DEA Places Diphenidine in Schedule I, Effective October 21, 2026

The Drug Enforcement Administration has permanently placed diphenidine, a dissociative hallucinogen, in Schedule I of the Controlled Substances Act, the strictest category of federal drug control. The final rule, signed on September 11, 2026 by DEA Administrator Terrance C. Cole, takes effect on October 21, 2026 and was published in the Federal Register of September 21, 2026 (Vol. 91, No. 181) as FR Doc. 2026–19231, under Docket No. DEA–1155. It amends 21 CFR Part 1308, adding diphenidine as paragraph (d)(117) to the list of hallucinogenic substances in § 1308.11.

Diphenidine (1-(1,2-diphenylethyl)piperidine) is a dissociative hallucinogen of the 1,2-diarylethylamine class that has been identified in the United States’ illicit drug market. It was first synthesized in 1924 but was not encountered for recreational use until 2014, and it has no approved medical use in the United States.

The action is taken in part to meet United States obligations under the 1971 United Nations Convention on Psychotropic Substances. On June 10, 2021, the Secretary General of the United Nations advised the Secretary of State that the Commission on Narcotic Drugs, at its 64th session in April 2021, had voted to place diphenidine in Schedule II of the 1971 Convention (CND Decision 64/5).

From Proposed Rule to Final Scheduling

DEA published a notice of proposed rulemaking on May 26, 2026 (91 FR 30519), proposing to add diphenidine to the hallucinogenic substances list under 21 CFR 1308.11(d), with a deadline of June 25, 2026 for comments and hearing requests. DEA received no hearing requests and two comments from individuals: one supporting the placement, the other opposing it on the grounds that Schedule I could discourage scientific research.

DEA responded that the potential impact of a rule on research opportunities has no bearing on whether a substance meets the three statutory criteria for Schedule I. On November 26, 2022, in response to DEA’s January 24, 2022 request, the Department of Health and Human Services provided its scientific and medical evaluation and scheduling recommendation. DEA concluded that diphenidine has high potential for abuse, has no currently accepted medical use in treatment in the United States, and lacks accepted safety for use under medical supervision.

What the Rule Requires of Handlers

• Registration with DEA for anyone who manufactures, distributes, reverse distributes, imports, exports, engages in research, conducts instructional activities or chemical analysis with, or possesses diphenidine.
• Surrender or transfer of existing stocks to a DEA-registered person before the effective date.
• Schedule I security, labeling and packaging requirements.
• A manufacturing quota assigned under 21 U.S.C. 826.
• Initial and biennial inventories, plus records and reports to the Automation of Reports and Consolidated Orders System.
• Order forms for distribution, and compliance with import and export rules.
• Retail sales to the general public are not allowed, and possession outside CSA authorization is unlawful and may be prosecuted.

Research Continuation and Legal Review

Researchers already registered to conduct research with another Schedule I substance may continue research on diphenidine if they submit a completed registration application or modification no later than 90 calendar days after the rule takes effect. That continuation does not authorize any other handling, such as distribution.

DEA certified that the rule will not have a significant economic impact on a substantial number of small entities, and the Office of Information and Regulatory Affairs determined it is not a major rule under the Congressional Review Act; DEA is submitting a copy to both Houses of Congress and to the Comptroller General. For further information, the rule directs inquiries to Dr. Terrence L. Boos of the Drug and Chemical Evaluation Section, Diversion Control Division.

With the effective date of October 21, 2026, diphenidine joins the substances subject to the full set of federal Schedule I controls, from registration and quotas to criminal liability. Manufacturers, distributors, laboratories and researchers handling the compound have roughly one month from publication to register, surrender stocks or file the paperwork that keeps their work lawful.

Source: Federal Register, Vol. 91, No. 181, September 21, 2026, Rules and Regulations, p. 59695 (official reference: FR Doc. 2026–19231).