Diphenidine is Schedule I from October 21: the May proposal is now a final rule

Diphenidine, a dissociative hallucinogen of the 1,2-diarylethylamine class, becomes a Schedule I controlled substance in the United States on October 21, 2026, under a final rule published in the Federal Register on September 21, 2026.

The final rule itself is what makes the change: with its issuance, DEA places diphenidine in Schedule I of the Controlled Substances Act [1], adding it at 21 CFR 1308.11(d)(117) among the hallucinogenic substances, under DEA drug code 7292 [1]. The scheduling reaches diphenidine's salts, isomers, and salts of isomers wherever they can exist [1]. None of this is in force yet. Until October 21, 2026, handling diphenidine is not a federal controlled-substance offence by reason of this docket. From that date, the controls and criminal penalties that come with Schedule I apply [1]. Anyone currently holding diphenidine who is unwilling or unable to obtain a Schedule I registration has to surrender or transfer all of it before October 21, 2026 [1].

This final rule closes out a proposal DEA published on May 26, 2026, which set a comment period running to June 25, 2026 [2]. Two comments came in — one supporting the move, one opposing it — and nobody asked for a hearing [1]. DEA states that Schedule I placement does not stop research on diphenidine; researchers can register with DEA to do it [1]. DEA's own finding is that diphenidine has a high potential for abuse, no currently accepted medical use in the United States, and lacks accepted safety for use under medical supervision [1].

The rule frames the action partly as treaty compliance. The United Nations Commission on Narcotic Drugs placed diphenidine in Schedule II of the 1971 Convention on Psychotropic Substances in April 2021 (CND Decision 64/5) [1], and the US was notified of that decision on June 10, 2021 [1]. The Department of Health and Human Services provided its scientific and medical evaluation and scheduling recommendation for diphenidine on November 26, 2022 [1]. DEA says the scheduling lets the US meet its obligations under that Convention [1]. Diphenidine was first synthesized in 1924 but not encountered for recreational use until 2014 [1].

References

1. Schedules of Controlled Substances: Placement of Diphenidine in Schedule I — Federal Register
2. Schedules of Controlled Substances: Placement of Diphenidine in Schedule I — Federal Register