-counter products. The 2018 ASRA/AAPM/ASA consensus guidelines on IV ketamine, authored by Cohen and colleagues in Regional Anesthesia & Pain Medicine, recommend that pre-procedure assessment for IV ketamine include a comprehensive medication review—including supplements and OTC medications. Not "if you remember." Comprehensive.

Things we ask about explicitly, because patients often do not volunteer them:

This is not a recommendation to stop any of these things. It is a recommendation to brief your clinician on what you are actually taking. The conversation lives between you and your prescribing provider; our job is to incorporate that information into a safe ketamine session.

How to brief Marla and the CRNA

The most useful thing you can do before your first infusion is build a single-page medication list and bring it. Format does not matter; completeness does. We suggest these columns:

Include your prescription medications, every supplement, every OTC product you take more than once a week, any cannabis or kratom use, and any substance you used recreationally in the past month. The list becomes the working document for the consult and stays in your chart. Marla, our CRNA, reviews it before every session and updates it as your regimen changes.

For the day of the session, we will send specific fasting instructions tied to your appointment time. Bring your usual morning medications with you if you take them after waking; we will confirm whether to take them with a sip of water or to wait until after the infusion. Wear comfortable clothes. Arrange a driver. Plan your meals around the session with a light dinner the night before and a light meal afterward.

This article is educational, not a recommendation to stop, start, or modify any medication. The point is the conversation. The more accurate the list, the better the session. We would rather you tell us about the kratom and the gummies and the morning latte than discover them later. To learn more about how the clinical infrastructure works, see our pages on how it works and safety.