Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
BUTABARBITAL vs PENTOTHAL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Butabarbital is a barbiturate that acts as a central nervous system depressant. It enhances the activity of GABA, an inhibitory neurotransmitter, by binding to the GABA-A receptor and prolonging the opening of chloride ion channels, leading to neuronal hyperpolarization and reduced excitability.
Potentiates GABA-A receptor activity, enhancing inhibitory neurotransmission; also reduces excitatory glutamate signaling.
Sedative,Hypnotic for short-term treatment of insomnia,Preoperative sedation
Induction of general anesthesia,Induction of coma for increased intracranial pressure,Status epilepticus (off-label)
50-100 mg orally or intramuscularly 3-4 times daily; maximum 400 mg/day.
Induction: 3-5 mg/kg IV; Maintenance: 25-75 mg IV as needed; Rectal: 25 mg/kg (max 1.5 g) for induction.
Terminal elimination half-life is 30-50 hours in adults, which may be prolonged in elderly or patients with hepatic impairment, leading to accumulation with repeated dosing.
Terminal elimination half-life is 5-12 hours (mean 8 hours) in adults. Prolonged with hepatic impairment, obesity, or high doses due to saturation of redistribution and metabolism.
Hepatic metabolism via cytochrome P450 enzymes (primarily CYP2C9 and CYP3A4); undergoes hydroxylation and glucuronidation; active metabolites include hydroxybutabarbital.
Hepatic; primarily via CYP2C9 and other CYP450 enzymes.
Primarily renal, with approximately 60-80% of the dose eliminated as metabolites (mostly hydroxylated and conjugated) and less than 5% as unchanged drug. Minor biliary/fecal excretion occurs (<10%).
Hepatic metabolism (approx. 80%), renal excretion of metabolites (20-30%) and unchanged drug (0.3-1%). Biliary/fecal elimination is negligible.
Approximately 20-25% bound to plasma proteins, predominantly albumin.
Approximately 72-86% bound, primarily to albumin (with some binding to lipoproteins).
Approximately 1.0 L/kg, indicating distribution throughout total body water and extensive tissue binding.
Vd = 1.0-2.5 L/kg (mean 1.5 L/kg). High Vd due to extensive tissue distribution, including brain and fat; correlates with high lipid solubility.
Oral bioavailability is nearly 100% (50-70% reported in some texts, but butabarbital is completely absorbed; first-pass metabolism is minimal).
IV: 100%. Rectal: approximately 60-80% (with variability). IM: approximately 60-70%. Oral: negligible due to extensive first-pass metabolism (not used clinically).
GFR 10-50 m L/min: reduce dose by 25%; GFR <10 m L/min: reduce dose by 50%.
No specific GFR-based adjustment; use with caution in severe renal impairment due to prolonged effects.
Child-Pugh class A: no adjustment; Child-Pugh class B: reduce dose by 50%; Child-Pugh class C: avoid use.
Reduce dose by 50% in Child-Pugh B and C; monitor for prolonged sedation.
Children 2-6 years: 25-50 mg orally 3-4 times daily; children 6-12 years: 50-100 mg orally 3-4 times daily; maximum 200 mg/day.
Induction: 5-6 mg/kg IV; Maintenance: 1-2 mg/kg IV as needed; Rectal: 25 mg/kg (max 1.5 g).
Initiate at 25-50 mg orally 3 times daily; increase cautiously to avoid excessive sedation and falls, maximum 200 mg/day.
Reduce induction dose to 2-3 mg/kg IV; use lower maintenance doses; increased risk of hypotension and respiratory depression.
Butabarbital has no FDA boxed warning.
WARNING: RESPIRATORY DEPRESSION AND APNEA; RESUSCITATIVE EQUIPMENT AND PERSONNEL MUST BE IMMEDIATELY AVAILABLE. INTRA-ARTERIAL INJECTION MAY CAUSE ARTERIAL SPASM, THROMBOSIS, AND GANGRENE.
Risk of dependence, tolerance, and withdrawal symptoms upon discontinuation; respiratory depression, especially with high doses or in patients with respiratory compromise; CNS depression may impair ability to drive or operate machinery; concomitant use with other CNS depressants (e.g., alcohol, opioids) increases risk of profound sedation and respiratory depression; geriatric patients may be more sensitive to effects; use with caution in patients with hepatic or renal impairment.
Respiratory depression, hypotension, laryngospasm, bronchospasm, cardiac arrhythmias, extravasation risk, and acute porphyria exacerbation.
Hypersensitivity to barbiturates; porphyria (can exacerbate); severe respiratory insufficiency; history of addiction to sedative-hypnotics; acute or chronic pain (may cause paradoxical excitement); pregnancy (especially third trimester) and lactation.
Hypersensitivity to barbiturates, acute porphyria, severe respiratory or cardiovascular instability, and inadequate airway management capability.
Grapefruit juice may decrease metabolism of butabarbital; avoid concurrent consumption. Alcohol increases CNS depression and should be avoided. No specific food restrictions otherwise.
No specific food interactions. However, avoid alcohol for at least 24 hours due to additive CNS depression.
First trimester: Associated with increased risk of major congenital malformations, specifically oral clefts (relative risk ~2.0). Second/third trimester: Chronic use may lead to fetal dependence and withdrawal syndrome; neonatal respiratory depression if used near term; increased risk of neurobehavioral effects. Barbiturates cross the placenta rapidly.
PENTOTHAL (thiopental) crosses the placenta. First trimester: limited human data, animal studies show no consistent teratogenicity. Second trimester: no specific malformation risk. Third trimester: prolonged maternal administration may cause neonatal respiratory depression, hypotonia, and withdrawal. Use only if clearly needed.
