Sodium Oxybate

Note: Sodium oxybate is the sodium salt of GHB (γ-hydroxybutyrate). As a regulated pharmaceutical (Schedule III with restricted REMS distribution), it has its own problems and dosing distinct from non-medical GHB use. See GHB for the broader pharmacology and recreational context.

GABAB Agonist; Endogenous GHB receptor agonist

Sodium Oxybate

Xyrem; Xywav (lower-sodium formulation with Ca/Mg/K salts)

Sodium oxybate is the sodium salt of GHB, formulated as a high-purity oral solution dosed in grams. It is among the most effective treatments for cataplexy and excessive daytime sleepiness in narcolepsy. Because its half-life is so short, it must be taken in two doses separated by 2.5–4 h during the night. Pharmacy-distributed only through a REMS program; the same compound outside that channel is Schedule I.

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Problems

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Titration strategies

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Effects

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Pharmacokinetics

Absorption

~25% oral bioavailability; markedly reduced by food.

Distribution

Negligible plasma protein binding.

Metabolism

Endogenous pathway via GHB dehydrogenase to succinic acid, then TCA cycle. No CYP involvement.

Elimination

Almost entirely metabolic; ~5% renal.

Interactions

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Monitoring

Sleep quality; daytime sedation; respiratory status (caution in sleep apnea or with concurrent CNS depressants).

Patient counseling

Take only in bed and only when ready to sleep — onset is rapid. Severe sedative interactions with alcohol or other CNS depressants. Significant sodium load (~1100 mg per 4.5 g/night) — consider Xywav for sodium-restricted patients.

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See also

GHB, GBL, Modafinil, Pitolisant

References

Summary

Classes

GABAB Agonist; Endogenous GHB receptor agonist

Common uses

Cataplexy in narcolepsy▲0▼, Excessive daytime sleepiness in narcolepsy▲0▼, Idiopathic hypersomnia▲0▼

Pharmacy

Starting dose

2.25 g at bedtime + 2.25 g 2.5–4 h later; titrate weekly to 6–9 g/night total

Preparations

0.5 g/mL oral solution

US FDA Max

9 g/night

Pharmacology

Routes

Oral (must be taken in bed; effects within minutes)

Onset

15–30 min (fasting)

Duration

~3 h per dose (twice-nightly schedule required)

Half-life

30–60 min

Bioavailability

~25% (high first-pass)

Pregnancy

Category C

Legal status

Schedule III; REMS-restricted (Schedule I if outside the pharmaceutical channel — same molecule as illicit GHB)

Purported mechanism

Agonist at the metabotropic GABAB receptor and the endogenous γ-hydroxybutyrate (GHB) receptor. Produces deep sleep with increased slow-wave architecture, suppression of REM intrusion, and cataplexy reduction.