Temazepam

# Research Output: Temazepam

## Chemical Identity

**Verified from PubChem CID 5391 [Ref 1] and PubChem REST API [Ref 40]:**

| Property | Value |
|---|---|
| PubChem CID | 5391 |
| CAS | 846-50-4 |
| Molecular formula | C₁₆H₁₃ClN₂O₂ |
| Molecular weight | 300.74 g/mol |
| Canonical SMILES | `CN1C2=C(C=C(C=C2)Cl)C(=NC(C1=O)O)C3=CC=CC=C3` |
| InChI | `InChI=1S/C16H13ClN2O2/c1-19-13-8-7-11(17)9-12(13)14(18-15(20)16(19)21)10-5-3-2-4-6-10/h2-9,15,20H,1H3` |
| InChIKey | SEQDDYPDSLOBDC-UHFFFAOYSA-N |
| IUPAC name | 7-chloro-3-hydroxy-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2-one |
| XLogP | 2.2 |
| Melting point | 119–121 °C |
| Solubility (water) | Very slightly soluble (<1 in 10,000) |
| Solubility (ethanol) | Sparingly soluble |
| Solubility (chloroform) | Freely soluble |
| Density | 1.34 g/cm³ |

**Discrepancies with seed data:**
- Seed data was missing SMILES, molecular formula, molecular weight, InChIKey, CAS, and PubChem CID. All are now confirmed from PubChem [Ref 1, Ref 40].
- IUPAC name in seed data is confirmed correct.
- The brief listed no stereochemistry. Temazepam is a racemic mixture; both enantiomers are present in pharmaceutical preparations. A thesis investigated chiral analysis of temazepam enantiomers from human plasma (Morrison 1996, University of Glasgow), but published clinical data on differential enantiomer activity was not found in this search.

**Physical properties note:** Temazepam is insoluble in water at body temperature. Gel capsule contents solidify when injected intravenously, causing mechanical vascular occlusion in addition to direct endothelial cytotoxicity [Ref 34].

---

## Pharmacology

### Mechanism of Action

Temazepam is a non-selective positive allosteric modulator (PAM) of GABA-A receptors. It binds to the benzodiazepine binding site located at the interface between α and γ subunits of the GABA-A receptor pentamer, potentiating chloride ion influx and causing neuronal membrane hyperpolarization. This produces CNS depression affecting the limbic, thalamic, and hypothalamic regions [Ref 33]. Chweh et al. (1984 [Ref 8]) demonstrated that benzodiazepines whose receptor binding is strongly modulated by GABA (muscimol-coupled receptors) possess potent hypnotic activity; temazepam was among those tested.

Unlike alpha-1-selective agents such as zaleplon or zolpidem, temazepam is non-selective across α1, α2, α3, and α5 GABA-A subunit variants, contributing to its broader anxiolytic, amnestic, muscle-relaxant, and anticonvulsant properties in addition to hypnotic effects.

**Specific Ki values for temazepam** at individual GABA-A receptor subtypes were not retrieved in this search. Published binding data in the literature characterizes temazepam by class-level properties (non-selective benzodiazepine receptor agonist); no substance-specific Ki tables were returned from PubMed or OpenAlex searches. **[FLAG: Ki/EC50 values at GABA-A α-subtypes are absent from the literature search — class inference only. Recommend referencing Hiemke TDM guidelines [Ref 48] for reference ranges.]**

### Pharmacokinetics

All values from human studies; summary from StatPearls [Ref 33], primary PK studies [Ref 2, Ref 3, Ref 4, Ref 5], and renal failure study [Ref 6]:

| Parameter | Value | Source |
|---|---|---|
| Bioavailability | High; minimal first-pass metabolism (~8%) | [Ref 33] |
| Tmax (oral, soft gel) | 1.2–1.6 hours | [Ref 33]; faster than hard capsule [Ref 3] |
| Tmax (oral, hard cap) | 2–3 hours | [Ref 19] |
| Terminal half-life | 3.5–18.4 hours (mean 8.8 h) | [Ref 33]; individual variation wide |
| Volume of distribution | 1.40 L/kg | [Ref 33] |
| Plasma protein binding | ~96% | [Ref 33] |
| Primary metabolism | Phase II glucuronide conjugation (O-glucuronide) | [Ref 4, Ref 36] |
| Secondary metabolism | Minor CYP-mediated oxidation to oxazepam | [Ref 4] |
| CYP450 interactions | None significant — no CYP substrate/inhibitor involvement | [Ref 33, Ref 36] |
| Excretion | 80–90% renal (O-conjugate metabolite) | [Ref 33] |

