NEMBUTAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NEMBUTAL (NEMBUTAL).
Barbiturate that enhances GABA-A receptor activity, increasing chloride ion conductance and neuronal hyperpolarization. At high doses, has direct inhibitory effects on excitatory AMPA and kainate receptors.
| Metabolism | Primarily hepatic via hydroxylation and glucuronidation; CYP2C19 major enzyme. |
| Excretion | Renal elimination of unchanged drug accounts for approximately 30-35% of a dose; the remainder is hepatically metabolized. Less than 5% is excreted unchanged in feces. |
| Half-life | Terminal elimination half-life is 40-120 hours (mean ~80 hours). The prolonged half-life contributes to accumulation with repeated dosing and residual sedation. |
| Protein binding | Approximately 60-70% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 0.5-1.0 L/kg. This relatively high Vd indicates extensive distribution into tissues, including brain and adipose tissue. |
| Bioavailability | Oral: approximately 70-90%; IM: nearly 100% but absorption may be erratic; IV: 100%. |
| Onset of Action | IV: 30-60 seconds; IM: 10-15 minutes; Oral: 15-40 minutes |
| Duration of Action | Hypnosis lasts 15-30 minutes after IV administration due to redistribution; however, residual central nervous system depression (sedation) persists for 4-6 hours. Duration is dose-dependent. |
Induction of anesthesia: 50-120 mg IV as a single dose. Maintenance of anesthesia: additional doses of 20-40 mg IV as needed. For sedation (preoperative): 100-200 mg IM or 1-5 mg/kg IV 1-1.5 hours before procedure. For status epilepticus: loading dose of 5-15 mg/kg IV slow push, then 1-5 mg/kg/h IV infusion.
| Dosage form | ELIXIR |
| Renal impairment | CrCl 10-50 mL/min: administer 75% of usual dose. CrCl <10 mL/min: administer 50% of usual dose. For anuria: not recommended. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 25-50%. Child-Pugh Class C: avoid use or reduce dose by 50-75% with caution. |
| Pediatric use | Sedation: 2-6 mg/kg/dose IM or IV (max 100 mg). Induction of anesthesia: 3-5 mg/kg IV. Maintenance of anesthesia: 1-2 mg/kg IV as needed. Status epilepticus: loading dose 15-20 mg/kg IV slow push, then 2-5 mg/kg/h IV infusion. Doses should be individualized; reduce in neonates. |
| Geriatric use | Elderly patients may require lower doses (25-50% reduction) due to increased sensitivity to CNS depressant effects and prolonged half-life. Avoid rapid IV administration. Monitor for respiratory depression and delirium. Use smallest effective dose. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NEMBUTAL (NEMBUTAL).
| Breastfeeding | Pentobarbital is excreted in breast milk with M/P ratio approximately 0.4. Due to potential for infant sedation and withdrawal, avoid breastfeeding or use with caution; if used, monitor infant for drowsiness and feeding difficulties. |
| Teratogenic Risk | Pregnancy Category D. First trimester: Risk of congenital malformations including cleft palate and cardiovascular defects; second and third trimesters: Risk of fetal dependence, withdrawal syndrome, and respiratory depression at birth; chronic use may lead to neonatal sedation and floppy infant syndrome. |
■ FDA Black Box Warning
May produce drug dependence; risk of abuse and withdrawal syndrome. Administration should be by or under the direction of a physician experienced in IV anesthetics.
| Serious Effects |
["Hypersensitivity to barbiturates","History of porphyria","Severe respiratory insufficiency","Pre-existing hypotension or shock"]
| Precautions | ["Respiratory depression; risk of hypotension and laryngospasm","Use caution in hepatic or renal impairment","May cause paradoxical excitement in pain states","Risk of Stevens-Johnson syndrome and other severe cutaneous reactions","Resuscitative equipment and personnel should be immediately available"] |
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| Fetal Monitoring |
| Monitor maternal vital signs, sedation level, respiratory function, and signs of withdrawal. Fetal monitoring: Assess fetal heart rate patterns, growth via ultrasound, and biophysical profile. Neonatal: Observe for respiratory depression, hypotonia, and withdrawal symptoms. |
| Fertility Effects | Pentobarbital may cause menstrual irregularities and anovulation via induction of hepatic enzymes affecting sex hormone metabolism. Animal studies show reduced fertility; human data limited. |