Clobazam
Quick Facts
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Seizures associated with Lennox–Gastaut syndrome (LGS) | ≥2 years of age | Adjunctive | FDA Approved |
Clobazam is the only 1,5-benzodiazepine in clinical use; the substitution of the nitrogen at position 5 (rather than 4, as in diazepam, lorazepam, and other 1,4-benzodiazepines) is thought to underlie its relatively favourable ratio of anticonvulsant to sedative effect compared with conventional benzodiazepines. In the United States it is approved only as adjunctive therapy for LGS in patients aged 2 years and older; in many other countries it has additional approvals for anxiety disorders and refractory epilepsies.
Clobazam was approved in the US in 2011 on the basis of two randomized trials in LGS — the Phase II OV-1002 study and the pivotal Phase III OV-1012 (CONTAIN) study — which demonstrated a dose-dependent reduction in weekly drop-seizure frequency. Most patients in pivotal trials were already receiving valproate, lamotrigine, levetiracetam, or topiramate.
Refractory focal and generalized epilepsies (other than LGS): Used as adjunctive therapy in adults and children with seizures not adequately controlled on other antiepileptic drugs. Clobazam has been marketed for general epilepsy use in many countries (including Canada, the UK, and EU) for decades. Evidence: moderate quality.
Dravet syndrome: Frequently used as adjunctive therapy alongside valproate, stiripentol, fenfluramine, or cannabidiol. Evidence: moderate quality (consensus recommendations and observational data).
Anxiety disorders, including generalized anxiety: Approved indication outside the US (e.g., as Frisium); off-label in the US, where other benzodiazepines and SSRIs are first-line. Evidence: moderate quality.
Catamenial epilepsy: Sometimes used cyclically around menses for seizure clustering. Evidence: low quality (small case series).
Dosing
Dosing is by body weight, divided into two strata at the 30 kg cutoff. Any total daily dose above 5 mg should be split into two divided doses; a 5 mg total daily dose may be given once daily. Titration should not proceed faster than weekly, because clobazam reaches steady state in approximately 5 days but its more abundant active metabolite, N-desmethylclobazam, takes about 9 days. The tables below organize dosing by clinical scenario rather than by tablet strength.
Standard LGS Dosing — Adults & Pediatric Patients ≥2 Years
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| LGS adjunctive therapy — body weight ≤30 kg | 5 mg/day (single or divided) | Day 7: 10 mg/day in 2 divided doses | 20 mg/day in 2 divided doses (from day 14) | Effectiveness increases with increasing dose Do not escalate faster than weekly |
| LGS adjunctive therapy — body weight >30 kg | 10 mg/day in 2 divided doses | Day 7: 20 mg/day in 2 divided doses | 40 mg/day in 2 divided doses (from day 14) | Same titration schedule applies regardless of age (≥2 y) Tablet may be taken whole, broken on the score, or crushed in applesauce |
| Discontinuation / dose reduction | — | Reduce total daily dose by 5–10 mg/day on a weekly basis | Avoid abrupt cessation | If withdrawal symptoms develop, pause taper or return to prior dose, then reduce more slowly Abrupt withdrawal may precipitate status epilepticus or other life-threatening reactions |
Dose Adjustment in Special Populations
| Population | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Geriatric (≥65 years) | 5 mg/day (regardless of weight) | Titrate to half the standard weight-based maintenance, as tolerated | Same as standard (20 or 40 mg/day by weight); additional titration may begin on day 21 | Plasma concentrations are higher in the elderly at any given dose Proceed slowly; increased fall and sedation risk |
| Known CYP2C19 poor metabolizers | 5 mg/day | Titrate to half the standard weight-based maintenance | Standard maximum (20 or 40 mg/day); additional titration may begin on day 21 | N-desmethylclobazam levels are 3–5× higher in poor metabolizers — dose-related adverse-event risk is correspondingly higher Genotyping not routine; consider in patients with disproportionate sedation |
| Mild–moderate hepatic impairment (Child–Pugh 5–9) | 5 mg/day (both weight groups) | Titrate to half the standard weight-based maintenance | Standard maximum; additional titration may begin on day 21 | Limited PK data — proceed slowly Severe hepatic impairment: no dosing recommendation can be given |
| Renal impairment (mild–moderate) | Standard starting dose | Standard maintenance | Standard maximum | No dose adjustment required Severe renal impairment / ESRD: essentially no clinical experience; dialysability of clobazam and N-desmethylclobazam is unknown |
Although clobazam itself accumulates over about 5 days, its principal pharmacologically active species in blood is the metabolite N-desmethylclobazam (N-DMC). At therapeutic doses, plasma N-DMC concentrations are 3–5× those of the parent compound and require approximately 9 days to reach steady state. Adverse events that emerge a week or more after a dose change typically reflect rising N-DMC, not parent drug — a useful framing when counselling families during titration.
