BUTABARB
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BUTABARB (BUTABARB).
Barbiturate that binds to GABA-A receptor subunits, potentiating GABAergic inhibition by increasing chloride ion conductance and reducing neuronal excitability.
| Metabolism | Hepatic metabolism via CYP2C9 and CYP2C19; minor pathways involve glucuronidation. |
| Excretion | Renal excretion of unchanged drug and metabolites. Approximately 70-80% of a dose is eliminated in urine as metabolites (hydroxy and glucuronide conjugates) and <5% as parent drug. Minimal biliary/fecal elimination (<5%). |
| Half-life | Terminal elimination half-life is 30-60 hours (mean ~40 hours) in adults with normal renal and hepatic function. Longer in elderly or patients with liver disease. |
| Protein binding | Approximately 20-25% bound to plasma proteins (albumin). |
| Volume of Distribution | 0.5-0.6 L/kg in adults. Higher Vd suggests distribution into total body water and tissues; may increase in obesity. |
| Bioavailability | Oral: 95-100% (well absorbed). Rectal: 80-90%. IM: 80-100%. |
| Onset of Action | Oral: 30-60 minutes. IV: within 2-5 minutes. IM: 10-15 minutes. Rectal: 15-30 minutes. |
| Duration of Action | Oral: 6-10 hours (sedative/hypnotic effects). IV/IM: 4-6 hours. Duration may be prolonged in hepatic impairment or with repeated dosing due to accumulation. |
15-30 mg orally 3-4 times daily as needed; maximum 200 mg/day. IV/IM: 50-200 mg for sedation.
| Dosage form | ELIXIR |
| Renal impairment | eGFR 30-50 mL/min: reduce dose by 25%. eGFR <30 mL/min: avoid use or use 50% reduction with caution. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: contraindicated. |
| Pediatric use | 0.5-1 mg/kg/dose orally every 6-8 hours; maximum 30 mg/dose. Not recommended for children under 6 years. |
| Geriatric use | Initiate at 7.5-15 mg orally 2-3 times daily; increase slowly. Avoid in frail elderly. Monitor for paradoxical excitation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BUTABARB (BUTABARB).
| Breastfeeding | Barbiturates are excreted into breast milk in low concentrations. M/P ratio is approximately 0.5-0.6. Chronic high-dose use may lead to infant sedation and difficulty feeding. Monitor infant for signs of drowsiness, lethargy, or poor suckling. Use caution, especially in neonates or preterm infants. |
| Teratogenic Risk | Butabarbital is a barbiturate classified as FDA Pregnancy Category D. First trimester: Increased risk of congenital malformations, particularly oral clefts, neural tube defects, and cardiovascular anomalies. Second and third trimesters: Potential for fetal dependence, withdrawal syndrome, and impaired brain development. Chronic use may cause fetal growth restriction and preterm birth. |
■ FDA Black Box Warning
May be habit forming; potential for abuse and dependence. Abrupt discontinuation may precipitate life-threatening withdrawal symptoms.
| Serious Effects |
Hypersensitivity to barbiturates, porphyria, severe respiratory insufficiency, history of substance abuse.
| Precautions | Respiratory depression, especially when combined with other CNS depressants; tolerance and dependence; withdrawal seizures; use with caution in hepatic impairment and elderly. |
| Food/Dietary | Avoid grapefruit juice as it may inhibit metabolism and increase sedative effects. Take with food if gastrointestinal upset occurs. Limit caffeine intake as it may reduce sedative efficacy. |
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| Fetal Monitoring | Monitor maternal vital signs, sedation level, and cognitive function. Fetal assessment: serial growth ultrasounds (every 4-6 weeks) for growth restriction, nonstress tests or biophysical profile in third trimester. Neonatal monitoring: observe for withdrawal signs (tremors, irritability, hypertonia, poor feeding) for 24-48 hours postpartum. |
| Fertility Effects | Barbiturates may alter menstrual cycle regularity via hypothalamic-pituitary-ovarian axis suppression. Enzyme induction (CYP450) can affect sex hormone metabolism. No direct evidence of reduced fertility, but potential for ovulatory dysfunction. |
| Clinical Pearls |
| Butabarbital is a short-acting barbiturate with a rapid onset; monitor for respiratory depression, especially when combined with other CNS depressants. Use with caution in hepatic impairment due to prolonged half-life. Tolerance and dependence develop with prolonged use; abrupt discontinuation may precipitate withdrawal seizures. Barbiturates induce CYP450 enzymes, potentially reducing efficacy of oral contraceptives, warfarin, and corticosteroids. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency without consulting your doctor. · Avoid alcohol and other CNS depressants (e.g., benzodiazepines, opioids) as they may cause severe sedation or respiratory depression. · Do not drive or operate heavy machinery until you know how this medication affects you. · Do not stop taking abruptly; withdrawal can cause anxiety, tremors, and seizures. Taper under medical supervision. · This medication may be habit-forming; store in a safe place to prevent misuse. · Notify your doctor if you are pregnant, planning to become pregnant, or breastfeeding. · Inform your doctor of all medications you take, including herbal supplements and over-the-counter drugs. |