Grapefruit juice

A common fruit juice; it inactivates an intestinal drug-metabolizing enzyme (CYP3A4) and can raise blood levels of some oral medicines.

psilodex.org/m/grapefruit-juice · data v2026.10.05

Clinical contraindication: None listed; No label contraindication covering psilocybin was found. This is not a finding that the combination has been shown to be without risk.
Psilocybin evidence: No psilocybin data
Half-life: Does not apply; Effect duration: Intestinal CYP3A4 inhibition can last about 24 hours after one serving

Named in state rules?

Not namedColorado

Not namedOregon

PendingNew Mexico

Cite asPsilodex, “Grapefruit juice”, v2026.10.05. psilodex.org/m/grapefruit-juice

Clinical data and state rules are separate facts. Both are shown; neither is a decision.

What it is used for

FDA status

Not FDA-approved

A food, not a drug.

Sources [1]

01 Interaction with psilocybin

It may slightly slow how the body clears oral psilocybin for about a day after a glass (not studied with psilocybin).

Detail Grapefruit juice irreversibly blocks CYP3A4, a drug-processing enzyme, in the intestinal wall. This raises blood levels of some oral drugs, with effects lasting about 24 hours after a glass (Bailey 2004). CYP3A4 broke down psilocin in lab studies (Thomann 2024). So grapefruit juice may slightly raise psilocin levels from oral psilocybin. However, the body removes psilocin mainly by glucuronidation and conversion to 4-HIAA. There are no psilocybin data. Sources [1][2][3][4]

Human data with psilocybin: No psilocybin data; based on how it works
Effect duration: Intestinal CYP3A4 inhibition can last about 24 hours after one serving The enzyme is inactivated irreversibly, so the effect lasts until new enzyme is made; repeated servings can add up. Source

Evidence types on this record

No psilocybin dataNo psilocybin data: no human data with psilocybin or another classic psychedelic; the text draws on the medication's own pharmacology and its label or reference facts

02 Pharmacology relevant to psilocybin

None listed

No pharmacology properties of concern are listed for this record.

03 State rules

Plain-language summary · official text governs

CO4 CCR 755-1

Not named

No provision names this medication or its class.

Colorado · checked 2026-10-04

OROAR 333-333

Not named

No provision names this medication or its class.

Oregon · checked 2026-10-04

NM7.35.3 NMAC (proposed)

Pending

New Mexico's clinical rules (proposed 7.35.3 NMAC) are not final. No provision naming this medication has been found.

New Mexico · checked 2026-10-04

04 Conditions to ask about

None linked

No condition named in state rules is linked to this medication.

05 Sources

Bailey DG, Dresser GK. Interactions between grapefruit juice and cardiovascular drugs. Am J Cardiovasc Drugs 2004;4(5):281–297. — Abstract: "Irreversible inactivation of intestinal cytochrome P450 (CYP) 3A4 is produced by commercial grapefruit juice given as a single normal amount (e.g. 200-300 mL) or by whole fresh fruit segments." "Enhanced oral drug bioavailability can occur 24 hours after juice consumption."
Uno T, Yasui-Furukori N. Effect of grapefruit juice in relation to human pharmacokinetic study. Curr Clin Pharmacol 2006;1(2):157–161. — Abstract: "The predominant mechanisms of GFJ-drug interaction are thought to be due primarily to the inhibition of intestinal CYP3A4 activity without an apparent inhibition of hepatic CYP3A4."
Propafenone hydrochloride tablets (Strides) · FDA label (DailyMed) — 5.4 Drug Interactions "Drugs that inhibit these CYP pathways (such as desipramine, paroxetine, ritonavir, sertraline for CYP2D6; ketoconazole, erythromycin, saquinavir, and grapefruit juice for CYP3A4; and amiodarone and tobacco smoke for CYP1A2) can be expected to cause increased plasma levels of propafenone."
Thomann J, Kolaczynska KE, Stoeckmann OV, et al. In vitro and in vivo metabolism of psilocybin’s active metabolite psilocin. Front Pharmacol 2024;15:1391689. — Abstract: "recombinant CYP2D6 and CYP3A4 enzymes metabolized nearly 100% and 40% of psilocin, respectively." "MAO-A transformed psilocin into minimal amounts of 4-HIAA and 4-HTP." "In conclusion, MAO-A, CYP2D6, and CYP3A4 are involved in psilocin's metabolism." Introduction: "Around 33% of a psilocybin dose is renally excreted as 4-HIAA."

Record history

v2026.10.02First published.
2026-10-04Last reviewed against its sources.

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