Sodium Oxybate Drug Information

Sodium oxybate oral solution is indicated for the treatment of cataplexy or excessive daytime sleepiness (EDS) in patients with narcolepsy. Pediatric use information is approved for Jazz Pharmaceuticals Inc.’s XYREM (sodium oxybate) Oral Solution. However, due to Jazz Pharmaceuticals Inc.’s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Sodium oxybate oral solution is a central nervous system depressant indicated for the treatment of cataplexy or excessive daytime sleepiness (EDS) in patients with narcolepsy .

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Adult Patients Sodium oxybate was studied in three placebo-controlled clinical trials (Trials N1, N3, and N4, described in Sections 14.1 and 14.2) in 611 patients with narcolepsy (398 subjects treated with sodium oxybate, and 213 with placebo). A total of 781 patients with narcolepsy were treated with sodium oxybate in controlled and uncontrolled clinical trials. Section 6.1 and Table 4 present adverse reactions from three pooled, controlled trials (N1, N3, N4) in patients with narcolepsy.

Adverse Reactions Leading to Treatment Discontinuation: Of the 398 patients with narcolepsy treated with sodium oxybate, 10.3% of patients discontinued because of adverse reactions compared with 2.8% of patients receiving placebo. The most common adverse reaction leading to discontinuation was nausea (2.8%). The majority of adverse reactions leading to discontinuation began during the first few weeks of treatment. Commonly Observed Adverse Reactions in Controlled Clinical Trials: The most common adverse reactions (incidence ≥5% and twice the rate seen with placebo) in patients treated with sodium oxybate were nausea, dizziness, vomiting, somnolence, enuresis, and tremor.

Adverse Reactions Occurring at an Incidence of 2% or Greater: Table 4 lists adverse reactions that occurred at a frequency of 2% or more in any treatment group for three controlled trials and were more frequent in any sodium oxybate oral solution treatment group than with placebo. Adverse reactions are summarized by dose at onset. Nearly all patients in these studies initiated treatment at 4.5 g per night.

In patients who remained on treatment, adverse reactions tended to occur early and to diminish over time. Table 4: Adverse Reactions Occurring in ≥2% of Adult Patients and More Frequently with Sodium Oxybate Oral Solution than Placebo in Three Controlled Trials (N1, N3, N4) by Body System and Dose at Onset Adverse Reaction Placebo (n=213) % Sodium Oxybate Oral Solution 4.5g (n=185) % Sodium Oxybate Oral Solution 6g (n=258) % Sodium Oxybate Oral Solution 9g (n=178) % ANY ADVERSE REACTION 62 45 55 70 GASTROINTESTINAL DISORDERS Nausea 3 8 13 20 Vomiting 1 2 4 11 Diarrhea 2 4 3 4 Abdominal pain upper 2 3 1 2 Dry mouth 2 1 2 1 GENERAL DISORDERS AND ADMINISTRATIVE SITE CONDITIONS Pain 1 1 <1 3 Feeling drunk 1 0 <1 3 Edema peripheral 1 3 0 0 MUSCULOSKELETAL AND CONNECTIVE TISSUE DISORDERS Cataplexy 1 1 1 2 Muscle spasms 2 2 <1 2 Pain in extremity 1 3 1 1 NERVOUS SYSTEM DISORDERS Dizziness 4 9 11 15 Somnolence 4 1 3 8 Tremor 0 0 2 5 Disturbance in attention 0 1 0 4 Paresthesia 1 2 1 3 Sleep paralysis 1 0 1 3 PSYCHIATRIC DISORDERS Disorientation 1 1 2 3 Irritability 1 0 <1 3 Sleepwalking 0 0 0 3 Anxiety 1 1 1 2 RENAL AND URINARY DISORDERS Enuresis 1 3 3 7 SKIN AND SUBCUTANEOUS TISSUE DISORDERS Hyperhidrosis 0 1 1 3 Dose-Response Information In clinical trials in narcolepsy, a dose-response relationship was observed for nausea, vomiting, paresthesia, disorientation, irritability, disturbance in attention, feeling drunk, sleepwalking, and enuresis. The incidence of all these reactions was notably higher at 9 g per night.

In controlled trials in narcolepsy, discontinuations of treatment due to adverse reactions were greater at higher doses of sodium oxybate oral solution. Pediatric use information is approved for Jazz Pharmaceuticals Inc.’s XYREM (sodium oxybate) Oral Solution. However, due to Jazz Pharmaceuticals Inc.’s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Postmarketing Experience

The following adverse reactions have been identified during postapproval use of sodium oxybate. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure: arthralgia, decreased appetite, fall*, fluid retention, hangover, headache, hypersensitivity, hypertension, memory impairment, nocturia, panic attack, vision blurred, and weight decreased. *The sudden onset of sleep in patients taking sodium oxybate, including in a standing position or while rising from bed, has led to falls complicated by injuries, in some cases requiring hospitalization.

Alcohol, Sedative Hypnotics, and

CNS Depressants Sodium oxybate is contraindicated for use in combination with alcohol or sedative hypnotics. Use of other CNS depressants may potentiate the CNS-depressant effects of sodium oxybate .

Divalproex Sodium

Concomitant use of sodium oxybate with divalproex sodium results in an increase in systemic exposure to GHB, which was shown to cause a greater impairment on some tests of attention and working memory in a clinical study . An initial dose reduction of sodium oxybate oral solution is recommended when used concomitantly with divalproex sodium . Prescribers are advised to monitor patient response closely and adjust dose accordingly if concomitant use of sodium oxybate oral solution and divalproex sodium is warranted.

