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thiopental (Pentothal)

Tradename: Pentothal. DEA controlled substance: class 3. Indication: - induction of anesthesia - hypnosis as lone therapy for short procedures with minimal painful stimuli - in combination with other anesthetics for surgery - adjunct for endotracheal intubation in head injury patients - control of convulsive states - epilepsy - treatment of elevated intracranial pressure - hypoxia, cerebral ischemia [6] - narcoanalysis [6] Contraindications: - variegate or acute intermittent porphyria Caution: 1) asthma 2) unstable aneurysms 3) pharyngeal infections (cough, laryngospasm & bronchospasm may occur) 4) hypotension Dosage: 1) induction of anesthesia a) neonates: 3-4 mg/kg b) infants: 5-8 mg/kg c) children 1-12 years: 5-6 mg/kg d) adults: 3-5 mg/kg 50-75 mg every 20-40 seconds, repeated as necessary 2) 1.5-5 mg/kg has been used to reduce intracranial pressure in neurosurgical patients repeated as needed 3) seizures: a) children: 2-3 mg/kg/dose, repeat as needed b) adults: 25-100 mg PRN Injection: 500 mg, 5 g (25%). Dosage adjustment in renal failure: - creatinine clearance < 10 mL/min: 75% of normal dose Pharmacokinetics: 1) rapid onset & duration of action (within 30-60 seconds) 2) high lipid solubulity 3) metabolized by the liver; pentobarbital is metabolite 4) duration of anesthesia is approximately 5-30 minutes 5) elimination 1/2life is 3-8 hours Adverse effects: 1) common (> 10%) - pain of IM injection 2) less common (1-10%) - cramping, diarrhea, rectal bleeding 3) uncommon (< 1%) - radial nerve palsy, hemolytic anemia, thrombophlebitis, hypotension, peripheral vascular collapse, seizures, tremor, headache, nausea/vomiting, involuntary muscle movement, twitching, rigidity, respiratory depression, hiccups, coughing, circulatory depression, myocardial depression, cardiac arrhythmias, rhinitis, emergence delirium, prolonged somnolence & recovery, anxiety, erythema, pruritus, urticaria, apnea, laryngospasm, bronchospasm, sneezing, dyspnea, anaphylaxis 4) other a) extravasation or intra-arterial injection causes necrosis due to pH of 10.6 b) accumulation may occur with chronic dosing due to lipid solubility c) prolonged recovery may result from redistribution of thiopental from fat stores Drug interactions: 1) CNS depressants 2) barbiturates induce cyt P450 1A2, 2C9 & 3A4 -> may diminish levels of drugs metabolized by cyt P450 1A2, 2C9 & 3A4 Laboratory: 1) specimen: a) serum, plasma (heparin, EDTA) b) stable for at least 24 hours at room temperature & 8 weeks at 20 degrees C 2) methods: GLC, GC-MS, HPLC Mechanism of action: 1) ultra-short-acting barbiturate 2) depresses CNS to produce anesthesia & hypnosis without analgesia 3) enhances chloride conduction in the presence of GABA 4) depresses transmission at autonomic ganglia 5) causes retrograde amnesia

Interactions

drug interactions drug adverse effects (more general classes)

Related

cytochrome p450 1A2 (cytochrome P3-450, phenacetin deethylase, cytochrome p450-4, CYP1A2) cytochrome P450 2C9; cytochrome P450 BP-1; cytochrome P450 MP-4; S-mephenytoin-4-hydroxylase; limonene 6-monooxygenase; limonene 7-monooxygenase (CYP2C9, CYP2C10) cytochrome P450 3A4 (cytochrome P450 C3, nifedipine oxidase, P450-PCN1, NF-25, CYP3A4)

General

barbiturate sedative/hypnotic (tranquilizer)

Properties

MISC-INFO: elimination route LIVER 1/2life 6-7 HOURS therapeutic-range 1-5 UG/ML 7-130 UG/ML protein-binding 75-90% elimination by hemodialysis - pregnancy-category C safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. Clinical Guide to Laboratory Tests, 3rd edition, NW Tietz ed, WB Saunders, Philadelphia, 1995
  2. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  3. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  4. Clinical Guide to Laboratory Tests, NW Tietz (ed) 3rd ed, WB Saunders, Philadelpha 1995
  5. Prescriber's Letter 13(3): 2006 Cytochrome P450 drug interactions Detail-Document#: 220233 (subscription needed) http://www.prescribersletter.com
  6. Deprecated Reference