Flualprazolam

# Research Output: Flualprazolam

## Chemical Identity

**Confirmed via PubChem (CID: 10359044) [database_lookup]:**

| Property | Value |
|---|---|
| PubChem CID | 10359044 |
| IUPAC Name | 8-chloro-6-(2-fluorophenyl)-1-methyl-4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepine |
| Molecular Formula | C₁₇H₁₂ClFN₄ |
| Molecular Weight | 326.8 g/mol |
| InChIKey | MPZVLJCMGPYWQQ-UHFFFAOYSA-N |
| CAS Number | 28910-91-0 |

**Physical properties (web-retrieved from chemical databases):**
- Physical appearance: Off-white powder
- Melting point: 203–204 °C
- Solubility: Soluble in dichloromethane and methanol; partially soluble in water

**SMILES:** Not returned by the PubChem API endpoint used. Available at https://pubchem.ncbi.nlm.nih.gov/compound/10359044. The canonical SMILES can be retrieved directly from PubChem CID 10359044.

**Brief seed data cross-check:** The seed data's IUPAC name (8-chloro-6-(2-fluorophenyl)-1-methyl-4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepine) matches PubChem exactly. Molecular formula (C₁₇H₁₂ClFN₄), MW (326.8), and InChIKey are unset in the seed data — PubChem is the source of record. PubChem CID 10359044 should be written to the database. The seed fields for SMILES and molecular formula should also be populated from PubChem.

**Structural relationship to alprazolam:** Flualprazolam differs from alprazolam by the addition of a single fluorine atom at the 2-position of the phenyl ring (ortho-fluorophenyl substitution instead of unsubstituted phenyl). This single substitution dramatically alters pharmacokinetics (Canfield et al. 2023 [Ref 6]).

---

## Pharmacology

### Mechanism of Action

Flualprazolam is a full agonist at the benzodiazepine binding site of the GABA-A (γ-aminobutyric acid type A) receptor — the same mechanism as all classical benzodiazepines. It acts as a positive allosteric modulator, enhancing the effect of GABA at chloride ion channels, producing anxiolytic, sedative, hypnotic, anticonvulsant, and muscle-relaxant effects. It has no approved medical indication in any jurisdiction.

As a triazolobenzodiazepine (sharing the triazolo ring fusion with alprazolam and triazolam), flualprazolam is structurally similar to both. The 2-fluorophenyl substituent identifies it as an analog of alprazolam (Ntoupa et al. 2021 [Ref 22]).

### Receptor Binding Affinity

No direct experimental GABA-A receptor binding affinity (Ki or EC₅₀) data for flualprazolam at specific subunit combinations has been identified in the published literature. Manchester et al. (2022 [Ref 8]) used quantitative structure-activity relationship (QSAR) modelling to predict GABA-A binding affinity for a panel of designer benzodiazepines including flualprazolam, as well as measuring blood-to-plasma ratios. The specific QSAR-predicted Ki value for flualprazolam is reported in the full paper but was not available from the abstract alone.

**FLAG FOR REVIEW:** No direct binding assay data (e.g., radioligand binding, functional assay) for flualprazolam has been found in the literature. The Manchester 2022 QSAR predictions are the closest available estimate. The full Manchester 2022 paper should be consulted for the predicted Ki value.

Brunetti et al. (2021 [Ref 4]) classify flualprazolam as "potent" relative to other designer benzodiazepines, consistent with the forensic evidence showing pharmacological effects at blood concentrations of 4–15 ng/mL (Youso et al. 2022 [Ref 7]; Heide et al. 2020 [Ref 5]).

### Pharmacokinetics

**Human data (very limited — one case report):**

Wagmann et al. (2020 [Ref 1]) is the primary human pharmacokinetic study. An 18-year-old male was admitted to the emergency department after suspected flualprazolam ingestion. Plasma concentration was measured at 8 μg/L (8 ng/mL). Seven metabolites were tentatively identified via in vitro incubations with pooled human liver S9 fraction and HepaRG cells, then confirmed in the human biosamples.