Pregnancy Risk Summary There are no adequate data on the developmental risk associated with the use of sodium oxybate in pregnant women. Oral administration of sodium oxybate to pregnant rats (150, 350, or 1,000 mg/kg/day) or rabbits (300, 600, or 1,200 mg/kg/day) throughout organogenesis produced no clear evidence of developmental toxicity; however, oral administration to rats throughout pregnancy and lactation resulted in increased stillbirths and decreased offspring postnatal viability and growth, at a clinically relevant dose . In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown.

Clinical Considerations Labor or Delivery Sodium oxybate has not been studied in labor or delivery. In obstetric anesthesia using an injectable formulation of sodium oxybate, newborns had stable cardiovascular and respiratory measures but were very sleepy, causing a slight decrease in Apgar scores. There was a fall in the rate of uterine contractions 20 minutes after injection.

Placental transfer is rapid and gamma-hydroxybutyrate (GHB) has been detected in newborns at delivery after intravenous administration of GHB to mothers. Subsequent effects of sodium oxybate on later growth, development, and maturation in humans are unknown. Data Animal Data Oral administration of sodium oxybate to pregnant rats (150, 350, or 1,000 mg/kg/day) or rabbits (300, 600, or 1,200 mg/kg/day) throughout organogenesis produced no clear evidence of developmental toxicity.

The highest doses tested in rats and rabbits were approximately 1 and 3 times, respectively, the maximum recommended human dose (MRHD) of 9 g per night on a body surface area (mg/m 2 ) basis. Oral administration of sodium oxybate (150, 350, or 1,000 mg/kg/day) to rats throughout pregnancy and lactation resulted in increased stillbirths and decreased offspring postnatal viability and body weight gain at the highest dose tested. The no-effect dose for pre- and post-natal developmental toxicity in rats is less than the MRHD on a mg/m 2 basis.

Pediatric Use Juvenile Animal Toxicity Data In a study in which sodium oxybate (0, 100, 300, or 900 mg/kg/day) was orally administered to rats during the juvenile period of development (postnatal days 21 through 90), mortality was observed at the two highest doses tested. Deaths occurred during the first week of dosing and were associated with clinical signs (including decreased activity and respiratory rate) consistent with the pharmacological effects of the drug. Reduced body weight gain in males and females and delayed sexual maturation in males were observed at the highest dose tested.

The no-effect dose for adverse effects in juvenile rats is associated with plasma exposures (AUC) less than that at the maximum recommended human dose (9 g/night). Pediatric use information is approved for Jazz Pharmaceuticals Inc.’s XYREM (sodium oxybate) Oral Solution. However, due to Jazz Pharmaceuticals Inc.’s marketing exclusivity rights, this drug product is not labeled with that pediatric information.

Sodium oxybate oral solution is contraindicated for use in: combination with sedative hypnotics . combination with alcohol . patients with succinic semialdehyde dehydrogenase deficiency . In combination with sedative hypnotics or alcohol Succinic semialdehyde dehydrogenase deficiency

Human Experience Information regarding overdose with sodium oxybate oral solution is derived

largely from reports in the medical literature that describe symptoms and signs in individuals who have ingested GHB illicitly. In these circumstances the co-ingestion of other drugs and alcohol was common, and may have influenced the presentation and severity of clinical manifestations of overdose. In adult clinical trials two cases of overdose with sodium oxybate oral solution were reported.

In the first case, an estimated dose of 150 g, more than 15 times the maximum recommended dose, caused a patient to be unresponsive with brief periods of apnea and to be incontinent of urine and feces. This individual recovered without sequelae. In the second case, death was reported following a multiple drug overdose consisting of sodium oxybate oral solution and numerous other drugs.

Signs and Symptoms Information about signs and symptoms associated with overdosage with

sodium oxybate oral solution derives from reports of illicit use of GHB. Patient presentation following overdose is influenced by the dose ingested, the time since ingestion, the co-ingestion of other drugs and alcohol, and the fed or fasted state. Patients have exhibited varying degrees of depressed consciousness that may fluctuate rapidly between a confusional, agitated combative state with ataxia and coma. Emesis (even when obtunded), diaphoresis, headache, and impaired psychomotor skills have been observed.

No typical pupillary changes have been described to assist in diagnosis; pupillary reactivity to light is maintained. Blurred vision has been reported. An increasing depth of coma and acidosis have been observed at higher doses.

Myoclonus and tonic-clonic seizures have been reported. Respiration may be unaffected or compromised in rate and depth. Cheyne-Stokes respiration and apnea have been observed.

Bradycardia and hypothermia may accompany unconsciousness, as well as muscular hypotonia, but tendon reflexes remain intact.

Recommended Treatment of Overdose General symptomatic and supportive care should be instituted

immediately, and gastric decontamination may be considered if co-ingestants are suspected. Because emesis may occur in the presence of obtundation, appropriate posture (left lateral recumbent position) and protection of the airway by intubation may be warranted. Although the gag reflex may be absent in deeply comatose patients, even unconscious patients may become combative to intubation, and rapid-sequence induction (without the use of sedative) should be considered.

Vital signs and consciousness should be closely monitored. The bradycardia reported with GHB overdose has been responsive to atropine intravenous administration. No reversal of the central depressant effects of sodium oxybate can be expected from naloxone or flumazenil administration.

The use of hemodialysis and other forms of extracorporeal drug removal have not been studied in GHB overdose, but have been reported in cases of acidosis associated with GHB ingestions of 125 g or greater; however, due to the rapid metabolism of sodium oxybate oral solution, these measures may not be warranted.

Poison Control Center As with the management of all cases of drug

overdosage, the possibility of multiple drug ingestion should be considered. The healthcare provider is encouraged to collect urine and blood samples for routine toxicologic screening, and to consult with a regional poison control center (1-800-222-1222) for current treatment recommendations.