Cultivation of psilocybin mushrooms remains a federal offense in the United States. Content is provided for educational, harm-reduction, and research purposes in jurisdictions where such activity is legal.

The CodexField ManualDrug Interactions

Drug Interactions

Psilocybin acts primarily on the serotonin system. A number of common medications and substances interact with that system — some dangerously, some predictably, some in ways worth knowing even if the risk is low. This reference organizes them by tier.

⚠ Not medical advice

This page is an educational reference. It does not cover every possible combination and does not account for your individual health history, dose, or regimen. If you are on any prescription medication, discuss this with a prescriber who knows your full picture before making any decision.

How psilocybin works

Psilocybin is converted in the body to psilocin, which is a partial agonist at serotonin receptors — primarily 5-HT2A, but also 5-HT2C and 5-HT1A. Most interaction risk stems from compounds that also affect the serotonin system, either by flooding it (serotonin syndrome risk) or by blocking psilocin’s receptor targets (blunting).

§ 01Dangerous

Do not combine

These combinations carry a risk of serious harm or death. They represent hard contraindications — there is no safe way to manage them with careful dosing.

MAO inhibitors (MAOIs)

Phenelzine (Nardil), tranylcypromine (Parnate), selegiline (Emsam), isocarboxazid (Marplan), linezolid, methylene blue

MAOIs block the enzyme that breaks down serotonin and psilocin. Combined with psilocybin, serotonin accumulates to dangerous levels.

Serotonin syndrome — hyperthermia, seizures, cardiac arrhythmia — can be fatal. No safe dose exists for this combination. Ayahuasca intentionally combines an MAOI (harmine) with DMT; treat it as a separate compound with its own protocols, not as a general guide to MAOI safety.

Lithium

Lithium carbonate, lithium citrate (Lithobid, Eskalith)

Mechanism not fully understood. Multiple case reports describe seizures and psychotic episodes when lithium is combined with psilocybin or LSD.

This combination is considered among the most dangerous in the psychedelic literature. If you are on lithium for bipolar disorder, this is a hard contraindication.

§ 02Unsafe

Do not combine

These combinations do not have the fatality profile of the dangerous tier, but carry a high enough risk that experienced harm-reduction practitioners treat them as combinations to avoid.

Tramadol

Ultram, ConZip

Tramadol is an opioid analgesic with serotonin–norepinephrine reuptake inhibition. It also lowers the seizure threshold independently.

The combination of serotonergic activity plus a lowered seizure threshold makes this pairing particularly risky.

MDMA (same session)

MDMA, ecstasy, molly

MDMA floods the synapse with serotonin, dopamine, and norepinephrine. Combined with psilocybin's serotonergic activity, the load on the cardiovascular and thermoregulatory systems rises significantly.

"Candyflipping" is practiced deliberately by some experienced users, but it requires careful timing, lower doses of each, and a sober sitter. The margin for error is narrow. Do not combine on a first experience with either substance.

§ 03Caution

Use with caution

These combinations are not reliably dangerous in the same way, but they alter the experience in significant ways — often unpredictably — and raise the overall risk profile meaningfully.

SSRIs (selective serotonin reuptake inhibitors)

Fluoxetine (Prozac), sertraline (Zoloft), escitalopram (Lexapro), paroxetine (Paxil), citalopram (Celexa), fluvoxamine (Luvox)

Chronic SSRI use downregulates 5-HT2A receptors — the primary target of psilocybin. This blunts or eliminates the effect of psilocybin, sometimes completely.

The main harm is indirect: people who find psilocybin isn't working compensate by redosing, which is how accidental overdoses happen. At very high psilocybin doses, serotonin-syndrome risk re-emerges. If you are tapering an SSRI to use psilocybin therapeutically, do so only under medical supervision and respect a minimum 2–4 week washout (5 weeks for fluoxetine, which has a long half-life).