**Chronopharmacokinetics:** Müller et al. (1987 [Ref 5]) found that evening administration produces slower absorption (t½-abs 0.53 h), lower Cmax (362 ng/mL vs 510 ng/mL), and prolonged distribution half-life compared with morning dosing, though AUC was comparable — a chronopharmacokinetic effect of unlikely clinical significance.

**Formulation effects:** Soft gelatin capsules show significantly faster absorption and higher early plasma peaks than hard gelatin capsules (Fuccella et al. 1977 [Ref 2], 1979 [Ref 3]). A comparison of four 7.5 mg capsules vs one 30 mg capsule showed bioequivalence (Abolin et al. 1993 [Ref 7]).

**Renal disease:** In end-stage renal disease patients, Cmax was lower and free temazepam fraction was higher (4.4–8.8% vs ~4% normal). Terminal t½ ranged 11–77 hours in dialysis subjects. Aluminum hydroxide co-administration did not affect absorption (Kroboth et al. 1985 [Ref 6]).

**Elderly:** Because temazepam is metabolized by glucuronide conjugation (not CYP oxidation), age-related changes in clearance are minimal compared to oxidatively-metabolized benzodiazepines such as diazepam. However, increased pharmacodynamic sensitivity in elderly patients produces enhanced sedation and psychomotor impairment at any given plasma concentration (Greenblatt et al. 1991 [Ref 36]).

---

## History

Temazepam was **synthesized in 1964** as part of the broad benzodiazepine research program at Hoffmann-La Roche — the same company responsible for the first benzodiazepine, chlordiazepoxide (Leo Sternbach, 1955). Oxazepam was synthesized in 1961, nitrazepam in 1962, and temazepam (the N-methyl, 3-hydroxy derivative of diazepam) emerged in 1964. It is structurally a 3-hydroxybenzodiazepinone, making it a direct Phase II metabolite-based structure avoiding the CYP-heavy oxidation pathway [Ref 36].

Clinical investigations began in the early 1970s, with the first human pharmacokinetic studies published in 1977 (Fuccella et al. [Ref 2]). The **soft gelatin capsule formulation** was specifically developed after early work showed that the solution form produced the fastest and most powerful onset [Ref 3].

**Market introduction:**
- United Kingdom: Marketed as **Normison** and **Euhypnos** (Wyeth); exact UK launch date not verified in this search but clinical literature from 1977–1979 shows it was in active clinical investigation.
- United States: **FDA approved 1981** under brand name **Restoril** (Sandoz Pharmaceuticals).
- Other brand names: Remestan, Tenox, Norkotral.

**1980s–1990s abuse crisis:**
By the mid-1980s, temazepam gel capsules had become a popular recreational drug in the UK and Ireland. Street names included **"Jellies," "Rugby Balls,"** and **"Eggs."** Users discovered that heating the capsules produced a liquid that could be injected, yielding faster and more intense effects. IV misuse of temazepam gel capsules was **first reported in Scotland in 1987** [Ref 34]. Throughout 1990–1992, Glasgow and Edinburgh saw dramatic increases in drug-related deaths, with temazepam (often combined with heroin and alcohol) identified as a major contributor (Seymour et al. 2001 [Ref 32]).

**Regulatory response to gel capsule injection harm:**
- UK NHS withdrew gel capsule formulation in **1996** after education campaigns failed to control misuse [Ref 34].
- Australia: Reports of injection emerged in Sydney circa 2001; authority prescriptions required from 2002; capsule formulations completely withdrawn from market in **March 2004** [Ref 34].
- The withdrawal of gel capsules led to an "almost total disappearance" of injecting misuse of the formulation in the UK [Ref 34].

