THCPO: the THCP ester, a narcotic in France since 2024

Sellers use the "O" suffix to flag an acetate ester. The maker takes a cannabinoid carrying a hydroxyl group (an OH, or alcohol group) and runs a reaction that swaps that group for an acetate. That is how THC turns into THC-O, HHC into HHC-O, HHCP into HHCPO and THCP into THCPO.

Two transformations are therefore stacked in THCPO. Extending the side chain from 5 to 7 carbons gives THCP, which the plant produces only in trace amounts. Acetylation at position 1 of the core comes next, and the plant never carries it out.

The molecule is real and on the market. In 2025, a Japanese public institute used nuclear magnetic resonance to identify it in oils sold online, alongside other esters such as THC-O-propionate and THCP-O-butanoate. In Germany, THCPO traces turned up in 7 of 79 samples seized in Rhineland-Palatinate between 2021 and 2023, all of them flowers.

Searched on PubMed in September 2026, THCPO brings up only analytical work on seized or purchased products. No study has described its pharmacology, its toxicity or its fate in the human body.

Data are scarce even for THC-O, an older and more widespread molecule. A consumer survey published in 2023 tested the sellers' claim that THC-O has psychedelic effects: 79% rated the experience "not at all" or "a little" psychedelic. Online reviews of THCPO cannot replace a measurement, since they state neither what the product contained nor the dose.

The best-documented risk lies in the acetate group, whatever the cannabinoid attached to it. It was first described with vitamin E acetate, an additive in some vaping liquids: when heated, the group releases ketene, a gas toxic to the lungs.

In 2022, Portland State University chemists vaped three cannabinoid acetates (Δ⁸-THC-O, CBN-O and CBD-O) and found ketene in every condensate, one of them from a commercial product. A University of California, Davis study published in 2026 put numbers on the effect. In a commercial vape device, the acetate group broke down into ketene with more than 99% efficiency, giving 1 to 4% ketene relative to the cannabinoid mass. Without the acetate, the same cannabinoids produced no ketene.

THCPO was not tested, but it carries the same acetate group at the same position as THC-O, and nothing suggests it would behave otherwise when heated.

THCPO is not named in the ANSM decision of 22 May 2024, in force since 3 June 2024. The decision relies on a generic definition: any derivative of the benzo[c]chromene core, the chemical skeleton of THC, carrying certain substitutions is a narcotic. Two of those substitutions match THCPO exactly:

THCP and HHCPO, the ester of HHCP, are named by the ANSM. HHC-O was classified earlier, from 13 June 2023, along with HHC and HHCP; our timeline of the HHC ban traces these steps.

Narcotics penalties apply. Under article L3421-1 of the Public Health Code, use carries one year in prison and a €3,750 fine, with a fixed fine of €500. Possession, transport and sale come under article 222-37 of the Criminal Code, which provides for up to 10 years in prison.

Whatever the trade name, a resin, flower or cartridge sold as THCPO is a narcotic if it contains the molecule.

The label does not always mention THCPO. In the German study, esters appeared mostly as traces, mixed with other synthetic cannabinoids. In June 2025, the ANSM and Anses reported several hundred poisonings since early 2024 among users of products sold as containing CBD, most often due to undeclared THC or synthetic cannabinoids.

Three checks lower this risk:

1. The certificate of analysis shows the batch number of the product on sale and lists which cannabinoids were tested; our guide to reading a certificate of analysis explains each line.
2. The lab searched for semi-synthetics (HHC, THCP, "O" esters) and reports them as "not detected".
3. Price and sales pitch fit a CBD product. A "stronger" effect promised on a "hemp" product should put you on guard.

For more, see our advice on spotting synthetic cannabinoids and our article on PTC.