Oxazepam

7-chloro-3-hydroxy-5-phenyl-1,3-dihydro-1,4-benzodiazepin-2-one

Overview

Oxazepam belongs to Depressants / Benzodiazepines.

Key safety note: Oxazepam is a comparatively mild, short-to-intermediate benzodiazepine, but it carries the class's core risks.[2]
Effects
Subjective effects vary. What a substance feels like depends on dose, individual physiology, mindset, and setting. The points below describe commonly reported effects, not guaranteed, uniform, or desirable outcomes.
  • Reduced anxiety, calm and relaxation, drowsiness and easier sleep, with muscle relaxation.
  • Impaired coordination, concentration and short-term memory, and dizziness: coming on relatively gradually because of the slow absorption.
  • With regular use: tolerance, dependence, and rebound anxiety/insomnia and other withdrawal symptoms on stopping.
Dosing & duration
Harm-reduction note: These are commonly cited reference ranges, not a recommendation or a “safe” dose. Potency, purity, body chemistry, tolerance, and drug combinations vary widely. Start low, go slow, wait for full effects before redosing, and never assume an unknown product matches these figures. Missing data is not evidence of safety.

Oral (tablets/capsules), prescribed and dose-adjusted by a clinician. Figures are therapeutic (prescribing) context, not a recreational guide.. Oxazepam is a prescription medicine for short-term use. The lowest effective dose and shortest course are used, with lower doses in the elderly. Its slow onset means effects build over 30–120 minutes, so redosing before it takes hold risks overshooting. It should not be combined with alcohol, opioids or other sedatives, and users should not drive while affected.

Dose ranges

Anxiety (adult)

10–30 mg, 3–4 times daily

Insomnia (at night)

15–30 mg

Elderly / debilitated

Lower doses (e.g. 10 mg up to 3×/day), titrated

Duration

onset

≈30–120 min (slow)

total

Several hours (short–intermediate)

after effects

Possible next-morning drowsiness. Rebound anxiety/insomnia on stopping

Chemical & Physical Properties
FormulaC15H11ClN2O2
Molar mass286.71 g/mol
StateSolid
Melting point205–206 °C
Boiling pointNot reported
DensityNot reported
Vapor pressure4.2×10⁻¹² mmHg at 25 °C (estimated)
pKapKa1 1.55 (-C=N-), pKa2 10.9 (-OH) (estimated)
LogP2.24
Solubilityless than 1 mg/mL at 19 °C (NTP, 1992), Soluble in alcohol, chloroform, dioxane, 1 g soluble in >10,000 mL water, 220 mL alcohol, 270 mL chloroform, 2200 mL ether
Refractive indexNot reported
Identifiers & Synonyms
CAS604-75-1
CAS (enantiomer)
PubChem CID4616
InChIKeyADIMAYPTOBDMTL-UHFFFAOYSA-N
InChIInChI=1S/C15H11ClN2O2/c16-10-6-7-12-11(8-10)13(9-4-2-1-3-5-9)18-15(20)14(19)17-12/h1-8,15,20H,(H,17,19)
SMILESC1=CC=C(C=C1)C2=NC(C(=O)NC3=C2C=C(C=C3)Cl)O