**Metabolism:**
- Phase I: Hydroxylation at the alpha position (→ α-hydroxy flualprazolam) and at the 4-position of the phenyl ring (→ 4-hydroxy flualprazolam). Additional metabolites identified include hydroxylation products and ring-opened forms. A monohydroxylated metabolite (3-hydroxy-flualprazolam) was also identified in rabbit blood (Ling et al. 2022 [Ref 9]).
- Phase II: Glucuronidation of hydroxylated metabolites. α-Hydroxy flualprazolam glucuronide, 4-hydroxy flualprazolam glucuronide, and the parent compound glucuronide were the most abundant signals in human urine — far more abundant than the parent compound (Wagmann et al. 2020 [Ref 1]).
- Total: 11 metabolites identified across species (7 phase I, 4 phase II) in a 2026 in vitro multi-species study (Dai et al. 2026 [Ref 10]).

**CYP enzymes involved:** CYP3A4 is the primary cytochrome P450 enzyme involved in flualprazolam biotransformation. UGT1A4 is the primary UDP-glucuronosyltransferase involved in phase II conjugation. Wagmann et al. (2020 [Ref 1]) note that genetic polymorphisms in CYP3A4 and UGT1A4, as well as drug-drug and drug-food interactions (particularly CYP3A4 inhibitors such as azole antifungals, macrolide antibiotics, grapefruit juice), may substantially alter flualprazolam exposure. Wu & Fu (2022 [Ref 11]) note that genetic polymorphism effects on designer BZD metabolism remain largely uncharacterized.

**Recommended detection targets in urine:** α-Hydroxy flualprazolam glucuronide and 4-hydroxy flualprazolam glucuronide (most abundant). If conjugate cleavage is performed, the corresponding phase I hydroxy metabolites. Sofalvi et al. (2020 [Ref 36]) developed an assay monitoring α-hydroxyflualprazolam alongside the parent compound.

**Recommended detection targets in blood:** Both hydroxylated metabolites can also be detected in blood (Wagmann et al. 2020 [Ref 1]).

**Species differences in metabolism:** Humans and mice primarily produce 4- and α-hydroxylated metabolites. Fish, bovine, sheep, and pig mainly generate 4-hydroxylated metabolites. Benzene-ring hydroxylated metabolites more abundant in rats and livestock (Dai et al. 2026 [Ref 10]).

**Rat pharmacokinetics (Canfield et al. 2023 [Ref 6]):**
In a rat model (2 mg/kg subcutaneous), flualprazolam displayed:
- Approximately 2-fold increase in volume of distribution vs. alprazolam
- Approximately 2-fold increase in clearance vs. alprazolam
- Significantly increased half-life — approximately double that of alprazolam in the same model
- Overall greater systemic exposure than alprazolam at equivalent doses

The increased volume of distribution and extended half-life from fluorine substitution at the ortho-phenyl position explains the greater overall body burden and potential for prolonged effects compared to alprazolam.

**Detection window in blood (rabbit model):** Approximately 36 hours (Ling et al. 2022 [Ref 9]).

**Human blood concentrations in forensic cases:**
- Postmortem: Mean 20 ng/mL, median 8.2 ng/mL, range 2.0–620 ng/mL (n=167; Papsun et al. 2021 [Ref 3])
- DUID (impaired driving): Mean 22 ng/mL, median 14 ng/mL, range 4.4–68 ng/mL (n=22; Papsun et al. 2021 [Ref 3])
- DUID (Sedgwick County): Range 4–69 ng/mL, mean 20.9 ng/mL, median 15 ng/mL (n=19; Youso et al. 2022 [Ref 7])
- Living forensic cases (Norway): Median 0.0080 mg/L (0.0033–0.056 mg/L; n=10; Heide et al. 2020 [Ref 5])
- Postmortem (Sweden/Finland): Median 18.0 ng/g, range 3.0–68 ng/g (n=33; Kriikku et al. 2020 [Ref 2])

**Immunoassay cross-reactivity:** Commercial immunoassay benzodiazepine screens (Abbott ARCHITECT, Roche cobas, Siemens Dimension Vista) cross-react with flualprazolam, producing presumptive positive results. Standard confirmatory LC-MS/MS panels for prescription BZDs may fail to confirm designer BZDs, risking misclassification as false positives. Flualprazolam detected in 11/35 ED specimens with apparent false-positive BZD screens (Puzyrenko et al. 2022 [Ref 20]).

