Benzodiazepine — Long-acting Pregnancy: SPC §4.6: preclinical studies show reproductive toxicity and the possibility of congenital malformations cannot be excluded; epidemiological evidence indicates anticonvulsants act as teratogens, though attribution to a specific drug is difficult. Clonazepam should only be given to pregnant women if the potential benefits outweigh the risk to the foetus, and during pregnancy only if there is a compelling indication. High doses in the last trimester or during labour can cause fetal heart-rate irregularities and neonatal hypothermia, hypotonia, mild respiratory depression and poor feeding; chronic later-pregnancy use may cause neonatal physical dependence and withdrawal. Both pregnancy itself and abrupt discontinuation can exacerbate epilepsy. Breast-feeding: passes into breast milk in small amounts only, but mothers on clonazepam should not breastfeed — if there is a compelling indication for clonazepam, breastfeeding should be discontinued.

Clonazepam (Psychiatric Use)

Brand names: Rivotril

This monograph covers clonazepam used in a psychiatric context, where this long-acting benzodiazepine may be used short term for severe anxiety or agitation; it is not licensed as a first-line anxiolytic.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Panic disorder (US labelling): 0.25 mg twice daily initially, increased after 3 days to the target dose of 1 mg/day for most patients

Route: Oral (tablets swallowed whole with water)

Frequency: Twice daily initially; once the 1 mg/day target is reached, giving one dose at bedtime may reduce daytime somnolence

Max: 4 mg/day (panic disorder, US label). Increases above 1 mg/day should be made in increments of 0.125–0.25 mg twice daily every 3 days; doses of 2, 3 and 4 mg/day were LESS effective than 1 mg/day in the fixed-dose study and caused more adverse effects

INDICATION SOURCING: the fetched UK SPC (Clonazepam Aristo 0.5 mg Tablets) gives posology for EPILEPSY only and contains no psychiatric-indication regimen, so the panic-disorder dose above is taken from the US (openFDA/DailyMed) label §DOSAGE AND ADMINISTRATION — verify against current UK practice and licensing before publication. US label wording: 'The initial dose for adults with panic disorder is 0.25 mg twice daily. An increase to the target dose for most patients of 1 mg/day may be made after 3 days... some individual patients may benefit from doses of up to a maximum dose of 4 mg/day.' DISCONTINUATION (panic disorder, US label): taper gradually, decreasing by 0.125 mg twice daily every 3 days until completely withdrawn; if withdrawal reactions develop, pause the taper or return to the previous dose and then decrease more slowly. FOR REFERENCE, the UK SPC epilepsy regimen on the same molecule (a DIFFERENT indication — do not apply to psychiatric use): adults initial dose should not exceed 1 mg/day; maintenance normally 4–8 mg; total daily dose divided into 3 or 4 doses through the day; larger doses may be given at the physician's discretion up to a maximum of 20 mg daily; maintenance should be attained after 2–4 weeks. Elderly (UK SPC): particularly sensitive to centrally depressant drugs and may become confused — initial dose should not exceed 0.5 mg/day. Hepatic impairment (UK SPC): severe hepatic impairment — do not treat with clonazepam; mild to moderate — adjust dose to individual requirements, probably lower. Do not interrupt treatment abruptly: withdraw by gradually reducing the dose because of the risk of precipitating status epilepticus. PAEDIATRIC: the US label states 'Safety and effectiveness in pediatric patients with panic disorder below the age of 18 have not been established', and there is no paediatric psychiatric dose in either label, so no structured paedDose is recorded. (The per-kg figures in both labels — UK maintenance ranges of 0.5–1 mg/day for infants 0–1 year, 1–3 mg/day for children 1–5 years, 3–6 mg/day for school children 5–12 years; US 0.01–0.03 mg/kg/day initially, not exceeding 0.05 mg/kg/day, to a maintenance of 0.1–0.2 mg/kg/day — are for SEIZURE DISORDER, not psychiatric use.) Verify any under-18 use against a children's formulary.

Dose adjustments

Renal

SPC §4.4: use with caution in impairment of renal or hepatic function and in the elderly or debilitated — dosage should generally be reduced (no numeric reduction stated). US label: metabolites are excreted by the kidneys, so caution is needed in renal impairment to avoid excess accumulation.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known hypersensitivity to benzodiazepines, or to the active substance or any of the excipients
Acute pulmonary insufficiency; severe respiratory insufficiency
Sleep apnoea syndrome
Myasthenia gravis
Severe hepatic insufficiency (US label: clinical or biochemical evidence of significant liver disease)
Patients in a coma, and patients known to be abusing pharmaceuticals, drugs or alcohol
US label additionally: acute narrow-angle glaucoma (may be used in open-angle glaucoma receiving appropriate therapy)

Side effects

Somnolence, slowed reaction, muscular hypotonia, dizziness and ataxia — occur relatively frequently, usually transient, generally resolving during treatment or on dose reduction; partly preventable by slow dose escalation
Impaired concentration, restlessness, confusional state and disorientation; depression; drug dependence; rarely loss of libido
Paradoxical reactions: excitability, irritability, aggression, agitation, nervousness, hostility, anxiety, sleep disturbances, nightmares, vivid dreams, psychotic disorders, and activation of new seizure types
Anterograde amnesia at therapeutic doses (risk increases with higher doses), sometimes with inappropriate behaviour; in long-term or high-dose treatment reversible dysarthria, incoordination, gait disorder, ataxia, nystagmus (common) and diplopia
Allergic reactions with very rare anaphylaxis and rare angioedema; cardiac failure including cardiac arrest reported; rarely respiratory depression (particularly after intravenous administration); isolated cases of reversible incomplete precocious puberty in children

Interactions

Opioids — concomitant use may result in sedation, respiratory depression, coma and death; limit dose and duration and follow patients closely
Alcohol and CNS depressants — concomitant use should be avoided; may increase clinical effects including severe sedation and clinically relevant respiratory and/or cardiovascular depression
Other centrally acting medicines and other anticonvulsant/antiepileptic agents — dose of each drug may need adjusting; multiple anticonvulsants increase CNS-depressant adverse effects
Phenytoin — clonazepam has the potential to influence phenytoin concentrations; monitor phenytoin levels on co-administration
Carbamazepine and phenobarbital — clonazepam does not appear to alter their pharmacokinetics (US label)

Clinical monograph

How it works

It potentiates GABA-mediated inhibition at the GABA-A receptor, producing anxiolytic, sedative and anticonvulsant effects.

Prescribing in practice

It carries a substantial risk of tolerance and dependence and should be reserved for short-term use, with any longer course tapered rather than stopped abruptly.
Concurrent opioids, alcohol or other CNS depressants greatly increase the risk of sedation and fatal respiratory depression.
Its long duration of action favours accumulation and daytime sedation, requiring caution and reduced dosing in the elderly and in hepatic impairment.

Monitoring

Monitor sedation, response, and for signs of tolerance or dependence, reviewing the need for continued treatment regularly.

Counselling the patient

This medicine can cause drowsiness and affect driving and concentration.
Avoid alcohol while taking it.
Do not stop it suddenly after regular use, as withdrawal effects can occur.

Evidence & guidelines

Benzodiazepines such as clonazepam are recommended for short-term use only because of dependence risk, in line with NICE and MHRA guidance.

Reference: NICE CG185 (Bipolar Disorder); NICE CG22 (Anxiety); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways