Short answer: Clonazepam (Klonopin) is a long-acting benzodiazepine used for panic disorder and certain seizure disorders. It is a Schedule IV controlled substance. It works well for many people but causes dependence, and it must be tapered rather than stopped suddenly.
Key takeaways
- What it is: Clonazepam is a long-acting benzodiazepine and a Schedule IV controlled substance in the US.
- Main uses: Panic disorder; seizures.
- Timing: effects start in 20 to 60 minutes and last 6 to 12 hours.
- Most dangerous mix: Opioids (oxycodone, fentanyl, codeine), which can cause slowed breathing, coma, death.
- Naloxone: it does not reverse this drug, but give it whenever opioids could be involved.
- Dependence risk: High.
- Legal route: only with a prescription from a DEA-registered clinician, filled by a licensed pharmacy.
What is clonazepam?
Clonazepam is approved for panic disorder with or without agoraphobia, and alone or as an add-on for several seizure types, including Lennox-Gastaut syndrome and absence seizures.
Off-label, it is sometimes used for REM sleep behavior disorder, restless legs, and akathisia.
Quick facts
| Fact | Clonazepam |
|---|---|
| Generic name | Clonazepam |
| Brand names | Klonopin |
| Drug class | Long-acting benzodiazepine |
| US legal status | Schedule IV, prescription only |
| Approved uses | Panic disorder; seizure disorders (Lennox-Gastaut, akinetic, myoclonic, absence) |
| Forms | Tablets, orally disintegrating tablets |
| Onset | 20 to 60 minutes |
| Half-life | 30 to 40 hours |
| Broken down by | CYP3A4 |
How long does clonazepam last?
- Starts working: 20 to 60 minutes
- Effects last: 6 to 12 hours
- Half-life: 30 to 40 hours
Its half-life is 30 to 40 hours, so it takes about a week to clear. Urine tests can detect it for 5 to 10 days or longer.
Timing varies with the dose, the form, how it is taken, liver and kidney function, age, and other drugs taken at the same time.
What are the biggest risks of clonazepam?
The FDA requires boxed warnings, its strongest, on clonazepam products, including:
- Taking benzodiazepines with opioids can cause profound sedation, slowed breathing, coma, and death.
- Benzodiazepines can be misused and can lead to addiction, which raises the risk of overdose and death.
- Regular use can cause physical dependence. Stopping suddenly or cutting the dose quickly can cause withdrawal reactions, including seizures, that can be life-threatening.
Common side effects include drowsiness, dizziness, poor coordination, fatigue, depression, and memory problems.
Suicidal thoughts: like other antiseizure medicines, clonazepam carries a warning about a small increase in suicidal thoughts and behavior.
What should you never mix with clonazepam?
| Combined with | What happens | Label guidance |
|---|---|---|
| Opioids (oxycodone, fentanyl, codeine) | Slowed breathing, coma, death | Boxed warning; avoid unless no alternative |
| Alcohol | Stronger sedation and slowed breathing | Avoid |
| Other sedatives, sleep medicines, gabapentinoids | Additive drowsiness and impaired coordination | Use caution |
| Strong CYP3A4 inhibitors (ketoconazole, clarithromycin) | Raise clonazepam levels | Use caution |
| Carbamazepine, phenytoin | Lower clonazepam levels | Monitor seizure control |
Check any combination with the DoseUses combination checker or ask a pharmacist.
What are the signs of a clonazepam overdose, and what should you do?
Clonazepam overdose causes deep drowsiness, confusion, poor coordination, slowed reflexes, and coma. With opioids or alcohol, breathing can stop.
If someone may have overdosed
- Call 911 if the person is unresponsive, hard to wake, or breathing slowly.
- For advice when the person is awake and stable, call Poison Help at 1-800-222-1222 (US, free, 24 hours).
- If opioids could be involved, including pills not from a pharmacy, give naloxone if you have it. Naloxone does not reverse clonazepam, but it will not harm the person.
- Stay with the person and place them on their side if they are drowsy or vomiting.
What is clonazepam withdrawal like, and how long does it last?
People who take clonazepam regularly, even as prescribed, can become physically dependent within weeks. Its long half-life means withdrawal often begins a few days after the last dose.
- Days 2 to 5Symptoms beginRebound anxiety, insomnia, restlessness, sweating, and tremor.
- Weeks 1 to 4Acute withdrawalPanic, irritability, muscle pain, nausea, sensitivity to light and sound, and in severe cases seizures or delirium.
- MonthsProtracted symptoms in some peopleA minority have lingering anxiety, poor sleep, low mood, or tingling that can last weeks to more than 12 months.
See the withdrawal timelines and the full clonazepam withdrawal guide.
Is clonazepam legal?
In the United States, clonazepam is a Schedule IV controlled substance. The only legal way to get it is with a prescription from a clinician registered with the Drug Enforcement Administration (DEA), filled by a licensed pharmacy. Depending on state law, that can be a physician, nurse practitioner, or physician assistant.
- Refills: a Schedule IV prescription can be refilled up to five times within six months of the date it was written. After that, a new prescription is needed.
- Telehealth: federal flexibilities let DEA-registered clinicians prescribe Schedule II to V medicines after a telemedicine visit, without a prior in-person exam, through December 31, 2026. A permanent DEA rule was under final review in late 2026. State rules can be stricter.
- Monitoring: prescribers and pharmacists in most states check a prescription drug monitoring program, a database of controlled-substance prescriptions, before prescribing or dispensing.
Outside the United States
| Country | Status |
|---|---|
| United Kingdom | Class C; prescription only |
| Canada | Schedule IV (targeted substance); prescription only |
| Australia | Schedule 4 prescription medicine |
| International | Schedule IV of the 1971 Convention on Psychotropic Substances |
Frequently asked questions about clonazepam
Is clonazepam the same as Klonopin?
Yes. Klonopin is the brand name for clonazepam.
How long does clonazepam stay in your system?
Its half-life is 30 to 40 hours, so it takes about a week to clear. Urine tests can detect it for 5 to 10 days or longer.
Is clonazepam better than Xanax for panic disorder?
Clonazepam lasts longer, which avoids between-dose rebound anxiety. Both carry the same risks of dependence. Antidepressants and therapy are first-line treatments.
Can clonazepam be stopped suddenly?
No. Stopping suddenly can cause severe withdrawal and, in people with epilepsy, prolonged seizures.
Sources
- Klonopin (clonazepam) prescribing information, DailyMed, US National Library of Medicine.
- FDA warns about serious risks and death when combining opioid pain or cough medicines with benzodiazepines, US Food and Drug Administration, 2016.
- FDA requiring Boxed Warning updated to improve safe use of benzodiazepine drug class, US Food and Drug Administration, 2020.
- Joint Clinical Practice Guideline on Benzodiazepine Tapering, American Society of Addiction Medicine, 2025.
- Controlled Substance Schedules, DEA Diversion Control Division.
- 21 CFR 1306.22, Refilling of prescriptions (Schedules III and IV), Electronic Code of Federal Regulations.
- Prescribing controlled substances via telehealth, US Department of Health and Human Services.
- BeSafeRx: Your Source for Online Pharmacy Information, US Food and Drug Administration.
This guide summarizes the sourced DoseUses Clonazepam profile, written from FDA labels, DEA rules, and federal health agencies. It is educational and is not medical advice. Last updated October 5, 2026.