**Blood-to-plasma ratio:** Measured by Manchester et al. (2022 [Ref 8]); specific numerical value in full paper.

---

## History

### Synthesis and Early History

Flualprazolam was first synthesized in 1976 and covered by patent US3987052A ("6-phenyl-4H-s-triazolo[4,3-a][1,4]benzodiazepines"), filed by J.B. Hester Jr. (Ref 27). This patent covers the broader class of triazolo-benzodiazepine compounds. The compound was never developed for clinical or commercial use by any pharmaceutical company, having been investigated as part of the broader mid-20th century benzodiazepine drug discovery effort.

Flualprazolam was first described in the forensic scientific literature in 2019, coinciding with its appearance in forensic case material. Qian et al. (2019 [Ref 21]) published one of the first forensic identifications — in an anesthesia robbery case — representing its early deployment in drug-facilitated crime contexts.

### Emergence on NPS Markets

Flualprazolam first appeared on European drug markets in 2018, as reported by the EMCDDA/EUDA monitoring systems. The UNODC Early Warning Advisory (March 2020 [Ref 38]) identified flualprazolam and etizolam as among the most frequently detected designer benzodiazepines, found in 48% of postmortem cases and 83% of DUID cases examined (2019–April 2020 surveillance data).

In the United States, DEA chemical intelligence reported first identification in 2018. The Oregon Poison Center identified a cluster of flualprazolam intoxications in June 2019 — 6 adolescents presented over one week after ingesting counterfeit alprazolam tablets (Blumenberg et al. 2020 [Ref 19]). Between August 2019 and February 2020, flualprazolam was quantitatively confirmed in 197 forensic blood samples at one major US forensic laboratory alone (Papsun et al. 2021 [Ref 3]).

By 2020–2021, flualprazolam was frequently detected in counterfeit Xanax tablets globally, including in New Zealand (Ref 37) and in UNODC reports (Ref 39). From mid-2018 onward, flualprazolam was also detected as an adulterant in the unregulated opioid supply in Vancouver, Canada, associated with atypical overdose presentations (Laing et al. 2021 [Ref 29]).

A market shift was observed post-2022 in some jurisdictions (notably San Francisco), with bromazolam increasingly replacing flualprazolam following its DEA scheduling (Rodda 2024 [Ref 40]).

### Clinical/Institutional History

No clinical trials have been registered or conducted for flualprazolam in any jurisdiction (ClinicalTrials.gov search: 0 results). It has no approved medical use anywhere in the world.

---

## Subjective Effects

### Published Descriptions from Clinical/Forensic Sources

Clinical effects documented in the Blumenberg et al. (2020 [Ref 19]) case series of 6 adolescents (Oregon, June 2019):
- **Sedation** — present in all 6 patients; duration <6 hours from time of ingestion in all cases
- **Slurred speech**
- **Confusion**
- **Mild respiratory depression**

No effects unexpected for benzodiazepine intoxication were observed. None of the 6 patients required intubation, mechanical ventilation, ICU admission, or antidotal therapy.

The UK ACMD advisory (2021 [Ref 23]) documents the following clinical profile: drowsiness, psychomotor impairment, unsteadiness and incoordination, memory loss, and confusion. At higher doses: unconsciousness and respiratory depression, especially in combination with alcohol or other CNS depressants.

The Wagmann et al. (2020 [Ref 1]) case report describes the clinical presentation as including sedation, loss of consciousness, memory loss, and disinhibition in the context of suspected flualprazolam ingestion.

