Antidepressant Tapering for Psychedelic-Assisted Therapy: A Canadian Clinical Guide

Antidepressant tapering is one of the most clinically consequential decisions in the preparation phase of psychedelic-assisted therapy. SSRIs, SNRIs, MAOIs, and tricyclic antidepressants interact differently with each psychedelic substance — some interactions are clinically irrelevant, some attenuate the therapy, and at least one is life-threatening. This article is a Canadian guide to how antidepressant tapering is approached across ketamine, esketamine, psilocybin, and MDMA-assisted therapy, what the taper itself involves, how discontinuation syndrome is managed, and how coordinated care model coordinates tapers with the patient's existing prescriber.

Key takeaways

• Antidepressant tapering is a medical decision, supervised by a prescribing physician. Patients must not self-taper antidepressants, with or without psychedelic-assisted therapy in the picture.
• Ketamine and Spravato (esketamine) are generally compatible with SSRIs and SNRIs. Patients are typically continued on their oral antidepressant during ketamine and esketamine treatment; the per-label Spravato pathway specifically requires concurrent oral antidepressant.
• Psilocybin and MDMA generally require an SSRI/SNRI taper before dosing because chronic SSRI/SNRI use substantially attenuates subjective effects. Most clinical protocols (Goodwin 2022 COMP001 for psilocybin; Mitchell 2021/2023 MAPP1/MAPP2 for MDMA-AT) require taper.
• MAOIs are a contraindication to psilocybin and an absolute contraindication to MDMA (life-threatening serotonin syndrome / hypertensive crisis risk).
• Discontinuation syndrome is real: dizziness, nausea, "brain zaps," irritability, flu-like symptoms. It is managed with gradual taper rather than abrupt cessation.
• Relapse risk during taper is a substantial clinical concern and is one of the most important reasons taper is prescriber-led.
• ATMA CENA's coordinated care model keeps the existing prescriber primary: the family physician or psychiatrist running the taper does not lose the patient to ATMA CENA; they remain the medication clinician throughout.

Why this matters: different antidepressants, different psychedelics, different rules

Antidepressants and psychedelics both act on serotonergic, noradrenergic, and (in some cases) dopaminergic systems, but their pharmacology is sufficiently different that "antidepressant + psychedelic" is not a single interaction. It is a matrix of interactions, and the matrix matters clinically.

The relevant antidepressant classes are:

• SSRIs (selective serotonin reuptake inhibitors) — fluoxetine, sertraline, paroxetine, citalopram, escitalopram, fluvoxamine
• SNRIs (serotonin-norepinephrine reuptake inhibitors) — venlafaxine, desvenlafaxine, duloxetine
• MAOIs (monoamine oxidase inhibitors) — phenelzine, tranylcypromine, moclobemide (a reversible MAOI-A available in Canada), selegiline
• Tricyclics (TCAs) — amitriptyline, nortriptyline, imipramine, clomipramine, desipramine
• Atypicals — bupropion, mirtazapine, vortioxetine, vilazodone, trazodone

The psychedelic substances accessible in Canadian clinical pathways are:

• Ketamine (off-label psychiatric use of a Health Canada-approved anaesthetic)
• Esketamine / Spravato (Health Canada-approved for treatment-resistant depression since May 2020)
• Psilocybin (Schedule III; clinical access via Health Canada's Special Access Program)
• MDMA (Schedule I; clinical access via Health Canada's Special Access Program)

The interactions below are organized by psychedelic, because the substance is what determines the rule.

Ketamine + SSRI / SNRI: generally compatible

Ketamine's primary mechanism is glutamatergic — NMDA receptor antagonism with downstream AMPA receptor potentiation, BDNF release, and synaptic plasticity changes. This mechanism is pharmacologically distinct from the monoamine-reuptake mechanism of SSRIs and SNRIs.

