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Does Xyrem cause weight gain or loss?

Medically reviewed by Philip Thornton, DipPharm. Last updated on Aug 28, 2023.

Official answer


Xyrem (sodium oxybate) can cause weight loss, which is thought to be due to the medication enabling people to increase their physical activity and decrease their calorie intake.

Xyrem is a central nervous system (CNS) depressant used to treat cataplexy or excessive daytime sleepiness (EDS) in patients 7 years of age and older with narcolepsy. Narcolepsy is commonly associated with weight gain after disease onset, which can lead to obesity.

Xyrem and weight loss - a beneficial adverse reaction

Weight decrease was found to be a common adverse reaction in patients treated with Xyrem and it is recommended that people who notice a change in their weight while taking Xyrem call their doctor right away. This is especially true if they are experiencing any symptoms of mental health problems such as feeling depressed, anxious, or have unusual or disturbing thoughts, for example.

Although weight decrease is reported as being an adverse reaction or side effect of Xyrem, it is also seen as a beneficial effect of the drug because narcolepsy is commonly associated with being overweight or obese.

Xyrem can help to favorably reduce weight in children with pediatric type 1 narcolepsy during the first year of treatment. Xyrem has also been found to reduce BMI (body mass index) in adults, particularly in those with a higher BMI at the beginning of treatment.

  • Food and Drug Administration (FDA). Xyrem. September 2020. [Accessed September 7, 2021]. Available from:
  • Dominguez A, Soca Gallego L, Parmar M. Sodium Oxybate. [Updated 2021 Jun 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  • Plazzi G, Ruoff C, Lecendreux M, et al. Treatment of paediatric narcolepsy with sodium oxybate: a double-blind, placebo-controlled, randomised-withdrawal multicentre study and open-label investigation. Lancet Child Adolesc Health. 2018;2(7):483-494. doi:10.1016/S2352-4642(18)30133-0.
  • Schinkelshoek MS, Smolders IM, Donjacour CE, et al. Decreased body mass index during treatment with sodium oxybate in narcolepsy type 1. J Sleep Res. 2019;28(3):e12684. doi:10.1111/jsr.12684.
  • Ponziani V, Pizza F, Zenesini C, Vignatelli L, Pession A, Plazzi G. BMI changes in pediatric type 1 narcolepsy under sodium oxybate treatment. Sleep. 2021;44(7):zsaa295. doi:10.1093/sleep/zsaa295.

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