### Subjective Effects from User Reports

Orsolini et al. (2020 [Ref 12]) conducted a netnographic study of online psychonaut trip reports for designer benzodiazepines including flualprazolam. Designer BZDs are described as producing effects broadly consistent with classical benzodiazepines: anxiolysis, sedation, hypnosis, muscle relaxation, and disinhibition. Users report effects at very low doses, consistent with the documented potency at 4–15 ng/mL blood concentrations.

Self-medication rationale: Holborn et al. (2023 [Ref 34]) documented that users of designer BZDs including flualprazolam frequently report motivation of anxiety and insomnia management.

### Duration Data

The brief's duration data (onset 20–40 min, peak 1–2 hours, offset 2–6 hours, total 5–8 hours, aftereffects 6–24 hours oral) is consistent with general triazolobenzodiazepine pharmacology and with the clinical case series (sedation <6 hours in 6 adolescents). However, the aftereffects duration of 6–24 hours plausibly reflects the extended half-life documented by Canfield et al. (2023 [Ref 6]). No controlled human duration study exists.

**FLAG FOR REVIEW:** Duration data in the seed is based on community consensus and class inference, not a controlled study. The extended rat half-life (approximately double alprazolam's) suggests total duration and aftereffects could be longer than alprazolam's comparable parameters. This should be flagged as inferred from rat PK data.

### Effect Profile Assessment (Effects Taxonomy)

The 23 seed effect slugs are broadly consistent with the clinical literature. The following assignments are supported by published evidence:

**Well-supported by literature:**
- `sedation` [body] — core effect; present in all clinical cases [Refs 1, 19, 5, 7]
- `motor-control-impairment` [body] — documented in DUID cases; psychomotor impairment [Refs 5, 7, 23]
- `muscle-relaxation` [body] — class effect of GABA-A positive allosteric modulators
- `respiratory-depression` [body] — documented in clinical cases and deaths [Refs 2, 19, 23]
- `amnesia` → `memory-suppression` [thinking] — documented in Wagmann 2020 case, ACMD [Refs 1, 23]
- `cognitive-impairment` → `analysis-suppression` [thinking] — class effect, DUID evidence [Refs 5, 7]
- `disinhibition` [self] — documented [Ref 1]
- `anxiety-suppression` → `anxiety` is listed as a WITHDRAWAL effect (rebound anxiety)
- `dizziness` [body] — consistent with psychomotor impairment, ACMD [Ref 23]
- `delusions-of-sobriety` [thinking] — a recognized hazard of potent BZDs; documented in context [Refs 3, 7]
- `thought-deceleration` [thinking] — sedation-class effect

**Plausible (class inference, limited specific data):**
- `dreaming-enhancement` [perception] — benzodiazepines known to suppress REM early and rebound dream enhancement with tolerance/cessation
- `visual-acuity-suppression` [perception] — consistent with sedation/psychomotor impairment
- `seizure-threshold-reduction` [body] — paradoxically listed but may refer to withdrawal seizure risk; needs clarification in generation
- `sexual-arousal-enhancement` [body] — disinhibition-mediated; user-reported for BZDs
- `sexual-arousal-suppression` [body] — physiological depressant effect at higher doses
- `tactile-euphoria` [body] — user-reported BZD effect
- `cognitive-euphoria` [thinking] — anxiety relief can present as euphoria, especially in anxious individuals
- `compulsive-redosing-urge` [thinking] — consistent with dependence liability
- `thought-disorganization` [thinking] — at higher doses
- `emotional-suppression` [feeling] — consistent with CNS depression
- `irritability` [feeling] — withdrawal-phase effect, documented for BZD class
- `ego-inflation` [self] — disinhibition-mediated

**Needs clarification:**
- `seizure-threshold-reduction` — as listed, this could be confused with the withdrawal seizure risk (BZDs raise seizure threshold during use; withdrawal lowers it). The generation agent should distinguish these carefully.

---

## Safety & Toxicity

### LD50 / Therapeutic Index

No LD50 or therapeutic index data has been identified in the published literature for flualprazolam in any species. The seed data note "Inferred from pharmacological class — not sourced from literature" is accurate.

