Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PENTOTHAL vs FIORINAL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Potentiates GABA-A receptor activity, enhancing inhibitory neurotransmission; also reduces excitatory glutamate signaling.
FIORINAL is a combination of butalbital (barbiturate), aspirin (NSAID), and caffeine. Butalbital potentiates GABA-A receptor activity, producing sedative-hypnotic effects. Aspirin inhibits cyclooxygenase (COX-1 and COX-2), reducing prostaglandin synthesis, which provides analgesic and antipyretic effects. Caffeine is a non-selective adenosine receptor antagonist, enhancing analgesic efficacy.
Induction of general anesthesia,Induction of coma for increased intracranial pressure,Status epilepticus (off-label)
Relief of tension-type headache,Relief of migraine headache (off-label)
Induction: 3-5 mg/kg IV; Maintenance: 25-75 mg IV as needed; Rectal: 25 mg/kg (max 1.5 g) for induction.
1-2 capsules (butalbital 50 mg, acetaminophen 300 mg, caffeine 40 mg) orally every 4 hours as needed, not exceeding 6 capsules per day.
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.
Butalbital 35-50 hours, aspirin 15-20 minutes (salicylate 2-3 hours at low doses, >20 hours at high doses), caffeine 3-5 hours. Prolonged in hepatic/renal impairment.
Hepatic; primarily via CYP2C9 and other CYP450 enzymes.
Butalbital is extensively metabolized in the liver via hydroxylation and glucuronidation, primarily by CYP2C9 and CYP2C19. Aspirin is hydrolyzed to salicylic acid, then conjugated with glycine (salicyluric acid) and glucuronidated. Caffeine is metabolized by CYP1A2 to paraxanthine, theobromine, and theophylline.
Hepatic metabolism (approx. 80%), renal excretion of metabolites (20-30%) and unchanged drug (0.3-1%). Biliary/fecal elimination is negligible.
Renal: 60% butalbital (mostly unchanged), 10% aspirin (salicylates, majorly as metabolites), 3% caffeine (metabolites and unchanged). Fecal: <5% overall.
Approximately 72-86% bound, primarily to albumin (with some binding to lipoproteins).
Butalbital 20-40% (albumin), aspirin 80-90% (albumin, concentration-dependent), caffeine 25-36% (albumin).
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.
Butalbital 0.8 L/kg, aspirin 0.15-0.2 L/kg, caffeine 0.6-0.8 L/kg. Indicates extensive tissue distribution for butalbital and caffeine.
IV: 100%. Rectal: approximately 60-80% (with variability). IM: approximately 60-70%. Oral: negligible due to extensive first-pass metabolism (not used clinically).
Oral: butalbital ~100%, aspirin 50-75% (first-pass metabolism), caffeine ~100%.
No specific GFR-based adjustment; use with caution in severe renal impairment due to prolonged effects.
No specific guidelines; contraindicated in severe renal impairment (Cr Cl <30 m L/min) due to acetaminophen accumulation. Use with caution in moderate impairment.
Reduce dose by 50% in Child-Pugh B and C; monitor for prolonged sedation.
Contraindicated in severe hepatic impairment (Child-Pugh Class C). For mild to moderate (Child-Pugh A or B), reduce dose by 50% or extend dosing interval.
Induction: 5-6 mg/kg IV; Maintenance: 1-2 mg/kg IV as needed; Rectal: 25 mg/kg (max 1.5 g).
Not recommended for pediatric use; safety and efficacy not established.
Reduce induction dose to 2-3 mg/kg IV; use lower maintenance doses; increased risk of hypotension and respiratory depression.
Start at lowest effective dose (e.g., 1 capsule every 4 hours) due to increased sensitivity to butalbital (sedation, confusion) and risk of acetaminophen hepatotoxicity; maximum daily acetaminophen dose 2 g.
WARNING: RESPIRATORY DEPRESSION AND APNEA; RESUSCITATIVE EQUIPMENT AND PERSONNEL MUST BE IMMEDIATELY AVAILABLE. INTRA-ARTERIAL INJECTION MAY CAUSE ARTERIAL SPASM, THROMBOSIS, AND GANGRENE.
None.
Respiratory depression, hypotension, laryngospasm, bronchospasm, cardiac arrhythmias, extravasation risk, and acute porphyria exacerbation.
