Coexisting conditions and clinical referral

Learning Objectives

By the end of this module, the trainee will be able to:

• State the boundary of the facilitator's role in this criterion: to recognize coexisting conditions and route them to the right professional, not to diagnose or treat them.
• Explain the mechanism of serotonin syndrome as it arises from ayahuasca combined with serotonin increasing medication, at the level of monoamine oxidase A inhibition and synaptic serotonin.
• Describe the Hunter Serotonin Toxicity Criteria as a clinical recognition framework derived and validated in serotonergic overdose populations, recognize its examination features, and explain its limits outside that context.
• Describe the cardiac liability of ibogaine at the level of the QT interval and the mechanism of torsades de pointes, and state the screening and monitoring it requires.
• Use a medication interaction framework to identify the drug classes that most often change or halt a plan, including selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, lithium, and tramadol.
• Distinguish pharmacodynamic from pharmacokinetic interactions, and give an example of each as it applies to psychedelic work.
• Identify the medical comorbidities that require clearance before proceeding, and distinguish psychiatric conditions that are contraindications from those that are indications.
• Distinguish the interaction profiles of the major compound classes, classic serotonergic psychedelics, MDMA, ketamine, ayahuasca, and ibogaine, well enough to know what a medication review is protecting against in each case.
• Apply the medical-intervention threshold, distinguishing medical care that is separable from the administration (often lawful, and best routed through the client's own treating team) from care that is inseparable from it (which cannot be made lawful and safe together, and is a stop), and route the legal question to counsel (see Criterion 41).
• Complete a structured coexisting-conditions review and a defensible referral, coordinated with the prescriber.

Key Terms

The medical-intervention threshold. The rule that where safe participation requires a medical intervention (ECG and cardiac monitoring, electrolyte management, intravenous access, a prescriber-supervised washout), that requirement is the practice of medicine, which an unlicensed facilitator may not provide. Whether a clinician may lawfully provide it turns on separability. Taught in full at Criterion 41.

Separable and inseparable medical care. Separable care stands on its own clinical footing and does not require the clinician to handle or administer the substance (pre-session cardiac clearance, a prescriber managing the client's own medication, a contracted clinician on site for emergency response), and is frequently lawful and often the right arrangement. Inseparable care functions only if delivered during and as an integral part of the administration (continuous cardiac monitoring with IV access through an ibogaine session), which makes the clinician a participant in an unlawful act where the substance is Schedule I. Even separable arrangements can carry clinician exposure, which is a question for counsel.

Coexisting condition. Any medical, psychiatric, or pharmacological factor present alongside the person's reason for seeking the work that alters risk or requires additional expertise to manage safely.

Serotonin syndrome (serotonin toxicity). A spectrum of toxicity involving neuromuscular excitation, autonomic changes, and altered mental status. Severe toxicity can be life threatening. Concurrent MAO inhibition with serotonin releasing or reuptake inhibiting agents is a major interaction concern; the label “serotonergic” alone does not establish equivalent risk (Malcolm & Thomas, 2022; Chiew & Isbister, 2025).

Hunter Serotonin Toxicity Criteria. Widely used clinical recognition rules derived and tested in patients admitted after serotonergic drug overdose. Clonus, hyperreflexia, agitation, sweating, tremor, hypertonia, and temperature elevation inform the pattern. Their reported diagnostic performance belongs to that toxicology population; they are not a universally validated rule for every therapeutic medication or psychedelic exposure (Dunkley et al., 2003; Chiew & Isbister, 2025).

Clonus. Rhythmic involuntary muscle contractions that may be inducible, spontaneous, or ocular. It is an important discriminating feature in the Hunter framework. Its absence does not independently rule out toxicity, and marked rigidity can obscure it. Examination and differential diagnosis belong to qualified clinicians (Dunkley et al., 2003; Chiew & Isbister, 2025).

Monoamine oxidase inhibitor (MAOI). A drug that blocks the enzyme monoamine oxidase, raising synaptic monoamine levels. The harmala alkaloids in ayahuasca act as reversible MAO-A inhibitors, which is what renders oral DMT active (Ruffell et al., 2020; Halman et al., 2024).