Butabarbital is excreted into breast milk in low concentrations. The milk-to-plasma ratio (M/P) is approximately 0.4–0.6. With therapeutic doses, infant serum levels are usually low; however, chronic high maternal doses may cause sedation or withdrawal in the nursing infant. Caution is recommended; alternate agents may be preferred if infant sedation occurs.
Thiopental is excreted in breast milk. M/P ratio is approximately 0.4–0.8. Infant dose is low (<1% of maternal weight-adjusted dose), but caution is advised due to potential CNS depression. American Academy of Pediatrics considers compatible with breastfeeding, but monitor infant for sedation.
Pregnancy can alter butabarbital pharmacokinetics due to increased hepatic metabolism and volume of distribution. Serum concentrations may decrease; therapeutic drug monitoring is recommended if used chronically. Dose adjustments may be necessary to maintain efficacy, but due to risks, use is generally avoided. If used, start with lowest effective dose and monitor for clinical response and toxicity.
Pregnancy may increase volume of distribution and clearance, but dosing adjustments for thiopental are not routinely recommended. Use lowest effective dose due to increased sensitivity to barbiturates. For cesarean section, standard induction doses (3-5 mg/kg IV) are used; reduced doses may be needed if combined with other sedatives.
Butabarbital is a short-acting barbiturate with rapid onset. It is primarily used for sedation and insomnia but has high abuse potential. Avoid use in patients with porphyria, severe hepatic impairment, or respiratory insufficiency. Abrupt discontinuation after prolonged use may precipitate withdrawal including seizures. Barbiturates induce CYP3A4 and other hepatic enzymes, reducing efficacy of oral contraceptives, warfarin, and corticosteroids. Use with caution in elderly due to increased risk of falls and cognitive impairment.
Pentothal (thiopental) is an ultra-short-acting barbiturate used for induction of anesthesia. It causes dose-dependent respiratory depression and hypotension. Administer only in a controlled setting with resuscitation equipment. Note that it is highly alkaline (p H 10-11) and extravasation causes severe tissue necrosis. Also, it is contraindicated in porphyria.
Take exactly as prescribed; do not increase dose or frequency without consulting your doctor.,Do not stop taking suddenly as withdrawal reactions such as anxiety, tremors, or seizures can occur.,May cause drowsiness or dizziness; do not drive or operate machinery until you know how this medicine affects you.,Avoid alcohol and other central nervous system depressants (e.g., benzodiazepines, opioids) as they increase risk of severe sedation and respiratory depression.,Use effective contraception while taking this medication as it may reduce hormonal contraceptive effectiveness.,Store in a secure place away from children and others, as it can cause dependence and is habit-forming.
You will receive this medication only under the supervision of an anesthesiologist.,It will cause you to fall asleep quickly and you may feel drowsy for several hours after the procedure.,Do not drive or operate machinery for at least 24 hours after receiving this medication.,Inform your doctor if you have a history of porphyria, liver disease, or allergies to barbiturates.,You may experience a bad taste or cough upon injection.
"Butabarbital, a barbiturate, induces cytochrome P450 (CYP) enzymes, enhancing the hepatic metabolism of ketamine, a dissociative anesthetic primarily metabolized by CYP3A4 and CYP2B6. This interaction reduces ketamine's systemic exposure and anesthetic efficacy, potentially leading to suboptimal sedation or anesthesia. Additionally, concurrent use may increase the risk of respiratory depression and hypotension due to additive central nervous system (CNS) depressant effects."
"Butabarbital, a barbiturate, is a potent CNS depressant that acts primarily by potentiating GABA-A receptor activity. Metaxalone is a centrally acting muscle relaxant with sedative properties. Coadministration results in additive or synergistic CNS depression, leading to increased risk of excessive sedation, respiratory depression, impaired psychomotor function, and potential coma or death, especially at higher doses or in vulnerable patients."
"Butabarbital, a barbiturate sedative-hypnotic, induces hepatic cytochrome P450 enzymes, particularly CYP3A4, which are responsible for metabolizing the atypical antipsychotic paliperidone. This induction decreases plasma concentrations of paliperidone, potentially reducing its therapeutic efficacy in treating schizophrenia or bipolar disorder. Concomitant use may lead to relapse of psychiatric symptoms or necessitate dose adjustments."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about BUTABARBITAL vs PENTOTHAL, answered by our medical review team.
BUTABARBITAL is a Barbiturate that works by Butabarbital is a barbiturate that acts as a central nervous system depressant. It enhances the activity of GABA, an inhibitory neurotransmitter, by binding to the GABA-A receptor and prolonging the opening of chloride ion channels, leading to neuronal hyperpolarization and reduced excitability.. PENTOTHAL is a Barbiturate Anesthetic that works by Potentiates GABA-A receptor activity, enhancing inhibitory neurotransmission; also reduces excitatory glutamate signaling.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between BUTABARBITAL and PENTOTHAL depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of BUTABARBITAL is: 50-100 mg orally or intramuscularly 3-4 times daily; maximum 400 mg/day.. The standard adult dose of PENTOTHAL is: Induction: 3-5 mg/kg IV; Maintenance: 25-75 mg IV as needed; Rectal: 25 mg/kg (max 1.5 g) for induction.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between BUTABARBITAL and PENTOTHAL in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. BUTABARBITAL is classified as Category C. First trimester: Associated with increased risk of major congenital malformations, specifically oral clefts (relative risk ~2.0). Second/third trimester: Chronic use may lead to fe. PENTOTHAL is classified as Category C. PENTOTHAL (thiopental) crosses the placenta. First trimester: limited human data, animal studies show no consistent teratogenicity. Second trimester: no specific malformation risk.. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.