2C-T-21

Uncontrolled hypertension, Coronary artery disease, Cardiac arrhythmias

Uncontrolled hypertension, coronary artery disease, and cardiac arrhythmias represent relative contraindications. Acute cardiovascular effects — blood pressure elevation and heart rate increase — are documented for the related compound 2C-B in controlled human studies (Papaseit 2018) and expected for 2C-T-21. The confirmed 5-HT₂B partial agonism (EC₅₀ = 102 nM, Emax = 32%, Halberstadt 2023) raises theoretical concern for cardiac valvulopathy with repeated exposure, though no published data confirm this for any 2C-T compound.

Epilepsy, History of seizures, Lowered seizure threshold

Seizure disorders, including epilepsy and conditions associated with lowered seizure threshold, represent a relative contraindication. Risk is elevated when 2C-T-21 is combined with other agents that reduce seizure threshold, such as lithium, tramadol, or stimulants.

Schizophrenia, Schizoaffective disorder, Bipolar I with psychotic features, Family history of psychotic disorders

Personal or family history of psychotic disorders — including schizophrenia, schizoaffective disorder, and bipolar I with psychotic features — is an absolute contraindication. 5-HT₂A receptor agonism, the primary mechanism of 2C-T-21 (Ki = 27 nM), is well-established to precipitate or exacerbate psychotic episodes in individuals with genetic or clinical predisposition.

Significant liver disease, Hepatic insufficiency

Significant hepatic impairment is a relative contraindication. 2C-T-21 metabolism is expected to depend on MAO-A/B and CYP2D6 for first-pass clearance (by analogy to 2C-T-2 and 2C-T-7, Theobald & Maurer 2007). Impaired hepatic function may reduce metabolic clearance, leading to elevated plasma concentrations and prolonged or intensified effects.

Pregnancy, Lactation

Pregnancy and lactation are absolute contraindications. No reproductive toxicology, teratogenicity, or lactation transfer data exist for 2C-T-21 or any compound in the 2C-T series. The precautionary principle mandates absolute contraindication in the absence of safety evidence.

Phenelzine, Tranylcypromine, Moclobemide, Harmaline, Banisteriopsis caapi, Syrian rue

Concurrent use of monoamine oxidase inhibitors — pharmaceutical (phenelzine, tranylcypromine, moclobemide) or botanical (harmaline, Banisteriopsis caapi, Syrian rue) — is absolutely contraindicated. MAO-A and MAO-B are the primary metabolic enzymes for 2C-T class compounds (Theobald & Maurer 2007), and 2C-T-21 itself directly inhibits both MAO-A and MAO-B (Wagmann et al. 2019). Exogenous MAOI co-administration would substantially impair 2C-T-21 clearance while simultaneously producing additive monoamine oxidase inhibition, creating compounding pharmacokinetic and pharmacodynamic risk for serotonin syndrome and hypertensive crisis.

SSRIs, SNRIs, Tricyclic antidepressants, Triptans, Lithium, Tramadol

Concurrent use of serotonergic medications — SSRIs, SNRIs, tricyclic antidepressants, triptans, lithium, and tramadol — constitutes a relative to absolute contraindication depending on the specific agent. Additive serotonergic load increases serotonin syndrome risk. Lithium specifically produces synergistic serotonergic activity and lowers the seizure threshold, warranting absolute contraindication. Tramadol carries dual risk of serotonergic synergy and seizure threshold reduction.