If you have seizures caused by Lennox-Gastaut syndrome (LGS), your doctor may prescribe Onfi for you. It’s a prescription drug that’s used to treat seizures from LGS in adults and some children.
To learn more about seizures from LGS and how Onfi is used to treat them, see the “What is Onfi used for?” section below.
Onfi comes as tablets and as a suspension (a type of liquid mixture). You’ll take either form by mouth.
In this article, we describe how Onfi is taken as well as its uses, side effects, and more.
Like most drugs, Onfi may cause mild or serious side effects. The lists below describe some of the more common side effects that Onfi may cause in adults and children, including toddlers. These lists don’t include all possible side effects.
Keep in mind that side effects of a drug can depend on:
- your age
- other health conditions you have
- other medications you may be taking
Your doctor or pharmacist can tell you more about the potential side effects of Onfi. They can also suggest ways to help reduce side effects.
Mild side effects
Here’s a short list of some of the mild side effects that Onfi can cause. To learn about other mild side effects, talk with your doctor or pharmacist, or read Onfi’s medication guide.
Mild side effects of Onfi that have been reported include:
- aggressive behavior*
- ataxia (trouble with muscle movement and coordination)
- fatigue (lack of energy)
- trouble sleeping
- upper respiratory infections, such as the common cold
Mild side effects of many drugs may go away within a few days or a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.
* For more information on this side effect, see the “Side effect focus” section below.
Serious side effects
Serious side effects from Onfi can occur, but they aren’t common. If you have serious side effects from Onfi, call your doctor right away. But if you think you’re having a medical emergency, call 911 or your local emergency number.
Serious side effects of Onfi that have been reported include:
- severe skin reactions, such as Stevens-Johnson syndrome or toxic epidermal necrolysis
- mood changes, thoughts of suicide, or suicidal behaviors
- boxed warnings:
- risk of addiction and misuse*
- allergic reaction*
Note: Allergic reaction wasn’t reported in studies of Onfi. But it can still happen with this drug.
* For more information on this side effect, see the “Side effect focus” section below.
If you think someone is at immediate risk of self-harm or hurting another person:
- Call 911 or your local emergency number.
- Stay with the person until help arrives.
- Remove any guns, knives, medications, or other things that may cause harm.
- Listen, but don’t judge, argue, threaten, or yell.
If you or someone you know is considering suicide, get help from a crisis or suicide prevention hotline. Try the National Suicide Prevention Lifeline at 800-273-8255.
Side effect focus
Learn more about some of the side effects Onfi may cause.
Onfi has boxed warnings. A
Risk of addiction and misuse. Taking Onfi can lead to addiction and misuse. Misusing Onfi means the drug is taken in a way that’s different from how it was prescribed. With addiction, a drug is used even if it’s causing harmful outcomes.
Addiction and misuse weren’t reported in studies of Onfi. But addiction and misuse have been reported with other benzodiazepines. (Keep in mind that Onfi belongs to the group of drugs called benzodiazepines.)
Risk of withdrawal and dependence. You may develop physical dependence with Onfi. With dependence, your body gets used to a drug and has trouble functioning without it.
Dependence on Onfi can lead to life threatening withdrawal if you suddenly stop taking the drug. A few withdrawal symptoms you may have if Onfi is suddenly stopped include:
- aches, pains, or muscle spasms
- nausea and vomiting
- trouble sleeping
Withdrawal and dependence weren’t reported in studies of Onfi. But these side effects may still be possible with the drug.
What might help
If you’re concerned about the risk of addiction or misuse with Onfi, talk with your doctor. They’ll monitor your risk before treatment with this drug. They’ll also periodically assess your risk during treatment with Onfi.
You shouldn’t suddenly stop taking Onfi without first discussing it with your doctor. If your doctor recommends that it’s safe to stop this drug, they’ll gradually lower your Onfi dosage over time. Doing so will help lessen your risk for withdrawal symptoms.
