PENTOTHAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PENTOTHAL (PENTOTHAL).
Potentiates GABA-A receptor activity, enhancing inhibitory neurotransmission; also reduces excitatory glutamate signaling.
| Metabolism | Hepatic; primarily via CYP2C9 and other CYP450 enzymes. |
| Excretion | Hepatic metabolism (approx. 80%), renal excretion of metabolites (20-30%) and unchanged drug (0.3-1%). Biliary/fecal elimination is negligible. |
| Half-life | 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. |
| Protein binding | Approximately 72-86% bound, primarily to albumin (with some binding to lipoproteins). |
| Volume of Distribution | 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. |
| Bioavailability | IV: 100%. Rectal: approximately 60-80% (with variability). IM: approximately 60-70%. Oral: negligible due to extensive first-pass metabolism (not used clinically). |
| Onset of Action | IV: 30-60 seconds (rapid loss of consciousness). Rectal: 5-10 minutes (sedation/hypnosis). IM: 10-15 minutes (hypnosis). |
| Duration of Action | IV: 5-10 minutes for single induction dose (due to redistribution); after repeated doses or infusion, prolonged (hours) due to accumulation. T1/2 context: single dose effect ends by redistribution; elimination half-life relevant for recovery after prolonged use. |
| Action Class | Barbiturate |
| Brand Substitutes | Anesthal 500mg Injection, Thipen 500mg Injection, Pentone 500mg Injection, THIOSOL 500 MG INJECTION, Thiopental 500mg Injection |
Induction: 3-5 mg/kg IV; Maintenance: 25-75 mg IV as needed; Rectal: 25 mg/kg (max 1.5 g) for induction.
| Dosage form | SUSPENSION |
| Renal impairment | No specific GFR-based adjustment; use with caution in severe renal impairment due to prolonged effects. |
| Liver impairment | Reduce dose by 50% in Child-Pugh B and C; monitor for prolonged sedation. |
| Pediatric use | Induction: 5-6 mg/kg IV; Maintenance: 1-2 mg/kg IV as needed; Rectal: 25 mg/kg (max 1.5 g). |
| Geriatric use | Reduce induction dose to 2-3 mg/kg IV; use lower maintenance doses; increased risk of hypotension and respiratory depression. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PENTOTHAL (PENTOTHAL).
| Breastfeeding | 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. |
| Teratogenic Risk | 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. |
■ FDA Black Box Warning
WARNING: RESPIRATORY DEPRESSION AND APNEA; RESUSCITATIVE EQUIPMENT AND PERSONNEL MUST BE IMMEDIATELY AVAILABLE. INTRA-ARTERIAL INJECTION MAY CAUSE ARTERIAL SPASM, THROMBOSIS, AND GANGRENE.
| Serious Effects |
Hypersensitivity to barbiturates, acute porphyria, severe respiratory or cardiovascular instability, and inadequate airway management capability.
| Precautions | Respiratory depression, hypotension, laryngospasm, bronchospasm, cardiac arrhythmias, extravasation risk, and acute porphyria exacerbation. |
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| Fetal Monitoring | Monitor maternal vital signs (heart rate, blood pressure, respiratory rate) continuously. Fetal heart rate monitoring is recommended during administration near delivery. Assess neonatal Apgar scores and respiratory effort at birth. Observe for maternal and fetal hypotension. |
| Fertility Effects | No known direct effects on human fertility. Animal studies show no impairment of fertility at clinically relevant doses. Use during labor does not impact long-term fertility. |