Clonazepam (Klonopin): dosage, uses, and side effects

If you’ve experienced panic attacks or seizures, you know how frightening these attacks can be. You may try to avoid situations that could trigger another episode, or you may feel constantly worried about when the next attack might happen. 

If you have panic disorder or a seizure disorder, your healthcare provider may prescribe clonazepam (Klonopin) for you. It’s a benzodiazepine (“benzo”) medication known for its calming, sedative, and anticonvulsant (anti-seizure) effects.

Keep reading to learn more about clonazepam, its uses, typical dosage, side effects, and risks. 

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Clonazepam is a prescription-only anxiolytic medication and is the generic version of Klonopin. It belongs to a drug class called benzodiazepines. 

Benzodiazepines work by attaching to specific receptors in your brain, enhancing the activity of a brain chemical called gamma-aminobutyric acid (GABA). GABA slows down certain signals within the brain and central nervous system (CNS). Clonazepam is thought to work for seizure or anxiety disorders by calming overstimulation in the brain and providing anxiolytic or anti-anxiety effects (Bounds, 2020; Roche, 2021). 

Clonazepam (Klonopin) is approved by the Food and Drug Administration (FDA) to treat (Roche, 2021): 

• Panic disorder in adults. Panic disorder is an anxiety disorder in which you have recurrent panic attacks, sudden episodes of intense fear with no apparent reason.

• Seizure disorders, also known as epilepsy, in adults and children. For this use, clonazepam is usually prescribed as part of a regimen with other medications called anti-epileptic drugs (AEDs). Together, this regimen helps to prevent and control seizures.

Clonazepam (Klonopin) can also be used “off-label” to treat other conditions. This is when a healthcare provider prescribes a drug to treat conditions other than its FDA-approved uses; a common practice when they decide that a medication is appropriate for their patient (FDA, 2018). 

Off-label uses for clonazepam (Klonopin) include (Basit, 2021):

• Mania: a psychological condition that causes a person to experience changes in their mood and behavior, such as intense euphoria (feeling “high”) and hyperactivity. Mania often occurs as a symptom of bipolar disorder.

• Restless leg syndrome: a nervous system disorder that causes a constant uncontrollable urge to move the legs, interrupting a person’s sleep.

• Insomnia: a sleep disorder in which a person has trouble falling asleep or staying asleep.

• Tardive dyskinesia: random uncontrolled movements that can occur as a side effect of taking certain antipsychotic medications.

• REM sleep behavior disorder: a type of sleep disorder that causes people to act out their dreams while asleep.

Clonazepam (Klonopin) is an oral medication (a drug that you take by mouth). Tablets are available in three strengths: 0.5 milligrams (mg), 1 mg, and 2 mg. The drug is also available in an ODT (orally disintegrating tablet), which is a tablet that dissolves in your mouth. Clonazepam ODT comes in five strengths: 0.125 mg, 0.25 mg, 0.5 mg, 1 mg, and 2 mg (Roche, 2021; Alembic, 2018).

The usual dosage of clonazepam depends on the condition that it is prescribed to treat. An example of a typical starting dosage to treat panic disorder is clonazepam 0.25 mg to 0.5 mg two times per day. Your healthcare provider may increase or adjust your dose over time, depending on the severity of your symptoms and if you develop any bothersome side effects (Roche, 2021).

Healthcare professionals may mention a drug’s “half-life” to describe how long its effects last. A drug’s half-life is the length of time it takes for the body to eliminate half of one dose.

Clonazepam’s half-life is 30 to 40 hours. A dose typically starts to work within 30 minutes and reaches its maximum effects within one to four hours. Its effects usually last 6 to 12 hours or longer (Basit, 2021; Roche, 2021).

You should not change your dose or stop taking this medication without talking to your healthcare provider. If you’ve taken it for a while, suddenly stopping the drug can cause withdrawal symptoms. For more information about withdrawal with clonazepam (Klonopin), see the Warnings section below.

Like all medications, clonazepam (Klonopin) may cause side effects. The most common side effects reported with clonazepam include (Roche, 2021):

• Sleepiness

• Dizziness

• Fatigue

• Problems with memory

• Trouble with coordination

Rarely, people taking clonazepam (Klonopin) may develop other serious side effects. For example, changes in mood or behavior can occur, such as new or worsening depression and suicidal thoughts or actions.