QT prolongation. A lengthening of the cardiac QT interval, the time from ventricular depolarization to repolarization, that raises the risk of the ventricular arrhythmia torsades de pointes. Ibogaine is a known QT-prolonging agent (Cherian et al., 2024).

Torsades de pointes. A polymorphic ventricular tachycardia that can arise on a prolonged QT interval and can degenerate into ventricular fibrillation and sudden cardiac death. It is the specific arrhythmia the ibogaine cardiac precaution is designed to prevent.

Pharmacodynamic interaction. An interaction in which agents affect the same physiological system, producing an additive, synergistic, or opposing effect. An example is an SSRI reducing serotonin reuptake while an MAOI reduces serotonin breakdown, increasing serotonin toxicity risk. Receptor adaptation is also pharmacodynamic.

Pharmacokinetic interaction. An interaction that changes the absorption, distribution, metabolism, or elimination of a drug, altering its concentration and duration, for example competition at cytochrome P450 enzymes (Halman et al., 2024).

Washout. A clinician-directed interval after a medication is discontinued, when clinically appropriate, allowing drug concentrations or persistent effects to diminish. Timing depends on elimination and, for irreversible enzyme inhibition, enzyme recovery. A washout is not automatically required for every interaction; medication changes require the prescribing clinician and an appropriately qualified psychedelic medicine clinician.

Scope of practice. The set of activities a practitioner is trained, competent, and authorized to perform. Recognizing the edge of one's scope and referring beyond it is the core skill of this criterion.

Core Teaching

The facilitator's role: recognize and route

This criterion defines a boundary as much as a task. A facilitator is not being asked to diagnose or treat coexisting conditions. They are being asked to recognize them and route the person to the professional who can. The most dangerous errors in this field cluster at exactly this point: a facilitator either fails to detect a condition that changes the risk profile or detects it and proceeds anyway rather than referring. The pharmacology here is unforgiving, and it does not care about good intentions. This module pairs with Criterion 1, which surfaces these conditions during readiness screening; Criterion 2 is the discipline of routing them correctly.

Clinically important serotonin toxicity interactions

Ayahuasca combines DMT with harmala alkaloids that act as reversible MAO-A inhibitors. MAO inhibition substantially alters DMT pharmacokinetics by reducing its metabolism and making orally administered DMT bioavailable. This interaction is fundamental to ayahuasca pharmacology. Risk assessment must account for the MAOI involved, DMT exposure, cardiovascular effects, and any additional serotonergic medications or substances. For medications or substances that substantially increase intrasynaptic serotonin, including SSRIs, SNRIs, MDMA, tramadol, and other serotonin releasing or serotonin reuptake inhibiting agents, concurrent MAO inhibition can substantially increase the risk of serotonin toxicity. Some combinations are contraindicated and require prescriber directed management. For example, an SSRI reduces serotonin reuptake while MAO-A inhibition reduces its breakdown. This mechanism is different from direct serotonin receptor agonism (Malcolm & Thomas, 2022; Halman et al., 2024; Sarparast et al., 2022).

A randomized placebo-controlled trial reported rapid antidepressant effects of ayahuasca in treatment-resistant depression (Palhano-Fontes et al., 2019). People will seek this work, and some will arrive on antidepressants. The facilitator who does not obtain and review the full medication list, by name, is not competent to sit with ayahuasca, because the hazard is a property of the pharmacology and no amount of ceremony changes it.

