What chemical precursors for fentanyl are now under international control and when were they listed?
Executive summary
International controls on fentanyl precursor chemicals have expanded in stages: two long-known precursors were placed under the 1988 Convention in 2017, three more were added by the Commission on Narcotic Drugs in March 2022 and entered into force on 23 November 2022, and two additional piperidone precursors were scheduled following a unanimous March 2024 decision that took formal effect in late 2024; these moves reflect successive international attempts to close pathways traffickers used to evade earlier controls [1] INCB/INCB_precursors_report-English.pdf" target="blank" rel="noopener noreferrer">[2] [3].
1. The first formal international listings — NPP and ANPP
The initial, high-profile international response to the re-emergence of illicit fentanyl manufacture was the placement of two immediate precursors—N‑Phenethyl‑4‑piperidone (NPP) and 4‑anilino‑N‑phenethylpiperidine (ANPP)—onto the strictest control list (Table I) of the 1988 Convention in 2017, a move that required UN member states to adopt national controls on these substances and prompted parallel domestic scheduling actions such as China’s 2018 controls [1] DEAGOVDIR-008-20%20Fentanyl%20Flow%20in%20the%20United%20States_0.pdf" target="blank" rel="noopener noreferrer">[4].
**2. The 2022 expansion — 4‑AP, 1‑boc‑4‑AP and norfentanyl (effective 23 November 2022)**
In March 2022 the Commission on Narcotic Drugs decided to add three additional fentanyl-related precursors—N‑Phenyl‑4‑piperidinamine (commonly called 4‑AP), tert‑Butyl 4‑(phenylamino) piperidine‑1‑carboxylate (1‑boc‑4‑AP), and norfentanyl—to Table I of the 1988 Convention, and that scheduling decision entered into force on 23 November 2022, bringing those three chemicals under the convention’s most restrictive international controls [2] [5] [6].
3. The 2024 scheduling move — 4‑piperidone and 1‑boc‑4‑piperidone (adopted March 2024; effective December 2024)
Building on the 2022 action, the Commission unanimously adopted in March 2024 the INCB recommendation to place two more fentanyl‑suitable precursors—4‑piperidone and 1‑boc‑4‑piperidone—into Table I; under the 1988 Convention decisions take effect 180 days after communication to parties, with reporting noting the decision became effective in December 2024, further expanding the roster of internationally controlled fentanyl precursors [3] [6].
4. Which named chemicals are now internationally controlled and when they were listed — concise catalogue
Summarizing the internationally listed precursors: N‑Phenethyl‑4‑piperidone (NPP) and 4‑anilino‑N‑phenethylpiperidine (ANPP) were scheduled in 2017 [1]; N‑Phenyl‑4‑piperidinamine (4‑AP), 1‑boc‑4‑AP, and norfentanyl were added in March 2022 with effect 23 November 2022 [2] [5]; and 4‑piperidone and 1‑boc‑4‑piperidone were adopted by the Commission in March 2024 and became effective later in 2024 under the treaty’s 180‑day rule [3] [6].
5. Enforcement reality and the adaptive illicit market — shifting precursors and loopholes
Despite the evolving international schedules, reporting by enforcement and oversight bodies documents that illicit manufacturers have repeatedly shifted to substitute or analogue precursors to evade controls, prompting successive rounds of scheduling and national measures; the INCB and national agencies have explicitly framed the 2022 and 2024 listings as responses to traffickers’ adaptations and as tools to enable seizure and diversion prevention, while U.S. and other domestic actions (e.g., DEA listings and sanctions) complement but do not replace treaty scheduling [5] [3] [7] [8].
6. Divergent national implementation and geopolitical friction
Member‑state implementation has varied and become a diplomatic flashpoint: U.S. reporting emphasises China as a major source of precursor chemicals and has pushed for better information‑sharing and export controls, while national schedules and export licensing regimes differ and some non‑controlled analogues continue to move in trade; congressional and INCSR reporting notes that international listings do not instantly eliminate flows and that countries have continued to detect non‑scheduled precursors and esters that require monitoring [9] [10] [11].
7. What reporting does not settle — gaps and limits
Available documents make the scheduling timeline and the specific chemicals clear, but they do not quantify how much illicit production the listings have prevented nor do they fully map all substitutable chemicals traffickers might use next; reporting by the INCB, UNODC, U.S. agencies and congressional analyses highlights seizures and policy measures while acknowledging the challenge of assessing total trafficking volumes and the emergence of new, unscheduled analogues [2] [12] [10].