Onfi (clobazam) is a prescription brand-name medication. It’s approved by the Food and Drug Administration (FDA) to reduce seizures in people who have a rare type of epilepsy called Lennox-Gastaut syndrome (LGS). Onfi is approved for use in adults and children ages 2 years and older.

Onfi is an adjunctive treatment, which means you’ll take it with other drugs that treat epilepsy. If you and your doctor agree that Onfi is working to reduce the number of seizures you have, you’ll likely take it long-term.

Here are some fast facts on Onfi:

  • Active ingredient: clobazam
  • Drug class: benzodiazepine
  • Drug forms: oral tablet, oral liquid solution

Like other drugs, Onfi can cause side effects. Although rare, some side effects caused by Onfi can be long term. Read on to learn about potential common, mild, and serious side effects. For a general overview of Onfi, including details about its uses, see this article.

Onfi can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days or weeks. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the main side effects more commonly reported by people who took Onfi in clinical trials:

  • constipation
  • feeling very sleepy or drowsy
  • fever
  • lethargy (lack of energy and motivation)
  • drooling

Mild side effects can occur with Onfi use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Onfi’s medication guide.

Mild side effects that have been reported with Onfi include:

  • constipation
  • feeling very sleepy or drowsy
  • fever
  • lethargy (lack of energy and motivation)
  • drooling
  • insomnia (trouble sleeping)
  • feeling more angry than usual
  • aggression*
  • vomiting
  • ataxia (trouble coordinating or controlling your muscles)
  • upper respiratory infection
  • pneumonia
  • urinary tract infection (UTI)
  • cough

* For more information about this side effect, see “Side effect specifics” below.

These side effects may be temporary, lasting a few days or weeks. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Onfi and want to tell the FDA about it, visit MedWatch.

Onfi may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Onfi’s medication guide.

If you develop serious side effects while taking Onfi, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

* For more information about this side effect, see “Side effect specifics” below.
Onfi has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA).
‡ An allergic reaction is possible after using Onfi. But this side effect wasn’t reported in clinical studies.

Learn more about some of the side effects that Onfi may cause.

Boxed warnings

Onfi has several boxed warnings. A boxed warning is a serious warning from the Food and Drug Administration (FDA).

Severe, life-threatening side effects if taken with opioids. Taking Onfi with an opioid can cause serious side effects. These include respiratory depression (slowed or weak breathing), and sedation (feeling very drowsy or tired). Rarely, use with opioids can cause coma and (very rarely) death.

Addiction and misuse. The active drug in Onfi, clobazam, is classified as a benzodiazepine. This type of drug has a risk for misuse and addiction. Misuse refers to using a drug in a way other than how it’s prescribed, such as taking too much. Life-threatening side effects, including coma and death, have been reported in people who misuse benzodiazepines, including Onfi.

Onfi is a controlled substance due to the risk for addiction and misuse. This means that there are additional rules for how it can be prescribed and used, in order to minimize these risks.

Dependence and withdrawal. Onfi can cause physical dependence. This means your body becomes used to having the drug in your system and needs it to feel normal. Suddenly stopping Onfi can cause withdrawal symptoms, such as:

  • anxiety
  • diarrhea
  • heart palpitations (feeling like your heart is skipping a beat)
  • feeling irritable or restless
  • headache
  • tremors (shaking)
  • insomnia (trouble sleeping)

What you can do

Managing effects if taken with opioids. Your doctor will prescribe Onfi with an opioid only if there are no other treatments options for you. They’ll prescribe the lowest possible Onfi dose to lower your risk for side effects. They’ll also monitor you for any symptoms of respiratory depression or sedation.

If you have any of the following symptoms, get emergency medical help:

  • excessive sleepiness
  • slowed or shallow breathing
  • stops or pauses in breathing

Preventing or treating addiction and misuse. Take Onfi exactly as your doctor prescribes. Never share Onfi with another person, or take it in any way other than how it’s prescribed for you.

