XYWAV

Clinical safety rating: caution

Comprehensive clinical and safety monograph for XYWAV (XYWAV).

How it works

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.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for XYWAV (XYWAV).

Breastfeeding

Oxybate is excreted into human breast milk. The milk-to-plasma (M/P) ratio is approximately 0.5. Based on this ratio and typical maternal doses, the estimated infant dose via breast milk is about 0.2-0.4 mg/kg/day, which is a small fraction of the maternal weight-adjusted dose. However, due to the potential for serious adverse reactions in the breastfed infant, including sedation, respiratory depression, and growth impairment, breastfeeding is not recommended during XYWAV therapy. Women should be advised to either discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother.

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.

Warnings & precautions

■ 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.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Concurrent use with alcohol or other CNS depressants","Succinic semialdehyde dehydrogenase deficiency","Hypersensitivity to oxybate salts or any component of the formulation"]

Clinical Precautions

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"]

Clinical Tips & Counseling

Drug interactions

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XYWAV

Clinical safety rating: caution

Comprehensive clinical and safety monograph for XYWAV (XYWAV).

How it works

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for XYWAV (XYWAV).

Breastfeeding

Teratogenic Risk

Warnings & precautions

■ FDA Black Box Warning

Side Effect Profile

Serious Effects

Absolute Contraindications

["Concurrent use with alcohol or other CNS depressants","Succinic semialdehyde dehydrogenase deficiency","Hypersensitivity to oxybate salts or any component of the formulation"]