Xywav (calcium/magnesium/potassium/sodium oxybates) is a prescription drug that’s used to treat certain sleep disorders. The drug comes as a liquid solution that you swallow. It’s taken once or twice at night.

Xywav is used to treat excessive daytime sleepiness and cataplexy in adults and some children with narcolepsy. It’s also prescribed for adults with idiopathic hypersomnia (excessive daytime sleepiness of unknown cause).

The active ingredients in Xywav are calcium, magnesium, potassium, and sodium oxybates. (An active ingredient is what makes a drug work.) Xywav is a central nervous system (CNS) depressant.

This article describes the dosages of Xywav, as well as its strength and how to take it. To learn more about Xywav, see this in-depth article.

The table below highlights the basics of Xywav’s dosage for adults. All doses are listed in grams (g). See “What’s the dosage of Xywav in children?” below for information about recommended dosages for children.

ConditionStarting dosageMaintenance dosageMaximum dosage
narcolepsy4.5 g, divided into 2 doses6–9 g, divided into 2 doses9 g, divided into 2 doses
idiopathic hypersomnia• 3 g or less as a single dose, or
• 4.5 g or less, divided into 2 doses
weekly increase of 1.5 g per night*• 6 g given as a single dose, or
• 9 g, divided into 2 doses

* The maintenance dosage is determined by gradually increasing the dosage each week until symptoms are improved.

Keep reading for more details about Xywav’s dosage.

What is Xywav’s form?

Xywav is available as a liquid solution that you swallow.

What strength does Xywav come in?

Xywav comes in a strength of 0.5 grams per milliliter (g/mL).

What are the usual dosages of Xywav?

Your doctor will likely start you on a low dosage and adjust it over time to reach the right amount for you. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

The information below describes dosages that are commonly used or recommended. But be sure to take the dosage your doctor prescribes for you. They’ll determine the best dosage to fit your needs.

Dosage for narcolepsy

The usual starting dosage of Xywav for adults with narcolepsy is 4.5 g at night. This dosage is divided into two doses. You’ll take the first dose at bedtime and the second dose 2.5–4 hours later. Your doctor may divide your dosage into two equal doses. Or they may divide the dosage unequally and recommend that you take a different amount for the first and second doses.

Each week, your doctor will increase your nightly dosage by 1.5 g until you reach the best dosage for you. At the maintenance dosage, you should experience fewer cataplexy attacks and less sleepiness during the day. The recommended nightly dosage ranges from 6–9 g. The maximum dosage is 9 g.

Dosage for idiopathic hypersomnia

For adults with idiopathic hypersomnia, the typical dosage of Xywav depends on whether you’re taking the drug once or twice per night. And if you’re taking Xywav twice per night, your doctor may split your dosage into two equal doses or two different doses.

The following table summarizes the dosage for idiopathic hypersomnia.

Dose frequencyStarting dosage*Weekly dosage increase*Maximum dosage
once per night3 g per night1.5 g per night6 g per night
twice per night4.5 g per night1.5 g per night9 g per night

* These are the maximum starting dosage and dosage change recommendations. Your doctor may prescribe a lower dosage for you.

Each week, your doctor will increase your nightly dosage by 1.5 g until you reach the best dosage for you. At the maintenance dosage, you should experience less sleepiness during the day.

What’s the dosage of Xywav for children?

Xywav is used to treat symptoms of narcolepsy in children ages 7 years and older. Two doses are taken each night. The values in the table below apply to the dose taken at bedtime and the second dose taken 2.5–4 hours later.

The dosage is based on your child’s body weight in kilograms (kg). One kilogram is approximately 2.2 pounds (lb). The table below shows dosage recommendations provided by the manufacturer, but your child’s doctor will determine the best dosage for them.

Body weightStarting dose†Weekly dose increase†Maximum dose
20–30 kg1 g or less0.5 g3 g
30–45 kg1.5 g or less0.5 g3.75 g
45 kg or more2.25 g or less0.75 g4.5 g

* The starting doses and weekly dose increases shown are the maximum recommended values. Your child’s doctor may prescribe a different dose.

The two doses each night may be the same, or your child’s doctor may recommend different doses for each of the two doses.

The dosage will be slowly increased each week until your child has fewer cataplexy episodes and less sleepiness during the day. For more information about Xywav’s dosage for children, talk with your child’s doctor.

Is Xywav used long term?

Yes, Xywav is usually a long-term treatment. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely take it long term.

Dosage adjustments

If you have liver problems, your doctor will likely prescribe a lower dosage of Xywav when you first begin treatment. The dosage will be divided into two doses.

Your doctor will also prescribe a lower dosage of Xywav if you take the drug divalproex sodium (Depakote).

