Onfi (Clobazam) - Oral


Using benzodiazepines, such as Onfi (clobazam), with opioids increases the risk of profound sedation, respiratory depression (breathing problems), coma, and death. These drugs should only be prescribed together to people for whom alternative treatment options are inadequate.

What Is Onfi? 

Onfi (clobazam) is an oral prescription antiepileptic drug (AED) that comes in tablet and liquid suspension formulations. It is used every day to prevent seizures in adults and in children ages 2 years and older.

Onfi belongs to a class of medications called benzodiazepines, which are known as central nervous system depressants. It works by binding to and affecting the action of gamma-aminobutyric acid (GABA). GABA is an amino acid in the brain responsible for passing information between the brain’s nerve cells and the spinal cord.

Onfi is a controlled substance, meaning it can be abused or lead to dependence.

Drug Facts

Generic Name: Clobazam

Brand Name(s): Onfi, Sympazan

Drug Availability: Prescription

Therapeutic Classification: Anticonvulsant

Available Generically: Yes

Controlled Substance: Potential for abuse

Administration Route: Oral

Active Ingredient: Clobazam

Dosage Form(s): Tablet, suspension, film

What Is Onfi Used For? 

The Food and Drug Administration (FDA) approved Onfi as an adjunctive AED therapy, also referred to as add-on therapy, to prevent seizures from Lennox-Gastaut syndrome (LGS). Symptoms of LGS typically emerge during early childhood and include multiple types of seizures and developmental delay. LGS-related seizures are especially persistent and often resistant to therapy. 

As an adjunctive AED treatment, Onfi is intended for use along with another AED because it isn’t expected to fully prevent seizures on its own. 

Onfi (Clobazam) Drug Information

Onfi (Clobazam) Drug Information

How to Take Onfi 

A healthcare provider will prescribe Onfi to take as one or two doses per day, with or without food. Take it at the same time each day. Shake the suspensions well before each use.

Because Onfi is a controlled substance, selling or giving the medication to others is illegal and can cause harm.


Keep this medication away from the reach of children and pets. 

Store the tablets and oral suspension in the original container at temperatures between 68 and 77 degrees F. The oral suspension should be stored in an upright position and used within 90 days of opening. Discard any remaining medication in the oral suspension container that is not used within 90 days after opening the bottle.

Off-Label Uses 

Healthcare professionals sometimes prescribe Onfi for the treatment of several conditions besides LGS that are not mentioned in the FDA’s approved packaging label. This is known as off-label use.

Common off-label uses include:

  • Dravet syndrome, a disorder that is characterized by multiple seizure types and developmental problems
  • Generalized seizures and partial seizures 
  • Monotherapy for seizure prevention in epilepsy 
  • Anxiety symptoms or anxiety disorders

How Long Does Onfi Take to Work?

Onfi begins to work quickly in the body, with its onset ranging from half an hour to four hours or sooner after taking it. It can take five to nine days for Onfi to work properly.

What Are the Side Effects of Onfi?

This is not a complete list of side effects, and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 1-800-FDA-1088.

Onfi can cause several different side effects. Be sure to tell your healthcare provider if you or your child experience any reactions to the medication. Have a plan ready in case you or your child experience serious or potentially life-threatening problems.

Common Side Effects

The most common side effects of Onfi are:

These side effects can be mild, but for some people, they can be persistent or cause significant distress. Medical management can help relieve some of the common side effects. 

Severe Side Effects

Serious adverse effects of Onfi can be dangerous or life-threatening and require medical attention. 

Serious side effects of Onfi may include:

Get medical attention promptly if you or your child develop a rash while taking Onfi. Seek urgent medical care if you or your child begin to have suicidal thoughts or behaviors. 

Serious reactions can occur at any time—when first starting the medication or after you have taken it for a while without side effects. The healthcare provider who prescribed you Onfi may switch you to a different medication and discontinue Onfi if you develop intolerable or severe side effects.

Long-Term Side Effects

Taking Onfi can lead to physical dependence and substance use/misuse disorder. Only take this medication as directed by your medical provider. When you stop taking it, you need to do so under the supervision of a health professional.