Tablets can be administered whole, broken along the functional score, or crushed in applesauce, and all formulations may be taken with or without food. The oral suspension must be shaken before each dose and dispensed in its original bottle with the supplied dosing syringe; discard any remainder 90 days after first opening.
Pharmacology
Mechanism of Action
Clobazam is the only 1,5-benzodiazepine in clinical use; classical agents such as diazepam, lorazepam, and midazolam are 1,4-benzodiazepines. Like other benzodiazepines it potentiates GABAergic neurotransmission by binding the benzodiazepine site of the GABAA receptor, increasing the frequency of chloride channel opening in response to GABA and thereby enhancing inhibitory tone in the cortex and limbic system. The 1,5 substitution pattern is associated with a different conformational fit that may favour anticonvulsant over hypnotic activity at clinically used doses, although sedation remains a prominent and dose-related effect.
The principal active species in plasma is N-desmethylclobazam, formed by hepatic N-demethylation. N-DMC is one-fifth to equipotent with parent clobazam at the GABAA receptor on a molar basis, but circulates at 3–5× higher concentrations at therapeutic doses, so it accounts for a substantial share of clinical effect. Variability in CYP2C19 — the main enzyme that clears N-DMC — is a major determinant of inter-individual differences in efficacy and tolerability.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Rapid and extensive after oral dosing; tablet Tmax 0.5–4 h, oral suspension Tmax 0.5–2 h; relative bioavailability of tablet vs solution ~100%; food does not significantly affect absorption | Tablet, suspension, and oral film are interchangeable on a milligram basis under fasted conditions; can be given with meals to manage GI upset |
| Distribution | Highly lipophilic; apparent Vd at steady state ~100 L; clobazam ~80–90% protein-bound, N-DMC ~70% | Wide tissue distribution including CNS; protein binding is moderate, so displacement interactions are uncommon |
| Metabolism | Extensively hepatic. N-demethylation primarily by CYP3A4, with lesser contributions from CYP2C19 and CYP2B6. The active metabolite N-desmethylclobazam is then metabolized mainly by CYP2C19. Clobazam is a weak CYP3A4 inducer and a CYP2D6 inhibitor in vivo | Strong/moderate CYP2C19 inhibitors and CYP2C19 poor-metabolizer status raise N-DMC exposure several-fold; CYP2D6 substrates (e.g., dextromethorphan) may need lower doses |
| Elimination | ~82% of a radiolabelled dose excreted in urine, ~11% in feces; only ~2% of parent recovered unchanged in urine. Mean t½: clobazam 36–42 h; N-DMC 71–82 h. Time to steady state: ~5 days clobazam, ~9 days N-DMC | Long half-lives mean dose changes take days to fully manifest in plasma — wait at least a week between escalations; abrupt cessation drives a slow but sustained withdrawal |
Therapeutic drug monitoring is not routinely required, but combined plasma clobazam plus N-DMC concentrations are sometimes useful in patients with disproportionate sedation, suspected CYP2C19 poor-metabolizer status, or significant interactions (e.g., concomitant cannabidiol). In a population PK/PD analysis from CONTAIN, clobazam was approximately three times more potent than N-DMC by EC50, but high N-DMC concentrations strongly drive sedation-type adverse events.