If either of these apply to you and you have questions about your dosage of Xywav, talk with your doctor or pharmacist.

The dosage of Xywav you’re prescribed may depend on several factors. These include:

  • the type and severity of the condition you’re taking the drug to treat
  • whether you have any side effects from Xywav
  • your age
  • other conditions you have*
  • other medications you take*

* See “dosage adjustments” above.

Xywav is available as a liquid solution. Before bedtime, you’ll prepare each dose by mixing the Xywav liquid solution with 60 mL (¼ cup) of water. Put the prepared dose (or doses) next to your bed.

Stop eating at least 2 hours before you plan to go to bed. Xywav should not be taken within 2 hours of eating.

When you’re in bed, drink your dose of Xywav. Most people will fall asleep within 15 minutes, and some people fall asleep within 5 minutes.

If you’re taking a second dose, have an alarm set for the time. It’s usually 2.5–4 hours after the first dose. When your alarm goes off, drink the second dose. Stay in bed after the second dose.

For information on the expiration, storage, and disposal of Xywav, talk with your doctor or pharmacist. You can also see the “Xywav expiration, storage, and disposal” section of this article.

Accessible drug containers and labels

Some pharmacies provide medication labels that:

  • have large print
  • use braille
  • feature a code you can scan with a smartphone to change the text to audio

Ask your pharmacist if they offer these accessibility features.

Let your pharmacist know if you have trouble opening medication bottles. They may have tips to help, or they may be able to supply easy-open containers.

If you’re prescribed two doses each night, and you sleep through and miss your second dose of Xywav, skip the missed dose. Return to your usual schedule of two doses the following night.

Talk with your doctor about recommendations for what to do if you miss your first dose. Your doctor may recommend that you still take the first dose up to a certain time in the night. Or they may recommend that you only take the second dose (if you’re on a two-dose regimen). But do not take two doses of Xywav at once to make up for a missed dose.

If you need help remembering to take your dose of Xywav on time, try using a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.

Xywav is a controlled substance and is classified as a Schedule III prescription drug. This means it has some risk of misuse. With misuse, a drug is taken in a way other than how a doctor prescribes it. Examples of misuse include using the drug more often or at higher doses than recommended by your doctor. Another way a person can misuse Xywav is by taking it with other central nervous system depressants.

You should take Xywav only as your doctor has prescribed. Misuse increases the risk of overdose, which can lead to trouble breathing, coma, and even death.

Do not take more Xywav than your doctor prescribes, as this can lead to harmful effects.

Symptoms of overdose

Symptoms caused by an overdose of Xywav may include:

What to do in case you take too much Xywav

If you think you’ve taken too much Xywav, you should immediately call 911 (or your local emergency number). If someone is available at home, you should alert them, too.

Taking Xywav may cause dependence. With dependence, your body needs the drug to function as usual.

If your body has become dependent on Xywav and you suddenly stop taking it, you may experience withdrawal symptoms. Examples of withdrawal symptoms that have been reported in studies after abruptly stopping Xywav include:

  • insomnia (trouble sleeping)
  • anxiety
  • visual hallucinations (seeing things that aren’t there)
  • auditory hallucinations (hearing things that aren’t there)

The active ingredients in Xywav contain a chemical group called gamma hydroxybutyrate (GHB). This is naturally found in the body in small amounts but can also be synthetic (manufactured). When synthetic GHB isn’t part of a drug like Xywav, it has no medical purpose. On its own, it’s an illegal drug that’s misused.

The manufacturer of Xywav lists symptoms that have been reported following withdrawal of GHB. This is because it’s possible that Xywav could cause similar withdrawal symptoms, especially if Xywav has been misused (taken in a way other than how a doctor prescribes it). Withdrawal symptoms from GHB include those in the bulleted list above plus:

If you and your doctor decide to stop or lower your dosage of Xywav, it can be done safely by decreasing your dosage slowly over time. This can help reduce your risk of withdrawal symptoms after you stop treatment.

If you have any questions or concerns about the risk of dependence and withdrawal with Xywav, talk with your doctor.

The sections above describe the usual dosages provided by the manufacturer. If your doctor recommends Xywav for you, they’ll prescribe the dosage that’s right for you.

Remember, you should not change your dosage of Xywav without your doctor’s recommendation. Only take Xywav exactly as prescribed. Talk with your doctor if you have questions or concerns about your current dosage.

Here are some examples of questions you may want to ask your doctor:

  • When would you recommend one dose versus two doses at night?
  • If my dosage is increased more slowly, does that decrease my risk of side effects?
  • Is it better to split my total dose of Xywav equally or unequally?

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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 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.