⚠️ Medical Disclaimer
This severity rating system is for educational purposes only. It does not replace professional medical consultation. Always consult a qualified healthcare provider before combining any substances with medications.
Table of Contents
Severity Rating Overview
Our four-tier severity rating system classifies psilocybin-medication interactions based on clinical risk, pharmacological mechanisms, and available research evidence. This system helps individuals and healthcare providers make informed decisions about safety.
Level 4: SEVERE
Contraindicated
Life-threatening potential. Combination must be avoided under all circumstances.
DO NOT COMBINELevel 3: MODERATE
High Caution
Significant interaction with potential for serious harm. Medical supervision essential.
AVOID / SUPERVISED ONLYLevel 2: MILD
Moderate Caution
Noticeable interaction affecting efficacy or side effects. Caution warranted.
PROCEED WITH CAUTIONLevel 1: MINIMAL
Standard Precautions
Little to no known clinically significant interaction. Normal safety practices apply.
STANDARD PRECAUTIONSLevel 4: Severe (Contraindicated)
Defining Criteria for Level 4
- Life-threatening potential: Documented cases or strong theoretical basis for fatal outcomes
- Serotonin syndrome risk: High probability of severe serotonin toxicity
- Psychotic decompensation: Risk of severe, prolonged psychotic episodes
- Cardiovascular crisis: Hypertensive emergency, arrhythmia, cardiac event risk
- Seizure risk: Significantly lowered seizure threshold
- No safe dose: Even small combinations carry substantial risk
Level 4 Medications
| Medication | Class | Primary Risk | Minimum Washout |
|---|---|---|---|
| Phenelzine (Nardil) | MAOI | Serotonin syndrome, hypertensive crisis | 14+ days |
| Tranylcypromine (Parnate) | MAOI | Serotonin syndrome, hypertensive crisis | 14+ days |
| Isocarboxazid (Marplan) | MAOI | Serotonin syndrome, hypertensive crisis | 14+ days |
| Selegiline (high dose) | MAO-B Inhibitor | Serotonin syndrome at higher doses | 14+ days |
| Lithium | Mood Stabilizer | Severe psychotic episodes, seizures, cardiac events | 7+ days (supervised) |
| Tramadol | Opioid/SNRI | Serotonin syndrome, seizures | 3-5 days |
| Linezolid | Antibiotic (MAOI) | Serotonin syndrome | 14 days after last dose |
| Methylene Blue (IV) | Diagnostic/Treatment | Serotonin syndrome (MAOI activity) | 14 days |
| Syrian Rue / Harmine | Natural MAOI | Serotonin syndrome | 24-48 hours |
⚠️ Why MAOIs Are Particularly Dangerous
Monoamine oxidase inhibitors (MAOIs) prevent the breakdown of serotonin. When combined with psilocybin (which increases serotonin activity), this can cause dangerous accumulation of serotonin leading to:
- Hyperthermia (fever >104°F / 40°C)
- Severe muscle rigidity
- Seizures
- Cardiovascular collapse
- Death in severe cases
⚠️ The Lithium-Psilocybin Danger
Multiple case reports document severe reactions when lithium is combined with psychedelics:
- Prolonged psychotic states (lasting days to weeks)
- Seizures
- Cardiac arrhythmias
- Severe confusion and agitation
- Hospitalization required in most documented cases
Never combine lithium with psilocybin under any circumstances.
