Xywav Dosages: Your GoodRx Guide

Xywav is a combination of calcium, magnesium, potassium, and sodium oxybates. It’s a prescription medication that’s FDA approved to treat narcolepsy in people 7 years of age and older. It’s also approved to treat a rare sleep disorder called idiopathic hypersomnia in adults.

In this guide, we’ll review common Xywav dosages. But keep in mind that your or your child’s prescriber may recommend a different dosage than what’s discussed here. Make sure to follow your prescriber’s instructions and ask any questions about your Xywav dosage before you start taking it.

What’s the typical Xywav dosage for adults?

Xywav is available as an oral solution (liquid) that comes as 0.5 g/mL. Your dosage will depend on why you’re taking it. 

Narcolepsy

For adults, the initial Xywav dosage is 2.25 g by mouth at bedtime, followed by another 2.25 g taken 2.5 to 4 hours later. This equals 4.5 grams in total.

If your symptoms don’t improve, your prescriber may increase your dose on a weekly basis. Usually, your dose won’t increase by more than 1.5 g per day on any given week. 

In most cases, your dose will end up being between 6 g to 9 g per night (split into two doses). For example, a nightly dose of 6 g might mean you take 3 g at bedtime and then another 3 g in 2.5 to 4 hours. The maximum dose is 9 g per night.

Idiopathic hypersomnia 

For idiopathic hypersomnia, Xywav can be taken either once at bedtime or twice per night (like the dosage plan for narcolepsy). The recommended starting dosages are:

• Up to 3 g by mouth once at bedtime. Depending on your response, your prescriber may raise your dose on a weekly basis. The maximum dose is 6 g.

• Up to 2.25 g by mouth twice a night. The first dose should be taken at bedtime, and the second dose should be taken 2.5 to 4 hours after the first dose. Your prescriber may raise your dose every week to a maximum dose of 9 g per night (split into two doses).

While you and your prescriber are working together to find the right Xywav dosage for you, follow their instructions closely. Make sure you understand how much to increase your dose by (it shouldn’t be more than 1.5 g per night in any given week). Your prescriber may recommend you switch from a twice nightly regimen to a once nightly regimen, or vice versa, depending on how you respond to Xywav.

What’s the typical Xywav dosage for children? [[nav title="Dosage for children"]

For children 7 years and older with narcolepsy, their Xywav dosage depends on how much they weigh.

For a child weighing 20 kg (44 lbs) to 29 kg (64 lbs), the usual starting dose is 1 g or less, given twice per night (for a total of 2 g or less each night). Your child will take one dose at bedtime, and then a second dose 2.5 to 4 hours later. The maximum nightly dose is 6 g (in divided doses).

For a child weighing 30 kg (66 lbs) to less than 45 kg (99 lbs), the usual starting dosage is 1.5 g or less, given twice per night (for a total of 3 g or less each night). One dose is given at bedtime, and then another dose 2.5 to 4 hours later. The maximum nightly dose is 7.5 g (in divided doses).

Children weighing 45 kg (99 lbs) or more receive an adult dose. The maximum dose per night is also the same (9 g).

Your child’s prescriber may increase their dose on a weekly basis, depending on how they respond to Xywav. The maximum dosage depends on their weight.

The optimal dose hasn’t been studied for children weighing less than 20 kg (44 lbs).

Are there any dosage adjustments for health conditions?

Your prescriber may recommend a lower Xywav dosage than what’s discussed above. This may be due to other health conditions, medications you take, or your age.

Liver problems

You may need a lower Xywav dosage if you have liver problems. If your liver isn’t functioning as well as it could, Xywav can build up in your body and cause unwanted side effects such as nausea, headache, and dizziness. Because of this, the typical starting dose of Xywav should be cut in half, and divided into two doses.

Depakote interaction

Depakote (Divalproex sodium) is a medication that’s used to treat certain types of seizures and bipolar disorder. It can also be used to prevent migraines. When taken with Xywav, Depakote can increase levels of oxybate (the active ingredient in Xywav). This can raise your risk of several brain-related side effects like tiredness, dizziness, and confusion.

To minimize your risk, your prescriber will likely start you on a Xywav dosage that’s at least 20% lower than the typical dosage. They’ll also monitor you more closely for side effects. 

Age

People 65 years or older are more likely to experience Xywav side effects, especially headaches. To reduce the risk of side effects, your prescriber may recommend a lower Xywav dosage and raise your dose more slowly.

How do you take Xywav?

Taking Xywav correctly is important for staying safe and getting the most out of your medication. A few key instructions for preparing and taking Xywav are:

• Mix your Xywav solution with water. Before bedtime, mix each Xywav dose you’ll take that night with one-fourth a cup (60 mL) of water. Use the special syringe and two child-resistant containers that came with your prescription to prepare your dose(s). Only prepare the doses you’ll use that night. Any prepared doses must be used within 24 hours.

• Ask your prescriber when to take your first Xywav dose of the night. Some people who sleep for more than 8 hours a night may need to take Xywav after an initial period of sleep, instead of at their bedtime. Ask your prescriber what dosing regimen is best for you.

• Time your Xywav dose correctly. Take Xywav while you’re in bed and at least 2 hours after eating. Most people will fall asleep within 5 to 15 minutes of taking Xywav. If your prescriber recommends a second dose of Xywav, set an alarm for the time that they suggest. The second dose is usually taken 2.5 to 4 hours after the first dose. You should stay in bed when you take the second dose, so make sure to store your doses near your bed where they’ll be easy to reach.

Can I switch from Xyrem to Xywav?

Xyrem (sodium oxybate) is a medication that’s similar to Xywav. But Xywav contains much less sodium (salt) than Xyrem even though they contain the same amount of oxybate (the active ingredient). 

Xywav may be preferred for people with medical conditions where getting too much salt may be dangerous, such as high blood pressure, heart failure, and kidney problems.

Your prescriber may recommend switching from Xyrem to Xywav if the amount of salt in Xyrem is problematic for you. Typically, your new dose of Xywav will be the same as your original Xyrem dosage. Your prescriber may adjust your Xywav dose if needed.

What happens if you miss a dose of Xywav?

If you’re taking Xywav twice a night and you miss your second dose, skip it. The following night, resume your usual dosing schedule of two doses. 

Never take two doses at once to make up for a missed dose. To avoid missing your second Xywav dose of the night, set an alarm.

Before starting Xywav, chat with your prescriber about what to do if you miss your first dose. They may recommend that you still take a single dose if you have a certain number of hours of sleep remaining in the night. 

What should you do if you take too much Xywav?

Taking too much Xywav can increase your chances of experiencing side effects, such as blurry vision, coordination problems, and confusion. It can also cause severe side effects like extremely low heart rate, seizures, and coma.

If you’ve taken too much Xywav, call Poison Control at 1-800-222-1222. Seek immediate medical attention if your symptoms seem severe.

Good to know: Xywav is a controlled substance. So regularly taking too much Xywav can increase your risk of dependence and misuse. Only take Xywav exactly as prescribed to minimize your risk of misuse.

Why trust our experts?

Written by:

Makaela Premont, PharmD

Makaela Premont, PharmD, is a pharmacist and the founder of uniquelymickie.com, a website dedicated to helping pharmacy students and pharmacists create a life that they enjoy. She received her Doctorate of Pharmacy from the University of South Carolina and is a licensed pharmacist in North Carolina.

Edited by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Daphne Berryhill, RPh

Daphne Berryhill, RPh, has two decades of experience as a clinical pharmacist. She spent most of her career in the Chicago area practicing in-home infusion.

Our editorial standards

Meet our experts