Recognizing serotonin toxicity: the Hunter criteria

Recognition is the facilitator’s task; diagnosis and management belong to qualified medical care. Serotonin toxicity is a clinical assessment rather than a serum serotonin test. The Hunter Serotonin Toxicity Criteria are widely used for pattern recognition, but were derived from 473 SSRI alone overdose admissions and tested against 2,222 serotonergic overdose admissions, including that derivation group. Their higher sensitivity and specificity than Sternbach criteria were demonstrated in that overdose context, not universally across therapeutic or psychedelic exposures (Dunkley et al., 2003). With a pharmacologically relevant exposure, the Hunter patterns are spontaneous clonus; inducible clonus with agitation or diaphoresis; ocular clonus with agitation or diaphoresis; tremor with hyperreflexia; or hypertonia with temperature above 38 degrees Celsius and ocular or inducible clonus. Other causes of these findings and the clinical trajectory must be assessed, and severe rigidity can obscure clonus. Toxicity ranges from mild manifestations to severe, life threatening illness. Severe toxicity, especially rapidly rising temperature and rigidity, is a medical emergency. In nonmedical facilitation settings, suspected toxicity warrants prompt medical assessment because facilitators should not independently determine severity or manage a potentially evolving syndrome. Activate the emergency pathway for the concerning patterns described here rather than waiting to complete a diagnostic checklist (Chiew & Isbister, 2025).

The cardiac liability: ibogaine and the QT interval

Ibogaine carries a separate and equally severe risk that is cardiac rather than serotonergic. It prolongs the QT interval, the electrocardiographic measure of the time the ventricles take to depolarize and repolarize. A prolonged QT interval is the substrate for torsades de pointes, a polymorphic ventricular tachycardia that can degenerate into ventricular fibrillation and sudden death. This is the specific pathway from an abnormal tracing to a fatal event, and it is why the QT number is not a formality. In a prospective observational study of magnesium-ibogaine therapy in veterans with traumatic brain injury, magnesium was given with the intention of reducing cardiac risk, alongside screening and monitoring (Cherian et al., 2024). Without a control group, the study cannot establish that magnesium prevented QT prolongation or cardiac complications. The operational consequence is strict. Any program working with ibogaine that lacks pre-treatment cardiac screening, continuous cardiac monitoring during administration, and genuine emergency capability is operating outside the bounds the evidence permits. This is not a setting a facilitator improvises.

The medical-intervention threshold: when the required safeguard cannot lawfully be supplied

Everything this criterion requires has an uncomfortable implication that should be stated plainly, because a facilitator who follows the workup faithfully will otherwise walk into it unprepared. Look at what the safeguards in this criterion actually are. A baseline electrocardiogram and an assessment of the QT interval is a medical investigation. Cardiology clearance and continuous cardiac monitoring during administration is medical care. Correcting and maintaining electrolytes, and holding intravenous access against a possible arrhythmia, is medical care. A washout of a serotonergic antidepressant before an ayahuasca-type brew is medication management, directed by a prescriber, and it is medical care. Each of these is the practice of medicine rather than an adjunct to a ceremony, and none of them may lawfully be performed by an unlicensed facilitator. That, by itself, is why this criterion routes rather than manages. The harder point sits one step further on. In the United States, a licensed clinician cannot lawfully administer, dispense, or prescribe a Schedule I substance outside federally authorized research, which includes psilocybin, MDMA, the DMT in ayahuasca, and ibogaine. So when the workup in this criterion identifies a client whose safe participation depends on a medical intervention, the intervention that would make them safe cannot lawfully be attached to the substance they are seeking. An unlicensed facilitator who supplies it is practicing medicine without a license. And a licensed clinician who administers the substance, or whose care is delivered as an integral part of administering it, is working with a Schedule I substance unlawfully, and risks the protection of the credential that made them competent to help, together with their professional liability cover. The safeguard that would make the client safe cannot simply be arranged in the way an ordinary medical referral can.

That statement needs a distinction, because in practice the picture is less uniform than a flat prohibition suggests, and the distinction is the one a facilitator should actually reason with. The question is whether the medical care is separable from the administration of the substance. Separable medical care stands on its own clinical footing and does not require the clinician to handle, administer, or participate in giving the substance. A cardiologist who evaluates a client and assesses their QT interval is practicing ordinary medicine. A prescriber who manages a client's antidepressant, or who supervises a taper for legitimate clinical reasons the patient independently has, is practicing ordinary medicine. A physician or paramedic contracted to be on site and to respond to a medical emergency, as they would at any gathering, is providing emergency care rather than administering a controlled substance. Care of this kind is frequently lawful and is often the right answer, and organizations do contract clinicians on precisely this basis. Inseparable medical care is different in kind. Continuous cardiac monitoring with intravenous access and electrolyte management through an ibogaine session is not standby emergency cover; the safeguard only functions if it is delivered during the administration and as an integral part of it, which makes the clinician a participant in the administration rather than a bystander to it. Where the safeguard is inseparable from the unlawful act, the claim that the clinician never touched the substance is thin cover, and the exposure is real.