Side Effects
Adverse-event data below are drawn from the placebo-controlled Phase III CONTAIN trial (Study 1), in which 179 patients with LGS received clobazam at one of three target dose levels (low, medium, high) and 59 received placebo over 15 weeks. Frequencies are presented for the highest-dose group (closest to the typical maintenance dose of 20 mg/day or 40 mg/day) where the absolute incidence is most relevant; the all-ONFI rate is shown when more representative.
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Somnolence or sedation (combined) | High dose 32% · all-ONFI 26% · placebo 15% | Dose-related; usually emerges in the first month and may diminish with continued treatment. Listed in the PI as one of the adverse reactions occurring ≥10% more often than placebo at any dose |
| Pyrexia (fever) | Low dose 17% · all-ONFI 13% · placebo 3% | Among the reactions singled out in the PI as occurring ≥10% more frequently than placebo |
| Upper respiratory tract infection | High dose 14% · all-ONFI 12% · placebo 10% | Modest absolute increase over placebo |
| Lethargy | High dose 15% · all-ONFI 10% · placebo 5% | Top single reason for treatment discontinuation in the LGS placebo-controlled trial |
| Drooling (sialorrhea) | High dose 14% · all-ONFI 9% · placebo 3% | Identified in the PI as occurring ≥10% more often than placebo at any dose |
| Aggression | High dose 14% · all-ONFI 8% · placebo 5% | Behavioural reactions are well-recognized with benzodiazepines and may be more common in pediatric and intellectually disabled populations |
| Irritability | Medium dose 11% · all-ONFI 7% · placebo 5% | Often coincident with insomnia or aggression |
| Constipation | High dose 10% · all-ONFI 5% · placebo 0% | Listed in the PI as occurring ≥10% more often than placebo at the high dose |
| Ataxia | High dose 10% · all-ONFI 5% · placebo 3% | Suggests excess GABAergic effect; review concomitant CNS depressants and consider dose reduction |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Vomiting | all-ONFI 7% · placebo 5% | Modest dose-related increase |
| Insomnia | all-ONFI 5% · placebo 2% | Paradoxical reaction; consider dose redistribution toward bedtime |
| Cough | all-ONFI 5% · placebo 0% | — |
| Sedation (recorded separately from somnolence) | High dose 9% · all-ONFI 5% · placebo 3% | Distinguished in trial coding from somnolence; clinical management is the same |
| Fatigue | all-ONFI 5% · placebo 2% | — |
| Pneumonia | High dose 7% · all-ONFI 4% · placebo 2% | Possibly related to sedation, drooling, and aspiration risk in this population |
| Urinary tract infection | all-ONFI 4% · placebo 0% | — |
| Psychomotor hyperactivity | all-ONFI 4% · placebo 3% | Paradoxical agitation |
| Decreased appetite | High dose 7% · all-ONFI 3% · placebo 3% | Monitor weight in pediatric patients |
| Increased appetite | High dose 5% · all-ONFI 3% · placebo 0% | Monitor weight |
| Dysarthria | High dose 5% · all-ONFI 3% · placebo 0% | Suggests level at upper end of range |
| Dysphagia | High dose 5% · all-ONFI 2% · placebo 0% | Aspiration concern, particularly in patients with pre-existing swallowing dysfunction |
| Bronchitis | High dose 5% · all-ONFI 2% · placebo 0% | — |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Profound sedation, respiratory depression, coma, or death (especially with concomitant opioids or other CNS depressants) | Frequency not established; risk ↑ with opioid co-use | Hours to days | Reserve combination for patients with no adequate alternative; use lowest effective doses; monitor closely; counsel on overdose risk |
