Q.01

What is a controlled substance schedule under the US Controlled Substances Act? Explain the five DEA schedules (I to V) and the criteria for each, give examples, and tell me where the official list lives (21 CFR 1308) and how a substance gets scheduled or rescheduled.

The Controlled Substances Act (CSA) places every federally controlled drug or chemical in one of five schedules. Each schedule is defined by findings under 21 U.S.C. 812(b) about three things: potential for abuse, currently accepted medical use (CAMU) in the US, and dependence liability. The schedule then decides which DEA controls apply (registration, quotas, import/export permits and so on). The official list is in 21 CFR Part 1308, and DEA changes it through Federal Register rules.

Approach. I searched the current eCFR text of 21 CFR Part 1308 (sections 1308.11 to 1308.15) for example listings in each schedule. I also searched DEA's Federal Register scheduling rules affecting Part 1308 (1994 onward), using the statutory phrasing for each schedule and terms for temporary scheduling, petitions, the eight factors and marijuana rescheduling. About 60 rule extracts were reviewed. The criteria and procedure below are taken from how DEA itself restates 21 U.S.C. 811 and 812 in those rules. I did not read the statute text directly.

The five schedules

ScheduleStatutory findings (21 U.S.C. 812(b))Examples in 21 CFR 1308 (DEA drug code)
I (1308.11)High potential for abuse; no CAMU; lack of accepted safety for use under medical supervision [1]Heroin (9200) [2]; LSD (7315) [3]; psilocybin (7437) [4]; marihuana (7360) [5]
II (1308.12)High potential for abuse; a CAMU, or a CAMU with "severe restrictions"; abuse may lead to severe psychological or physical dependence [1]Fentanyl (9801) [6]; oxycodone (9143) [7]; cocaine (9041) [8]; methamphetamine (1105) [9]; amphetamine (1100) [10]
III (1308.13)Potential for abuse less than Schedules I and II; abuse may lead to moderate or low physical dependence or high psychological dependence [11]. In the 2024 marijuana proposal, DEA treated a CAMU finding as required before a substance can leave Schedule I [12]Ketamine (7285) [13]; buprenorphine (9064) [14]; testosterone, within the anabolic steroid code 4000 [15]
IV (1308.14)Low potential for abuse relative to Schedule III; CAMU; abuse may lead to limited physical or psychological dependence relative to Schedule III [16]Alprazolam (2882) [17]; diazepam (2765) [18]; zolpidem (2783) [19]; tramadol (9752, listed under its chemical name) [20]
V (1308.15)Low potential for abuse relative to Schedule IV; CAMU; abuse may lead to limited physical or psychological dependence relative to Schedule IV [21][22]Pregabalin (2782) [23]; lacosamide (2746) [24]; brivaracetam (2710) [25]

How DEA tests "accepted medical use": DEA first asks whether FDA has approved the drug. If not, it has traditionally used a five-part test [26]:

  1. The drug's chemistry is known and reproducible.
  2. There are adequate safety studies.
  3. There are adequate, well-controlled studies proving efficacy.
  4. Qualified experts accept the drug.
  5. The scientific evidence is widely available.

Where the official list lives

21 CFR Part 1308 has one section per schedule: 1308.11 (I), 1308.12 (II), 1308.13 (III), 1308.14 (IV) and 1308.15 (V). Each section is divided into lettered categories (for example opiates, hallucinogens, depressants, stimulants), and each entry carries a four-digit DEA Controlled Substances Code Number. Temporary Schedule I listings go in 1308.11(h) [27].

How a substance gets scheduled, rescheduled or removed

  1. Who can start it (21 U.S.C. 811(a)). Proceedings to add, move or remove a substance can be started by the Attorney General on his own motion, at the request of the HHS Secretary, or on a petition from any interested party [28]. Scheduling authority is delegated to the DEA Administrator (28 CFR 0.100) [29].

    • Petition examples: moving hydrocodone combination products from III to II (2014) [29] and removing fenfluramine from control (2022) [30].

  2. HHS scientific evaluation (811(b) and (c)). HHS and DEA must consider eight factors [1]:

    1. Actual or relative potential for abuse.
    2. Scientific evidence of pharmacological effect.
    3. Current scientific knowledge.
    4. History and current pattern of abuse.
    5. Scope, duration and significance of abuse.
    6. Risk to public health.
    7. Psychic or physiological dependence liability.
    8. Whether the substance is an immediate precursor of a substance already controlled.

    HHS's recommendation binds DEA on the scientific and medical questions in factors 1, 4 and 5 [31].

  3. Formal rulemaking. Regular scheduling is done "on the record after opportunity for a hearing" under 5 U.S.C. 556 and 557, and the final decision can be challenged in court [32]. Interested persons may request a hearing, or waive one, under 21 CFR 1308.44 [33]. The final rule then amends the relevant 1308 section.

  4. Temporary scheduling (811(h)). To avoid an imminent hazard to public safety, DEA can place a substance in Schedule I for two years, without the 811(b) evaluation. The placement can be extended by up to one year if permanent proceedings are started.

    • Conditions: a 30-day Federal Register notice of intent, and notice to HHS [34][32].
    • Temporary orders can only go into Schedule I and cannot be challenged in court.
    • Recent example: bromazolam, by temporary order in March 2026 [34].

  5. Treaty-driven scheduling (811(d)(1)). Where the 1961 Single Convention or other treaty obligations require control, DEA may pick the schedule it considers most appropriate "without regard to" the 812(b) findings or the 811(a) and (b) procedures [35]. A 1977 D.C. Circuit decision held that an HHS evaluation is still needed in some cases, for example when more than one schedule would meet the treaty obligation [11].

Recent rescheduling activity to watch

  • Marijuana. DEA proposed moving marijuana from Schedule I to III in May 2024 (89 FR 44597) [36]. A final rule effective April 28, 2026 (91 FR 22714), issued under the treaty route (811(d)(1)), placed two things in Schedule III [37][38]:

    • FDA-approved drug products containing marijuana;
    • marijuana held under a state medical marijuana licence.

    The current 1308.11 text I searched still lists "Marihuana" (7360) and "Marihuana Extract" (7350) in Schedule I [5][39].

  • Cipepofol was placed in Schedule IV by a final rule of August 27, 2026 [40].

  • Suvorexant, lemborexant and daridorexant: an August 11, 2026 proposal would move them from Schedule IV to V [41].

I can look up the schedule, drug code and rulemaking history of a specific substance next if useful.

Q.02