Two honest qualifications belong with that distinction. The first is that separability mitigates the problem rather than dissolving it. A clinician who provides care in and around a setting where a Schedule I substance is being administered may still face exposure that this workbook is not competent to adjudicate, including questions of aiding and abetting, professional licensing-board discipline, and the exclusion of unlawful activity from professional liability coverage. Whether a given arrangement is defensible is a legal question with real consequences for the clinician, and it belongs with an attorney rather than with a facilitator's judgment, which is the raise-and-route discipline taught in Criterion 41. The second qualification is more constructive, and it points to what a facilitator should generally do. Where a client has a medical condition or a medication that bears on their safety, the most appropriate route is frequently to bring the client's own treating team into the process: the prescriber who knows their psychiatric medication, the cardiologist who knows their heart, the physician who manages their blood pressure. That care is separable by nature; it is already lawful, it is already established, and it improves the quality of the decision rather than merely satisfying a form. Coordinating with the client's existing providers, with consent, is the same care-coordination discipline the workbook builds elsewhere, and it is the version of medical involvement that is both lawful and genuinely protective. What remains true after all of this is the core of the threshold: where the safeguard a client needs can only be delivered as part of the administration itself, and the substance is Schedule I, there is no arrangement that makes that lawful and safe together, and the finding is a stop and a routing to a lawful setting rather than a logistics problem to be solved. The full legal structure, and the duty to convey it to clients, is taught in Criterion 41. What belongs here, in the screening function, is the recognition that a required medical safeguard is a gate, that separable care can often be arranged lawfully and should be, and that inseparable care cannot be.

Other medication interactions that change the plan

Beyond those two, several drug classes recur as decision points. Lithium combined with classic psychedelics has been associated with seizures and warrants specific inquiry rather than a general medication question (Johnson, Richards, & Griffiths, 2008; Halman et al., 2024). Prescribed MAOIs require compound specific review: psilocybin and LSD cannot be assigned the same serotonin toxicity mechanism as serotonin releasing or reuptake inhibiting agents. MDMA should not be grouped with classic psychedelics in this interaction category. Because MDMA substantially increases extracellular serotonin and other monoamines, concurrent MAO inhibition presents a serious toxicity risk. Tramadol inhibits serotonin reuptake and lowers the seizure threshold; it belongs in a complete medication review even when used for pain. At the pharmacodynamic level, chronic SSRI exposure may alter psychedelic response through changes in serotonergic receptor expression, signaling, and adaptation. Pharmacokinetic interactions should be discussed separately and limited to processes involving absorption, distribution, metabolism, and elimination. For example, inhibition or induction of a relevant cytochrome P450 enzyme may change the exposure and duration of a drug metabolized through that pathway. Effects on psychedelic response vary by drug and study; receptor adaptation does not establish a uniform degree or duration of blunting (Malcolm & Thomas, 2022; Halman et al., 2024; Sarparast et al., 2022).

Pharmacodynamic and pharmacokinetic: why the distinction is practical

Pharmacodynamic interactions change effects on a physiological system. Combining serotonin reuptake inhibition with reduced serotonin breakdown can substantially increase serotonin toxicity risk. Direct receptor agonism is a different mechanism, so psilocybin or LSD plus an MAOI cannot be evaluated from the word “serotonergic” alone. Pharmacokinetic interactions change drug exposure through absorption, distribution, metabolism, or elimination. For example, inhibition of an enzyme involved in a psychedelic’s metabolism may increase or prolong exposure and change risk. MAO inhibition reducing DMT metabolism is another pharmacokinetic example. Both kinds of interaction require review of the specific drugs, doses, other exposures, and clinical context. Medication decisions belong to the prescribing clinician in coordination with an appropriately qualified psychedelic medicine clinician; a facilitator does not direct discontinuation or a washout (Malcolm & Thomas, 2022; Halman et al., 2024; Sarparast et al., 2022).