| Stevens–Johnson syndrome / toxic epidermal necrolysis | Postmarketing reports — frequency not established | Especially within first 8 weeks of initiation or re-introduction | Discontinue at the first sign of rash unless clearly not drug-related; do not resume if SCAR suspected |
| Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) / multi-organ hypersensitivity | Postmarketing reports — frequency not established; some fatal | Variable; often weeks | Discontinue if no alternative cause for fever, rash, lymphadenopathy, hepatitis, or other organ involvement |
| Acute withdrawal reactions on abrupt discontinuation (seizures, status epilepticus, delirium, psychosis, suicidality, life-threatening reactions) | Frequency not established; risk ↑ with higher doses, longer use, abrupt stop, or flumazenil | Days after dose reduction or cessation | Always taper; if withdrawal emerges, return to prior dose then taper more slowly |
| Protracted withdrawal syndrome (anxiety, cognitive impairment, depression, insomnia, paresthesia, motor symptoms) | Variable | Persists weeks to >12 months after withdrawal | Counsel before initiation; consider very slow taper; specialist support for severe cases |
| Suicidal ideation and behaviour (AED class effect) | ~0.43% on any AED vs ~0.24% on placebo (FDA pooled meta-analysis) | As early as 1 week into therapy | Counsel patients/caregivers; assess mood at each contact |
| Neonatal sedation and/or withdrawal syndrome (use late in pregnancy) | Not quantified | First days of life | Anticipate respiratory depression, lethargy, hypotonia, hyperreflexia, irritability, tremors, feeding difficulties; arrange neonatal monitoring |
| Angioedema, urticaria, facial/lip edema, anaphylactoid reactions | Postmarketing | Minutes to hours | Discontinue immediately and provide emergency care |
| Hematologic abnormalities (anemia, eosinophilia, leukopenia, thrombocytopenia) | Postmarketing | Variable | Investigate any unexplained fever, bruising, fatigue; eosinophilia may be a DRESS marker |
| Severe psychiatric reactions (delirium, depression, hallucination, delusion, paradoxical agitation) | Postmarketing | Variable | Reduce or discontinue clobazam; specialist mental-health input |
| Aspiration / respiratory depression | Postmarketing; risk ↑ in LGS population (drooling, dysphagia) | Variable | Assess swallowing and airway; cautious dose escalation in patients with pre-existing aspiration risk |
Patients with LGS frequently have baseline cognitive, motor, and swallowing impairment, and sedation plus drooling on clobazam can compound aspiration risk. If sedation persists or worsens, review concomitant CNS depressants (especially opioids), screen for occult CYP2C19 inhibition (e.g., omeprazole, fluconazole), consider whether the patient is a CYP2C19 poor metabolizer, and reduce dose before discontinuing — most sedation is dose-related and dissipates with a smaller daily dose.
Drug Interactions
Clobazam interacts pharmacodynamically (additive CNS depression) and pharmacokinetically (CYP2C19 metabolism of N-desmethylclobazam, weak CYP3A4 induction, in vivo CYP2D6 inhibition). Strong or moderate inhibition of CYP2C19 raises N-DMC exposure by up to five-fold and is the most clinically important PK interaction class. The cards below highlight the most relevant pairings; the full medication list (including OTC and supplements) should be reviewed at every visit.
Monitoring
Routine therapeutic drug monitoring is not required, but clinical monitoring during titration, dose changes, addition or discontinuation of CYP2C19 inhibitors (especially cannabidiol), and any reduction in clobazam dose is essential. The schedule below combines initiation-phase, ongoing chronic-therapy, and triggered checks.