---

## Subjective Effects

Published descriptions from controlled studies [Ref 15, Ref 17, Ref 18, Ref 19, Ref 41, Ref 46]:

**Core effects (clinically documented):**
- **Sedation** — primary intended effect; dose-dependent depth
- **Reduced sleep onset latency** — Glass et al. 2008 [Ref 41]: 25 min vs 37 min placebo in elderly (p = 0.03)
- **Increased total sleep time** — Glass et al.: 6.9 h vs 6.3 h placebo (p = 0.02)
- **Reduced nocturnal awakenings** — Glass et al.: 1.5 vs 2.0 (p < 0.001)
- **Muscle relaxation** — pharmacological class effect [Ref 33]
- **Anxiolysis** — documented in premedication studies [Ref 22, Ref 23, Ref 26]
- **Anterograde amnesia** — dose-dependent; impaired recall of events following dosing [Ref 22]; Bailie et al. (1989 [Ref 22]) found cognitive deficits apparent 30 min post-surgery, largely recovered at 4 h
- **Psychomotor impairment** — morning-after effects; significant for temazepam 30 mg, minimal for 15 mg in elderly [Ref 39]
- **Disinhibition** — documented class effect

**Effects documented in post-marketing surveillance and case reports [Ref 33]:**
- Vivid dreams, nightmares
- Behavioral changes (violent outbursts, paranoia — rare)
- Rebound insomnia on discontinuation

**Dreaming:** Temazepam, like benzodiazepines generally, suppresses slow-wave (delta) and REM sleep — class effect documented for the BZD family. Whether it paradoxically enhances dream recall during the tapering/rebound phase is noted in the literature for the class; direct temazepam-specific REM/slow-wave polysomnography data was not recovered in this search. **[FLAG: Specific polysomnographic staging data for temazepam not found — class inference applies.]**

**Effect of duration on efficacy:** Kales et al. 1986 [Ref 17] demonstrated that temazepam's sleep maintenance efficacy declined significantly with intermediate-term use (>2 weeks), with tolerance developing to this effect. Allen et al. 1987 [Ref 18] reported maintained efficacy over 1–3 months in some patients with no tolerance, suggesting heterogeneity. Temazepam does not show meaningful efficacy for sleep onset (vs sleep maintenance) when hard-capsule formulations are used, due to slow absorption [Ref 19].

**Duration data from controlled studies:**
- Onset of sleep-promoting effect: 30–60 min (hard capsule), faster for soft gel
- Duration of primary effects: 7–8 hours (consistent with seed data [Ref 17])
- Morning-after (hangover) effects: Moderate; Kales 1983 [Ref 19] noted significant morning sleepiness; Glass 2008 [Ref 41] found psychomotor impairment persisted in the morning in elderly at 15 mg

---

## Safety & Toxicity

### Acute Toxicity

**Overdose presentation:** Sleepiness, confusion, ataxia, respiratory depression, and coma in severe cases [Ref 33]. Temazepam alone is rarely fatal; lethality significantly increases with co-administration of CNS depressants.

**Interaction-related lethality:** The co-administration of opioids, alcohol, and/or benzodiazepines produces a defined increase in rates of adverse events, overdose, and death (Gudin et al. 2013 [Ref 43]). This is the primary mechanism of benzodiazepine-related deaths and is explicitly noted in the seed data and confirmed in the epidemiological literature.

**Claimed comparative toxicity:** StatPearls [Ref 33] states temazepam demonstrates "approximately 10 times more hazardous than diazepam" in overdose. The primary source for this claim was not independently verified in this search. **[SAFETY FLAG: The "10× more hazardous than diazepam" claim from StatPearls could not be traced to an original primary source in this search. It should not be treated as a verified quantitative toxicity ratio without further investigation.]**

**LD50:** No human LD50 data found. Animal-specific LD50 data was not returned in searches. **[FLAG: LD50 data absent from literature retrieved.]**

### IV Injection Toxicity

Temazepam is very slightly soluble in water and directly damages vascular endothelium [Ref 34]. Gel capsule contents solidify at body temperature after injection, causing mechanical occlusion in addition to chemical injury. Pathological findings (Dodd et al. 1994 [Ref 29]): histological evidence of limb ischaemia in all 9 cases examined. Clinical outcomes (Nott et al. 1993 [Ref 30]): all 11 patients suffered severe ischaemia; radial artery injection invariably led to tissue loss and amputation. Complications included abscesses, cellulitis, skin ulcers, nerve damage, deep vein thrombosis, gangrene, compartment syndrome, and rhabdomyolysis [Ref 33, Ref 34].