Medical comorbidities that require evaluation

The medical conditions that most often require clearance before proceeding are cardiovascular disease and uncontrolled hypertension, given the sympathomimetic load these compounds place on the system (Johnson, Richards, & Griffiths, 2008); seizure disorders, given the lowered threshold some combinations produce; and hepatic or renal impairment, given their effect on drug clearance. Metabolism is not an abstraction here. Psilocybin is a prodrug, rapidly dephosphorylated to its active form psilocin, which is then cleared hepatically, so significant hepatic impairment can alter exposure and duration (Nichols, 2016). Pregnancy is a standard exclusion in the absence of safety data. None of these findings is the facilitator's to manage alone. Each is a trigger for medical evaluation.

Psychiatric comorbidities: contraindication or indication

Risk related to bipolar spectrum disorders, mania, and psychosis must be evaluated in relation to the specific intervention. Different psychedelic and psychedelic adjacent compounds act through different pharmacological systems and cannot be assigned a single serotonergic mechanism of psychiatric risk. Current mood state, history of mania or psychosis, medication regimen, sleep disruption, substance use, family history, and compound specific evidence should inform screening and clinical decision making. Active psychosis, mania, or acute suicidality calls for clinical assessment before a proposed session. Stable histories and family history may warrant specialist review or exclusion under a particular protocol; trial exclusions do not establish identical risk across compounds. Ketamine has been investigated in bipolar depression with mood stabilizing treatment, using small controlled and open label studies (Bahji et al., 2021). Depression, anxiety, and post traumatic stress may be reasons people seek treatment, with evidence specific to the intervention (Davis et al., 2021; Mitchell et al., 2021). A facilitator recognizes symptoms and routes the case to appropriately qualified psychiatric care; they do not diagnose or settle medication suitability.

A note on compound classes

The interactions above are not uniform across every substance, because the compounds are not pharmacologically identical, and a medication review is only protective if the reviewer knows what class they are working with. The classic serotonergic psychedelics, psilocybin, LSD, DMT, act primarily through 5-HT2A agonism. MDMA is an entactogen that acts largely by releasing serotonin, dopamine, and norepinephrine, which gives it a heavier serotonergic load than the classic agonists and its own 5-HT2B considerations relevant to cardiac and valvular risk (McIntyre, 2023); a recent analysis comparing repeated low-dose exposure to known cardiotoxins argues the theoretical valvular risk of chronic 5-HT2B agonism should not be dismissed (Rouaud, Calder, & Hasler, 2024). Ketamine is a dissociative NMDA receptor antagonist with a different interaction profile entirely, weighted toward blood pressure, bladder, and dependence considerations rather than serotonergic ones. Ayahuasca adds the MAO-A inhibition discussed above. Ibogaine adds the QT liability. A facilitator does not need to be a pharmacologist, but they do need to know which class they are working with and which interactions that class carries, because the medication review is only as good as the questions the reviewer knows to ask.

Clinical and Decision Tools

Tool 1. Medication and substance interaction matrix

Review every entry on the person’s medication and supplement list against this matrix. High concern findings defer the proposed psychedelic session pending prescriber and medical coordination. “Stop” below refers to the proposed session, never to stopping prescribed medication. Limited evidence is not evidence of safety, and this matrix does not provide individual clearance.

Tool 2. Serotonin syndrome recognition (Hunter criteria)

Serotonin toxicity exists on a spectrum; severe toxicity is a medical emergency. The Hunter patterns below provide useful recognition features and were derived and validated in overdose populations, not all therapeutic medication or psychedelic exposure settings. A facilitator does not diagnose toxicity, rule it out, or decide that a suspected case is mild enough to manage independently. Suspected toxicity in a nonmedical setting warrants prompt medical assessment; activate the emergency response for these concerning patterns. Onset can be within hours of an interacting exposure (Dunkley et al., 2003; Chiew & Isbister, 2025).