Report Side Effects

Onfi may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Onfi Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage forms (film, suspension, or tablets):
    • For seizures:
      • Adults and children 2 years of age and older weighing more than 30 kilograms (kg)—Dose is based on body weight and must be determined by your doctor. The starting dose is usually 10 milligrams (mg) per day, given as 2 divided doses per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 40 mg per day.
      • Adults and children 2 years of age and older weighing 30 kg or less—Dose is based on body weight and must be determined by your doctor. The starting dose is usually 5 mg as a single dose per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 20 mg per day.
      • Older adults—Dose is based on body weight and must be determined by your doctor. The starting dose is usually 5 mg as a single dose per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 40 mg per day.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor.


The prescribed dose of Onfi may vary depending on the person's body weight. Older adults (aged 65 years and older) and children generally start with smaller doses.

No dose adjustment is necessary for people with mild to moderate kidney impairment. Severe kidney impairment was not studied. However, your medical provider may adjust your dose if you have liver impairment.

Missed Doses

If you miss a dose, take the medication as soon as you can. Skip the missed dose if it is almost time for your next dose. Do not double up on doses.

What Happens If I Take Too Much Onfi? 

Taking too much Onfi increases the risk of side effects.

Potential consequences of overdosing on Onfi include: 

  • Severe drowsiness 
  • Diminished responsiveness 
  • Confusion 
  • Impaired balance 
  • Breathing difficulty 
  • Low blood pressure 
  • Coma or death

If you take too much of this medication be sure to seek medical attention promptly. You will need to be observed, and you may need treatment for your side effects.

Taking Onfi with opioids or alcohol increases the risk of serious side effects and can be fatal.

Treatment of an overdose might involve: 

  • Intravenous fluids  
  • Gastric lavage 
  • Activated charcoal
  • Respiratory support
  • Plasma substitute administration 
  • Sympathomimetic agents

What Happens If I Overdose On Onfi?

If you think you or someone else may have overdosed on Onfi (clobazam), call your healthcare provider or the Poison Control Center (1-800-222-1222).

If someone collapses or isn’t breathing after taking Onfi, call 911. 


Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check your or your child's progress at regular visits to make sure this medicine is working properly and to check for unwanted effects.

This medicine will add to the effects of alcohol and other CNS depressants (medicines that make you drowsy or less alert). Some examples of CNS depressants are antihistamines or medicine for hay fever, allergies, and colds, sedatives, tranquilizers, or sleeping medicine, prescription pain medicine or narcotics, medicine for seizures or barbiturates, muscle relaxants, or anesthetics (numbing medicines), including some dental anesthetics. This effect may last for a few days after you stop using this medicine. Check with your doctor or dentist before taking any of these medicines with clobazam.

This medicine may cause some people to be dizzy, drowsy, or less alert than normal.

This medicine may be habit-forming. If you feel that the medicine is not working as well, do not use more than your prescribed dose. Call your doctor for instructions.

Do not change your dose or suddenly stop using this medicine without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely. This may help prevent a possible worsening of your seizures and reduce the possibility of withdrawal symptoms such as changes in behavior, discouragement, feeling sad or empty, irritability, lack of appetite, loss of interest or pleasure, trouble concentrating, seeing or hearing things that others do not see or hear, thoughts of killing oneself, trouble sleeping, unusual movements, responses, or expressions.

Symptoms of an overdose include: blurred vision, change or loss of consciousness, confusion, dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position, pale or blue lips, fingernails, or skin, shakiness, unsteadiness, trembling, or other problems with muscle control or coordination, sweating, trouble breathing, or unusual drowsiness, dullness, tiredness, weakness or feeling of sluggishness. Call your doctor right away if you notice these symptoms.

Serious skin reactions can occur with this medicine. Check with your doctor right away if you have blistering, peeling, or loosening of the skin, red skin lesions, severe acne or skin rash, sores or ulcers on the skin, or fever or chills with this medicine.

If you or your child develop any unusual or strange thoughts and behavior while taking this medicine, be sure to discuss it with your doctor. Some of the changes that have occurred in people taking this medicine are like those seen in people who drink too much alcohol. Clobazam may cause confusion, worsening of depression, hallucinations (seeing, hearing, or feeling things that are not there), suicidal thoughts, and unusual excitement, nervousness, or irritability.

