SECOBARBITAL SODIUM
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Secobarbital enhances the activity of gamma-aminobutyric acid (GABA) at GABA-A receptors, increasing chloride ion influx and causing neuronal hyperpolarization, leading to CNS depression.
| Metabolism | Hepatic via CYP2C9, CYP2C19, and CYP3A4; major metabolite is hydroxyphenobarbital. |
| Excretion | Renal excretion of unchanged drug (about 25-50%) and metabolites; the remainder is eliminated via hepatic metabolism and fecal excretion. Less than 5% is excreted unchanged in feces. |
| Half-life | Terminal elimination half-life is approximately 15-40 hours (mean ~30 hours) in adults. In neonates, half-life may be prolonged (up to 100 hours). Half-life increases in hepatic impairment and with advanced age. |
| Protein binding | Approximately 45-60% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is approximately 0.8-1.5 L/kg (mean ~1.0 L/kg). High Vd indicates extensive tissue distribution, including brain and fat. |
| Bioavailability | Oral: approximately 70-90% (but reduced due to first-pass metabolism). Rectal: 40-50% (variable). Intramuscular: nearly 100%. |
| Onset of Action | Oral: 10-30 minutes. Intramuscular: 10-15 minutes. Intravenous: 1-3 minutes (peak effect). Rectal: 15-30 minutes. |
| Duration of Action | Hypnotic effect: 3-6 hours after single oral dose; residual sedation (hangover) may persist for 8-12 hours. Duration is dose-dependent and prolonged with repeated use due to accumulation. |
Oral: 100-200 mg at bedtime for insomnia; IM: 150-200 mg as a single dose; IV: 50-250 mg as a single dose, administered slowly (not to exceed 50 mg per 15 seconds).
| Dosage form | INJECTABLE |
| Renal impairment | GFR 10-50 mL/min: Administer every 12-16 hours; GFR <10 mL/min: Administer every 24-36 hours. Hemodialysis: Moderately dialyzable; supplemental dose may be needed. |
| Liver impairment | Child-Pugh Class A: No adjustment; Child-Pugh Class B: Reduce dose by 50%; Child-Pugh Class C: Avoid use or reduce dose by 75% with close monitoring. |
| Pediatric use | Sedation: Oral or IM, 5-10 mg/kg/dose, max 100 mg/dose; Preoperative sedation: IM, 3-5 mg/kg/dose, max 100 mg/dose; Insomnia (adolescents): 100-200 mg at bedtime. |
| Geriatric use | Reduce initial dose by 50% (e.g., 50-100 mg for insomnia); avoid use of doses >100 mg due to increased risk of cognitive impairment, falls, and excessive sedation. |
| 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 | Excreted into breast milk; infant plasma levels may be 50-100% of maternal levels. M/P ratio not established. Avoid breastfeeding during maternal use due to potential CNS depression, poor feeding, and withdrawal in neonates. If used, monitor infant for sedation, respiratory depression, and jaundice. |
| Teratogenic Risk | First trimester: Crosses placenta; associated with increased risk of congenital malformations, particularly cleft lip/palate and neural tube defects, based on case-control studies. Second trimester: Risk of persistent pulmonary hypertension of the newborn and intrauterine growth restriction. Third trimester: Chronic use may lead to neonatal withdrawal syndrome (hyperirritability, tremors), and floppy infant syndrome due to CNS depression. Neonatal bleeding risk due to vitamin K deficiency. |
■ FDA Black Box Warning
Secobarbital is contraindicated in patients with porphyria. It may be habit forming. Abrupt discontinuation can precipitate life-threatening withdrawal symptoms.
| Common Effects | Sedation |
| Serious Effects |
["History of porphyria","Severe respiratory insufficiency","Hypersensitivity to barbiturates","Marked hepatic impairment"]
| Precautions | ["Risk of respiratory depression, especially in elderly or debilitated patients","Potential for drug dependence and abuse","May cause paradoxical excitement in some patients","Use with caution in patients with hepatic or renal impairment","May precipitate acute intermittent porphyria"] |
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| Fetal Monitoring | Maternal: Serum barbiturate levels, hepatic and renal function, CBC with differential, prothrombin time. Fetal: Ultrasound for growth and anatomy, fetal movement counts, nonstress test/biophysical profile in third trimester. Neonatal: Apgar scores, monitoring for withdrawal symptoms (Finnegan scale) and coagulation status. |
| Fertility Effects | No specific human data; barbiturates may induce hepatic enzymes affecting sex hormone metabolism. Potential for menstrual irregularities and impaired ovulation due to hypothalamic-pituitary-ovarian axis disruption. Animal studies indicate reduced fertility at high doses. |