Level 3: Moderate (High Caution)
Defining Criteria for Level 3
- Significant effect alteration: Substantially reduced, enhanced, or unpredictable effects
- Elevated adverse event risk: Higher probability of concerning side effects
- Moderate SS risk: Some potential for serotonin syndrome at higher doses
- Therapeutic interference: May significantly undermine medication efficacy
- Complex discontinuation: Stopping medication for psilocybin carries its own risks
- Medical supervision recommended: Should not be undertaken without professional guidance
Level 3 Medications
| Medication | Class | Interaction Effect | Notes |
|---|---|---|---|
| Fluoxetine (Prozac) | SSRI | Significantly reduces effects; some SS risk | Long half-life (4-6 week washout) |
| Paroxetine (Paxil) | SSRI | Significantly reduces effects; difficult withdrawal | Severe discontinuation syndrome |
| Venlafaxine (Effexor) | SNRI | Reduces effects; moderate SS risk | Requires very slow taper |
| Duloxetine (Cymbalta) | SNRI | Reduces effects; some SS risk | Discontinuation can be difficult |
| Clomipramine (Anafranil) | TCA | Reduces effects; highest SS risk among TCAs | Strong serotonin reuptake inhibition |
| Risperidone (Risperdal) | Antipsychotic | Blocks psychedelic effects almost completely | Strong 5-HT2A antagonist |
| Olanzapine (Zyprexa) | Antipsychotic | Significantly blocks effects | 5-HT2A antagonist |
| Haloperidol (Haldol) | Antipsychotic | Blocks effects; used as trip terminator | D2 and 5-HT2A blockade |
| Carbamazepine (Tegretol) | Anticonvulsant | May reduce effects; enzyme inducer | Complex pharmacokinetic interaction |
📚 Research Note: SSRIs and Psilocybin
Clinical studies have shown that chronic SSRI use leads to 5-HT2A receptor downregulation, which is the primary target of psilocybin. This results in:
- Significantly blunted subjective effects
- Reduced therapeutic outcomes in some studies
- Lower risk of acute adverse effects (due to dampened effects)
- Some residual serotonin syndrome risk, particularly at higher doses
Level 2: Mild (Moderate Caution)
Defining Criteria for Level 2
- Noticeable effect modification: Reduced or enhanced effects, but not dramatically
- Low-moderate risk: Some adverse event potential, but generally manageable
- Minimal SS risk: Low probability of serotonin syndrome
- Can proceed with awareness: Not strictly contraindicated, but requires caution
- Dose adjustment may help: Lower doses of either substance may mitigate risk
- Informed decision possible: Risks are generally understood and predictable
Level 2 Medications
| Medication | Class | Interaction Effect | Notes |
|---|---|---|---|
| Sertraline (Zoloft) | SSRI | Mildly-moderately reduces effects | Lower risk profile than some SSRIs |
| Escitalopram (Lexapro) | SSRI | Mildly reduces effects | Relatively clean pharmacology |
| Citalopram (Celexa) | SSRI | Mildly reduces effects | Similar to escitalopram |
| Bupropion (Wellbutrin) | NDRI | May slightly lower seizure threshold | No serotonergic interaction |
| Mirtazapine (Remeron) | NaSSA | May mildly reduce effects | Has 5-HT2A antagonist properties |
| Trazodone | SARI | May mildly reduce effects | Weak 5-HT2A antagonist |
| Quetiapine (Seroquel) | Antipsychotic | Reduces effects; can terminate trips | Sometimes used intentionally as "trip killer" |
| Buspirone (Buspar) | Anxiolytic | Minimal effect; possible mild SS risk | 5-HT1A partial agonist |
| Alprazolam (Xanax) | Benzodiazepine | May reduce intensity/anxiety | Can be used as emergency intervention |
| Lorazepam (Ativan) | Benzodiazepine | May reduce intensity | Useful for anxiety management |
| Amphetamine (Adderall) | Stimulant | Increased cardiovascular strain, anxiety | Skip dose on day of use |
| Methylphenidate (Ritalin) | Stimulant | Increased cardiovascular effects | Skip dose on day of use |
Level 1: Minimal (Standard Precautions)
Defining Criteria for Level 1
- No known clinically significant interaction: Based on current research and mechanism
- Different receptor targets: Medication works through non-serotonergic pathways
- No pharmacokinetic interaction: Doesn't affect psilocybin metabolism
- Standard precautions apply: Normal psilocybin safety guidelines sufficient
- Medication can be continued: No need for washout period
- Monitor underlying condition: Be aware of how the condition might affect experience
Level 1 Medications
Levothyroxine (thyroid)
Metformin (diabetes)
Lisinopril (blood pressure)
Amlodipine (blood pressure)
Atorvastatin (cholesterol)
Omeprazole (acid reflux)
Most antibiotics
Birth control pills
Ibuprofen (pain)
Acetaminophen (pain)
Antihistamines (allergies)
Insulin (diabetes)
Clinical Rating Criteria
Our severity ratings are determined by evaluating multiple factors:
1. Pharmacological Mechanism
- Primary receptor targets: 5-HT2A involvement increases interaction potential
- Serotonin system effects: MAOIs, SSRIs, SNRIs all affect serotonin
- Receptor binding affinity: Higher affinity = stronger interaction
- Metabolic pathways: CYP450 enzyme interactions can alter drug levels
2. Clinical Evidence Base
- Case reports: Documented adverse events in combination use
- Clinical trials: Formal studies examining combinations