Tool 3. Compound-specific required workup

Read this tool with the threshold in mind. The required workup states what safety demands. It does not make an unlawful setting safe. Ask whether the medical care is SEPARABLE from the administration. Separable care (cardiac clearance beforehand, a prescriber managing the client's own medication, a contracted clinician on site for emergency response) does not require the clinician to handle or administer the substance, is frequently lawful, and is often the right answer; involving the client's own treating team is usually the best route. INSEPARABLE care (continuous cardiac monitoring with IV access and electrolytes delivered during and as part of an ibogaine administration) makes the clinician a participant in an unlawful act, and there is no arrangement that makes it lawful and safe together. That finding is a stop and a routing to a lawful setting rather than a task to arrange. Even separable arrangements can carry clinician exposure (aiding and abetting, board discipline, liability-cover exclusions), which is a question for an attorney. Ketamine is the contrast: prescribable, so the safeguard and the law coexist. See Criterion 41.

Tool 4. Interaction type and matched response

Sort each flagged interaction into its type to choose the correct next step.

Tool 5. Referral decision guide

Each finding below is a trigger for referral, not for facilitator management. Route with clear reasoning and, with signed release, coordinate with the receiving professional.

Cardiac finding or QT concern: cardiology evaluation and clearance.

Serotonergic or interacting medication: the prescribing clinician, coordinating with an appropriately qualified psychedelic medicine clinician, for compound specific review of interactions, withdrawal risk, and whether any medication change or deferral is appropriate.

Psychiatric contraindication or ambiguity: psychiatric evaluation.

Hepatic, renal, or seizure history: primary care or the relevant specialist.

Signs of serotonin toxicity in session: emergency medical services, immediately; this is not a referral for later.

Worked Examples: Completed Coexisting-Conditions Reviews

The following models the reasoning and documentation this criterion should produce. Details are fictional.

Worked Example 1: A serotonergic stop-and-refer

Client: J.T., 47, seeking ayahuasca work for depression and grief.

Medication and supplement review: Reports sertraline 100 mg daily, prescribed for two years. Also takes a magnesium supplement and occasional over-the-counter ibuprofen. No other agents.

Interaction analysis: Sertraline is a selective serotonin reuptake inhibitor. Ayahuasca contains harmala alkaloids acting as MAO-A inhibitors. The combination stacks reduced serotonin reuptake against reduced serotonin breakdown, a pharmacodynamic serotonergic collision that carries a serotonin syndrome risk. This is a hard stop, not a matter for negotiation (Ruffell et al., 2020; Halman et al., 2024).

Medical review: No cardiac history; blood pressure normal on two readings. No hepatic or renal concerns reported.

Psychiatric review: No personal or family history of psychotic or bipolar disorder. Depression and grief are the presenting reasons, not exclusions.

Decision and referral: Defer the proposed ayahuasca session. The prescribing clinician and an appropriately qualified psychedelic medicine clinician review the sertraline interaction, treatment needs, and risks of changing medication. Continuing necessary treatment may mean the proposed session is inappropriate; a taper or washout is not an automatic next step. Any medication change belongs to the prescriber. Reassessment depends on the documented clinical plan and the person’s stability, not a self-selected stop date. Document the rationale and, with signed release, share it with the prescriber.

Worked Example 2: An ibogaine cardiac gate

Client: A.R., 39, seeking ibogaine for opioid use disorder after multiple relapses. Highly motivated, reports being in good health.

Medication and supplement review: Takes an over-the-counter proton pump inhibitor for reflux and, on inquiry, an antiemetic obtained abroad whose name they do not know. No prescribed psychiatric medication.

Interaction and cardiac analysis: Ibogaine prolongs the QT interval and can precipitate torsades de pointes. The unnamed antiemetic is a specific concern, since several antiemetics are themselves QT-prolonging, which would be additive. No electrocardiogram has ever been done, so the baseline QT is unknown. This is a stop pending cardiac workup (Cherian et al., 2024).