In clinical practice, ketamine and esketamine are administered alongside ongoing oral antidepressants. Patients are typically not asked to taper their SSRI or SNRI before starting ketamine-assisted psychotherapy or Spravato. Three considerations:

• Pharmacological compatibility: there is no clinically significant pharmacokinetic interaction between ketamine and standard SSRIs or SNRIs at therapeutic doses, and no consistent attenuation of ketamine's antidepressant effect by concurrent SSRI/SNRI use in the published literature.
• Spravato per label: Spravato (esketamine nasal spray) is approved by Health Canada specifically as an adjunct to an oral antidepressant for treatment-resistant depression. The label requires concurrent oral antidepressant. Stopping the oral antidepressant during Spravato treatment is off-label.
• Benzodiazepines are a separate question: there is observational and limited trial-level evidence that benzodiazepines may attenuate the antidepressant effect of ketamine. Benzodiazepines are sometimes held the day of dosing (a clinical decision, not a hard rule), but this is distinct from antidepressant tapering.

For ketamine and esketamine, the answer to "do I need to come off my antidepressant?" is generally no — and for Spravato specifically, the answer is no by label.

Psilocybin + SSRI / SNRI: taper typically required

Chronic SSRI and SNRI use substantially attenuates the subjective effects of psilocybin. The mechanism is downregulation of 5-HT2A receptors with chronic SSRI/SNRI exposure; psilocybin's primary subjective effect is mediated by 5-HT2A agonism. Patients on chronic SSRIs frequently report blunted or absent subjective effects on standard psilocybin doses.

The clinical implication is that most psilocybin protocols require an SSRI/SNRI taper before psilocybin dosing. The Goodwin 2022 COMP001 trial (NEJM, PMID 36322843) and subsequent COMPASS Pathways protocols required SSRI/SNRI washout before dosing. The Carhart-Harris psilocybin-versus-escitalopram trial (Carhart-Harris 2021, PMID 33852780) similarly required participants to be off SSRIs at baseline.

Typical taper-to-washout windows used in clinical protocols:

• Sertraline, paroxetine, citalopram, escitalopram, venlafaxine, duloxetine: gradual taper over 2–4 weeks under prescriber supervision, with washout completed approximately 2 weeks before dosing.
• Fluoxetine: long half-life (~5–7 days for the parent compound, ~7–15 days for the active metabolite norfluoxetine) means clearance takes ~5 weeks after the last dose. Fluoxetine washout is therefore the longest planning window in psilocybin preparation.
• Vortioxetine, vilazodone: serotonergic mechanism; tapered similarly to SSRIs in most protocols.

This is not absolute. Some clinical and research programs are now exploring psilocybin in patients on stable SSRIs (the so-called "SSRI continuation" question), and the Goodwin team and others have signalled interest in characterizing this population. As of this writing, however, the standard of care in Canadian SAP psilocybin pathways is taper before dosing.

Psilocybin + MAOI: typically a contraindication

MAOIs (phenelzine, tranylcypromine, moclobemide, selegiline) inhibit the enzymatic breakdown of serotonin. Co-administration with serotonergic psychedelics carries serotonin syndrome risk. The interaction with psilocybin specifically has less RCT-level data than the MDMA-MAOI interaction, but the conservative clinical position — and the position taken in most SAP psilocybin protocols — is that MAOIs are a contraindication to psilocybin dosing.

Where psilocybin is being considered for a patient on an MAOI, the standard pathway is supervised cross-taper to a non-MAOI antidepressant by the prescribing psychiatrist, followed by a washout window appropriate to the MAOI (typically 2 weeks for irreversible MAOIs; shorter for moclobemide). This is psychiatrist-led work, not a decision the psychedelic-therapy team makes unilaterally.

MDMA + SSRI / SNRI: taper typically required

The interaction between MDMA and SSRIs/SNRIs is well-characterized in both pharmacology literature (Bonson and Murphy and colleagues, 1996; subsequent serotonergic-interaction reviews) and in clinical-trial protocols. Chronic SSRI/SNRI use substantially attenuates MDMA's subjective and therapeutic effects, principally by occupying the serotonin transporter that MDMA uses to release serotonin into the synapse, and by downregulating postsynaptic receptors.

The MAPP1 (Mitchell 2021, PMID 33972795) and MAPP2 (Mitchell 2023, PMID 37640273) phase 3 protocols for MDMA-AT required SSRI/SNRI taper and washout before the first MDMA dosing session. Typical taper windows used in MAPP-style protocols:

• Short-half-life SSRIs/SNRIs (sertraline, paroxetine, citalopram, escitalopram, venlafaxine, duloxetine): 2–4 week taper plus brief washout
• Fluoxetine: longer planning window (~5 weeks total clearance) given long half-life
• Vortioxetine and other serotonergic agents: tapered similarly

The clinical reasoning is twofold: SSRI/SNRI continuation attenuates the MDMA effect (reduced therapeutic benefit), and there is theoretical serotonin-syndrome risk with combined serotonin-releasing and serotonin-reuptake-blocking agents. Both arguments point in the same direction: taper before dosing.

