Drug Interaction Warnings: Psychedelics and Medications

Most dangerous combinations of a psychedelic and a medicine come down to a handful of mechanisms. Once you know them, the warnings on drug labels and retreat intake forms make sense. This article explains those mechanisms. For your own medicine and substance, use the interaction checker: it gives the cited evidence for each pair across ayahuasca, psilocybin, MDMA, ketamine and ibogaine, and says plainly when no evidence was found. An empty cell there means nobody has studied it, not that it is safe.

One rule runs through everything below: do not stop or change a prescribed medicine on your own. Stopping psychiatric medication abruptly can be dangerous, and ICEERS says it should only happen under strict medical supervision. (ICEERS, 2018) Take the question to the prescriber.

Four ways drugs interact

1. Adding the same effect. Two drugs that both raise serotonin, blood pressure or sedation can push it past a safe level.
2. Blocking breakdown. One drug stops the body clearing another, so levels climb. Ayahuasca works this way by design, and paroxetine roughly doubled exposure to ibogaine in one study. (Journal of Ethnopharmacology, 1999; Journal of Pharmacology and Experimental Therapeutics, 2003; Global Ibogaine Therapy Alliance (Internet Archive copy), 2016; Journal of Clinical Pharmacology, Glue P, Winter H, Garbe K, et al., 2015)
3. Blocking the effect. A medicine occupies or changes the target the psychedelic needs, so it feels weaker.
4. Withdrawal. Stopping a medicine, or alcohol, to make room for a psychedelic can cause harm of its own, including seizures. (Journal of Forensic Sciences, 2012; Global Ibogaine Therapy Alliance (Internet Archive copy), 2016)

Serotonin syndrome and MAO inhibition

Serotonin syndrome, or serotonin toxicity, happens when too much serotonin activity builds up. A review of serotonergic psychedelics found that true serotonin toxicity typically occurs with overdose or when a drug that increases serotonin is combined with an MAO inhibitor. (Psychopharmacology (Berl), 2022) Warning signs that need immediate medical attention include muscle jerks, extreme or fluctuating vital signs, agitation or coma, muscle rigidity, high fever and seizures. (Psychopharmacology (Berl), 2022)

Ayahuasca is the main case. The brew combines DMT with harmine and harmaline. These inhibit the enzyme monoamine oxidase A (MAO-A) and let DMT taken by mouth become active. (Journal of Ethnopharmacology, 1999; Journal of Pharmacology and Experimental Therapeutics, 2003) That built-in MAO inhibitor is why SSRIs with ayahuasca may cause serotonin syndrome with a potentially grave outcome, and why ICEERS calls combining MAOIs with SSRIs or other serotonergic medicines contraindicated. (Journal of Psychoactive Drugs, 1998; ICEERS, 2026) The same logic covers SNRIs, St John's wort and tramadol, whose label rules out MAO inhibitors. (ICEERS, 2026; Psychopharmacology (Berl), 2022; ICEERS, 2018; Rising Pharma Holdings, via DailyMed (US National Library of Medicine), 23 Oct 2026; Journal of Pharmacology and Experimental Therapeutics, 2003) The full picture, including what centres say about tapering, is in ayahuasca and antidepressants.

Prescribed MAO inhibitors with MDMA have killed people. Australian forensic researchers reported four deaths from serotonin toxicity after MDMA with moclobemide, two at commonly prescribed levels. (Forensic Science International, Pilgrim JL, Gerostamoulos D, Woodford N, Drummer OH, 2012; Journal of Analytical Toxicology, Pilgrim JL, Gerostamoulos D, Drummer OH, 2011)

Without an MAO inhibitor the risk looks lower. The same review rated serotonergic medicines as low risk with psychedelics that lack MAO inhibitors, such as psilocybin. (Psychopharmacology (Berl), 2022) Low risk is not no risk, and the review describes mechanisms, not a guarantee for any one person.