SNRIs (serotonin–norepinephrine reuptake inhibitors)

Venlafaxine (Effexor), duloxetine (Cymbalta), desvenlafaxine (Pristiq)

Similar receptor-downregulation effect as SSRIs, with the addition of norepinephrine activity that can raise heart rate and blood pressure.

Cannabis

THC, marijuana, high-potency concentrates

CB1 and 5-HT2A receptor systems interact. Cannabis can dramatically intensify and extend a psilocybin experience, often in ways that are difficult to predict.

In clinical settings, cannabis is excluded for good reason. The combination frequently amplifies anxiety and paranoia and has been associated with adverse outcomes in people without prior experience of either substance. If you combine them, use less of each and have a sober sitter present.

Stimulants

Amphetamines (Adderall, Vyvanse), cocaine, methamphetamine

Stimulants raise heart rate, blood pressure, and core temperature. Combined with psilocybin's mild cardiovascular effects, the load on the system increases.

The combination is not known to cause a specific toxidrome, but people with cardiovascular conditions face meaningful risk. Stimulants also elevate baseline anxiety, which raises the probability of a difficult experience.

St. John's Wort

Hypericum perforatum (herbal supplement)

St. John's Wort has mild MAOI activity and inhibits serotonin reuptake. Neither effect is as strong as prescription drugs in either class, but the combination is not neutral.

Often overlooked because it is an OTC supplement. Disclose it to any medical provider who knows you are using psilocybin.

§ 04Informational

Informational

These combinations are worth knowing about. None are considered acutely dangerous at typical doses, but each affects the experience in ways that matter.

Benzodiazepines

Diazepam (Valium), alprazolam (Xanax), clonazepam (Klonopin), lorazepam (Ativan)

Benzodiazepines act on GABA receptors, not serotonin. They do not cause serotonin syndrome. At sufficient doses they can reduce the intensity of a psilocybin experience and are used by harm-reduction practitioners to manage acute crises.

Benzos are the least dangerous of the "trip stopper" options available in a crisis. However, they do not reliably end an experience — they may only sedate. Do not build a habit of using benzos to manage every uncomfortable moment; psychological tolerance forms quickly and physical dependence follows.

Antipsychotics

Risperidone (Risperdal), quetiapine (Seroquel), haloperidol (Haldol), olanzapine (Zyprexa)

Typical and atypical antipsychotics are 5-HT2A antagonists. They partially or fully block psilocybin's mechanism of action.

Some harm-reduction guides list antipsychotics as a trip-interruption option. However, they carry their own side-effect profile (akathisia, extrapyramidal symptoms). Benzodiazepines are a safer first-line option in most acute settings.

Alcohol

Ethanol

Alcohol does not interact directly with the serotonin system in the way psilocybin does. The concern is secondary: dehydration, nausea amplification, and impaired judgment during an experience that already reduces impulse control.

Many experienced users avoid alcohol entirely in the 24 hours before and after. It is not a reliable "safety brake" and may increase the chance of a difficult experience.

Antihistamines

Diphenhydramine (Benadryl), doxylamine

First-generation antihistamines have mild anticholinergic and mild serotonin-antagonist activity. They may slightly reduce psilocybin's effects and add sedation.

Not a meaningful concern at standard doses, but worth knowing if you are using an antihistamine for sleep the night before.

§ 05Resources

  • TripSit drug combinations chart — wiki.tripsit.me/wiki/Drug_combinations — a community-maintained interaction database covering many substances beyond psilocybin.
  • Fireside Project — firesideproject.org / 62-FIRESIDE — free psychedelic peer support line, 24/7. Use during or after a difficult experience.
  • DanceSafe — dancesafe.org — reagent testing kits and harm-reduction resources for events.
  • Johnson et al. (2008), “Human hallucinogen research: guidelines for safety” — the foundational clinical safety framework; includes contraindication criteria used in research trials.
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This reference will be updated as the clinical literature develops. If you know of a missing combination or an error, reach the community.