### Respiratory System

In severe normocapnic COPD patients, temazepam 10 mg did not significantly affect breathing or gas exchange (Stege et al. 2010 [Ref 42]). However, standard clinical guidance contraindicates benzodiazepines in sleep apnea due to muscle relaxation effects on upper airway tone. Respiratory depression is the mechanism of death in polydrug overdose scenarios.

### Pregnancy

**FDA Pregnancy Category X.** Animal studies documented fetal harm including exencephaly and rib abnormalities. Human data associates in utero BZD exposure with neonatal withdrawal syndrome (floppy infant syndrome, respiratory depression, hypothermia) [Ref 33].

### Elderly

Falls risk is the primary safety concern in elderly patients. Mets et al. (2010 [Ref 38]) reviewed evidence that hypnotics including temazepam impair body balance and standing steadiness. Wysowski et al. (1996 [Ref 37]) found temazepam and triazolam had similar hip fracture risk (RR 0.92, 95% CI 0.72–1.17) — both should be used with caution. Meta-analysis (Glass et al. 2005 [Ref 13]) found adverse cognitive events were 4.78× more common with sedatives vs placebo in the elderly (95% CI 1.47–15.47).

### Overdose Management

Flumazenil (benzodiazepine receptor antagonist) can reverse BZD effects but should NOT be used routinely: meta-analysis of 13 RCTs (Penninga et al. 2016 [Ref 44]) found significantly more adverse events (RR 2.85) and SAEs (RR 3.81 — supraventricular arrhythmia, convulsions) with flumazenil vs placebo. Primary management is supportive care.

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## Harm Reduction

**Published risk reduction strategies [Ref 33, Ref 43, Ref 44]:**

1. **Combination use:** Avoid concurrent use with opioids, alcohol, other CNS depressants, barbiturates, antihistamines, antipsychotics. The opioid + BZD combination is a leading cause of drug-related deaths.
2. **Duration:** Guidelines universally recommend short-term use only — 7–10 days (prescribing information [Ref 33]); maximum 4 weeks per Ashton guidelines [Ref 20] and European Insomnia Guideline [Ref 14]. Tolerance and dependence develop with extended use.
3. **Injection:** Never inject temazepam in any formulation. Direct vascular endothelium toxicity and insolubility cause severe, often irreversible vascular injury [Ref 29, Ref 30, Ref 34].
4. **Dose:** Use lowest effective dose, especially in elderly. Dose-dependent increase in cognitive impairment, psychomotor impairment, and fall risk [Ref 41].
5. **Discontinuation:** Taper rather than abruptly stop after >2 weeks of use. Abrupt discontinuation risks withdrawal seizures, delirium.
6. **Elderly:** Particular caution warranted; increased pharmacodynamic sensitivity even when PK unchanged [Ref 36]. CBT-I is the preferred first-line treatment for chronic insomnia in any age group [Ref 12, Ref 14].
7. **Flumazenil:** Should not be used routinely for BZD overdose; supportive care is preferred [Ref 44].
8. **Contraindications:** Pregnancy (Category X), sleep apnea, myasthenia gravis, acute alcohol intoxication, severe depression with suicidal ideation, history of BZD hypersensitivity [Ref 33].

---

## Tolerance & Dependence

### Tolerance

The seed data states tolerance builds "within a couple of days of continuous use" — broadly consistent with published literature for hypnotic effect.

- Kales et al. (1986 [Ref 17]) — sleep lab study: significant tolerance to sleep maintenance effect developed within an "intermediate term" (14–22 nights). Short-term (first 3 nights) efficacy was maintained.
- Allen et al. (1987 [Ref 18]) — 3-month study (n = 175): temazepam 30 mg maintained efficacy without tolerance development in a clinical sample; withdrawal showed improved (not worsened) sleep vs baseline, suggesting partial resolution of insomnia rather than rebound.
- Kales (1990 [Ref 19]) — noted quazepam maintained efficacy where temazepam lost sleep maintenance efficacy with intermediate use.
- Benzodiazepine-class tolerance involves downregulation and conformational changes at GABA-A receptor subunits.