-
Sedation, drowsiness, ataxia
At each titration step; first month then periodically
Routine Most sedation begins in the first month and may diminish with continued therapy. Persistent sedation should prompt review of concomitant CNS depressants and CYP2C19 inhibitors before considering dose reduction. -
Seizure diary (drop and total seizures)
Continuous; review at each visit
Routine Maintenance dose can be individualized within each weight band according to seizure response; effectiveness increased with higher doses in CONTAIN. -
Mood & suicidality
At each visit
Routine AED class effect — ask about new or worsening depression, anxiety, agitation, intrusive thoughts, or behavioural changes. Aggression and irritability are also recognized clobazam-specific reactions. -
Skin examination
Especially during first 8 weeks of initiation or re-introduction
Routine Discontinue at first sign of rash unless clearly not drug-related. Mucosal involvement, blistering, fever, lymphadenopathy, or facial swelling warrants emergency evaluation for SJS/TEN, DRESS, or angioedema. -
Aspiration / swallowing risk
Baseline and after dose escalation
Routine LGS patients commonly have baseline dysphagia; drooling and sedation from clobazam may compound aspiration risk. Speech and language therapy review where appropriate. -
Respiratory status
When opioids or other CNS depressants are added
Trigger-based Counsel on signs of respiratory depression (shallow/slowed breathing, excessive sleepiness). Consider naloxone supply for households where opioid use is anticipated. -
CBC and LFTs
Baseline; with rash, fever, or unexplained systemic symptoms
Trigger-based Eosinophilia or hepatic enzyme rise with rash suggests DRESS — discontinue and evaluate. -
Plasma clobazam & N-DMC levels
Selected scenarios
Trigger-based Consider when sedation is disproportionate to dose, when adding/removing strong or moderate CYP2C19 inhibitors (including cannabidiol), in suspected CYP2C19 poor metabolizers, or in hepatic impairment. Routine TDM is not required. -
Abuse / misuse / addiction risk
Before prescribing and throughout therapy
Routine Schedule IV controlled substance — assess risk using a standardized tool, counsel on safe storage and disposal, and avoid combining with other agents associated with abuse. -
Withdrawal symptoms
During and after any taper
Routine Anxiety, insomnia, tremor, paresthesia, headache, GI symptoms; severe forms include seizures and delirium. Pause taper or return to prior dose if symptoms emerge. -
Body weight (pediatric)
Each visit
Routine Dosing thresholds are weight-banded (≤30 kg vs >30 kg); reassess when a child crosses the threshold. Also monitors for appetite-related effects.
Disproportionate sedation, ataxia, or drooling at modest clobazam doses (e.g., 5–10 mg/day) — especially in a patient also taking omeprazole, fluconazole, fluvoxamine, or cannabidiol — is far more likely to reflect elevated N-desmethylclobazam exposure than the parent compound. Reducing the clobazam dose by half, or replacing the offending CYP2C19 inhibitor where feasible, usually solves the problem without abandoning the drug.
Contraindications & Cautions
Opioid co-use: Concomitant use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing for patients with no adequate alternative; use lowest effective doses and shortest durations; monitor closely.
Abuse, misuse, and addiction: Use of benzodiazepines, including clobazam, exposes users to risks of abuse, misuse, and addiction, which can lead to overdose or death. Assess each patient’s risk before prescribing and throughout treatment.
Dependence and withdrawal: Continued use may cause clinically significant physical dependence. Abrupt discontinuation, rapid dose reduction, or administration of flumazenil may precipitate acute withdrawal reactions, which can be life-threatening (including seizures). Use a gradual taper. A protracted withdrawal syndrome lasting weeks to more than 12 months has been reported.
Absolute Contraindications
- Hypersensitivity to clobazam or any product ingredient, including a history of serious dermatologic reactions (such as SJS or TEN) attributable to clobazam.
Note: hypersensitivity is the only absolute contraindication listed in the Onfi prescribing information. The cautions below reflect class-wide benzodiazepine risk and clinical practice.
Relative Contraindications — Specialist Input Recommended
- Concomitant opioid therapy — combine only when no adequate alternative exists (see Boxed Warning).