Lithium and seizures

Lithium is the clearest warning for classic psychedelics. An analysis of online reports found that 47% of 62 reports of lithium taken with a classic psychedelic, such as psilocybin or LSD, involved seizures and 39% involved medical attention. (Pharmacopsychiatry, 2021; Oregon Health Authority, Public Health Division, 2026) None of 34 reports involving lamotrigine described seizures, though these are self-selected reports and the authors call their conclusions provisional. (Pharmacopsychiatry, 2021) Oregon's licensed psilocybin programme bars anyone who has taken lithium in the last 30 days. (Oregon Health Authority, Public Health Division, 2026)

People on lithium are often being treated for bipolar disorder, and in a survey of 541 people with bipolar disorder who used psilocybin, 32.2% reported new or worse symptoms afterwards. (Journal of Psychopharmacology, 2023) That is two separate reasons for a conversation with the prescriber.

SSRIs and SNRIs: blunted effects, and the danger of stopping

Antidepressants that block serotonin reuptake often make psychedelics feel weaker. In a survey of 611 reports, the chance of weaker than expected psilocybin effects was 0.47 with SSRIs and 0.55 with SNRIs, and reduced effects may last up to 3 months after stopping. (Journal of Psychopharmacology, 2023; Neuropsychopharmacology, 1996) An older study found 28 of 32 people on these antidepressants for over 3 weeks reported decreased or virtually eliminated LSD effects. (Journal of Psychopharmacology, 2023; Neuropsychopharmacology, 1996) With MDMA, citalopram markedly reduced most psychological effects in a controlled study. (Neuropsychopharmacology, Liechti ME, Baumann C, Gamma A, Vollenweider FX, 2000; Psychopharmacology (Berl), Sarparast A, Thomas K, Malcolm B, Stauffer CS, 2022)

The risk here is behavioural. Someone who feels little may take more, or may stop their antidepressant to "make room". Stopping is the more serious danger: abruptly stopping psychiatric medication can be dangerous, and stopping medicine for a chronic illness to take ayahuasca can itself be dangerous. (ICEERS, 2018) Tricyclic antidepressants may work the other way: in a very small LSD study they were linked to stronger responses. (Behavioural Brain Research, 1996)

Stimulants and cardiovascular load: Adderall, Ritalin and LSD

Many people search for "Adderall and LSD". We found no controlled study of LSD taken together with amphetamine or methylphenidate, and the checker does not cover LSD. What is known is how each drug acts alone. In a controlled crossover study of 28 healthy people, LSD, MDMA and d-amphetamine all raised heart rate, blood pressure and body temperature to a comparable degree; LSD and MDMA raised heart rate more, and d-amphetamine raised blood pressure more. (Neuropsychopharmacology (Holze F, Vizeli P, Muller F, et al.), 2020)

Where a combination has been studied, the effects added up. Methylphenidate with MDMA produced significantly greater heart and blood pressure effects and adverse effects than either alone, without stronger psychological effects. (International Journal of Neuropsychopharmacology, Hysek CM, Simmler LD, Schillinger N, et al., 2014; Journal of Psychopharmacology, Vizeli P, Liechti ME, 2017) The Spravato label asks for close blood pressure monitoring when esketamine is used with amphetamines or methylphenidate. (Janssen Pharmaceuticals, via DailyMed (US National Library of Medicine), 24 Sep 2026) Psilocybin raises blood pressure and heart rate too, and NIDA says that may be dangerous for people with heart conditions. (National Institute on Drug Abuse (NIH); Psychiatry Research, 2024; EMCDDA (now EUDA), via Internet Archive snapshot 2024-06-18)

Stacking two drugs that each raise heart rate and blood pressure means more load on the heart. For someone with high blood pressure or a heart condition, that is the conversation to have with a doctor, using the screening checklist. With ibogaine, stimulants are rated dangerous: guidelines say ibogaine can amplify them and that use during or after treatment carries an overdose risk. (Global Ibogaine Therapy Alliance (Internet Archive copy), 2016)

Ibogaine and ketamine: heart, breathing and sedation

Ibogaine with QT-prolonging drugs

Ibogaine blocks hERG potassium channels in the heart, a mechanism for life-threatening arrhythmias. (Addiction Biology, 2014; Molecules, 2015) In a Dutch study of 14 patients, half reached a QTc over 500 ms. (Global Ibogaine Therapy Alliance (Internet Archive copy), 2016; Addiction, 2022; Addiction Biology, 2014) Guidelines say other QT-prolonging drugs make this worse, and methadone at large doses prolongs the QT interval itself. (Global Ibogaine Therapy Alliance (Internet Archive copy), 2016; Addiction, 2022; Addiction Biology, 2014) Ibogaine also resets opioid tolerance, so a usual dose afterwards can be an overdose. (Global Ibogaine Therapy Alliance (Internet Archive copy), 2016) Withdrawal from alcohol or benzodiazepines was an apparent risk factor in deaths. (Journal of Forensic Sciences, 2012; Global Ibogaine Therapy Alliance (Internet Archive copy), 2016) See ibogaine clinic safety.