Tell your doctor right away if you have any symptoms of withdrawal from Onfi. Your doctor will monitor your condition closely to make sure your symptoms don’t get worse. They may also prescribe certain treatments to help relieve your withdrawal symptoms.
Aggressive behavior can show up in the following ways:
What might help
If you have feelings of aggression while you’re taking Onfi, talk with your doctor.
It’s important to note that aggressive behavior can be a sign of mood changes. And these mood changes can sometimes lead to thoughts of suicide or suicidal behaviors.
Tell your doctor right away about any changes in your mood or behavior while you’re taking Onfi. They’ll talk with you about your mental health and suggest ways to help your mood.
But if you have thoughts of harming yourself or others, call 911 or your local emergency number. You can also call the National Suicide Prevention Lifeline, which is available 24 hours a day, at 800-273-8255.
Symptoms of a mild allergic reaction can include:
- flushing (temporary warmth, redness, or deepening of skin color)
A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, typically in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause trouble breathing.
Call your doctor right away if you have an allergic reaction to Onfi. But if you think you’re having a medical emergency, call 911 or your local emergency number.
Your doctor will explain how you should take Onfi. They will also explain how much to take and how often. Be sure to follow your doctor’s instructions. Below are commonly used dosages, but always take the dosage your doctor prescribes.
Onfi comes in two forms that you’ll take by mouth:
- suspension (a type of liquid mixture)
Onfi tablets come in two strengths: 10 milligrams (mg) and 20 mg.
Onfi suspension comes in one strength: 2.5 mg per milliliter (mg/mL) of liquid. To take this form of the drug, you’ll pull the liquid up into a syringe that’s provided with the drug. You’ll then use the syringe to take the suspension by mouth.
The adult and pediatric dosages of Onfi vary depending on body weight.
For instance, some people may take 5 mg once or twice per day. Other people may take 15 mg twice per day. Daily dosages of Onfi that are greater than 5 mg will be split into two separate doses.
Your doctor may start you out taking a low dosage of Onfi. Then, they’ll increase your dosage until the drug starts working for you.
Taking Onfi with other drugs
Onfi is used together with other epilepsy drugs. Examples of other epilepsy drugs include:
- levetiracetam (Keppra)
- cannabidiol (Epidiolex)
If you have questions about epilepsy drugs that are right for you, talk with your doctor.
Onfi and use with CBD oil
Keep in mind that most CBD oil products aren’t regulated by the Food and Drug Administration (FDA). This means there’s no guarantee the ingredients in these products are safe or effective for treating seizures.
But some people have found relief from seizures by using CBD oil products.
If you’re interested in using Onfi together with CBD oil, talk with your doctor. They can advise whether it’s safe for you to use these products together.
Onfi and boxed warning of risks if used with opioids
Examples of opioids include:
Before starting Onfi, tell your doctor about all other medications that you’re taking. If an opioid is prescribed for you while you’re taking Onfi, your doctor will discuss the risks with you. They’ll likely lower your dosage of Onfi to make sure your risk for side effects is as low as possible.
Questions about taking Onfi
Here are answers to some common questions about taking Onfi.
- What if I miss a dose of Onfi? If you miss a dose of this drug, take your missed dose as soon as you remember. Or if it’s almost time for your next dose, just skip the missed dose. Then you can take your next dose at its regular time. If you aren’t sure whether you should take a missed dose or skip it, talk with your doctor or pharmacist.
- Will I need to use Onfi long term? Yes, most likely. You’ll probably take Onfi long term if the drug is working for you and it isn’t causing bothersome side effects. Your doctor will tell you the length of time that’s right for you to take Onfi.
- Can Onfi be chewed, crushed, or split? Yes, if needed, you can split Onfi tablets in half. You can also crush Onfi tablets and mix them with applesauce.
- Should I take Onfi with food? You can take Onfi with food or without it.
- How long does Onfi take to work? Onfi starts working right away to treat your condition. But it may take a couple of weeks after your first dose for Onfi to start reducing your seizures.