- Pharmacovigilance data: Post-market surveillance reports
- Mechanistic studies: Laboratory evidence of interaction
3. Severity of Potential Outcomes
- Life-threatening: Immediate danger to life
- Serious: Hospitalization required, lasting harm possible
- Moderate: Medical attention may be needed
- Minor: Self-limiting, manageable effects
4. Probability of Adverse Outcome
- Highly likely: Interaction occurs in most combinations
- Likely: More often than not
- Possible: Occurs in some cases
- Rare: Infrequent but documented
| Factor | Level 4 | Level 3 | Level 2 | Level 1 |
|---|---|---|---|---|
| Outcome Severity | Life-threatening | Serious | Moderate | Minor/None |
| Probability | Highly likely/Likely | Likely/Possible | Possible | Rare/None |
| Evidence Quality | Strong | Moderate-Strong | Moderate | Limited/None |
| Mechanism | Clear, direct | Clear | Plausible | None known |
Complete Medication Database by Class
Antidepressants
Most Common Interactions| Medication | Class | Level | Key Concern |
|---|---|---|---|
| Phenelzine (Nardil) | MAOI | 4 | Serotonin syndrome, hypertensive crisis |
| Tranylcypromine (Parnate) | MAOI | 4 | Serotonin syndrome, hypertensive crisis |
| Fluoxetine (Prozac) | SSRI | 3 | Significant effect reduction; long half-life |
| Paroxetine (Paxil) | SSRI | 3 | Effect reduction; difficult withdrawal |
| Venlafaxine (Effexor) | SNRI | 3 | Effect reduction; discontinuation issues |
| Sertraline (Zoloft) | SSRI | 2 | Mild-moderate effect reduction |
| Escitalopram (Lexapro) | SSRI | 2 | Mild effect reduction |
| Bupropion (Wellbutrin) | NDRI | 2 | Seizure threshold (minor concern) |
| Mirtazapine (Remeron) | NaSSA | 2 | May reduce effects |
Mood Stabilizers & Antipsychotics
| Medication | Class | Level | Key Concern |
|---|---|---|---|
| Lithium | Mood Stabilizer | 4 | Psychosis, seizures, cardiac events |
| Risperidone (Risperdal) | Antipsychotic | 3 | Blocks psychedelic effects |
| Olanzapine (Zyprexa) | Antipsychotic | 3 | Blocks effects |
| Quetiapine (Seroquel) | Antipsychotic | 2 | Blocks/reduces effects (trip terminator) |
| Lamotrigine (Lamictal) | Anticonvulsant/MS | 2 | May alter effects; generally tolerated |
| Valproate (Depakote) | Anticonvulsant/MS | 2 | Limited data; caution advised |
Anxiolytics & Sedatives
| Medication | Class | Level | Key Concern |
|---|---|---|---|
| Alprazolam (Xanax) | Benzodiazepine | 2 | Reduces intensity; useful as trip killer |
| Lorazepam (Ativan) | Benzodiazepine | 2 | Reduces intensity; anxiety management |
| Diazepam (Valium) | Benzodiazepine | 2 | Reduces intensity; long-acting |
| Clonazepam (Klonopin) | Benzodiazepine | 2 | Reduces intensity |
| Buspirone (Buspar) | Azapirone | 2 | Minimal; possible mild SS risk |
| Zolpidem (Ambien) | Z-drug | 1 | No known significant interaction |
Evidence Basis
Our severity ratings are based on multiple sources of evidence:
Clinical Trial Data
Formal clinical trials, particularly from Johns Hopkins, Imperial College London, MAPS, and other research institutions, provide data on psilocybin administration in controlled settings, sometimes including participants on medications.
Case Reports
Published case reports in medical literature document adverse events from combination use, particularly for severe interactions like lithium-psilocybin.
Pharmacological Principles
Understanding of receptor mechanisms, metabolic pathways, and pharmacokinetics informs theoretical interaction potential even when clinical data is limited.
Harm Reduction Community Knowledge
Organizations like Zendo Project, MAPS, and harm reduction communities contribute anecdotal evidence that, while not peer-reviewed, represents real-world experience.
Practical Application
How to Use This Information
1. Identify Your Medications
List all medications, supplements, and substances you take regularly.
2. Check Each One
Look up each medication in our database or use the interactive checker.
3. Identify Highest Risk
Your overall risk is determined by the highest-risk medication.
4. Consult Professionals
For Level 3-4 medications, consult healthcare providers before any decision.
Decision Framework
| Highest Level | Recommended Action |
|---|---|
| Level 4 | Do not proceed. No psilocybin use while on this medication. Discuss alternatives with prescriber if interested in psychedelic therapy. |
| Level 3 | Strongly consider avoiding. If proceeding, only with medical supervision, proper washout, and careful monitoring. |
| Level 2 | Proceed with caution. Understand effects may be altered. Consider lower doses. Have safety protocols in place. |
| Level 1 | Standard precautions apply. Medication likely does not significantly interact. Focus on general psilocybin safety. |
Key Takeaways
- Level 4 (Severe): MAOIs and lithium are never safe to combine with psilocybin
- Level 3 (Moderate): Many antidepressants and antipsychotics require medical guidance
- Level 2 (Mild): Some SSRIs and benzodiazepines alter effects but aren't strictly contraindicated
- Level 1 (Minimal): Most common medications (blood pressure, thyroid, etc.) have no known interaction
- When in doubt, consult a professional
- This information is educational—not a substitute for medical advice