Clonazepam

Is clonazepam safe?

Clonazepam works well for panic disorder and for some hard-to-treat seizures, and at a modest dose, in someone who does not drink heavily or take opioids, a short course is reasonably safe. An overdose of clonazepam alone rarely kills a healthy adult. The trouble lies elsewhere: drowsiness is common, dependence builds with daily use, stopping quickly can trigger seizures, and mixed with opioids or alcohol it can stop breathing. We score it 39, just below alprazolam (40) and lorazepam (41).

A long-acting benzodiazepine

Clonazepam's half-life is typically 30 to 40 hours, far longer than alprazolam's or lorazepam's. Doses are usually split in two, or one is taken at bedtime to sleep through the drowsiness. The drug builds up over several days, and drowsiness, slowed thinking and unsteadiness can carry into the next day, especially in older people.

In the US panic disorder trials, side effects were common and rose with the dose:

The trial behind the label found that 1 mg a day worked best. Doses of 2, 3 and 4 mg a day were less effective and caused more side effects, which is a good reason to question any steady climb in dose.

Seizures: help and harm

For epilepsy, clonazepam is used alone or with other drugs for Lennox-Gastaut syndrome, akinetic and myoclonic seizures, and absence seizures that have not responded to other treatment. In seizure patients the label reports drowsiness in about 50%, unsteadiness in about 30% and behaviour problems in about 25%, which is higher than in the panic trials. Three more cautions come with it. Up to 30% of patients who first respond lose the effect, often within 3 months. In people with several seizure types it can bring on or worsen tonic-clonic seizures. And like all antiepileptic drugs, it carries a warning about suicidal thoughts and behaviour, so mood changes should be reported.

Stopping is the biggest risk for people with epilepsy, because sudden withdrawal can trigger seizures. Any reduction should be planned with the specialist.

Dependence and withdrawal

Since 2020 the FDA's boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary for all benzodiazepines has covered abuse, misuse, addiction, physical dependenceDrug dependenceThe body's adaptation to a drug taken regularly, so that stopping it suddenly causes withdrawal symptoms. It is not the same as addiction.More in the glossary and withdrawal. The risk grows with higher doses and longer use. Stopping abruptly or cutting quickly can cause withdrawal reactions that can be life-threatening, and some people develop protracted withdrawal lasting from weeks to more than 12 months.

In the UK, the MHRA announced in January 2026 that benzodiazepine packs and leaflets will carry stronger warnings, and asked prescribers to agree a plan for reducing or stopping treatment before it starts.

With opioids or alcohol

Benzodiazepines and opioids suppress breathing in different ways, and together the effect is much worse than either alone. In CDC data from 23 states, 92.7% of benzodiazepine overdose deaths in the first half of 2020 also involved an opioid, mostly illicit fentanyl, and deaths involving illicit benzodiazepines rose about sixfold between April–June 2019 and April–June 2020 (from 51 to 316). Pills sold as clonazepam outside pharmacies may be counterfeit. In England and Wales, clonazepam was mentioned on 23 drug-poisoning death records registered in 2024, far fewer than diazepam's 302 (ONS).

Signs of a dangerous overdose include extreme sleepiness, confusion, slurred speech, slow breathing and being hard to wake. Call emergency services. If opioids may be involved, give naloxone: it will not reverse clonazepam, but it can reverse the opioid. US Poison Help is 1-800-222-1222.

Who should be careful

Talk to your doctor or pharmacist before taking clonazepam if you take an opioid, zolpidem or another sleeping pill, gabapentin or pregabalin, or drink regularly; are older or frail; have sleep apnoea, lung disease or a history of depression or substance use; or are pregnant. Do not drive until you know how it affects you. A low score is not a reason to stop a prescribed medicine on your own, because withdrawal is one of the main risks.

How we scored it

Track record (90) is strong after 50 years of use. Dependence (15) and regulatory warnings (20) sit in the lowest band because of the class boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary. Interactions (30) match lorazepam's: opioids and alcohol are the danger, and enzyme inducers matter more than inhibitors. Overdose marginOverdose marginHow far a normal dose is from a harmful one. A wide margin means an accidental extra dose is unlikely to cause serious harm.More in the glossary (40) reflects a drug seldom fatal alone, and serious side effects (45) are a little below alprazolam's and lorazepam's (50) because drowsiness, depression and seizure-related cautions are frequent.