MDMA + MAOI: ABSOLUTE CONTRAINDICATION

MDMA combined with an MAOI carries a substantial risk of life-threatening serotonin syndrome and hypertensive crisis. This is one of the most important medication-safety statements in psychedelic-assisted therapy and it is unambiguous:

MAOI + MDMA is an absolute contraindication.

The pharmacology: MDMA causes massive serotonin release and inhibits its reuptake; an MAOI blocks serotonin's enzymatic degradation. The combination produces synaptic serotonin concentrations that can be lethal. Reported cases include hyperthermia, autonomic instability, seizures, rhabdomyolysis, and death.

In MAPS / MAPP-style MDMA-AT protocols, MAOIs are a hard exclusion. Where MDMA-AT is being considered for a patient on an MAOI, the patient is not advanced into MDMA preparation while still on the MAOI. The pathway is psychiatrist-led cross-taper to a non-MAOI antidepressant, followed by an appropriate washout window — typically 2 weeks for most irreversible MAOIs and shorter for moclobemide (a reversible MAOI-A). After the MAOI washout, separate SSRI/SNRI taper considerations apply if the patient was bridged to a serotonergic agent.

This is the single hardest line in antidepressant tapering for psychedelic-assisted therapy. There are no exceptions in current clinical practice.

MDMA + tricyclic antidepressants: caution

Tricyclic antidepressants (amitriptyline, nortriptyline, imipramine, clomipramine) have varying degrees of serotonergic activity. Clomipramine in particular is strongly serotonergic and is generally treated with the same caution as SSRIs in MDMA-AT protocols. Nortriptyline and desipramine are more noradrenergic and have a different profile. Tricyclics can also affect cardiac conduction (QT interval prolongation), which is a separate concern with MDMA's cardiovascular profile.

In current MAPP-style MDMA-AT protocols, tricyclics are handled case-by-case by the prescribing physician, with most protocols recommending taper before dosing for the more serotonergic agents. This is psychiatric-pharmacology territory and should be coordinated by the prescriber, not generalized.

Tapering principles: gradual, supervised, monitored

Across all these scenarios, the taper itself follows the same general clinical principles:

• Gradual, not abrupt. Antidepressants are tapered, not stopped. Abrupt cessation increases the severity of discontinuation syndrome and the likelihood of rebound symptoms.
• Prescriber-supervised. The taper is run by the prescribing physician — in most Canadian patients this is a family physician or a psychiatrist. The psychedelic-therapy team does not run the taper unilaterally.
• Hyperbolic dose reductions where appropriate. Modern tapering literature (Horowitz and Taylor 2019, Lancet Psychiatry; subsequent Maudsley Prescribing Guidelines updates) suggests that proportional ("hyperbolic") dose reductions — larger reductions at higher doses, smaller reductions at low doses — better match receptor-occupancy curves than fixed linear cuts. This is particularly relevant at the bottom of the taper, where the steepest receptor-occupancy changes occur.
• Symptom monitoring. The prescriber monitors for discontinuation syndrome and for return of the underlying disorder. Frequency of contact varies; weekly or biweekly check-ins are common during active taper.
• Slow down if symptoms emerge. Taper pace is adjusted to symptoms. If discontinuation symptoms emerge, the standard response is to slow the taper, not push through.
• Specific Canadian references. CANMAT antidepressant guidelines (Kennedy et al. 2016 and subsequent updates) and Health Canada product monographs for individual SSRIs and SNRIs provide the underlying clinical framework. The Maudsley Prescribing Guidelines and the Horowitz/Taylor hyperbolic-tapering literature are widely referenced for the taper schedule itself.

Discontinuation syndrome: what it is and how it is managed

Antidepressant discontinuation syndrome is a well-characterized clinical entity that occurs when serotonergic antidepressants are stopped or reduced too quickly. It is distinct from relapse of the underlying disorder.