Ketamine with benzodiazepines, opioids and alcohol

Ketamine's risks are different: sedation, breathing and blood pressure. The Spravato label says combining esketamine with central nervous system depressants such as benzodiazepines, opioids and alcohol may increase sedation, and 48% to 61% of trial patients developed sedation on Spravato alone. (Janssen Pharmaceuticals, via DailyMed (US National Library of Medicine), 24 Sep 2026) Respiratory depression has been reported after marketing, one reason patients are monitored for at least 2 hours after each dose. (Janssen Pharmaceuticals, via DailyMed (US National Library of Medicine), 24 Sep 2026) The ketamine therapy guide covers clinic treatment.

Other combinations worth asking about

Some pairs are less famous but still flagged in the sources:

• Bupropion with MDMA. In a controlled study, bupropion raised blood levels of MDMA and prolonged its effects, and MDMA raised bupropion levels. (Journal of Pharmacology and Experimental Therapeutics, Schmid Y, Rickli A, Schaffner A, et al., 2015)
• MAO inhibitors with ketamine. The Spravato label asks for close blood pressure monitoring. A review of 39 patients found rises in blood pressure and heart rate, clinically significant in one, with no hypertensive crisis, but the sample was small. (Janssen Pharmaceuticals, via DailyMed (US National Library of Medicine), 24 Sep 2026; Journal of Clinical Psychiatry, Veraart JKE, Smith-Apeldoorn SY, Kutscher M, et al., 2022)
• Antipsychotics, anticonvulsants and other centrally acting drugs with ibogaine. Guidelines say to avoid them or manage them with extreme vigilance, because the interactions are not well understood. (Global Ibogaine Therapy Alliance (Internet Archive copy), 2016)
• Alcohol with mushrooms or truffles. Dutch drug information services say alcohol increases the chance of a bad trip. (DRUGSinfo (Drugs Infolijn), Trimbos-instituut)

How good is this evidence?

Much of it is thin, and it helps to know which kind you are reading. The lithium and SSRI findings come from people's own online or survey reports, not trials. (Pharmacopsychiatry, 2021; Oregon Health Authority, Public Health Division, 2026; Journal of Psychopharmacology, 2023; Neuropsychopharmacology, 1996) The tricyclic finding comes from 10 people using LSD. (Behavioural Brain Research, 1996) The MDMA findings come from small laboratory studies in healthy volunteers and from coroners' case reviews. (Neuropsychopharmacology, Liechti ME, Baumann C, Gamma A, Vollenweider FX, 2000; Psychopharmacology (Berl), Sarparast A, Thomas K, Malcolm B, Stauffer CS, 2022; Forensic Science International, Pilgrim JL, Gerostamoulos D, Woodford N, Drummer OH, 2012; Journal of Analytical Toxicology, Pilgrim JL, Gerostamoulos D, Drummer OH, 2011) The ibogaine guidance comes from a practitioner guideline plus small studies. (Global Ibogaine Therapy Alliance (Internet Archive copy), 2016; Journal of Clinical Pharmacology, Glue P, Winter H, Garbe K, et al., 2015) A 2022 systematic review gathered 40 publications on psychiatric medicines taken with MDMA or psilocybin. (Neuropsychopharmacology, Liechti ME, Baumann C, Gamma A, Vollenweider FX, 2000; Psychopharmacology (Berl), Sarparast A, Thomas K, Malcolm B, Stauffer CS, 2022) That is not a large body of work. Where the checker shows no evidence, the honest answer is that nobody knows.

What to do with this

• Check your medicine and substance in the interaction checker, and read the source behind the answer.
• Tell any provider every medicine, supplement and recreational drug you take.
• Take any question about stopping, reducing or timing a medicine to your prescriber, not a retreat.
• Know the emergency signs above, and call 911 (US) or 112 (EU and UK) if they appear. More on risks and emergencies is in harm reduction basics and on the Safety page.