Clobazam (KLOH-bah-zam) is the generic name of the brand-name drugs known as Onfi® and Sympazan™ in the United States and Frisium (FRIH-zee-um) in some other countries. The name or look of the medicine may be different in generic forms of clobazam.

Clobazam is approved for add-on treatment of seizures in children 2 years old or greater and adults who have seizure types that can be associated with Lennox-Gastaut Syndrome (LGS). There are many different types of seizure seen with LGS, listed under "Used to Treat."


Updated: 17/10/2023

Brand Name(s)

Sympazan, Onfi

Used to Treat

Lennox-Gastaut Syndrome
Absence Seizures
Atonic Seizures
Atypical Absence Seizures
Focal Impaired Awareness or Complex Partial Seizures
Myoclonic Seizures
Refractory Seizures
Secondarily Generalized Seizures or Bilateral Tonic Clonic Seizure
Focal Aware Onset Seizure
Tonic-clonic Seizures



10 mg (white), the letters B and GL are printed on one side of the tablet.

Package Insert

Frequently Asked Questions

    How to take and store Clobazam?

    How to Take:

    • The dose of Onfi prescribed and how to increase it may vary with a person's body weight.
      •  For people who weigh less than 30 kg or 66 pounds, Onfi is usually started at 5 mg per day. Increase as directed to 20 mg each day. 
      • For people who weigh more than 30 kg or 66 pounds, the drug is usually started at 10 mg each day. Increase as directed to 40 mg each day. 
    • Onfi is generally taken twice a day. 
    • The dose is usually increased once a week or more slowly. It takes 5 to 9 days for the dose to reach a stable state in the body. 
    • Clobazam tablets should be swallowed whole, followed by at least a half a glass of water. They can also be split in half along the score or crushed and mixed with applesauce or another soft food. 
    • Clobazam can be taken with food or without food.
    • Do NOT stop taking this drug suddenly. Stopping this medicine suddenly can cause seizures that will not stop, hearing or seeing things that are not there, shaking, nervousness, or stomach and muscle cramps.

    Using the Oral Suspension:

    • If you are taking the Onfi oral suspension, shake the bottle well right before you take each dose.  
    • Measure your dose of Onfi oral suspension using the bottle adapter and dosing syringes that are given with the suspension. 

    Using Sympazan film formulation:

    • Open the package and take out the Sympazan film strip. 
    • Place it on your tongue and let it dissolve. 
    • Use only one film strip at a time. 
    • Do not use any liquids when you are placing the film on your tongue. It will dissolve on its own. If the film strip is swallowed by mistake, the medicine will still be absorbed into your system. 
    • Sympazan can be taken before or after food, just like other forms of clobazam. 

    How to Store:

    • Store the tablets and oral film strips at room temperature in a dry place that is out of the reach of children.  
    • Make sure to replace the cap securely after opening the oral suspension bottle and keep the bottle upright.  
    • Also, use Onfi oral suspension within 90 days of first opening the bottle.  Throw away any unused Onfi suspension after this time. 
    What if I forget?

    Ask the doctor or nurse what to do if you forget to take a dose. In general, a forgotten dose should be taken right away. If it is almost time for the next dose, just take one dose, not a double dose, and call the doctor's office for more advice.

    Use a pillbox, watch with an alarm, or an online seizure diary or device with reminders to help you take doses on time. 

    Taking the right amount of seizure medicine on time every single day is the most important step in preventing seizures!

    How does Clobazam affect the brain?

    How Clobazam works in the brain is not fully known. It's thought to affect neurotransmitters or substances in the brain that affect the way brain cells communicate. It seems to involve or increase activity at GABA receptors on certain brain cells.

    How does the body digest Clobazam?

    - Clobazam is absorbed quickly into the blood stream. The amount peaks or reaches its highest level within 30 minutes to 4 hours after a dose is taken. 

    - Taking the medication with or without food doesn't affect how it is absorbed into the body. 

    - The drug is distributed throughout the body quickly. The majority of the medicine is bound to proteins as it circulates through the bloodstream. 

    - Clobazam is metabolized or broken down in the liver to the parent or main drug and breakdown products called metabolite. The parent or main drug (clobazam) provides most of the activity in the brain to decrease or stop seizures. Yet the main metabolite can also be active in the brain in smaller amounts.  

    - Clobazam and its main metabolite last a long time in the body. The mean half-life (or how long it takes for the body to get rid of half of the drug) for clobazam ranges 36 to 42 hours. The metabolite may last longer in the body, up to 82 hours.