Questions for your doctor
You may have questions about Onfi and your treatment plan. It’s important to discuss all your concerns with your doctor.
Here are a few tips that might help guide your discussion:
- Before your appointment, write down questions like:
- How will Onfi affect my body, mood, or lifestyle?
- Bring someone with you to your appointment if doing so will help you feel more comfortable.
- If you don’t understand something related to your condition or treatment, ask your doctor to explain it to you.
Remember, your doctor and other healthcare professionals are available to help you. And they want you to get the best care possible. So, don’t be afraid to ask questions or offer feedback on your treatment.
If you have seizures caused by Lennox-Gastaut syndrome (LGS), your doctor may prescribe Onfi for you.
Onfi is prescribed to treat seizures from Lennox-Gastaut syndrome (LGS). It’s used in adults and children ages 2 years and older. For this condition, you’ll take Onfi in combination with other epilepsy drugs.
LGS is a type of severe epilepsy. Epilepsy is a condition that causes repeated seizures. Seizures happen because of changes in the electrical activity in your brain.
With LGS, seizures often happen daily. In addition to seizures, people with LGS also have trouble learning and problems with development. LGS can also lead to problems with attention, memory, and thinking.
Onfi works to reduce the number of seizures in people with LGS. The way Onfi works to treat LGS isn’t known for sure. It’s thought that the drug may affect the brain’s electrical activity.
Find answers to some commonly asked questions about Onfi.
Does Onfi cause weight gain?
It’s possible that taking Onfi could lead to weight gain.
If you’re concerned about weight gain while taking Onfi, talk with your doctor. They can recommend healthy ways to manage your body weight.
Can Onfi be used for anxiety?
In the United States, Onfi isn’t approved to treat anxiety.
Onfi is a type of drug called a benzodiazepine. Other benzodiazepines are approved to treat anxiety. These other benzodiazepines include:
- lorazepam (Ativan)
- alprazolam (Xanax)
Onfi might work to treat anxiety, but it’s not approved for this use in the U.S. The drug is approved in other countries for treating anxiety.
If you have anxiety, talk with your doctor about the treatment that’s best for you.
How does Onfi work?
Seizures happen because of changes in the electrical activity in your brain.
Onfi works to reduce the number of seizures that people with LGS have. The drug’s mechanism of action to treat LGS isn’t known for sure. (The way Onfi works in your body to treat your condition is called its mechanism of action.) But it’s thought that Onfi may affect your brain’s electrical activity.
If you have questions about the way Onfi works, talk with your doctor or pharmacist.
Costs of prescription drugs can vary depending on many factors. These factors include what your insurance plan covers and which pharmacy you use.
If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. You can also visit the Onfi manufacturer’s website to see if it has support options.
When considering Onfi treatment, it’s important to talk with your doctor. You should discuss your overall health and any medical conditions you may have with them.
These considerations and others are described below.
Taking medications, vaccines, foods, and other things with a certain drug can affect how the drug works. These effects are called interactions.
Before taking Onfi, be sure to tell your doctor about all medications you take (including prescription and over-the-counter types). Also describe any vitamins, herbs, or supplements you use. Your doctor or pharmacist can tell you about any interactions these items may cause with Onfi.
Interactions with drugs or supplements
Onfi can interact with several types of drugs, including:
- opioids (for details about this, see “Taking Onfi with other drugs” in the “How is Onfi taken?” section above)
- the antidepressant fluvoxamine
- the yeast infection drug fluconazole (Diflucan)
- the acid reflux drug omeprazole (Prilosec)
This list does not contain all types of drugs that may interact with Onfi. Your doctor or pharmacist can tell you more about these interactions and any others that may occur with use of Onfi.
Risk of addiction and misuse. Taking Onfi can lead to addiction and misuse. With misuse, a drug is taken in a way that’s different from how it was prescribed. With addiction, a drug is used even if it’s causing harmful outcomes.