**FLAG FOR REVIEW:** All LD50 and therapeutic index data for flualprazolam is absent from the published literature. Any value currently in the database is an inference from class.

### Overdose and Fatality Data

**Postmortem forensic data:**

Kriikku et al. (2020 [Ref 2]) report 33 deaths in Sweden and Finland with flualprazolam detected:
- 61% accidental deaths; 18% suicides
- Median postmortem blood concentration: 18.0 ng/g (range 3.0–68 ng/g)
- **13 of 33 cases had flualprazolam implicated in the cause of death**
- Polydrug use and opioid co-use were very common
- 82% male; median age 30 years

Papsun et al. (2021 [Ref 3]) report 197 forensic cases (Aug 2019–Feb 2020):
- Postmortem: mean 20 ng/mL, median 8.2 ng/mL, range 2.0–620 ng/mL (n=167)
- **Flualprazolam was found with opioids (primarily fentanyl) in 83% of cases**
- Significant overlap in blood concentrations between postmortem and impaired driving cases — suggesting that concentrations commonly encountered in living impaired persons overlap with lethal concentrations in polydrug settings

Brunetti et al. (2021 [Ref 4]) report that between 2008 and 2021, 141 deaths involving designer benzodiazepines were identified across reviewed literature, with flualprazolam among the top implicated substances alongside flubromazolam, etizolam, and phenazepam.

**Key safety finding:** Flualprazolam is rarely implicated as the sole cause of death. The vast majority of fatal cases involve polydrug use, with opioids (particularly fentanyl) the most common co-drug. The overlapping blood concentration ranges between fatal (postmortem) and non-fatal (impaired driving) cases suggest that context (particularly opioid co-use) is the primary determinant of lethality, not flualprazolam dose alone.

### Adverse Events in Clinical Settings

Blumenberg et al. (2020 [Ref 19]) — 6 adolescents:
- Sedation, slurred speech, confusion, mild respiratory depression
- All resolved within 6 hours
- No serious complications; no antidotal therapy required

Wagmann et al. (2020 [Ref 1]) — one adult case:
- Admitted to ED after suspected flualprazolam ingestion
- Plasma concentration 8 μg/L at time of measurement
- Clinical presentation included sedation, memory loss, disinhibition

### Drug-Facilitated Crime

Flualprazolam has been documented in drug-facilitated sexual assault and robbery contexts (Ling et al. 2022 [Ref 9]; Qian et al. 2019 [Ref 21]).

### Organ Toxicity

No specific hepatotoxicity, nephrotoxicity, or other organ-specific toxicity data has been identified for flualprazolam in the published literature. By class analogy, benzodiazepines are not typically associated with direct organ toxicity at therapeutic/recreational doses.

### Psychological Risks

Benzodiazepine-class psychological risks include amnesia (documented in the Wagmann 2020 case), disinhibition (documented), delusions of sobriety (flagged as a safety hazard in forensic literature — users may be severely impaired without subjective awareness), and dependence/withdrawal risk (class effect; see Tolerance & Dependence).

---

## Harm Reduction

### Key Hazards

1. **Opioid co-use is the primary lethality risk:** 83% of flualprazolam postmortem cases involved opioids (Papsun et al. 2021 [Ref 3]). The synergistic CNS and respiratory depression from combining benzodiazepines with opioids is well established. Flualprazolam should never be combined with opioids, alcohol, or other CNS depressants.

2. **Counterfeit pill risk:** Flualprazolam has been widely distributed in counterfeit alprazolam (Xanax) tablets (Blumenberg et al. 2020 [Ref 19]; UNODC 2021 [Ref 39]). Users purchasing "Xanax" from non-pharmacy sources may receive flualprazolam without knowledge.

3. **Delusions of sobriety / impaired judgment:** Forensic impaired driving data (Youso et al. 2022 [Ref 7]; Heide et al. 2020 [Ref 5]) document severe impairment at low blood concentrations. The compound is pharmacologically active at very low concentrations.