- History of substance use disorder, particularly with benzodiazepines, alcohol, or opioids — risk of misuse and addiction; if used, structured prescribing and monitoring are required.
- Severe hepatic impairment — no dosing recommendation can be given; consider alternative therapy.
- Severe renal impairment or end-stage renal disease — essentially no clinical experience; dialysability of clobazam and N-DMC is unknown.
- Pregnancy — animal studies show developmental toxicity at clinically relevant exposures; use late in pregnancy may cause neonatal sedation and/or withdrawal. Use only when potential benefit justifies fetal risk; coordinate with neurology and obstetrics; consider enrollment in the North American Antiepileptic Drug (NAAED) Pregnancy Registry.
- Severe respiratory disease — additive risk of respiratory depression, particularly with concurrent opioids or other CNS depressants.
- Myasthenia gravis — class-wide benzodiazepine caution due to potential worsening of muscle weakness.
- Acute narrow-angle glaucoma — class-wide benzodiazepine caution.
Use With Caution
- Elderly patients — higher plasma exposures, greater fall and sedation risk, slower phenytoin/benzodiazepine clearance; start at 5 mg/day regardless of weight.
- Known or suspected CYP2C19 poor metabolizers — N-DMC concentrations are 3–5× higher; reduce starting and target doses (see Dosing).
- Concomitant strong or moderate CYP2C19 inhibitors (fluconazole, fluvoxamine, ticlopidine, omeprazole, esomeprazole, cannabidiol) — exposure to N-DMC may rise several-fold; titrate cautiously.
- Patients with significant baseline aspiration or swallowing risk (common in LGS) — drooling and sedation may compound risk.
- Patients with depression or active suicidality — AED class effect on suicidality plus benzodiazepine disinhibition; monitor mood closely.
- Operators of vehicles or hazardous machinery — counsel on impaired alertness particularly during titration and after dose changes.
Patient Counselling
Purpose of Therapy
Explain that clobazam is being added to existing seizure medicines to help reduce drop attacks and other seizures associated with Lennox–Gastaut syndrome. It is not a cure and works alongside other antiepileptic drugs. Clobazam is a long-acting benzodiazepine and produces an active substance in the body (N-desmethylclobazam) that lasts even longer than the parent drug — which is why dose changes can take a week or more to fully take effect.
How to Take
Take clobazam exactly as prescribed. Doses above 5 mg per day are split into two doses (typically morning and evening). Tablets can be taken whole, broken along the score, or crushed and mixed in a spoonful of applesauce. The oral suspension must be shaken well before each dose and measured only with the supplied syringe; throw away any leftover suspension 90 days after the bottle is first opened. Take with or without food.
Sources
- Lundbeck. Onfi (clobazam) tablets and oral suspension — full prescribing information. Revised March 2024. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/202067s008,203993s010lbl.pdf Authoritative source for indication, dosing, the Boxed Warning (opioids, abuse/misuse/addiction, dependence/withdrawal), pharmacokinetics, adverse-reaction tables, and CYP2C19 guidance.
- U.S. Food and Drug Administration. DailyMed: Onfi (clobazam) tablet and oral suspension labelling. Available at: https://dailymed.nlm.nih.gov/ Maintained repository of current FDA-approved labelling for branded and generic clobazam products.
- Aquestive Therapeutics. Sympazan (clobazam) oral film — full prescribing information. Available at: https://dailymed.nlm.nih.gov/ Labelling for the oral-film formulation, which shares clobazam’s clinical profile but differs in administration.
- Ng YT, Conry JA, Drummond R, Stolle J, Weinberg MA; OV-1012 Study Investigators. Randomized, phase III study results of clobazam in Lennox–Gastaut syndrome (CONTAIN). Neurology. 2011;77(15):1473–1481. doi: 10.1212/WNL.0b013e318232de76 Pivotal Phase III trial demonstrating dose-dependent reduction of weekly drop seizures versus placebo; basis for FDA approval and the dose data in the Onfi PI.
