As with other drugs, Onfi (clobazam) can cause side effects, such as constipation, sleepiness, and fever. If you’re not able to tolerate side effects of Onfi, talk with your doctor or pharmacist.

Onfi is a brand-name drug approved by the Food and Drug Administration (FDA) to reduce seizures caused by a rare type of epilepsy called Lennox-Gastaut syndrome (LGS). It’s used 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.

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 in-depth Onfi article.

Boxed warnings

This drug has boxed warnings about risks of:

• severe, life threatening side effects if taken with opioids
• addiction and misuse
• dependence and withdrawal

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

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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 prescribing information.

Mild side effects that have been reported with Onfi include:

  • constipation
  • feeling very sleepy or drowsy
  • fever
  • lethargy
  • drooling
  • insomnia (trouble sleeping)
  • feeling more angry than usual
  • aggression (see “Side effect specifics” for details)
  • vomiting
  • ataxia (trouble coordinating or controlling your muscles)
  • upper respiratory infection
  • pneumonia
  • urinary tract infection (UTI)
  • cough
  • changes in appetite
  • mild allergic reaction

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 following list may not include all possible serious side effects of the drug. For more information, you can refer to Onfi’s prescribing information.

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 some of these side effects, see the “Side effect specifics” section.

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

  • Call or text the 988 Lifeline at 988 or chat at 988lifeline.org. Caring counselors are available to listen and provide free and confidential support 24/7.
  • Text HOME to the Crisis Text Line at 741741 to connect with a volunteer crisis counselor for free and confidential support 24/7.
  • Not in the United States? Find a helpline in your country with Befrienders Worldwide.
  • Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you’re not in the same household, stay on the phone with them until help arrives.

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 (also called abuse) 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 like usual. 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 treatment options for you. They’ll prescribe the lowest possible Onfi dosage 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 usual 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 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 it 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 your symptoms.

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

A serious allergic reaction called drug reaction with eosinophilia and systemic symptoms (DRESS) is possible with Onfi. This reaction affects the skin and organs. It can cause the above symptoms and others, such as fever, swollen lymph nodes, liver problems, and kidney problems. DRESS can be life threatening.

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. Mild symptoms can quickly become severe and life threatening, so it’s important to get medical help. Your doctor 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.

Does Onfi cause long-term side effects?

It’s possible, but Onfi isn’t likely to cause long-term side effects. If you experience side effects when you first start taking Onfi, they may reduce or go away after you take the drug for a while. Examples include drowsiness and constipation.

It’s also possible for some side effects to last long term, such as problems related to using opioids with Onfi or suddenly stopping Onfi.* But this is rare.

It’s important to note that the risk of dependence and withdrawal* increases the longer you take Onfi. If you need to stop taking Onfi, your doctor will work with you to gradually reduce your dose. This lowers your risk of withdrawal symptoms.

If you’re concerned about long-term side effects of Onfi, talk with your doctor.

* Onfi has boxed warnings for severe, life threatening side effects if taken with opioids, as well as for addiction, misuse, dependence, and withdrawal. For details, see the “Side effect specifics” section.

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 increase 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 vary 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.

The side effects of clobazam are the same as those caused by the brand-name Onfi. See the “Mild side effects” and “Serious side effects” sections 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 reportedTrusted Source with other medications used to treat seizures. Also, ED and other sexual problems may be caused by epilepsyTrusted Source 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” 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.

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.

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. This is called neonatal abstinence syndrome (or neonatal withdrawal syndrome).

Onfi is also known to pass into breast milk and can cause side effects in breastfed children. These effects can include difficulty 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.

If you take Onfi during pregnancy, you can consider joining the antiepileptic drug pregnancy registry. This registry collects information about how certain epilepsy drugs, such as Onfi, affect pregnancy. You can learn more at the registry website and by calling 888-233-2334.

Onfi has a boxed warning about the risk of 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.

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.