XYWAV
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYWAV (XYWAV).
XYWAV (calcium, magnesium, potassium, and sodium oxybates) is a mixture of oxybate salts. The exact mechanism of action is unknown, but it is thought to involve modulation of GABA-B receptors and possibly GHB receptors, leading to increased slow-wave sleep and reduced cataplexy.
| Metabolism | Metabolized via the citric acid cycle (Krebs cycle) to carbon dioxide and water, with no involvement of cytochrome P450 enzymes. Also undergoes some oxidation and conjugation. |
| Excretion | Primarily renal; >95% of the dose is eliminated as metabolites (3-hydroxypropionic acid, 4,5-dihydroxyhexanoic acid) and <5% as unchanged drug via urine. Fecal excretion accounts for <1%. |
| Half-life | Terminal half-life is approximately 1 hour (range 0.5–1.5 hours) for oxybate (GHB) component; the mixed salts formulation does not alter elimination. Short half-life necessitates twice-nightly dosing for sustained sleep. |
| Protein binding | <1% bound to plasma proteins (primarily albumin); negligible binding. |
| Volume of Distribution | 0.4–0.6 L/kg; indicates distribution primarily into total body water, with moderate tissue penetration. |
| Bioavailability | Oral: High (~88% relative to IV); first-pass metabolism minimal. Absorption is rapid with food reducing Cmax by ~50% and delaying Tmax. |
| Onset of Action | Oral: Onset of sedation/hypnotic effect occurs within 15–45 minutes; maximal plasma concentration at 0.5–2 hours. |
| Duration of Action | Approximately 2.5–4 hours per dose; sleep induction lasts for the first half of the night. Second dose is typically taken 2.5–4 hours after the first to maintain sleep. |
| Molecular Weight | 174.15 |
Oral, starting dose 2.25 g twice nightly, titrated weekly by 0.75 g per dose up to a maximum of 4.5 g twice nightly. Administer first dose at bedtime, second dose 2.5–4 hours later.
| Dosage form | SOLUTION |
| Renal impairment | Contraindicated in severe renal impairment (eGFR <30 mL/min/1.73 m²). For moderate impairment (eGFR 30–59 mL/min/1.73 m²), reduce starting dose to 1.5 g twice nightly and maximum to 3 g twice nightly. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For moderate impairment (Child-Pugh class B), reduce starting dose to 1.5 g twice nightly and maximum to 3 g twice nightly. No adjustment for mild (Child-Pugh class A). |
| Pediatric use | Not established for patients <18 years; safety and efficacy not studied. |
| Geriatric use | No specific dose adjustment recommended; use caution due to increased sensitivity to central nervous system effects and higher prevalence of renal impairment. Monitor closely. |
| 1st trimester | There are no adequate and well-controlled studies in pregnant women. Animal studies have shown developmental toxicity, including increased fetal mortality and reduced fetal body weight, at clinically relevant doses. Risk cannot be ruled out. |
| 2nd trimester | Same as T1; limited data. Potential risks based on animal studies and mechanism of action (CNS depression). |
| 3rd trimester | Use not recommended. May cause neonatal withdrawal syndrome or CNS depression after prolonged exposure. Consider alternative therapy. |
Clinical note
Comprehensive clinical and safety monograph for XYWAV (XYWAV).
| Placental transfer | Gamma-hydroxybutyrate (GHB), the active metabolite, crosses the placenta in animals. In humans, placental transfer is expected based on molecular weight and lipophilicity. No specific human studies on placental transfer have been conducted. |
| Breastfeeding | XYWAV is excreted into human breast milk. Based on a study of 6 women, the relative infant dose was approximately 1-2% of the maternal weight-adjusted dose. However, due to potential CNS depression in the infant, caution is advised. Monitor infant for excessive sedation, hypotonia, or respiratory depression. The American Academy of Pediatrics considers use compatible with breastfeeding if monitored. |
■ FDA Black Box Warning
XYWAV is a CNS depressant. Co-administration with alcohol or other CNS depressants may increase the risk of respiratory depression, hypotension, profound sedation, syncope, and death. Patients should be screened for substance abuse and monitored closely. Because of the rapid onset of CNS depression, XYWAV should only be taken at bedtime and while in bed.
| Serious Effects |
Concomitant use with alcohol or other CNS depressantsSuccinic semialdehyde dehydrogenase deficiencySevere liver impairment (Child-Pugh class C)History of hypersensitivity to XYWAV or any of its components
| Precautions | Central nervous system depression, Respiratory depression and sleep-disordered breathing, Abuse potential (Schedule III controlled substance), Depression and suicidality, Parasomnias (sleepwalking, confusional states), Hypertension, Use in patients with compromised respiratory function, Use in patients with hepatic impairment, Use in patients with alcohol or substance use disorder |
| Food/Dietary | Food significantly reduces the absorption of XYWAV. Patients should not consume any food for at least 2 hours prior to the first dose. The second dose should be taken on an empty stomach as well. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) - Limited data suggest risk, but may be compatible with careful monitoring. |
| Teratogenic Risk | XYWAV (calcium, magnesium, potassium, and sodium oxybates) is a combination of oxybate salts. Oxybate is the sodium salt of gamma-hydroxybutyrate (GHB). GHB is a CNS depressant. Data from animal studies show adverse effects on fetal development at clinically relevant doses. In humans, there are no adequate and well-controlled studies in pregnant women. Based on animal data and its mechanism of action, XYWAV may cause fetal harm when administered to a pregnant woman. The risk is highest during the first trimester for major malformations and throughout pregnancy for CNS depression and withdrawal in the neonate. Use during pregnancy should be avoided unless clearly needed; if used, the lowest effective dose and shortest duration are recommended. |
| Fetal Monitoring | For pregnant women exposed to XYWAV, fetal monitoring should include ultrasound assessment for growth and anatomy, especially if exposure occurred during the first trimester. After birth, neonates should be monitored for signs of CNS depression, respiratory depression, hypotonia, and withdrawal symptoms (e.g., tremors, irritability, feeding difficulties). Monitoring of maternal blood pressure, heart rate, and respiratory status is recommended due to XYWAV's CNS depressant effects. If used for postpartum depression or cataplexy, consider neonatal abstinence syndrome monitoring. |
| Fertility Effects | XYWAV may impair fertility in females based on animal studies that showed reduced fertility and increased preimplantation loss at clinically relevant doses. In humans, no formal fertility studies have been conducted. XYWAV affects the hypothalamic-pituitary-gonadal axis by altering neurotransmitter systems, potentially leading to menstrual irregularities, anovulation, or decreased libido. Reversal of these effects may occur upon drug discontinuation. Males: animal studies showed reduced sperm motility and counts; human data are lacking. Advise patients of potential transient fertility impairment. |
| Clinical Pearls | XYWAV (calcium, magnesium, potassium, and sodium oxybates) is a once-nightly formulation for narcolepsy. Doses should be taken at bedtime and again 2.5-4 hours later; food significantly delays absorption and reduces peak concentrations. Avoid alcohol and CNS depressants. Use with extreme caution in patients with respiratory depression, sleep apnea, or liver impairment. Monitor for suicidality or depression. |
| Patient Advice | Take XYWAV exactly as prescribed: one dose at bedtime and a second dose 2.5 to 4 hours later. · Prepare both doses before bedtime; use the provided measuring device for accurate dosing. · Do not eat for at least 2 hours before taking XYWAV; food reduces drug absorption. · Avoid alcohol, sedatives, sleep aids, and other CNS depressants while on XYWAV. · Do not drive or engage in hazardous activities for at least 6 hours after the last dose or until you know how the drug affects you. |