Risk of dependence and withdrawal. You may develop physical dependence with Onfi. (With dependence, your body gets used to a drug and has trouble functioning without it.) This can lead to life threatening withdrawal symptoms if you suddenly stop taking the drug.
For more information about these warnings, see the “What are Onfi’s side effects?” section above. Also, for information about risks when used with opioids, see “Taking Onfi with other drugs” in the “How is Onfi taken?” section above.
Onfi may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Onfi. Factors to consider include those in the list below.
- Mood changes, thoughts of suicide, or suicidal behaviors. Taking Onfi can increase your risk for thoughts of suicide, suicidal behaviors, and mood problems, such as depression. If you already have any of these conditions, or if you’ve had them in the past, your risk is even higher. Before taking Onfi, be sure to talk with your doctor about your mental health.
- Problems with your liver. If you have liver problems, your doctor may prescribe a dosage of Onfi for you that’s lower than usual. Be sure to tell your doctor about any liver problems you have before starting Onfi.
- Severe problems with your kidneys. Before starting Onfi, tell your doctor if you have severe kidney problems such as end stage kidney disease. Your doctor may prescribe a drug other than Onfi for you.
- Allergic reaction. If you’ve had an allergic reaction to Onfi or any of its ingredients, you shouldn’t take Onfi. Ask your doctor what other medications are better options for you.
Use with alcohol
It’s not safe to drink alcohol while you’re taking Onfi.
Both Onfi and alcohol can cause central nervous system (CNS) depression. (With CNS depression, the activity of your brain is slowed.) And CNS depression can lead to side effects such as drowsiness and lack of coordination.
Your risk for these side effects is even higher if you drink alcohol while you’re taking Onfi.
Drinking alcohol while you’re taking Onfi can also increase the amount of Onfi in your body. This can increase your risk for side effects from the drug. (For more information, see “What are Onfi’s side effects?” above.)
If you drink alcohol, talk with your doctor before starting Onfi.
Pregnancy and breastfeeding
It may not be safe to use Onfi while you’re pregnant or breastfeeding. If you have questions about using Onfi during pregnancy or while breastfeeding, talk with your doctor.
Yes, it’s possible that Onfi could be misused. Misusing Onfi means it’s taken in a way that’s different from how it was prescribed.
In fact, Onfi has a boxed warning for its risks of both misuse and addiction. (With addiction, a drug is used even if it’s causing harmful outcomes.)
To learn more about Onfi’s boxed warnings, see the “What are Onfi’s side effects?” section above.
Don’t take more Onfi than your doctor prescribes. Using more than this can lead to serious side effects.
Symptoms of overdose
Symptoms caused by an Onfi overdose can include:
- feeling sluggish or sleepy
- lack of coordination or muscle control
- low blood pressure
- respiratory depression (weak or slow breathing)
- in rare cases, coma or death
What to do in case you take too much Onfi
Call your doctor if you think you’ve taken too much Onfi. You can also call 800-222-1222 to reach the American Association of Poison Control Centers, or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.
If you have questions about using Onfi for epilepsy, talk with your doctor or pharmacist.
You may want to ask about other treatments for epilepsy. Below are a few resources you might find helpful:
Also, here’s a list of a few questions you may want to ask your doctor about Onfi:
- How is Onfi different from other drugs that treat epilepsy?
- What other epilepsy treatments should I take with Onfi?
- Will my seizures come back after I stop using Onfi?
Can I take Onfi to stop a seizure that’s currently happening?Anonymous patient
No, that’s not recommended.
Onfi starts working right away to decrease the number of seizures you have. It may take a couple of weeks after your first dose of Onfi to start reducing your number of seizures. But Onfi isn’t meant to stop a seizure that’s already happening.
If you’d like to know about medications you can take for a seizure that’s currently happening, ask your doctor or pharmacist.Melissa Badowski, PharmD, MPH, FCCPAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
Disclaimer: Healthline 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 other 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.