PENTOBARBITAL SODIUM
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Enhances gamma-aminobutyric acid (GABA) activity at GABA-A receptors, prolonging chloride channel opening and inhibiting neuronal firing.
| Metabolism | Primarily hepatic via microsomal enzyme system (CYP450); undergoes hydroxylation and glucuronidation; renal excretion of metabolites. |
| Excretion | Primarily renal excretion of inactive metabolites (hepatic metabolism via CYP). Approximately 25-50% unchanged in urine at alkaline pH; biliary/fecal elimination minimal (<5%). |
| Half-life | Terminal elimination half-life of 20-30 hours in adults. In prolonged ICU sedation, context-sensitive half-life can extend significantly (up to 50-100 hours) due to redistribution and accumulation. |
| Protein binding | Approximately 45-70% bound to albumin. |
| Volume of Distribution | Vd of 0.5-1.0 L/kg. Large Vd indicates extensive tissue distribution, contributing to prolonged elimination after chronic use. |
| Bioavailability | Oral: 70-90% (first-pass metabolism minimal); Rectal: approximately 90%; IM: complete. |
| Onset of Action | Intravenous: 30-60 seconds; Oral: 15-30 minutes; Rectal/IM: 10-15 minutes. |
| Duration of Action | Hypnosis: 15-30 minutes after single IV dose; recovery depends on redistribution. For sedation/EEG burst suppression, effects may persist for hours with continuous infusion. |
Induction of anesthesia: 100-150 mg IV given over 30-60 seconds; additional increments of 25-50 mg as needed. Hypnotic/sedative: 100-300 mg IM or 150-200 mg PO at bedtime. Anticonvulsant in emergencies: 5-7 mg/kg IV slow push over 1-2 minutes, may repeat every 15-30 minutes up to a maximum of 1 g. Rectal administration: 120-200 mg as a single dose for sedation.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 10-50 mL/min: prolong dosing interval by 50-100% or reduce dose by 25-50%. CrCl <10 mL/min: avoid use or administer at 50% of normal dose with extended interval. Hemodialysis: significantly removed; administer after dialysis if needed. |
| Liver impairment | Child-Pugh Class A: no adjustment necessary. Child-Pugh Class B: reduce dose by 25-50% and monitor for excessive sedation. Child-Pugh Class C: contraindicated or use with extreme caution at 50% or less of normal dose with prolonged dosing interval. |
| Pediatric use | Sedation for procedures: 2-6 mg/kg IM or IV (slow push) up to 100 mg maximum single dose. Induction of anesthesia: 5-7 mg/kg IV over 30-60 seconds, with additional increments of 25-50 mg as needed. Anticonvulsant: loading dose 15-20 mg/kg IV infused over 15 minutes, followed by maintenance infusion of 1-3 mg/kg/hour. Rectal sedation: 15-20 mg/kg as a single dose (max 150 mg). |
| Geriatric use |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants may enhance sedative effects Can cause respiratory depression and dependence.
| Breastfeeding | Pentobarbital is excreted into breast milk; milk-to-plasma ratio approximately 0.1-0.35. Infant serum levels low but may cause sedation. Caution advised; monitor infant for excessive drowsiness, poor feeding, and respiratory depression. Weigh benefits of breastfeeding against potential risks. |
| Teratogenic Risk | First trimester: Associated with increased risk of major malformations including cardiac defects and cleft palate. Second and third trimesters: Risk of adverse neurodevelopmental outcomes and neonatal withdrawal syndrome. Barbiturates cross placenta, may cause respiratory depression in neonate. Long-term exposure linked to cognitive impairment. |
■ FDA Black Box Warning
Risk of respiratory depression, apnea, and cardiac arrest; intravenous administration requires continuous monitoring; tolerance and dependence may develop; abrupt withdrawal can be life-threatening.
| Common Effects | insomnia |
| Serious Effects |
Hypersensitivity to barbiturates, acute intermittent porphyria, severe respiratory disease, status asthmaticus, severe hepatic impairment, history of drug abuse, use in patients with uncontrolled pain.
| Precautions | Respiratory depression, hypotension, laryngospasm, bronchospasm, caution in hepatic/renal impairment, elderly, debilitated, or patients with porphyria; risk of paradoxical excitation; injection site reactions; use only if resuscitation equipment is available. |
Loading safety data…
| Elderly patients are more sensitive to barbiturates; reduce dose by 25-50% compared to younger adults. Induction of anesthesia: 50-75 mg IV initially, titrate slowly. Sedative/hypnotic: 50-100 mg IM or PO at bedtime. Avoid use in patients with cognitive impairment, falls risk, or concurrent CNS depressant use. |
| Fetal Monitoring | Monitor maternal vital signs, respiratory rate, and sedation level. Fetal monitoring: assess fetal heart rate patterns and movements. Ultrasound for fetal growth if prolonged use. Neonatal monitoring for withdrawal syndrome (tremors, hypertonia, poor feeding) after delivery. |
| Fertility Effects | Animal studies show reduced fertility and fecundity. In humans, effects on fertility not well studied; may result in menstrual irregularities and altered hormone levels. Use may disrupt hypothalamic-pituitary-ovarian axis. |