Xyrem (sodium oxybate) is a brand-name drug prescribed for narcolepsy in adults and some children. Xyrem comes as an oral solution that’s typically taken at bedtime. The dosage can vary depending on several factors.

Specifically, Xyrem is approved by the Food and Drug Administration (FDA) to treat cataplexy or excessive daytime sleepiness associated with narcolepsy. It’s approved for this use in adults and children ages 7 years and older.

Xyrem belongs to a drug class called central nervous system (CNS) depressants. (A depressant lowers the activity of the CNS.) Xyrem isn’t available in a generic version.

Keep reading for specific information about the dosage of Xyrem, including its strength and how to take the medication. For a comprehensive look at Xyrem, see this article.

Note: This article describes typical dosages for Xyrem provided by the drug’s manufacturer. When taking Xyrem, always follow the dosage prescribed by your doctor.

Below is information about Xyrem’s form, strength, and typical dosage.

Xyrem form

Xyrem comes as an oral solution. You’ll need to dilute the solution before taking your Xyrem dose. For details, see the “How to take Xyrem” section below.

Xyrem strength

Xyrem comes in one strength of 0.5 grams per milliliter of solution (g/mL).

Typical dosages

Typically, your doctor will start by prescribing you a low dosage. Then they’ll adjust it over time to reach the amount that’s right for you. Your doctor will ultimately prescribe the smallest dosage that provides the desired effect.

The following information describes dosages that are commonly prescribed or recommended in adults. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to fit your needs.

Dosage for narcolepsy

Doctors prescribe Xyrem to treat cataplexy or excessive daytime sleepiness (EDS) associated with narcolepsy.

The starting dosage for narcolepsy is 4.5 g per night, divided into two doses: half (2.25 g) is taken at bedtime, and half is taken 2.5–4 hours later. For details about dividing your Xyrem dosage, see the “How to take Xyrem” section below.

After 1 week, your doctor may increase your dosage to 6 g per night. This is the typically recommended Xyrem dosage for narcolepsy.

If this dosage isn’t effective for your condition, your doctor may increase it further. Usually, they’ll increase your dosage by 1.5 g per night each week. The maximum dosage is 9 g Xyrem per night.

The table below summarizes Xyrem’s dosing schedule for the indicated nightly dosage:

Dosage (taken as 2 half doses)Amount to take at bedtimeAmount to take 2.5–4 hours later
4.5 g (starting dosage)2.25 g2.25 g
6 g3 g3 g
7.5 g3.75 g3.75 g
9 g (maximum dosage)4.5 g4.5 g

For more information about your specific dosage, talk with your doctor.

Children’s dosage

Xyrem is prescribed for cataplexy or EDS associated with narcolepsy in children ages 7 years and older.

Children’s dosages for narcolepsy are based on their body weight in kilograms (kg).* Your child’s doctor will determine the right dosage for your child. Typically, they’ll prescribe a low dosage to start. Then, they’ll adjust it over time to reach the amount that’s right for your child. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

* One kg equals about 2.2 pounds (lb).

Dosage for narcolepsy

As with adults, children take Xyrem at night in divided doses. (For details on preparing Xyrem, see the “How to take Xyrem” section below.) Your child will take their first dose at bedtime and the second dose a few hours later.

The table below shows the body weight-based dosage of Xyrem for narcolepsy in children:

Body weight in kgBody weight in lbStarting dosageMaximum dosage
20 kg* to less than 30 kgabout 44 lb to less than 66 lb• up to 1 g at bedtime
• up to 1 g 2.5–4 hours later
• 3 g at bedtime
• 3 g 2.5–4 hours later
30 kg to less than 45 kgabout 66 lb to less than 99 lb• up to 1.5 g at bedtime
• up to 1.5 g 2.5–4 hours later
• 3.75 g at bedtime
• 3.75 g 2.5–4 hours later
45 kg or moreabout 99 lb or more• up to 2.25 g at bedtime
• up to 2.25 g 2.5–4 hours later
• 4.5 g at bedtime
• 4.5 g 2.5–4 hours later

After 1 week, your child’s doctor may recommend increasing their dosage by 0.5–0.75 g per dose.

Talk with your child’s doctor if you have questions about their dosage.

* If your child weighs less than 20 kg (about 44 lb), their doctor will likely prescribe a smaller dosage.

Long-term treatment

Xyrem is meant to be a long-term treatment. If you and your doctor determine that Xyrem is safe and effective for you, you’ll likely take it long term.

Before you start taking Xyrem, your doctor will discuss your treatment plan with you.

The Xyrem dosage your doctor prescribes will depend on several factors. These include:

  • your age
  • body weight, for children
  • how your body responds to Xyrem
  • side effects you may have with Xyrem
  • the severity of the condition you’re taking Xyrem to treat
  • other medications you take
  • your liver and kidney function

Other medical conditions you have can also affect your Xyrem dosage.

Dosage adjustments

Your doctor may need to lower your Xyrem dosage if you take divalproex sodium (Depakote) with Xyrem. This drug can increase the level of Xyrem in your body. To find out what drugs may interact with Xyrem, see this article.