**Cross-tolerance:** With all benzodiazepines (confirmed in seed data [Ref 10]).

### Dependence

Lader (1994 [Ref 9]) reviewed benzodiazepine dependence; physical dependence manifests as a withdrawal syndrome on discontinuation comprising physical symptoms (photophobia, hyperacusis, unsteadiness, muscular spasm) and psychological symptoms. MacKinnon & Parker (1982 [Ref 10]) reviewed the benzodiazepine withdrawal syndrome including temazepam; withdrawal was documented even at recommended doses with short-term use — rebound insomnia particularly prominent with short-acting agents.

**Withdrawal characteristics:**
- Onset: 2–10 days after cessation (depending on half-life; temazepam medium t½ = 3.5–18.4 h → withdrawal typically beginning within 1–3 days)
- Symptoms: Rebound insomnia, anxiety, agitation, tremor, perceptual disturbances, autonomic hyperactivity; rarely — seizures and delirium
- Duration: Usually weeks; some patients experience prolonged syndrome lasting months
- Treatment: Supportive; gradual taper preferred; adjuvant melatonin studied in BZD withdrawal (Lähteenmäki et al. 2014 [Ref 24])

**Dependence formation:** Seed data characterizes temazepam as "extremely physically and psychologically addictive" — broadly supported by the literature for long-term use, though this characterization overstates typical short-course therapeutic use risk. **[FLAG: The seed characterization "extremely physically and psychologically addictive" is stronger than most published review language, which typically describes "physical dependence" risk with long-term use and abuse potential in those with substance use disorder histories. Recommend more nuanced framing.]**

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## Interactions

### Critical Interactions (Safety-Level)

| Interactant | Mechanism | Risk |
|---|---|---|
| Opioids | Additive CNS/respiratory depression | **Potentially fatal** — FDA boxed warning [Ref 33, Ref 43] |
| Alcohol | Additive CNS depression | **Potentially fatal** [Ref 43] |
| Barbiturates | Additive CNS depression | High risk [Ref 33] |
| Other benzodiazepines | Additive CNS depression | High risk |

### Moderate Interactions

| Interactant | Mechanism | Risk |
|---|---|---|
| Antihistamines (sedating) | Additive CNS depression | Moderate [Ref 33] |
| Antipsychotics | Additive sedation | Moderate [Ref 33] |
| MAO inhibitors | Activity disruption (mechanism unclear) | Moderate [Ref 33] |
| Phenothiazines | Additive CNS depression | Moderate [Ref 33] |

### Pharmacokinetic Interactions

Temazepam does NOT undergo significant CYP450 metabolism [Ref 33, Ref 36]. Therefore, the extensive pharmacokinetic drug interactions that affect CYP3A4/CYP2C19 substrates do NOT apply. This is a critical distinction from many other benzodiazepines (e.g., diazepam, alprazolam, triazolam) and confers fewer pharmacokinetic drug-drug interactions.

**Aluminum hydroxide:** No significant effect on temazepam absorption (Kroboth et al. 1985 [Ref 6]).

**Note:** Ondansetron had no interaction with temazepam in a volunteer study (abstract mention, PMID 1425620); this non-interaction is pharmacologically consistent with temazepam's Phase II metabolism.

---

## Legal Status

| Jurisdiction | Schedule/Classification | Notes |
|---|---|---|
| United States | **Schedule IV** (DEA/Controlled Substances Act) | 5 refills in 6 months [Ref 21] |
| United Kingdom | **Class C, Schedule 3** (Misuse of Drugs Regulations 2001) | Safe custody required; stricter than most Schedule 3 BZDs [Ref 35] |
| Australia | **Schedule 4** (Prescription Only) | Capsule formulations permanently withdrawn 2004 [Ref 34] |
| Canada | **Schedule IV** | Prescription required [Ref 35] |
| International | **Schedule IV** (UN Convention on Psychotropic Substances) | [Ref 35] |

**Note:** UK's Class C/Schedule 3 designation applies stricter controls than most benzodiazepines (which are Schedule 4 in the UK). This was likely driven by the documented injection misuse crisis of the 1990s.