    - This long half-life means that it takes a while for the drug to reach a steady amount in the system (up to 2 to 3 weeks) and it should not be stopped suddenly. 

    How well does the Clobazam work?

    The package insert summarizes information from the major studies used by the FDA to approve this drug. These studies have shown that clobazam can decrease the frequency of seizures in people with refractory or uncontrolled seizures but does not completely control them. The dose of clobazam used was important. People who were given the recommended higher dose had greater improvement in seizures than people who were given a lower dose of clobazam.

    What are the most common side effects of Clobazam?

    The side effects of clobazam are generally mild and usually disappear if the dose is reduced. They may also go away over time as a person gets used to the medicine. The side effects most often reported are:



    -Poor coordination


    -Restlessness or aggressiveness

    What to do

    If these problems do not go away within several days, or are really bothersome, call the doctor or prescribing health care professional. Sometimes the doctor can help with these side effects by changing the way the medicine is taken. For example, you may be told to: 

    -Reduce the overall amount of clobazam.

    -Change the amount taken at certain times, such as taking a higher amount of the clobazam at bedtime to lessen daytime sleepiness.

    -Give smaller amounts more often during the day. 

    No one should stop taking clobazam or change the amount they take or when they take it without their doctor's or prescriber's advice. 

    Be sure to read about the serious side effects so you will be aware of symptoms that might indicate the beginning of a serious reaction to clobazam. These serious problems are very rare but everyone who takes this medicine should at least be aware of them.

    People who have just started taking clobazam (or who have just started taking a larger amount) should be careful during activities that might be dangerous, until they know whether they are having any side effects.

    Long-term side effects

    Clobazam and other benzodiazepines are the medicines that are most likely to cause psychological dependence. When someone takes a benzodiazepine at a certain dosage for more than 2 to 4 weeks, the body (or specifically, the brain's receptors for the neurotransmitter GABA) becomes accustomed to it. Then if a dose is missed or reduced, a withdrawal process starts, with symptoms such as:


    -Increased heart rate


    -Generally feeling unwell

    Taking another pill relieves all of these symptoms. A person may then believe that he or she "needs" the medication. Yet, this is a very dangerous cycle, since long-term use can cause long-lasting changes in the brain's GABA receptors that lead to significant problems such as impaired cognition, decreased motivation, and depression. In this setting, lowering a dose quickly can cause severe symptoms of anxiety, insomnia, and illness, as well as seizures.

    Many times, a very gradual lowering of the benzodiazepine (often over many months or years) can lead to a dramatic improvement in attention, concentration, memory, and mood without worsening the seizures, insomnia, or anxiety for which the medication was originally prescribed.

    What are the most serious side effects of Clobazam?

    Most people who take clobazam have no side effects or mild side effects that go away in a short time with no lasting harm. Serious reactions, such as a drug-related skin rash, have been extremely rare. Call your doctor right away if you notice a rash soon after you start taking clobazam.

    Sleepy or poor coordination

    Like many other seizure medicines, clobazam makes some people feel sleepy or uncoordinated. If you've just started taking clobazam or have just had your dosage increased, be careful when doing things that could be dangerous until you know how it will affect you. Be especially cautious if you tend to be sensitive to medications or if you are taking another medicine that could make you sleepy.

    Changes in mood or thinking

    One of the great dangers in using medications like clobazam is the tendency to increase the dose if tolerance develops. To a certain extent, this is necessary, but side effects may be increased more than seizure control. If the dose is increased gradually over a long period, subtle changes in mood (such as irritability, depression, or decreased motivation) or problems such as impaired memory may go unnoticed or be considered natural for that person.

    High doses sometimes are prescribed for children and adults, especially those with developmental disabilities. Problems with thinking and behavior may be the result. If the dose has been increased gradually over many months or years, it can be hard to separate the effects of the clobazam (or other benzodiazepines) from the effects of other medications, seizures, and other neurological and psychological disorders.

    More frequent seizures

    An important concern when people with epilepsy take clobazam or other benzodiazepines is the risk that seizures will become more frequent or more severe if the medicine is lowered or stopped. Withdrawal syndrome usually begins as soon as the patient stops taking the medicine and lasts for 8 to 10 days. The longer the person has been taking clobazam and the higher the dose, the greater the tolerance and therefore the higher the risk of worsening seizure control. Even small, gradual dose reductions can temporarily increase seizure activity, but the long-term decrease in effects like drowsiness and depression often makes the change worthwhile.