4. **Extended duration and aftereffects:** The rat pharmacokinetics (approximately double the half-life of alprazolam) suggest impairment and sedation may persist longer than expected by analogy to alprazolam (Canfield et al. 2023 [Ref 6]).

5. **Immunoassay failure:** Standard drug screen immunoassays may cross-react (false positive for "benzodiazepines") but routine confirmatory panels may fail to specifically identify flualprazolam (Puzyrenko et al. 2022 [Ref 20]). This has clinical consequences — clinicians may not know the specific agent causing impairment.

6. **Drug-facilitated crime context:** Flualprazolam is potent at very low doses and has been used in drug-facilitated crimes (Ling et al. 2022 [Ref 9]).

### Testing and Identification

Standard benzodiazepine immunoassay strips will detect flualprazolam (cross-reactivity) but cannot specifically identify it. Specific detection requires LC-MS/MS or LC-QTOF-MS. Fentanyl test strips do not detect flualprazolam.

Flumazenil (the benzodiazepine receptor antagonist) should reverse flualprazolam effects as a full GABA-A agonist, consistent with standard benzodiazepine toxicology management.

### Emergency Response

Management follows standard benzodiazepine toxicology protocols: supportive care, airway management, flumazenil if indicated (noting risk of precipitating withdrawal seizures in dependent patients). Per Blumenberg et al. (2020 [Ref 19]), clinical effects resolved within 6 hours in adolescent cases without specific antidotal therapy.

### Harm Reduction in Australia

Freestone et al. (2026 [Ref 17]) provide narrative review of clinical management and harm reduction for novel BZDs in Australia, covering toxicity management, dependence, and withdrawal, applicable to flualprazolam by class.

---

## Tolerance & Dependence

### Tolerance Development

No flualprazolam-specific data on tolerance development rate or mechanism has been identified in the published literature. By class inference (GABA-A positive allosteric modulator), tolerance develops through receptor downregulation and subunit composition changes. Cross-tolerance with other benzodiazepines is expected and is the pharmacological basis for substitution detoxification protocols.

### Dependence

No flualprazolam-specific dependence liability studies exist. The compound's long half-life (approximately double alprazolam's in rats; Canfield et al. 2023 [Ref 6]) may contribute to a dependence profile intermediate between short-acting (high addiction potential) and long-acting (more gradual dependence development). No controlled data available.

### Cross-Tolerance and Detoxification

By class, cross-tolerance to other GABA-A agonists (diazepam, clonazepam, other benzodiazepines) is expected. Standard designer benzodiazepine detoxification protocols use diazepam substitution. Buitenhuis et al. (2025 [Ref 30]) document a case of successful bromazolam (a structurally similar designer BZD) detoxification using diazepam (6 mg bromazolam converted to 20 mg diazepam, successfully tapered). By structural analogy, a similar diazepam substitution approach could be applied to flualprazolam dependence.

Freestone et al. (2026 [Ref 17]) review dependence and withdrawal management for novel BZDs in Australia.

### Withdrawal

Benzodiazepine withdrawal syndrome is expected upon abrupt cessation in dependent users: rebound anxiety, insomnia, tremor, diaphoresis, and in severe cases, seizures. Seizure risk is a documented serious complication of benzodiazepine withdrawal class-wide.

**FLAG FOR REVIEW:** All tolerance and dependence data for flualprazolam is based on class inference from benzodiazepine pharmacology. No flualprazolam-specific clinical or animal dependence data has been identified in the published literature.

---

## Interactions

### Opioids (CRITICAL)

The most clinically significant interaction is with opioids. Benzodiazepine-opioid co-use produces synergistic CNS and respiratory depression. Flualprazolam was detected alongside opioids in 83% of postmortem cases (Papsun et al. 2021 [Ref 3]). Flualprazolam was significantly overrepresented in isotonitazene-related overdose deaths compared to other synthetic opioid deaths, suggesting co-distribution and/or deliberate co-use (Shover et al. 2020 [Ref 14]; Napoletano et al. 2022 [Ref 35]). This combination is potentially lethal.