Keep in mind that Onfi can be addicting even when taken at normal doses for treating seizures. Your doctor will monitor you for signs of addiction or misuse while you’re taking Onfi.

If you have any of the following serious symptoms while taking Onfi, call your doctor or get emergency medical help right away. Your family and loved ones should also be aware of these symptoms so they can help monitor for them. These could be signs of addiction or misuse:

Preventing withdrawal symptoms. To help avoid withdrawal symptoms, it’s very important that you don’t suddenly stop taking Onfi. Talk with your doctor first, and they’ll help with tapering (slowly reducing, or weaning off) your dosage over time. This lessens your risk of withdrawal.

If you have questions about dependence and withdrawal with Onfi, including how to safely stop taking the medication, talk with your doctor. Do not change your Onfi treatment without their recommendation.

Aggression

It’s possible to experience aggression as a side effect of Onfi. Aggression was reported in clinical trials, but wasn’t common. You’re more likely to have aggression with higher doses of Onfi.

What you can do

You should contact your doctor right away if you notice aggression while taking Onfi.

Although aggression itself may not be serious, changes in your behavior can be a sign of more serious side effects of Onfi. These can include addiction or misuse, or suicidal thoughts or behaviors.

If you experience aggression or other behavioral changes while taking Onfi, your doctor can evaluate you for other symptoms. They’ll determine whether it’s safe for you to keep taking Onfi.

Severe skin reactions

Onfi may rarely cause severe skin reactions, such as Stevens-Johnson Syndrome (SJS) or toxic epidermal necrolysis (TEN).

Symptoms of a severe skin reaction (such as SJS or TEN) may include:

  • rash or hives
  • sores in your mouth
  • skin blisters

You’re most likely to experience a severe skin reaction during your first 8 weeks of taking Onfi.

What you can do

Call your doctor right away if you develop a rash or any of the above symptoms. Your doctor will likely have you stop Onfi and evaluate you for a skin reaction.

Allergic reaction

As with most drugs, Onfi can cause an allergic reaction in some people. But this side effect wasn’t reported in clinical trials.

Symptoms can be mild or serious and can include:

  • rash
  • itching
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your lips, eyelids, feet, or hands
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Onfi. But if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Onfi may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Can Onfi’s side effects include weight gain?

Weight gain wasn’t reported as a side effect by people taking Onfi in clinical trials.

However, appetite changes are a possible side effect of Onfi. This can include increased appetite, which could lead to weight gain.

If you’re concerned about weight gain while taking Onfi, talk with your doctor. They can recommend ways to maintain a weight that’s healthy for you.

Do Onfi’s side effects vary depending on which strength I’m taking (10 mg, 20 mg, 2.5 mg/mL)?

Yes, Onfi’s side effects can vary depending on which strength you’re taking.

In general, Onfi’s side effects are dose-dependent. This means your chances of having side effects increases as your dose increases.

Your doctor will work to find the smallest Onfi dose that’s effective for you. If you have questions about Onfi’s side effects and dosages, talk with your doctor or pharmacist. You may also view the drug’s prescribing information to see specifics about how side effects varied with dose.

What are the side effects of generic Onfi?

Onfi contains the active drug clobazam. Clobazam is available in generic form. A generic drug is an exact copy of the active drug in a brand-name medication.

Side effects of clobazam are the same as those caused by brand-name Onfi. See the “Mild side effects” and “Serious side effects” sections above for lists of side effects.

Is erectile dysfunction a side effect of Onfi?

No, erectile dysfunction (ED) wasn’t reported as a side effect by people taking Onfi in clinical trials.

But ED and other sexual side effects have been reported with other medications used to treat seizures. Also, ED and other sexual problems may be caused by epilepsy itself.

If you have questions about ED or other sexual problems, talk with your doctor.

Could Onfi affect my heart rate?