Synonyms

  • Serax
  • Adumbran
Pharmacodynamics & Biochemistry

Oxazepam (Serax, Adumbran) is a short-to-intermediate-acting benzodiazepine. Like the rest of the class it is a positive allosteric modulator at the benzodiazepine site of the GABA-A receptor (the α/γ2 subunit interface): in the presence of GABA it increases the frequency of chloride-channel opening, enhancing inhibitory neurotransmission to produce anxiolysis, sedation, muscle relaxation and anticonvulsant effects. It is also a natural downstream metabolite of several other benzodiazepines, including diazepam, temazepam and prazepam. Its distinctive feature is its metabolism: oxazepam is cleared by direct glucuronidation (mainly UGT2B15) to an inactive glucuronide, WITHOUT the oxidative (CYP) metabolism that most benzodiazepines undergo and WITHOUT any active metabolites. Because this conjugation is well preserved in old age and liver disease, oxazepam does not accumulate the way long-acting, oxidatively-metabolised agents do, and it is one of the benzodiazepines preferred in the elderly and in hepatic impairment (alongside lorazepam and temazepam). Its half-life is roughly 6–9 hours and its onset is comparatively slow (30–120 min), which gives it less of an abrupt 'rush' and somewhat lower abuse appeal than fast-onset benzodiazepines. Oxazepam has a single chiral centre (C3) and is used as the racemate. Its two enantiomers interconvert (racemise) readily, and no therapeutic advantage of a single enantiomer over the racemate has been found. Its high-affinity benzodiazepine-site binding is not separately curated in the major binding database, so it is described here qualitatively rather than with a receptor-binding table.

Biological targets

  • GABA-A
Pharmacokinetics
BioavailabilityNot reported
TmaxSlow onset ≈30–120 min
Half-life≈6–9 h (short–intermediate)
VdNot reported
Protein bindingNot reported
MetabolismDirect hepatic glucuronidation (mainly UGT2B15) to an inactive glucuronide. No oxidative (CYP) metabolism and no active metabolites
ExcretionRenal (as the glucuronide)
Toxicology & Safety
Harm-reduction note: Toxicity and risk depend on dose, route, purity, combinations, setting, and individual health factors. Missing harms should never be interpreted as evidence of safety.

Not reported

Oxazepam is a comparatively mild, short-to-intermediate benzodiazepine, but it carries the class's core risks. It causes dose-dependent sedation, drowsiness, dizziness, impaired coordination, memory and reaction time, so it impairs driving and increases fall risk (though it accumulates less than long-acting agents). Like all benzodiazepines it produces tolerance, physical dependence and, on stopping after regular use, a withdrawal syndrome (rebound anxiety and insomnia, tremor, sweating and, after high-dose or abrupt cessation, seizures), so courses are kept short and doses tapered. It can cause respiratory depression, which becomes dangerous when combined with opioids, alcohol or other CNS depressants: the usual mechanism of benzodiazepine-related death. Its slow onset makes it somewhat less appealing recreationally, but it is still misused. Because it is directly conjugated rather than oxidised, it has fewer pharmacokinetic drug interactions than most benzodiazepines and is comparatively safe in liver disease and old age. Use cautiously in sleep apnoea, severe respiratory insufficiency, myasthenia gravis, and in pregnancy.[2]

Legal Status
Legal note: Legal status can change over time and may vary by country, region, formulation, analogue status, prescription context, and enforcement practice. Always confirm with current official sources before relying on this section.
Interactions & Contraindications

Drug interactions

Opioids Additive respiratory depression and sedation: a leading cause of benzodiazepine-related death (regulatory boxed warnings).[2]
Alcohol, Benzodiazepines, Gabapentinoids (gabapentin, pregabalin) Additive sedation and respiratory depression, including with barbiturates and sedating antihistamines.[2]

Contraindications

Respiratory disease or sleep apnoea sleep apnoea syndrome or severe respiratory insufficiency.[2]
Myasthenia gravis[2]
Combining with alcohol or other CNS depressants acute alcohol or other CNS-depressant intoxication.[2]
Pregnancy or breastfeeding and caution in the elderly.[2]
Usage & Context
  • A prescription anxiolytic and hypnotic for the short-term treatment of anxiety (including anxiety with depression) and insomnia, and for managing the symptoms of alcohol-withdrawal syndrome.
  • Particularly favoured in older people and in patients with impaired liver function, because its direct-conjugation metabolism avoids the accumulation and active metabolites of long-acting benzodiazepines.
  • Also encountered as the pharmacologically active endpoint of diazepam, temazepam and prazepam metabolism, and misused recreationally.
Sources & Evidence

Further Information