MPT

coronary artery disease, heart failure, uncontrolled hypertension, arrhythmia

Unsubstituted tryptamines may produce transient cardiovascular effects through serotonergic and adrenergic mechanisms. Individuals with pre-existing cardiovascular disease may be at elevated risk. No MPT-specific cardiovascular data exist.

schizophrenia, schizoaffective disorder, psychotic disorder NOS

Schizophrenia, schizoaffective disorder, and related psychotic spectrum conditions represent absolute contraindications for all 5-HT2A agonist psychedelics. MPT's presumed 5-HT2A agonism carries the same risk class as DPT, DMT, and psilocybin. No MPT-specific data exist; this is a class-level contraindication.

bipolar I disorder, bipolar II disorder

Bipolar disorder is a relative contraindication for 5-HT2A psychedelics due to risk of manic episode precipitation. No MPT-specific data exist; inferred from class-level reports across serotonergic psychedelics.

pharmaceutical MAOI use, beta-carboline alkaloid co-administration

Concurrent use of any MAO-A inhibitor — pharmaceutical (phenelzine, tranylcypromine, moclobemide) or botanical (harmaline, harmine from ayahuasca or Syrian rue) — is absolutely contraindicated. MAO-A is the primary metabolic pathway for non-ring-substituted tryptamines; inhibition may increase exposure by an order of magnitude. This pharmacokinetic mechanism is well-established across the tryptamine class.

lithium therapy

Lithium has been associated with increased seizure risk when combined with serotonergic psychedelics across multiple community reports. No controlled studies or published case series exist for any tryptamine–lithium combination. The mechanism is unknown.

SSRI therapy, SNRI therapy

SSRIs and SNRIs may blunt psychedelic effects through chronic 5-HT2A receptor downregulation while simultaneously increasing serotonin toxicity risk. The net clinical effect is unpredictable. Malcolm & Thomas 2022 reviewed this interaction class for psychedelic tryptamines.