Decision and referral: Do not proceed. Identify the antiemetic by name before anything else. Refer for cardiology evaluation including a baseline ECG and electrolytes. State plainly that ibogaine without pre-treatment cardiac screening, continuous monitoring, and emergency capability is outside the bounds the evidence supports, and that this program will not provide it without those elements in place. Document the reasoning. Note that opioid use disorder is a serious condition in its own right and warrant its own care pathway regardless of the ibogaine decision.

Case Vignettes

Work each vignette through the medication, medical, and psychiatric reviews, decide whether to proceed, defer, or refer, and identify precisely who must be involved. Fillable response sheets are in the companion worksheet PDF.

Vignette A

A person requests an ayahuasca retreat and, during the medication review, mentions they take an antidepressant but cannot remember its name and describes it as mild.

Guided questions: Why is not knowing the name unacceptable here? What is the specific mechanism you are screening for, and which interaction type is it? What has to happen, and who has to be involved, before this person could safely proceed?

Vignette B

On the morning of a psilocybin session, a participant offhandedly mentions a heart condition they did not disclose on their intake form, saying their cardiologist cleared them for exercise years ago.

Guided questions: Is an old exercise clearance sufficient here? What is the physiological concern with an undisclosed cardiac condition? Is this a proceed, defer, or stop, and what documentation do you need?

Vignette C

A person interested in ibogaine for opioid use disorder is highly motivated and reports no health problems, but has never had an electrocardiogram and takes an over-the-counter medication for acid reflux.

Guided questions: What is the specific ibogaine-related risk you must rule out, and what is the pathway from a prolonged QT interval to a fatal event? Why does the electrocardiogram matter here more than with psilocybin? What screening and monitoring are non-negotiable?

Vignette D

A person on an MAOI prescribed for depression asks about a psilocybin session, having read that psilocybin is a classic psychedelic and not an entactogen like MDMA. They reason that since psilocybin is not primarily a serotonin releaser, the MAOI is not a concern.

Guided questions: Which MAOI is prescribed, at what dose, and for what condition? How do its selectivity and reversible or irreversible effects matter? What other medications or substances are involved, especially stimulants, serotonergic antidepressants, opioids with serotonergic activity, sympathomimetics, and additional psychoactive substances? What cardiovascular, altered exposure, withdrawal, or underlying illness concerns need review? The participant correctly distinguishes direct serotonin receptor agonism from serotonin release or reuptake inhibition, but that distinction does not establish safety. Available evidence does not establish serotonin toxicity from psilocybin plus an MAOI alone. The interaction cannot be evaluated solely from the label “serotonergic.” This case requires individualized prescriber or clinical pharmacology review, coordinated with an appropriately qualified psychedelic medicine clinician, rather than an automatic serotonin syndrome conclusion or participant directed medication changes (Malcolm & Thomas, 2022; Halman et al., 2024).

Vignette E

During an ayahuasca ceremony that a colleague is facilitating, roughly two hours after dosing, a participant develops agitation, sweating, a fast heart rate, and, on examination, clonus at the ankles. The participant had stated on intake that they took no medications.

Guided questions: Which Hunter criteria are met, and what does that tell you? What is your immediate action? What does this event reveal about the completeness of the original medication review, and what would you change?

Role-Play and Practice Scripts

Practice in pairs, then switch. The aim is a complete, unhurried review that treats the medication list as a safety instrument rather than a formality.

The complete medication and supplement review

“I need the full list of everything you take, prescription, over the counter, and supplements, including anything occasional. Please tell me the exact names, and if you are not sure, we will look them up together before we go any further. Some combinations with these medicines are genuinely dangerous, so this is one of the most important things we do.”

Pinning down a vague medication

“You mentioned an antidepressant but are not sure of the name. That detail is not optional here, because the specific drug determines whether a combination is safe or dangerous. Let us find the exact name now, from your pharmacy, your prescriber, or the bottle, before we plan anything.” Practice holding the line on specificity without making the person feel interrogated.