Common symptoms include:

• Dizziness, lightheadedness, vertigo
• Nausea, gastrointestinal upset
• "Brain zaps" — brief electric-shock-like sensations in the head, often described as the most distinctive symptom
• Irritability, agitation, mood lability
• Flu-like symptoms — fatigue, headache, muscle aches, sweating
• Sleep disturbance, vivid dreams
• Sensory disturbances

Discontinuation syndrome is more common with shorter-half-life SSRIs and SNRIs (paroxetine and venlafaxine are the most-cited offenders) and less common with fluoxetine because of its long half-life. The standard management is gradual taper rather than abrupt cessation, and slowing the taper if symptoms emerge.

It is important to distinguish discontinuation syndrome from relapse. Discontinuation symptoms typically begin within days of dose reduction and resolve within 1–2 weeks. Relapse is the return of the original depressive or anxiety symptoms and follows a different timeline. Differentiating the two is part of why the taper is prescriber-supervised.

Relapse risk during taper: a substantial clinical concern

Tapering an antidepressant in a patient who has been depressed or anxious enough to require pharmacotherapy is, by definition, a period of elevated relapse risk. This is the most important reason taper is prescriber-led and is monitored:

• Some patients tolerate taper without relapse and proceed to psychedelic-assisted therapy as planned.
• Some patients experience emergent depressive or anxiety symptoms during taper that resolve with slower tapering or dose-holding.
• Some patients relapse — and the appropriate response is reinstatement of the antidepressant at an effective dose, not pushing through to dosing.

A taper that triggers relapse is a clinical signal, not a failure of preparation. The prescriber and the psychedelic-therapy team make a joint decision about whether to reinstate, attempt a different taper schedule, switch substances (for example to ketamine, where taper is generally not required), or pause psychedelic-assisted therapy entirely.

This is why patients are screened for acute suicidality, severe current depression, and high relapse risk before being advanced into a taper-required protocol. The preparation phase is partly designed to surface these risks before the patient is mid-taper and destabilized.

Restarting antidepressants after psychedelic dosing

Timing of antidepressant restart after psychedelic dosing is clinical-context-specific. There is no universal rule. Considerations include:

• The substance: psilocybin's residual receptor effects differ from MDMA's; ketamine's mechanism does not involve the same receptor downregulation question.
• Whether further dosing is planned: in protocols with multiple psychedelic doses, the antidepressant typically remains off through the dosing series.
• Clinical course: if the patient is doing well post-dosing and meaningfully improved, the prescriber may delay restart and observe; if symptoms re-emerge, restart is straightforward.
• Coordinated care communication: the timing decision is made jointly by the prescriber and the patient, with input from the psychedelic-therapy team about clinical course in integration.

This is one of several reasons preparation, dosing, and integration are run as a continuous clinical relationship rather than as discrete events.

How ATMA CENA coordinates antidepressant tapering: the coordinated care model

Most ATMA CENA patients arrive with an existing prescribing physician — usually a family physician, sometimes a psychiatrist. ATMA CENA's coordinated care model is built around keeping that prescriber primary:

• The existing prescriber runs the taper. They have the patient's full history, the prescribing relationship, and the Canadian regulatory authority to manage the medication.
• ATMA CENA's clinical team provides the substance-specific framework: which medication interacts with which psychedelic, what taper window the protocol calls for, when the dosing session is planned, and what signals to watch for during taper.
• A structured handoff conversation in preparation makes the coordination explicit. The prescribing physician, the patient, and ATMA CENA's clinical team agree on the taper schedule, the monitoring plan, and the contingencies if relapse or discontinuation symptoms emerge.
• The prescriber stays primary post-dosing as well. They make the restart decision in dialogue with the patient and the integration team.

ATMA CENA's coordinated care model is designed to prevent two failure modes that are common in non-coordinated psychedelic-therapy programs: the patient being asked to taper without prescriber involvement (unsafe), and the patient losing their existing therapeutic and prescribing relationships in the process of accessing psychedelic-assisted therapy (also unsafe, and unnecessary). See ATMA CENA's coordinated care model for the broader model.

Do not self-taper

The single most important practical message of this article: patients must not self-taper antidepressants. Self-tapering — adjusting doses without prescriber supervision, stopping medication abruptly, or "skipping ahead" of a prescribed taper schedule to be ready faster for a psychedelic dosing session — is unsafe. The risks include severe discontinuation syndrome, relapse of the underlying disorder, suicidality, and (for MAOIs especially) catastrophic interactions if the patient then proceeds to psychedelic dosing without an adequate washout.

