XYREM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYREM (XYREM).
Gamma-hydroxybutyrate (GHB) agonist at GABA-B and GHB receptors, modulating dopamine and serotonin activity.
| Metabolism | Primarily via the enzyme GHB dehydrogenase (unidentified) and to a lesser extent via beta-oxidation (Krebs cycle). Minor metabolism by CYP450 isoenzymes (not major). |
| Excretion | Primarily renal (≥95% as metabolites, mainly as CO2 and succinate via Krebs cycle); negligible biliary/fecal excretion. |
| Half-life | 0.5–1 hour; clinical context: requires twice-nightly dosing for sustained effects in narcolepsy. |
| Protein binding | ~1%; negligible binding to plasma proteins. |
| Volume of Distribution | 0.8–1.0 L/kg; consistent with total body water distribution. |
| Bioavailability | Oral: ~88% (fasted); reduced by high-fat meal. |
| Onset of Action | Oral: 15–45 minutes (sleep onset); may be delayed with food. |
| Duration of Action | 2–4 hours per dose; clinical note: divided dose (first at bedtime, second 2.5–4 hours later) to maintain overnight sleep. |
| Molecular Weight | 126.09 |
9 g orally per night divided into two doses: first dose of 4.5 g at bedtime, second dose of 4.5 g given 2.5 to 4 hours later. Titrate based on efficacy and tolerability; range 6 to 9 g per night.
| Dosage form | SOLUTION |
| Renal impairment | For GFR 30-59 mL/min: reduce total nightly dose by 50%. For GFR <30 mL/min or on dialysis: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: reduce initial dose by 50% (e.g., 4.5 g total nightly dose) and titrate cautiously. |
| Pediatric use | For narcolepsy with cataplexy in children ≥7 years: weight-based dosing. Body weight <20 kg: no data. 20-30 kg: 4 g total nightly dose divided; 30-45 kg: 6 g total; ≥45 kg: 9 g total; titrate in 1.5 g increments per night weekly. |
| Geriatric use | Start at lower end of dosing range (e.g., 6 g total nightly dose) due to potential age-related renal impairment; monitor for confusion, falls, and nocturnal wandering. |
| 1st trimester | Limited human data; animal studies show adverse effects at high doses. Use only if benefit outweighs risk. |
| 2nd trimester | Limited human data; potential for maternal sedation and withdrawal effects. Use only if benefit outweighs risk. |
| 3rd trimester | Risk of neonatal withdrawal symptoms. Avoid use near term if possible. |
Clinical note
Comprehensive clinical and safety monograph for XYREM (XYREM).
| Placental transfer | Crosses placenta; sodium oxybate detected in fetal plasma in animal studies. |
| Breastfeeding | Excreted in breast milk; potential for sedation in infant. Manufacturer recommends discontinuation of breastfeeding or drug. |
| Lactation Rating |
■ FDA Black Box Warning
Central nervous system (CNS) depression: Risk of respiratory depression, coma, and death. Concomitant use with alcohol or other CNS depressants is contraindicated. Abuse potential: Schedule III controlled substance; misuse can lead to dependence and withdrawal.
| Serious Effects |
Succinic semialdehyde dehydrogenase deficiency
| Precautions | CNS depression (including respiratory depression), abuse and dependence, sleep-related behaviors (e.g., sleepwalking), depression/suicidality, hypertension, and nocturnal hypoventilation. Monitor for respiratory impairment in patients with compromised respiratory function. |
| Food/Dietary | Take XYREM on an empty stomach. Food delays absorption and reduces peak concentration. Avoid high-fat meals within 2 hours of dosing. No specific food interactions, but timing relative to meals is critical. |
Loading safety data…
| L4 |
| Teratogenic Risk | Pregnancy Category B. No evidence of fetal harm in animal studies; no adequate human studies in first trimester. Avoid use during pregnancy unless benefit outweighs risk. |
| Fetal Monitoring | Anticipated weight gain, blood pressure, and signs of CNS depression in neonate if used near term. No specific fetal monitoring required. |
| Fertility Effects | No human data; animal studies show no impairment of fertility at clinically relevant doses. |
| Clinical Pearls | XYREM (sodium oxybate) is a CNS depressant used for cataplexy and excessive daytime sleepiness in narcolepsy. It is a Schedule III controlled substance. Must be taken in two equal doses: first at bedtime, second 2.5-4 hours later. Administer while patient is in bed due to rapid onset of sleep. Avoid use with alcohol or other CNS depressants. Monitor for respiratory depression, especially in patients with sleep apnea or obesity. Abrupt discontinuation can cause withdrawal symptoms. |
| Patient Advice | Take XYREM exactly as prescribed: first dose at bedtime, second dose 2.5 to 4 hours later. · Prepare both doses before bed; store mixed solution at room temperature and consume within 24 hours. · Do not drive or operate machinery for at least 6 hours after taking XYREM. · Avoid alcohol and other sedatives while taking XYREM. · Do not stop taking XYREM suddenly; withdrawal may occur. · If you miss a dose, skip it and wait for the next scheduled dose; do not double up. · Report symptoms of sleepwalking, confusion, or respiratory difficulty to your doctor. |