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. |
| Molecular Weight | 260.28 |
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 | Associated with congenital malformations (e.g., cleft lip/palate, cardiac defects) when used in the first trimester. Avoid use unless no alternative. |
| 2nd trimester | May impair fetal development; chronic use may lead to dependence and withdrawal in neonate. Use only if clearly needed. |
| 3rd trimester | Risk of neonatal depression, withdrawal syndrome, and bleeding due to vitamin K deficiency. Avoid use near term. |
Clinical note
CNS depressants may enhance sedative effects Can cause respiratory depression and dependence.
| Placental transfer | Rapidly crosses placenta; reaches fetal plasma concentrations similar to maternal levels. High lipid solubility facilitates transfer. |
| Breastfeeding | Small amounts excreted in breast milk; may cause infant sedation, poor feeding, and withdrawal. Monitor infant for drowsiness and weight gain. Manufacturer advises caution. |
■ 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 |
Known hypersensitivity to barbituratesPorphyria (acute intermittent, variegate, or hereditary coproporphyria)Severe respiratory insufficiencySevere hepatic impairmentMyasthenia gravis
| 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 |
| Food/Dietary | Avoid alcohol. High-fat meals may slow absorption. No specific dietary restrictions otherwise. |
Loading safety data…
| Lactation Rating | L4 (Possibly hazardous) |
| 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. |
| 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. |
| Clinical Pearls | Extreme caution in porphyria; avoid in pregnancy (category D); high abuse potential; taper to avoid withdrawal seizures; respiratory depression risk increased with alcohol or other CNS depressants; contraindicated in severe hepatic impairment; do not use intra-arterial injection (causes gangrene); use lower doses in elderly/debilitated; monitor for paradoxical excitement in children. |
| Patient Advice | Do not consume alcohol or other CNS depressants while taking this medication. · Do not drive or operate machinery until you know how the drug affects you. · Take exactly as prescribed; do not increase dose or frequency without consulting your doctor. · Stopping abruptly can cause withdrawal symptoms including seizures; taper under medical supervision. · Notify your doctor if you are pregnant, planning to become pregnant, or breastfeeding. · Store safely out of reach of children; this medication has a high risk of abuse and dependence. · Report any signs of allergic reaction (rash, difficulty breathing) or unusual bleeding/bruising. |