Birth control pills may not work as well while you are using this medicine. To keep from getting pregnant, use another form of birth control together with your birth control pills during therapy and for 28 days after you take the last dose.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Onfi? 

Do not take Onfi if you have a history of hypersensitivity to the drug or its ingredients. Hypersensitivity reactions can cause serious skin reactions. 

Onfi may cause harm to the fetus during pregnancy. Talk to your healthcare provider if you are pregnant or intend to become pregnant during therapy. 

Do not breastfeed while taking Onfi, as Onfi can pass through breast milk. People who are breastfeeding should talk with their healthcare provider about whether to stop nursing or stop taking this medication.

What Other Medications Interact With Onfi?

Onfi interacts with some medications. You may need to take special care in terms of dosing and/or monitoring side effects when using Onfi along with certain other medications. 

Additionally, some substances can lead to harmful adverse effects if used with Onfi. 

Onfi can interact with:

Hormonal contraceptives 

When taken together, Onfi can reduce how well hormonal contraceptives work. Talk to your healthcare provider about an alternative form of birth control if you are taking hormonal contraceptives to prevent pregnancy. Sometimes these medications are prescribed for other reasons, and their effectiveness might be affected by Onfi. 

Medications such as fluconazole, fluvoxamine, ticlopidine, and omeprazole

Your provider may need to adjust your prescribed dose of Onfi and/or your dose of these medications when taking them in combination. 


Often prescribed for pain control, opioids are sometimes misused and can lead to a high risk of serious side effects if taken with Onfi. 


Using alcohol with Onfi, even in moderation, can increase the risk of seizures or medication side effects.

What Medications Are Similar? 

Many medications with different mechanisms of action are used to treat epilepsy. Some of them can be combined, while others cannot. 

Other benzodiazepines used to treat epilepsy include:

  • Klonopin (clonazepam)
  • Ativan (lorazepam)

Nonbenzodiazepine AEDs used to treat LGS include Depakote (valproic acid), Banzel (rufinamide), Lamictal (lamotrigine), and Topamax (topiramate).

Frequently Asked Questions

  • What is Onfi used for?

    Onfi is used to prevent seizures in Lennox-Gastaut syndrome (LGS). It is sometimes off-label to treat anxiety or to prevent seizures in other types of epilepsy.

  • How does Onfi work?

    Onfi interacts with the gamma-aminobutyric acid (GABA) receptors to inhibit nerve activity in the brain. GABA is an amino acid in the brain that serves as the primary inhibitory neurotransmitter to pass information between the nerve cells and the spinal cord.

  • What drugs should not be taken with Onfi?

    You should not use alcohol or misuse opioids if you take Onfi. Your healthcare provider may adjust your prescription dose and monitor for side effects if you are also taking fluconazole, fluvoxamine, ticlopidine, or omeprazole. Additionally, Onfi can make hormonal contraceptives less effective.

  • How long does it take for Onfi to work?

    Onfi is absorbed in the body and begins to work quickly after it is taken, with an average time of onset ranging from half an hour to four hours or sooner.

  • What are the side effects of Onfi?

    Onfi can cause side effects that range from mild to severe, including tiredness, dizziness, diminished balance, severe skin reactions, and suicidal ideation.

  • What’s the right way to stop taking Onfi?

    If your healthcare provider recommends that you stop taking Onfi, they will give you a tapering schedule to slowly reduce the dose and possibly to replace it with another medication. Abruptly stopping can cause withdrawal seizures or status epilepticus, a dangerous complication of seizures.

How Can I Stay Healthy While Taking Onfi?

If you or your child are prescribed Onfi for treatment of LGS or another seizure condition, make sure to take Onfi and all your other medications as directed. Skipping doses or taking your AEDs on an inconsistent schedule can cause seizures.

In addition to taking anti-seizure medication, avoid seizure triggers such as:

  • Lack of sleep
  • Skipping meals
  • Alcohol or recreational drugs
  • Rapidly flashing lights

Additionally, stay away from situations in which having a seizure could be especially dangerous. Do not climb ladders, swim alone, or use sharp or heavy equipment.

If you are taking Onfi to treat anxiety, you may benefit from counseling or behavioral therapy in addition to your medical therapy.

Medical Disclaimer

Verywell Health's drug information is meant for education purposes only and not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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