If you are on an antidepressant and considering psychedelic-assisted therapy, the next step is a conversation with your prescribing physician, in coordination with the psychedelic-therapy clinical team. It is not a self-managed taper.

Frequently asked questions

I'm on sertraline. Do I need to come off it before psychedelic-assisted therapy? It depends on the substance. For ketamine or Spravato, generally no — patients are continued on sertraline. For psilocybin or MDMA-AT, generally yes — most clinical protocols require an SSRI taper, run by your prescribing physician over approximately 2–4 weeks plus a brief washout window. Your prescriber makes the decision.

I'm on fluoxetine. Why is the timeline longer? Fluoxetine has a long half-life (~5–7 days for the parent compound, ~7–15 days for the active metabolite), so clearance after the last dose takes approximately 5 weeks. Psilocybin and MDMA preparation timelines for fluoxetine patients are correspondingly longer.

I'm on an MAOI. Can I do MDMA-assisted therapy? Not while on an MAOI. MAOI + MDMA is an absolute contraindication because of life-threatening serotonin syndrome and hypertensive crisis risk. The pathway is a psychiatrist-led cross-taper from the MAOI to a non-MAOI antidepressant, followed by an appropriate washout window before MDMA preparation begins.

I'm on bupropion. Is that a problem? Bupropion is a noradrenergic-dopaminergic agent, not a serotonergic antidepressant, and is generally handled differently from SSRIs/SNRIs in psychedelic protocols. Cardiovascular and seizure-threshold considerations are reviewed by the prescriber. Specific decisions are case-by-case.

Can I just stop my antidepressant? No. Abrupt cessation of SSRIs, SNRIs, or MAOIs is unsafe and increases the severity of discontinuation syndrome and relapse risk. Tapering is gradual and is supervised by the prescribing physician.

What is "discontinuation syndrome"? A well-characterized cluster of symptoms — dizziness, nausea, "brain zaps," irritability, flu-like symptoms — that occurs when serotonergic antidepressants are stopped or reduced too quickly. It is managed with gradual taper and resolves with reinstatement or slower tapering. It is distinct from relapse.

What if I relapse during the taper? Reinstatement of the antidepressant is the appropriate clinical response. The prescriber and the psychedelic-therapy team make a joint decision about whether to attempt a slower taper later, switch to a substance that does not require taper (for example ketamine), or pause psychedelic-assisted therapy. Relapse during taper is a clinical signal, not a failure of preparation.

Will my antidepressant be restarted after the psychedelic dosing session? That depends on substance, clinical course, and your prescriber's judgment. There is no universal rule. The decision is made in coordinated care between the prescriber, the patient, and the clinical team during integration.

Who runs the taper — ATMA CENA or my family doctor? Your prescribing physician runs the taper. ATMA CENA's clinical team provides the substance-specific framework, coordinates timing with preparation, and supports the patient through the process — but the medication decisions stay with the prescriber. This is the coordinated care model.

Compliance disclaimer

This article is educational. Psilocybin and MDMA are Schedule III and Schedule I controlled substances in Canada respectively; clinical access in Canada is via Health Canada's Special Access Program on a case-by-case basis. Ketamine is a Health Canada-approved anaesthetic; psychiatric use is off-label and within Canadian off-label prescribing principles. Esketamine (Spravato) is Health Canada-approved for treatment-resistant depression. Tapering antidepressants is a medical decision made by a qualified prescribing physician and cannot be safely self-managed by the patient. Nothing in this article constitutes a clinical recommendation for any specific individual; medication decisions belong with the prescribing physician, in coordination with the psychedelic-therapy clinical team where applicable.

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Related articles

• The Preparation Phase of Psychedelic-Assisted Therapy
• Set and Setting in Psychedelic-Assisted Therapy
• Dosing Protocols Across Substances
• The Health Canada SAP Application Process — Complete Guide
• MDMA-Assisted Therapy: Side Effects and Safety
• Psilocybin: Side Effects and Safety
• ATMA CENA's coordinated care model — how ATMA CENA layers onto an existing prescribing relationship
• Psilocybin Therapy in Canada
• MDMA-Assisted Therapy in Canada
• Ketamine Therapy in Canada

Last updated: 2026-05-06