- Conry JA, Ng YT, Paolicchi JM, et al. Clobazam in the treatment of Lennox–Gastaut syndrome. Epilepsia. 2009;50(5):1158–1166. doi: 10.1111/j.1528-1167.2008.01935.x Phase II OV-1002 trial — one of the two studies that supported FDA approval.
- Ng YT, Conry J, Paolicchi J, et al. Long-term safety and efficacy of clobazam for Lennox–Gastaut syndrome: interim results of an open-label extension study. Epilepsy Behav. 2012;25(4):687–694. Open-label extension (OV-1004) data informing long-term tolerability and the absence of meaningful tolerance over multi-year therapy.
- Cross JH, Auvin S, Falip M, Striano P, Arzimanoglou A. Expert opinion on the management of Lennox–Gastaut syndrome: treatment algorithms and practical considerations. Front Neurol. 2017;8:505. doi: 10.3389/fneur.2017.00505 International expert consensus positioning clobazam alongside valproate, lamotrigine, rufinamide, and topiramate in LGS treatment algorithms.
- National Institute for Health and Care Excellence (NICE). Epilepsies in children, young people and adults (NG217). London: NICE; April 2022. Available at: https://www.nice.org.uk/guidance/ng217 UK guidance on AED selection in LGS, Dravet syndrome, and other refractory epilepsies, including a role for clobazam.
- U.S. Food and Drug Administration. Drug Safety Communication: FDA requiring Boxed Warning updated to improve safe use of benzodiazepine drug class. September 23, 2020. Available at: https://www.fda.gov/drugs/drug-safety-and-availability/fda-requiring-boxed-warning-updated-improve-safe-use-benzodiazepine-drug-class Class-wide labelling change adding abuse/misuse/addiction and dependence/withdrawal language to all benzodiazepines, including clobazam.
- Sankar R. GABAA receptor physiology and its relationship to the mechanism of action of the 1,5-benzodiazepine clobazam. CNS Drugs. 2012;26(3):229–244. doi: 10.2165/11599020-000000000-00000 Mechanistic review explaining the structural and pharmacodynamic differences between 1,5- and 1,4-benzodiazepines.
- Anderson LL, Absalom NL, Abelev SV, et al. Coadministered cannabidiol and clobazam: preclinical evidence for both pharmacodynamic and pharmacokinetic interactions. Epilepsia. 2019;60(11):2224–2234. doi: 10.1111/epi.16355 Mechanistic and preclinical study demonstrating CBD inhibition of CYP3A4 (clobazam) and CYP2C19 (N-DMC), and a separate pharmacodynamic synergy at GABAA.
- Sankar R, Wheless JW, Dravet C, et al. Pharmacokinetic and pharmacodynamic considerations for the clinical use of clobazam in pediatric epilepsy. Epilepsia. 2014;55 Suppl 1:S1–S25. Comprehensive pediatric PK/PD review covering N-DMC kinetics, CYP2C19 polymorphism, and dosing in children.
- Greenwich Biosciences. Epidiolex (cannabidiol) oral solution — full prescribing information. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/210365s023lbl.pdf Source for the quantified CBD–clobazam PK interaction (~3-fold increase in N-DMC AUC and Cmax) and the recommendation to consider clobazam dose reduction.
- Klotz U, Antonin KH. Pharmacokinetics and bioavailability of sodium valproate and clobazam — a basis for clinical use. Eur J Clin Pharmacol. 1977;12(6):443–450. Early human PK characterization of clobazam supporting its long half-life and active metabolite profile.
- U.S. Food and Drug Administration. Statistical review and evaluation: antiepileptic drugs and suicidality. May 23, 2008. Available via FDA archives. Source for the AED-class suicidality risk estimate (~0.43% on AEDs versus ~0.24% on placebo) cited throughout AED labelling, including the Onfi PI.