### Alcohol and Other CNS Depressants

Synergistic CNS depression is expected with alcohol, Z-drugs (zolpidem, zopiclone), opioids, barbiturates, and other benzodiazepines. The UK ACMD advisory (2021 [Ref 23]) specifically flags higher dose risk "when combined with alcohol or sedatives." Bromazolam postmortem cases (Hikin et al. 2024 [Ref in initial search]) show similar polydrug patterns applicable by class.

### CYP3A4 Inhibitors and Inducers

Because flualprazolam is primarily metabolized by CYP3A4 (Wagmann et al. 2020 [Ref 1]):
- **CYP3A4 inhibitors** (azole antifungals, clarithromycin, erythromycin, HIV protease inhibitors, grapefruit juice) will increase flualprazolam plasma concentrations — potentially markedly, given that this is the primary elimination pathway
- **CYP3A4 inducers** (rifampicin, carbamazepine, phenytoin, St John's Wort) will decrease concentrations and may precipitate withdrawal in dependent users

**FLAG FOR REVIEW:** No clinical drug-drug interaction studies exist for flualprazolam. All interaction data is inferred from CYP3A4 substrate status.

### UGT1A4 Interactions

UGT1A4 involvement in phase II conjugation (Wagmann et al. 2020 [Ref 1]) suggests potential interactions with UGT1A4 inhibitors (e.g., sorafenib, probenecid) and inducers, though no specific data exists.

### Flumazenil

Flumazenil is a competitive GABA-A benzodiazepine site antagonist and should reverse flualprazolam effects. Caution in dependent patients (risk of precipitating withdrawal seizures). This is inferred from class pharmacology.

---

## Legal Status

### United States

| Status | Effective Date | Reference |
|---|---|---|
| Not federally controlled | Prior to Dec 2022 | |
| Emergency/Temporary Schedule I | December 23, 2022 | Federal Register 2022-27278 [Ref 25] |
| DEA "Imminent Hazard" declaration | July 26, 2023 | DEA public statement [Ref 26] |
| Temporary Schedule I (renewed) | July 25, 2025 | Federal Register 2025-14037 |
| Permanent Schedule I | April 1, 2026 | Federal Register 2026-04112 [Ref 24] |

The DEA stated flualprazolam has no currently accepted medical use and poses imminent hazard to public safety. Clonazolam, diclazepam, etizolam, and flubromazolam were co-scheduled.

### United Kingdom

Flualprazolam became a **Class C** drug under the Misuse of Drugs Act 1971, effective **18 August 2021** (Circular 006/2021 [Ref 23]). It is controlled under **Schedule 1** of the 2001 Regulations (no accepted medical use; Home Office licence required). The Advisory Council on the Misuse of Drugs (ACMD) recommended control in November 2020 alongside flunitrazolam and norfludiazepam, citing "greater prevalence" and the compound's lack of any known legitimate medicinal use in the UK.

### International (UN Conventions)

The World Health Organization recommended flualprazolam for international scheduling as Schedule IV under the 1971 Convention on Psychotropic Substances in December 2019. The Commission on Narcotic Drugs adopted this recommendation at its 63rd regular session in **2020** [Ref 32]. This gives international scheduling authority, obligating signatory states to control the substance.

### Australia

Flualprazolam is listed as a controlled substance under the Australian Office of Drug Control (ODC). Victoria recorded 43 flualprazolam detections between 2018 and December 2022 (Drummer et al. 2024 [Ref 31]; Freestone et al. 2026 [Ref 17]).

### Other Jurisdictions

- **New Zealand:** Flualprazolam detected in fake Xanax tablets (Ref 37); controlled under NZ Misuse of Drugs Act 1975 (inferred from NPS class scheduling).
- **Canada:** Benzodiazepines as a class are controlled under the Controlled Drugs and Substances Act. Flualprazolam falls under this framework.
- **Nordic countries:** Detected in Swedish and Finnish forensic cases as early as 2016–2019 (Kriikku et al. 2020 [Ref 2]; Axelsson et al. 2022 [Ref 15]).
- **European Union:** Monitored by EMCDDA through EU Early Warning System from 2018. Among two most frequently seized designer BZDs in 2019–2020. EU-level scheduling status subject to individual member state law and the MDA/EU framework.