Risk of Reye's syndrome in children with viral illness,Aspirin hypersensitivity (e.g., asthma, nasal polyps),Gastrointestinal bleeding and ulceration,Hepatic impairment due to butalbital metabolism,Caffeine overdose from excessive use,Dependence and withdrawal with prolonged butalbital use
Hypersensitivity to barbiturates, acute porphyria, severe respiratory or cardiovascular instability, and inadequate airway management capability.
Hypersensitivity to butalbital, aspirin, or caffeine,Active peptic ulcer disease,Hemophilia or bleeding disorders,Concomitant use of anticoagulants,Children with chickenpox or influenza-like symptoms (risk of Reye's syndrome),Severe hepatic or renal impairment,Porphyria
No specific food interactions. However, avoid alcohol for at least 24 hours due to additive CNS depression.
Avoid excessive caffeine intake from coffee, tea, energy drinks, or chocolate as it may compound caffeine's stimulant effects and increase anxiety or insomnia. Alcohol should be strictly avoided due to additive CNS depression and increased GI bleeding risk with aspirin. No specific food restrictions besides moderation of caffeine-containing foods.
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.
First trimester: Butalbital is associated with neural tube defects, cleft palate; aspirin increases risk of gastroschisis, cardiac defects. Second trimester: Aspirin may cause premature closure of ductus arteriosus. Third trimester: Aspirin increases risk of intracranial hemorrhage, premature closure of ductus arteriosus; butalbital may cause neonatal withdrawal. Caffeine is not a major teratogen but high doses may increase miscarriage risk.
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.
Aspirin excreted in milk (M/P ratio ~0.03-0.3); risk of Reye syndrome. Butalbital excreted in low amounts; may cause neonatal sedation. Caffeine excreted (M/P ~0.5-0.7); may cause irritability. Avoid breastfeeding during chronic use.
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.
Due to increased renal clearance and volume of distribution, butalbital may require dose increase; aspirin may need higher doses due to increased plasma volume; no specific adjustment for caffeine. Monitor clinical response and toxicity.
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.
FIORINAL (butalbital/aspirin/caffeine) is a barbiturate-containing combination analgesic. Due to butalbital's high abuse potential and risk of withdrawal, it is reserved for tension-type headaches refractory to non-barbiturate therapies. Monitor for signs of barbiturate dependence, and limit quantity dispensed. Avoid in patients with porphyria, severe hepatic impairment, or hemorrhagic disorders (aspirin component). Caffeine may exacerbate anxiety or insomnia.
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.
This medication contains butalbital, which can be habit-forming; do not exceed prescribed dose or duration.,Avoid alcohol and other CNS depressants (e.g., benzodiazepines, opioids) as they increase sedation and respiratory depression risk.,Do not drive or operate heavy machinery until you know how this drug affects you.,Take with food to reduce stomach upset; if you experience black or bloody stools, stop and seek immediate medical attention (signs of GI bleeding from aspirin).,Do not use more than directed; sudden discontinuation can cause withdrawal symptoms (anxiety, tremors, seizures).,Keep out of reach of children; overdose may be fatal.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PENTOTHAL vs FIORINAL, answered by our medical review team.
PENTOTHAL is a Barbiturate Anesthetic that works by Potentiates GABA-A receptor activity, enhancing inhibitory neurotransmission; also reduces excitatory glutamate signaling.. FIORINAL is a Barbiturate Analgesic Combination that works by FIORINAL is a combination of butalbital (barbiturate), aspirin (NSAID), and caffeine. Butalbital potentiates GABA-A receptor activity, producing sedative-hypnotic effects. Aspirin inhibits cyclooxygenase (COX-1 and COX-2), reducing prostaglandin synthesis, which provides analgesic and antipyretic effects. Caffeine is a non-selective adenosine receptor antagonist, enhancing analgesic efficacy.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PENTOTHAL and FIORINAL 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 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.. The standard adult dose of FIORINAL is: 1-2 capsules (butalbital 50 mg, acetaminophen 300 mg, caffeine 40 mg) orally every 4 hours as needed, not exceeding 6 capsules per day.. 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 PENTOTHAL and FIORINAL 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. 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.. FIORINAL is classified as Category C. First trimester: Butalbital is associated with neural tube defects, cleft palate; aspirin increases risk of gastroschisis, cardiac defects. Second trimester: Aspirin may cause prem. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.