    Besides increased seizure activity, other symptoms of withdrawal include:



    -Poor coordination


    -Restlessness or aggressiveness

    Tell your doctor if you notice these symptoms when your dosage is being reduced.

    Suicidal feelings or thoughts

    On July 10, 2008, an advisory panel was convened by the Food and Drug Administration (FDA) to review data that the FDA had previously collected from drug studies showing an association between many of the antiepileptic drugs (AEDs) and suicidal ideation and behavior, which together are called suicidality. According to the FDA’s Alert, among the patients with epilepsy in these drug studies, 1 out of 1000 people taking the placebo (inactive substance) showed suicidality compared to approximately 3.5 out of 1000 people who took an AED. The FDA advisory panel voted to accept the FDA's data at its meeting on July 10.

    Taking antiepileptic medicines may increase the risk of having suicidal thoughts or actions;

    • Do not make any changes to the medication regimen without first talking with the responsible healthcare professional;
    • Pay close attention to any day-to-day changes in mood, behavior and actions. These changes can happen very quickly so it is important to be mindful of any sudden differences.

    Be aware of common warning signs that might be a signal for risk of suicide. Some of these are:

    • Talking or thinking about wanting to hurt yourself or end your life
    • Withdrawing from friends and family
    • Becoming depressed or having your depression get worse
    • Becoming preoccupied with death and dying
    • Giving away prized possessions

    We again urge patients and families to contact their doctor before stopping an epilepsy medication because this may possibly lead to seizures and worsening of mood.

    Can Clobazam be taken with other medicines?

    - Clobazam may interact with hormonal contraceptives or birth control, possibly making them less effective. Women of child-bearing age should talk to their health care providers about the best form of contraception for them. A barrier form of contraception should be used by women on clobazam who are taking hormonal birth control. 

    - Clobazam may affect some medications metabolized by certain liver enzymes. 

    - Clobazam may also be affected by some other medications that inhibit or affect certain liver enzymes (for example, fluconazole, fluvoxamine, ticlopidine, omeprazole).  The dose of clobazam may need to be adjusted. 

    - See the package insert for more information about possible drug interactions. 

    - Alcohol may also increase the amount of clobazam in the body by about 50%. 

    What are the dose ranges for Clobazam?

    Follow your doctor's directions. Call if you have any questions.

    Young adults and teenagers are usually advised to start by taking 10 milligrams (1 tablet) per day, at night. After about a week, the doctor may prescribe more tablets to get better control of the seizures. Very few people benefit from taking more than 2 or 3 tablets (20-30 mg) per day, however, and side effects usually become more of a problem at higher doses.

    If the seizures nearly always occur during sleep or first thing in the morning, the doctor may advise taking all the tablets at bedtime. If daytime seizures occur, the advice may be to take some twice a day. If the dose cannot be equally divided, take the larger amount at bedtime.

    Seniors (over age 65) generally require a lower initial dose and particular caution with any increases.

    For children, the starting dose is usually half a tablet (5 mg) per day, or even less for very small children. The dose can be increased every 5 to 7 days until the seizures are controlled or side effects become a problem. Giving more than 1 mg per kilogram (2.2 pounds) of the child's body weight per day seldom improves seizure control, however. This dose would represent 3 tablets (30 mg) for a 66-pound child or 2 tablets (20 mg) for a 44-pound child. These amounts would usually be divided into two doses per day.

    Be sure to use only the number of tablets that the doctor prescribes. If you think one or two extra pills were taken, call your doctor for advice. For a larger overdose, call your local poison control center or emergency room right away.

    No one should stop taking clobazam or change the amount they take without talking to the doctor first. Stopping any seizure medicine all at once can cause a serious problem called status epilepticus. It's particularly unsafe to stop taking any type of benzodiazepine abruptly. The resulting withdrawal symptoms are likely to be unpleasant or even dangerous.

    Read the package insert of Clobazam

    In the United States, companies that manufacture medicines are required to publish certain kinds of information about each product. This document is commonly known as a “package insert” because it is usually included with each package of the medicine.

    You can also read these documents (also called "prescribing information") online. The U.S. package insert for ONFI (clobazam) is found at:


    Primary Generalized Epilepsy

    Sign Up for Emails

    Stay up to date with the latest epilepsy news, stories from the community, and more.