Clonazepam

5-(2-chlorophenyl)-7-nitro-1,3-dihydro-2H-1,4-benzodiazepin-2-one

Overview

Clonazepam belongs to Depressants / Benzodiazepines.

Key safety note: Long-acting, high-potency benzodiazepine used for epilepsy and panic disorder.[3][4]
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.
  • Sedation, drowsiness, fatigue and reduced anxiety are the core effects. The anticonvulsant and muscle-relaxant actions underlie its therapeutic use.
  • Motor and cognitive impairment is common, especially early in treatment: ataxia, impaired coordination and balance, dizziness, slowed reactions and anterograde amnesia.
  • Tolerance to the sedative and anticonvulsant effects and physical dependence develop with continued use. Paradoxical reactions (agitation, irritability, disinhibition) occur in a minority of users.
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 and orally disintegrating tablets (0.5, 1 and 2 mg). Oral drops in some countries. Prescription-only. The figures below are medical reference ranges from the drug label, not recreational guidance. Effects are strongly potentiated by alcohol and other CNS depressants, and the drug should never be combined with opioids. Doses are individualised and tapered slowly on discontinuation.

Dose ranges

Seizure disorders (adult, start)

0.5 mg three times daily

Seizure disorders (titration / max)

increase by 0.5–1 mg every 3 days, maximum 20 mg/day

Panic disorder (adult)

0.25 mg twice daily for 3 days, then 0.5 mg twice daily (target ~1 mg/day, label maximum 1–4 mg/day)

Duration

onset

≈20–60 minutes (oral)

total

Long-acting: clinical effect persists many hours (half-life ≈30–40 h)

Chemical & Physical Properties
FormulaC15H10ClN3O3
Molar mass315.71 g/mol
StateSolid
Melting point237.5 °C
Boiling pointNot reported
DensityNot reported
Vapor pressureNot reported
pKapK1 = 1.5, pK2 = 10.5
LogP2.41
SolubilitySlightly soluble in water (<100 mg/L at 25 °C), Insoluble in benzene. Slightly soluble in acetone, methanol, chloroform
Refractive indexNot reported
Identifiers & Synonyms
CAS1622-61-3
CAS (enantiomer)
PubChem CID2802
InChIKeyDGBIGWXXNGSACT-UHFFFAOYSA-N
InChIInChI=1S/C15H10ClN3O3/c16-12-4-2-1-3-10(12)15-11-7-9(19(21)22)5-6-13(11)18-14(20)8-17-15/h1-7H,8H2,(H,18,20)
SMILESC1C(=O)NC2=C(C=C(C=C2)[N+](=O)[O-])C(=N1)C3=CC=CC=C3Cl

Synonyms

  • Klonopin
  • Rivotril
  • Clonazepam
Pharmacodynamics & Biochemistry

Clonazepam is a long-acting, high-potency benzodiazepine. It binds the benzodiazepine site of the GABA-A receptor (the α/γ2 subunit interface) and acts as a positive allosteric modulator, increasing the frequency with which the GABA-gated chloride channel opens. The resulting greater chloride influx hyperpolarises the neuron and reduces its firing, producing anticonvulsant, anxiolytic, sedative and muscle-relaxant effects. Its very high receptor affinity, sub-nanomolar Ki at the α1, α2 and α3 GABA-A subunits, together with a long elimination half-life makes clonazepam one of the more potent and slowly cleared benzodiazepines. Beyond its GABAergic action, clonazepam also has serotonergic activity (it influences serotonin synthesis and turnover), which has been proposed to contribute to its usefulness in panic disorder and certain movement disorders.

Biological targets

  • GABA-A

Binding & functional measurements

TargetMeasurementSpecies
GABAA receptor α1 subunitpKi 8.9Human
GABAA receptor α2 subunitpKi 8.8Human
GABAA receptor α3 subunitpKi 8.7Human
GABA-A α1β2γ2 receptorEC50 3.0 nMHuman
Pharmacokinetics
BioavailabilityOral ≈90%
Tmax≈1–4 h
Half-life≈30–40 h (reported range ≈19–60 h)
VdNot reported
Protein binding≈85%
MetabolismHepatic CYP3A4 nitro-reduction to 7-aminoclonazepam, followed by acetylation
ExcretionRenal (largely as metabolites)
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

Long-acting, high-potency benzodiazepine used for epilepsy and panic disorder. Tolerance and physical dependence develop with continued use, and abrupt discontinuation can precipitate a protracted, potentially life-threatening withdrawal syndrome (including seizures), so it must be tapered slowly. The greatest acute danger is additive CNS and respiratory depression when combined with opioids (an FDA boxed warning), alcohol or other sedatives.[3][4]

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 Profound sedation, respiratory depression, coma and death (FDA boxed warning). The combination should be avoided.[3][4]
Alcohol, Benzodiazepines Additive sedation and respiratory depression, including with barbiturates, sedating antihistamines and kratom.[4][3]
CYP3A4 inhibitors (ritonavir, azole antifungals, macrolides, grapefruit) Ketoconazole, itraconazole, clarithromycin or ritonavir raise clonazepam levels.[4]
CYP3A4 inducers (rifampicin, carbamazepine) Carbamazepine, phenytoin, phenobarbital or primidone lower clonazepam levels.[4]

Contraindications

Kidney or liver impairment significant or severe liver disease.[3]
Closed-angle glaucoma acute narrow-angle glaucoma.[3]
Known hypersensitivity to the drug hypersensitivity to clonazepam or other benzodiazepines.[3]
Respiratory disease or sleep apnoea severe respiratory insufficiency and sleep apnoea syndrome.[4]
Myasthenia gravis[4]
Usage & Context
  • Prescription benzodiazepine approved for seizure disorders (including Lennox–Gastaut syndrome and akinetic, myoclonic and absence seizures) and for panic disorder.
  • Used off-label for conditions such as acute mania, restless legs syndrome, REM sleep behaviour disorder, tardive dyskinesia and short-term insomnia.
  • Also encountered as a drug of misuse. Its potency and long duration make it sought-after and sharply raise overdose risk when combined with opioids or alcohol.
Sources & Evidence

Further Information