The FDA has given several boxed warnings for all benzodiazepine drugs, including clonazepam (Klonopin). Boxed warnings are the strongest type of warning from the FDA. Benzodiazepines are designated as schedule IV controlled substances because of these risks (DEA, n.d.; FDA, 2020):

• Risk of dangerous effects when benzodiazepines are combined with opioids: Taking clonazepam with opioids (such as painkillers) can cause harmful side effects. These include severe drowsiness, troubled breathing, coma, and, in rare cases, death. You should not take clonazepam with an opioid unless you and your healthcare provider have specifically discussed these dangers and have an established plan to monitor and manage these risks.

• Risk of drug abuse and addiction: Taking clonazepam can lead to addiction, even when taken as prescribed. It’s possible to develop the feeling that you need to take the drug in higher doses to get the desired effects. This can lead to abuse or taking the drug more than prescribed, raising your risk of overdose. 

• Risk of physical dependence and withdrawal: Taking clonazepam, especially long term and in high doses, can cause your body to become physically dependent, and withdrawal can occur if you suddenly stop taking it. Withdrawal symptoms can include seizures, psychosis (losing touch with reality), hallucinations, mood changes, tremors, abdominal pain, and muscle cramps. If you and your healthcare provider decide that you’ll stop taking clonazepam, they’ll tell you how to taper or gradually reduce your dose before you stop it completely.

Because clonazepam may cause sedation, sleepiness, and dizziness, you should not drive after taking this medication. Even if you no longer feel sleepy, clonazepam can continue to affect your ability to react quickly and cause impairment for 12 hours or longer after your last dose (Basit, 2021; Roche, 2021).

Before starting this medication, it’s important to tell your healthcare provider about your allergies, medical history, and current health conditions such as narrow-angle glaucoma. You should also let them know if you’re pregnant, breastfeeding, or have plans to become pregnant. Your healthcare provider can offer medical advice on the best treatment options for you.

Clonazepam (Klonopin) can interact with several types of other medications. Some drug interactions may increase the risk of side effects. 

Types of drugs that interact with clonazepam (Klonopin) include (Roche, 2021):

Central nervous system depressants 

As explained above, central nervous system depressants (CNS depressants or “downers”) can have harmful effects with clonazepam. Some examples of CNS depressants are:

• Alcohol

• Cough medications that contain codeine

• Opioids: painkillers such as hydrocodone, oxycodone, or tramadol and street drugs like heroin

• Muscle relaxers like carisoprodol (Soma)

• Sedatives (“sleeping pills”) like zolpidem (Ambien)

Medications known as CYP3A4 inhibitors or inducers 

Clonazepam (Klonopin) is broken down by specific enzymes in your body, mainly in the liver. One type of enzyme is called cytochrome P450 3A4 (abbreviated CYP3A4). Some drugs cause interactions because they either slow down or speed up this enzyme. Your healthcare provider can sometimes manage these combinations by adjusting your dosage.

There are two types of interactions that involve CYP3A4:

• CYP3A4 inhibitors: CYP3A4 inhibitors slow down the activity of this metabolic enzyme and can intensify clonazepam’s effects and side effects. Some examples of common inhibitors include (Zhou, 2008):

  • certain antidepressants such as fluoxetine (Prozac) and fluvoxamine (Luvox)

  • certain macrolide antibiotics such as clarithromycin (Biaxin) and erythromycin

  • ritonavir (Norvir), an HIV medication

• CYP3A4 inducers: Some medications known as CYP3A4 inducers speed up CYP3A4, breaking down clonazepam too quickly. This interaction can decrease clonazepam’s levels in your body, reducing how well it works. A few examples of common inducers include (Zhou, 2008):

  • phenytoin (Dilantin), a seizure medication 

  • rifampin (Rifadin), an antibiotic

These lists do not include all of the possible drug interactions with clonazepam. So, it is essential to talk with your healthcare provider and pharmacist about all of your current and recent medications. And check with your healthcare provider or pharmacist before starting a new medicine, including over-the-counter drugs and herbal supplements, while taking clonazepam.

Panic disorders and seizure disorders can be distressing. Your healthcare provider can work with you to determine what kind of treatment is best for your health and day-to-day needs.

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Current version

August 31, 2021

Written by

Patricia Weiser, PharmD

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.