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.