Coordinating a washout with a prescriber

“With your permission, I would like to contact your prescriber. Discontinuing an antidepressant is a medical decision that belongs with them, not with me, and I will not ask you to stop or change anything on your own. If they decide a supervised washout is appropriate, we coordinate the timing together.”

Explaining the ibogaine cardiac requirement

“Ibogaine can affect the electrical timing of the heart in a way that, in some people, causes a dangerous rhythm. That is why we require a heart tracing and a cardiologist’s clearance before, and continuous heart monitoring during. A program that skips these is not one I would trust with your safety.” Practice conveying a hard requirement as protection rather than obstruction.

Delivering a stop-and-refer decision

“Based on your medications, I cannot move forward safely right now, and I want to be precise about why. The combination carries a real risk of a dangerous reaction. Here is who needs to be involved, and here is what would have to be true before we could reconsider.”

Self-Assessment and Reflection

Knowledge check

1. Explain, at the level of the enzyme, why oral DMT requires an MAO inhibitor to be active, and why that same inhibition creates the serotonin syndrome risk with an SSRI.
2. Outline the Hunter recognition patterns and their overdose derivation and validation context. Why are clonus and hyperreflexia useful, and why should a facilitator neither diagnose a mild case nor wait for all criteria before obtaining medical help?
3. Describe the pathway from a prolonged QT interval to sudden cardiac death, and name the safeguards used in the observational ibogaine study and the limits of what its design can establish.
4. Distinguish a pharmacodynamic from a pharmacokinetic interaction, give one psychedelic-relevant example of each, and state the matched response to each.
5. Give two psychiatric presentations that are indications for the work and two that are contraindications.
6. Compare the interaction mechanisms and review priorities for psilocybin/LSD, DMT, 5 MeO DMT, MDMA, ketamine, ayahuasca, and ibogaine. Why does MAOI use require compound specific assessment rather than a single “serotonergic” category?

Reflection

1. Where in your own practice is the temptation strongest to proceed despite a borderline finding rather than refer? What structure would remove that temptation?
2. Do you currently have a vetted referral relationship with a prescriber and a cardiologist? If not, that gap is a safety liability. What is your plan to close it?
3. A participant arrives having under-reported their medications, which you discover only mid-session. What in your intake process could have surfaced it earlier, and what will you change?

Summary

Criterion 2 draws the line between recognition and treatment. The facilitator's job is to detect coexisting medical, psychiatric, and pharmacological conditions and route them to the right professional, not to manage them. Two interactions dominate the safety picture and together form the safety spine of this workbook: the serotonin toxicity risk when MAO inhibition overlaps with serotonin releasing or reuptake inhibiting agents, recognized through clinical exposure and examination assessment, with Hunter patterns derived and validated in overdose populations rather than every therapeutic or psychedelic context, and the fatal arrhythmia risk when ibogaine prolongs the QT interval and opens the door to torsades de pointes. MAOI interactions require separate assessment for psilocybin/LSD, DMT, 5 MeO DMT, and MDMA; limited evidence must not be treated as reassurance. Lithium, tramadol, and cytochrome P450 interactions round out the medication review, and sorting each interaction into its pharmacodynamic or pharmacokinetic type points to the correct response. Cardiac disease, seizure disorders, and hepatic or renal impairment trigger medical clearance, while the psychiatric read identifies active mania or psychosis and routes relevant histories for compound specific assessment, distinguishing current stop conditions from conservative trial exclusions. Held correctly, this criterion produces a documented review and a clear referral, and it depends on a facilitator who knows the limits of their own scope and the pharmacology of the class in front of them.

References

Davis, A. K., Barrett, F. S., May, D. G., Cosimano, M. P., Sepeda, N. D., Johnson, M. W., Finan, P. H., & Griffiths, R. R. (2021). Effects of psilocybin-assisted therapy on major depressive disorder: A randomized clinical trial. JAMA Psychiatry, 78(5), 481–489. https://doi.org/10.1001/jamapsychiatry.2020.3285

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