Your doctor may also need to adjust your dosage if you have liver damage or kidney disease. They may also need to adjust it if you’re age 65 years or older.

Be sure to tell your doctor about all medications you take and any health conditions you may have. Your doctor will prescribe the best dosage to meet your needs.

Xyrem comes as a solution that you swallow. You divide your daily Xyrem dose into two doses. To prepare your doses, you dilute (mix) Xyrem solution in water. The instructions for this are included with your prescription. You can also refer to these step-by-step instructions on the manufacturer’s website.

You take your first dose at bedtime and your second dose 2.5–4 hours after the first dose.

Your doctor will likely recommend taking Xyrem on an empty stomach. So you should plan to take your first dose at least 2 hours after eating. It’s important to take Xyrem while you’re in bed and ready to lie down. You may need to set an alarm to wake you up for your second dose. Be sure to stay in bed after taking each dose.

If you have questions about how to take Xyrem, talk with your doctor or pharmacist.


Some pharmacies offer labels with large print, braille, or a code you scan with a smartphone to convert text to speech. If your local pharmacy doesn’t have these options, your doctor or pharmacist might be able to recommend a pharmacy that does.

If you miss your first evening dose of Xyrem, take it as soon as you remember. If you sleep through your alarm or forget to take the second evening dose, skip it. Do not take two doses at once to make up for a missed dose. You’ll resume your regular schedule the next evening.

If you’re unsure whether to take a missed dose or skip it, talk with your doctor or pharmacist.

To help make sure that you don’t miss a dose, try using a medication reminder. This can include setting an alarm or putting a note where you’ll see it, such as on your bathroom mirror or bedside table. You could also download a reminder app on your phone.

Xyrem has a boxed warning about the risk of misuse. With misuse, a drug is taken or used in a way other than how it’s prescribed. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Misuse of Xyrem can result in harmful effects. These include severe difficulty breathing, overdose, seizures, coma, and even death in rare cases. (For information about overdose, see the “Xyrem and overdose” section below.)

Misuse also increases the risk of addiction. With addiction, a drug is taken even though it’s causing harm. Taking the drug more frequently or at higher doses than prescribed increases the risk of addiction. People who take Xyrem with other drugs or alcohol have an increased risk for this effect. To learn about Xyrem’s recommended dosages, see the “Xyrem dosage” section above.

Before prescribing Xyrem, your doctor will determine whether it’s safe for you to take. They may not prescribe Xyrem if you’ve ever had substance use disorder.

Talk with your doctor if you have questions about Xyrem and misuse.

It’s important that you do not take more Xyrem than your doctor prescribes. For some medications, taking more than the recommended amount may lead to harmful effects or overdose. For detailed information about Xyrem’s side effects, see this article.

Effects of overdose

Overdose effects of Xyrem can include:

If you take more than the recommended amount of Xyrem

Call your doctor right away if you believe you’ve taken too much Xyrem. Another option is to call America’s Poison Centers at 800-222-1222 or use its online tool. If you have severe symptoms, immediately call 911 or your local emergency number, or go to the nearest emergency room.

Treatment with Xyrem can cause dependence. With dependence, your body becomes used to a drug and needs it to function as usual. You may have withdrawal symptoms if you suddenly stop taking Xyrem after taking it regularly for some time. Withdrawal symptoms are side effects that can happen after you stop taking a drug that your body is dependent on.

Symptoms of withdrawal after abruptly stopping Xyrem include:

These symptoms can be very uncomfortable. However, they’re usually not life threatening.

You and your doctor will reevaluate your need for Xyrem throughout your treatment. Always follow your doctor’s instructions on how to stop taking Xyrem safely.

Below are some frequently asked questions about Xyrem.

Can you take Xyrem for insomnia? If so, what’s the dosage?

No, Xyrem is not used for insomnia. It’s prescribed to treat cataplexy or excessive daytime sleepiness caused by narcolepsy.

Because Xyrem isn’t used for insomnia, the drug’s manufacturer doesn’t provide recommended dosages for this condition.

If you have questions about managing insomnia, talk with your doctor. They can recommend treatment options that may work for you.

How long does it take for Xyrem to start working?

Xyrem starts to work after your first dose.* Typically, you’ll fall asleep about 5–15 minutes after taking it. For this reason, it’s recommended that you take the medication once you’re already in bed. In some cases, it may take up to 2 hours after taking your Xyrem dose to fall asleep. For details about taking Xyrem, see the “How to take Xyrem” section above.

Talk with your doctor if you have questions about what to expect with Xyrem treatment.

* You take Xyrem at bedtime in two doses a few hours apart. For details, see the “Xyrem dosage” section above.

The dosages in this article are typical dosages provided by the drug’s manufacturer. If your doctor recommends Xyrem for you, they’ll prescribe the dosage that’s right for you. Always follow the dosage that your doctor prescribes.

As with any drug, never change your dosage of Xyrem without your doctor’s recommendation. If you have questions about the dosage of Xyrem that’s best for you, talk with your doctor.

Besides learning about dosage, you may want other information about Xyrem. These additional articles might be helpful:

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.