---

## Clinical Trials

No clinical trials have been registered on ClinicalTrials.gov for flualprazolam. A search returned 0 results. No approved medical use; no research-use trials identified.

---

## Community Feedback Analysis

No community feedback was submitted in Part A2 of the substance brief.

---

## Gaps & Flags

### Safety-Critical Flags (require human review)

1. **⚠️ No LD50 data in any species.** The seed data "Toxicity — Acute: moderate; Chronic: moderate" notes "Inferred from pharmacological class — not sourced from literature." Confirmed: no LD50 or therapeutic index data exists in the published literature for flualprazolam. These values should remain flagged as class-inferred.

2. **⚠️ No human half-life or bioavailability data.** The only human PK datum is a single plasma concentration measurement (8 μg/L in one case report). All duration data relies on rat PK (approximately double alprazolam's half-life) or community consensus.

3. **⚠️ No specific GABA-A binding Ki values.** Manchester et al. (2022 [Ref 8]) provides QSAR-predicted values but these are computational estimates, not experimental binding data. The generation agent should be clear about this distinction.

4. **⚠️ Dose ranges in seed data (Threshold: 0.05 mg; Light: 0.1–0.3 mg; Common: 0.3–0.5 mg; Strong: 0.5–1 mg; Heavy: 1+ mg)** are community consensus estimates, not confirmed by controlled studies. Consistent with the compound's potency relative to alprazolam (which is itself clinically active at 0.25–0.5 mg). These ranges appear plausible but must remain flagged as community consensus.

5. **⚠️ `seizure-threshold-reduction` effect slug in the effect profile needs clarification.** Benzodiazepines raise seizure threshold during use; the seizure risk is during withdrawal. The generation agent should present this as a *withdrawal* risk, not an acute effect.

6. **⚠️ `sexual-arousal-enhancement` and `sexual-arousal-suppression` are both listed** — benzodiazepine effects on sexual arousal are dose-dependent and context-dependent (disinhibition at lower doses may enhance arousal; sedation at higher doses suppresses it). No flualprazolam-specific data exists. These are class-inferred.

7. **⚠️ Duration seed data (5–8 hours total; 6–24 hours aftereffects) may be conservative.** Given the rat data showing approximately double the half-life of alprazolam (which has a half-life of ~11 hours in humans), flualprazolam's human half-life could be on the order of 20+ hours, suggesting aftereffects could extend well beyond 24 hours in some users. This should be flagged as an open question requiring community input.

### Data Gaps (not safety-critical)

- **No SMILES string returned by PubChem API.** Available at PubChem CID 10359044. Generation agent or database team should retrieve from pubchem.ncbi.nlm.nih.gov.
- **No experimental physical property data** (melting point source unverified via API; ChemicalBook reports 203–204°C; web-retrieved only).
- **No cross-tolerance quantification.** Diazepam substitution ratio for flualprazolam detoxification is unknown; the bromazolam case (Ref 30) provides rough analogy only.
- **EU member-state legal status varies.** Individual EU country scheduling varies; no comprehensive review identified.
- **Australian specific scheduling date not confirmed** via primary source (ODC website timed out).
- **CYP3A4 interaction data is all inferred** — no clinical DDI studies exist for flualprazolam.
- **Full Canfield et al. 2023 PK parameters** (specific half-life values, Cmax, AUC) are in the full paper but the abstract did not provide numerical values. Generation agent should note approximate doubling of t½ vs alprazolam (rat data only).
- **No reproductive or developmental toxicity data.**
- **No immunotoxicity or carcinogenicity data.**
- **First synthesis date (1976) based on patent date** — unverified in primary chemical literature via API; treat as unverifiable but well-established historically.