Taking Onfi isn’t known to affect your heart rate. Changes in heart rate weren’t reported in clinical trials.

However, a fast heart rate can be a withdrawal symptom if you suddenly stop taking Onfi. It’s important to work with your doctor on tapering (slowly reducing) your dose if you want to stop taking Onfi. Onfi has a boxed warning about withdrawal and dependence (see “Side effect specifics” above for details).

If you’re experiencing changes in your heart rate, contact your doctor. They can help determine what might be causing this.

Can Onfi cause cognitive side effects?

Onfi can cause some cognitive side effects. But Lennox-Gastaut syndrome (LGS), the condition Onfi treats, also causes cognitive function to worsen over time.

Cognitive function refers to your ability to do mental actions like paying attention, thinking, and remembering.

Possible cognitive side effects of Onfi include:

If you have questions about cognitive side effects with Onfi, talk with your doctor or pharmacist. They can best address how to handle this side effect.

* Onfi has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). For more information, see “Side effect specifics” above.

This drug has boxed warnings about risks of:

Boxed warnings are serious warnings from the Food and Drug Administration (FDA). For details, see the “Side effect specifics” section above.

Other precautions

Be sure to talk with your doctor about your health history before you take Onfi. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:

Mood conditions, depression, or suicidal thoughts or behaviors. Onfi may increase your risk for suicidal thoughts or behaviors, depression, and other mood changes. If you have a condition that affects your mood, such as depression, taking Onfi could worsen your symptoms. Talk with your doctor about your mental health before you start taking Onfi. They can help determine the safest treatment for your condition.

Kidney problems. Talk with your doctor if you have severe kidney problems, or are on dialysis, before you take Onfi. They may prescribe a different medication for your condition.

Liver problems. Your doctor may start you on a lower Onfi dose than usual if you have liver problems. Depending on how severe your liver problems are, they may instead try a different medication to treat your condition. Talk with your doctor about any liver problems you have before you begin taking Onfi.

Allergic reaction. You shouldn’t take Onfi if you’ve ever had an allergic reaction to Onfi or any of its ingredients. Talk with your doctor about which other treatments are better choices for you.

Alcohol use with Onfi

You should not drink alcohol while taking Onfi.

Doing so can increase your risk for severe side effects. These include respiratory depression (slowed or weakened breathing) and sedation (feeling very drowsy or tired). Drinking alcohol while you’re taking Onfi can, rarely, lead to a coma or death.

If you drink alcohol, talk with your doctor before taking Onfi. They’ll likely recommend that you stop drinking, or may prescribe a different drug.

Pregnancy and breastfeeding while taking Onfi

Onfi might not be safe for use during pregnancy or while breastfeeding.

Using Onfi late in pregnancy may cause complications in newborns, such as problems with feeding and breathing. Onfi is also known to pass into breast milk, and can cause side effects in breastfed children. These effects can include poor feeding, excessive sleepiness, and lack of energy.

Before starting Onfi, talk with your doctor if you’re currently pregnant or breastfeeding, or considering pregnancy or breastfeeding. You and your doctor will decide together if you should take Onfi.

Onfi has a boxed warning about addiction and misuse. Boxed warnings are serious warnings from the Food and Drug Administration (FDA).

Misuse refers to using a medication other than how it’s prescribed for you. This can include taking a drug that isn’t prescribed to you, or taking a higher dose than prescribed.

For more information on misuse with Onfi, see the “Side effect specifics” section above.

Side effects from Onfi can occur, including mild and serious side effects. Some mild side effects of the drug go away with time and don’t require medical attention. Rarely, some side effects may be long lasting.

You should contact your doctor if you experience symptoms of serious side effects.

If you’d like to learn more about Onfi, talk with your doctor or pharmacist. You can also do some research on your own. These articles might help:

  • More information on Onfi. For details on other aspects of Onfi, refer to this article.
  • A look at seizures. For details about seizures, see our list of epilepsy articles.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.