Natriumthiopental

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chemical structure of thiopental sodium
sodium thiopental

sodium 5-ethyl-6-oxo-5-pentan-2-yl-2-
sulfanyl-pyrimidin-4-olate
CAS number
71-73-8Vorlage:Ref 		ATC code
N01AF03
Chemical formula C11H17N2NaO2S
Molecular weight 264.321 g/mol
Bioavailability ?
Metabolism ?
Elimination half-life 5.89Vorlage:Ref-26 hoursVorlage:Ref
Time to reach steady state ?
Excretion ?
Pregnancy category ?
Legal status US:Schedule III
Route(s) of administration Rectal, intravenous
Formulation(s) ?

Sodium thiopental also called Sodium Pentothal (a trademark of Abbott Laboratories), thiopental, thiopentone sodium, or trapanal is a rapid-onset, short-acting barbiturate general anesthetic.

Barbiturates

Barbiturates are a class of drugs that act on the GABAa receptor in the brain and spinal cord. The GABAa receptor is an inhibitory channel which decreases neuronal activity. Barbiturates have anesethetic, sedative, and hypnotic properties.

Uses

Thiopental is an ultra-short acting barbiturate and is most commonly used in the induction phase of general anaesthesia. Following intravenous injection the drug rapidly reaches the brain and causes unconsciouness within 30-45 seconds. At one minute, the drug attains a peak concentration of about 60% of the total dose in the brain. Thereafter, the drug distributes to the rest of the body and in about 5 minutes the concentration is low enough in the brain such that consciouness returns. Because of its pharmacokinetics, thiopental is never used for the maintenance of anesthesia in surgical procedures. Anesthesia is maintained by the inhaled anesthetics/fluorinated hydrocarbons. This class of drugs has an extremely rapid elimination such that stopping the inhaled anesthetics will allow rapid return of consciousness. Thiopental would have to be given in large amounts to maintain an anesthetic plane, and because of its 11.5-26 hour half-life, consciousness would take a long time to return. In addition, the rapid redistribution of the drug out of the brain would make it very difficult to maintain appropriate anesthesia.

In addition to anesthesia induction, thiopental can be used to induce medical comas. This is because the drug's half-life is much longer. Simply put, a large dose of the drug is given such that the distributive phase has a high enough concentration to maintain anesthesia. Patients with brain swelling, causing elevation of the intracranial pressure, either secondary to trauma or following surgery may benefit from this drug. Thiopental, and the barbiturate class of drugs, decreases neuronal activity and therefore decreases the production of osmotically active metabolites which in turn decreases swelling. Patients with significant swelling have improved outcomes following the induction of coma. Reportedly, thiopental has been shown to be superior to pentobarbitalVorlage:Ref in reducing intracranial pressure.

Along with pancuronium bromide and potassium chloride, thiopental is used in some states of the US to execute prisoners by lethal injection. A megadose is given which places the patient into a rapidly induced coma. In February 2006, a U.S. District judge ruled that an inmate in California could be executed with thiopental alone. It is expected that this will lengthen the execution from 10 minutes to 45 when compared with the standard 3 drug combination.[1] In the Netherlands, it is used for the purposes of assisted suicide to cause death after the induction of a coma by barbiturates.

It is still used in some places as a truth serum, recently used during the interrogation of Abu Faraj al-Libbi.Vorlage:Ref in Pakistan and Abu Salem in India.

Metabolism

Sodium thiopental is mainly metabolized to pentobarbital,Vorlage:Ref 5-ethyl-5-(1'-methyl-3'-hydroxybutyl)-2-thiobarbituric acid, and 5-ethyl-5-(1'-methyl-3'-carboxypropyl)-2-thiobarbituric acid.Vorlage:Ref

Side effects

As with nearly all anaesthetic drugs, thiopental causes cardiovascular and respiratory depression resulting in hypotension, apnea and airway obstruction. For these reasons, only anesthesiologists and other suitably trained doctors should give thiopental in an environment suitably equipped to deal with these effects. Side effects include headache, emergence delirium, prolonged somnolence and nausea. The hangover effects may last up to 36 hours.

History

Sodium thiopental was discovered in the early 1930s by Ernest H. Volwiler and Donalee L. Tabern, working for Abbott Laboratories. It was first used in human beings on March 8, 1934, by Dr. Ralph M. WatersVorlage:Ref in an investigation of its properties, which were short-term anesthesia and surprisingly little analgesia.Vorlage:Ref Three months later,Vorlage:Ref Dr. John S. Lundy started a clinical trial of thiopental at the Mayo Clinic at the request of Abbott.Vorlage:Ref

It is famously associated with a number of anaesthetic deaths in victims of the attack on Pearl Harbor. These deaths, relatively soon after its discovery, were due to excessive doses given to shocked trauma patients.

Trivia

  • The italian fictional gentleman thief, Diabolik, uses Pentothal on his victims to force them to reveal safes combinations.

External links

References and end notes

  1. Vorlage:Note THIOPENTAL SODIQUE Biam.
  2. Vorlage:Note Russo H, Bres J, Duboin MP, Roquefeuil B. "Pharmacokinetics of thiopental after single and multiple intravenous doses in critical care patients." Eur J Clin Pharmacol. 1995; 49(1-2):127-37. PMID: 8751034
  3. Vorlage:Note Morgan DJ, Blackman GL, Paull JD, Wolf LJ. "Pharmacokinetics and plasma binding of thiopental. II: Studies at cesarean section." Anesthesiology. 1981 Jun;54(6):474-80. PMID 7235275
  4. Vorlage:Note Pérez-Bárcena J, Barceló B, Homar J, Abadal JM, Molina FJ, de la Peña A, Sahuquillo J, Ibáñez J. "Comparison of the effectiveness of pentobarbital and thiopental in patients with refractory intracranial hypertension. Preliminary report of 20 patients]" [Article in Spanish] Neurocirugia (Astur). 2005 Feb;16(1):5-12; discussion 12-3. PMID 15756405 Fulltext
  5. Vorlage:Note Massoud Ansari in Karachi Truth drug fails to get al-Qa'eda No 3 to talk
  6. Vorlage:Note WINTERS WD, SPECTOR E, WALLACH DP, SHIDEMAN FE. "Metabolism of thiopental-S35 and thiopental-2-C14 by a rat liver mince and identification of pentobarbital as a major metabolite." Journal of Pharmacology Experimental Therapeutics. 1955 Jul;114(3):343-57. PMID 13243246
  7. Vorlage:Note Bory C, Chantin C, Boulieu R, Cotte J, Berthier JC, Fraisse D, Bobenrieth MJ. "[Use of thiopental in man. Determination of this drug and its metabolites in plasma and urine by liquid phase chromatography and mass spectrometry]" [Article in French] C R Acad Sci III. 1986;303(1):7-12. PMID 3093002
  8. Vorlage:Note This Month in Anesthesia History: March
  9. Vorlage:Note Steinhaus, John E. The Investigator and His ‘Uncompromising Scientific Honesty’ American Society of Anesthesiologists. NEWSLETTER. September 2001, Volume 65, Number 9.
  10. Vorlage:Note Imagining in Time—From this point in time: Some memories of my part in the history of anesthesia -- John S. Lundy, MD August 1997, AANA Archives-Library
  11. Vorlage:Note History of Anesthesia with Emphasis on the Nurse Specialist Archives of the American Association of Nurse Anesthetists. 1953

Vorlage:Barbiturates

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