---

## Clinical Trials

**Directly relevant to temazepam:**

1. **NCT02153788** — "Efficacy and Safety of Temazepam in HIV Seropositive Patients With Insomnia" — Phase 4, Completed, Duke University. Condition: Insomnia. Directly evaluates temazepam in an immunocompromised population.

2. **NCT00940550** — "Study to Investigate the Effects of Melatonin, Temazepam & Zolpidem on Sleep EEG in Men and Women" — Phase 1, Completed, University of Surrey. Sleep EEG including temazepam pharmacodynamics.

**Recent published RCT (not yet registered on trial registry):**
- Mendis et al. (2024 [Ref 11]) — Phase III multicenter RCT: temazepam vs melatonin vs placebo in advanced cancer insomnia (n = 21). Adjusted mean ISI reduction −9.1 vs placebo (95% CI −17.5 to 0.7, p = 0.04) for temazepam. Both temazepam and melatonin well tolerated.

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## Community Feedback Analysis

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

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## Gaps & Flags

### Safety-Critical Flags

1. **⚠️ SAFETY FLAG — "10× more hazardous than diazepam" claim:** This claim from StatPearls [Ref 33] could not be traced to a primary published source in this search. The generation agent must NOT present this as a verified quantitative ratio without identifying an original source (clinical toxicology study or epidemiological data).

2. **⚠️ SAFETY FLAG — LD50 data absent:** No published LD50 data for temazepam in humans or animals was recovered in this search. Acute toxicity data relies on class inference and case-level descriptions.

3. **⚠️ SAFETY FLAG — Dose ranges not independently confirmed in placebo-controlled trials:** Seed dose ranges (threshold 2 mg, light 5–10 mg, common 10–30 mg, strong 30–40 mg, heavy 40+ mg) are broadly consistent with prescribing information and clinical literature (Glass 2008 used 15 mg; Allen 1987 used 30 mg; Kales 1986 used 15 mg). Specific dose-response data at threshold/light doses not found in literature — these are sub-therapeutic doses below published clinical study ranges.

### Data Gaps

4. **Specific Ki / EC50 values:** No published substance-specific binding affinity data for temazepam at individual GABA-A receptor subunit variants was retrieved. The generation agent should characterize pharmacology based on class properties (non-selective BZD receptor agonist).

5. **Polysomnographic sleep staging data:** Direct temazepam-specific REM and SWS suppression data not found in this search. BZD class effect applies (suppression of slow-wave and REM sleep), but quantitative data for temazepam specifically is absent.

6. **UK market launch date:** The specific UK approval date and initial Normison/Euhypnos market launch year (believed to be late 1970s based on 1977 clinical publication activity [Ref 2]) was not found in a primary regulatory source. FDA approval date (1981) is confirmed.

7. **Enantiomeric activity:** Temazepam is chiral; pharmaceutical preparations are racemic. Differential activity of the (R)- vs (S)-enantiomers was not characterized in the published pharmacological literature retrieved.

8. **"Extremely addictive" seed characterization discrepancy:** Seed data characterizes dependence formation as "extremely physically and psychologically addictive." Published review literature typically uses more graduated language. This is a characterization discrepancy requiring editorial judgment, not a factual error per se.

9. **Sleep architecture effects (REM dreaming):** The seed effect profile includes "dreaming-enhancement" as a listed effect. BZDs typically suppress REM sleep during acute use, which would reduce dream activity. Dream enhancement may occur during rebound following discontinuation, or may reflect user-reported vivid dreams as an adverse effect (noted in StatPearls [Ref 33]). This is a potential contradiction with the seed effect profile. **[FLAG FOR EDITORIAL REVIEW: dreaming-enhancement listed as an effect, but BZD class effect is REM suppression during use; dreaming may be enhanced on rebound/withdrawal].**

10. **Historical Ki / IC50 data from original synthesis literature:** Access to the original Hoffmann-La Roche synthesis and pharmacology papers from 1964 was not possible through the APIs available in this search. These would be pre-digital era papers.