Natriumthiopental
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 and the barbiturates enhance the inhibitory action of the GABAA receptor. Barbiturates, benzodiazepines, and alcohol all bind to the GABAA receptor, yet the barbiturates bind with the highest affinity. This explains why overdoses of barbiturates may be lethal whereas overdoses of benzodiazepines alone are typically not lethal. Barbiturates have anesthetic, sedative, and hypnotic properties. Barbiturates do not have analgesic effects.Vorlage:Fact
Uses
Anesthesia
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 unconsciousness 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 5-10 minutes the concentration is low enough in the brain such that consciouness returns.
Thiopental is not used for the maintenance of anesthesia in surgical procedures because it has a long context-sensitive half-time, leading to a prolonged period before consciousness is regained. Instead, anaesthesia is usually maintained with an inhaled anesthetic agent. This class of drugs has a relatively rapid elimination, so that stopping the inhaled anesthetic 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.Vorlage:Fact
Medical-induced comas
In addition to anesthesia induction, thiopental can be used to induce medical comas. Even though the drug is described as an ultra-short acting barbiturate, the drug's half-life is much longer and giving a larger dose ensures adequate concentrations in the brain 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, decrease neuronal activity and therefore decrease the production of osmotically active metabolites which in turn decrease swelling. Patients with significant swelling have improved outcomes following the induction of coma. Reportedly, thiopental has been shown to be superior to pentobarbital[1] in reducing intracranial pressure.
Physician assisted suicide
Thiopental is used in some countries, such as the Netherlands, for the purposes of assisted suicide. Vorlage:Fact
Lethal injection
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. Executions using the three drug combination are usually effecting in approximately 10 minutes. The use of thiopental alone is hypothesized to cause death in approximately 45 minutes.[2]
Truth Serum
Thiopental is still used in some places as a truth serum. The barbiturate drugs as a class decrease higher cortical brain functioning. Since lying is more complex than the truth, suppression of the higher cortical functions may lead to the divulgement of the "truth." Reports indicate that thiopental has been used during the interrogation of Abu Faraj al-Libbi[3] in Pakistan and Abu Salem in India.
Psychiatry
Psychiatrists and hypnotists have also used thiopental to facilitate the answering of questions. Vorlage:Fact
Metabolism
Sodium thiopental is mainly metabolized to pentobarbital,[4] 5-ethyl-5-(1'-methyl-3'-hydroxybutyl)-2-thiobarbituric acid, and 5-ethyl-5-(1'-methyl-3'-carboxypropyl)-2-thiobarbituric acid.[5]
Dosage
The usual dose range for induction of anaesthesia using thiopentone is from 3 to 7 mg/kg, however, there are many factors which alter this. Premedication with sedatives such as benzodiazepines or clonidine will reduce requirements, as do specific disease states and other patient factors.
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. Waters[6] in an investigation of its properties, which were short-term anesthesia and surprisingly little analgesia.[7] Three months later,[8] Dr. John S. Lundy started a clinical trial of thiopental at the Mayo Clinic at the request of Abbott.[9]
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.
External links
References and end notes
- PubChem Substance Summary: Thiopental
- Pentothal Abbott Laboratories. 1993.
- ↑ 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
- ↑ [1]
- ↑ Massoud Ansari in Karachi Truth drug fails to get al-Qa'eda No 3 to talk
- ↑ 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
- ↑ 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
- ↑ This Month in Anesthesia History: March
- ↑ Steinhaus, John E. The Investigator and His ‘Uncompromising Scientific Honesty’ American Society of Anesthesiologists. NEWSLETTER. September 2001, Volume 65, Number 9.
- ↑ 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
- ↑ History of Anesthesia with Emphasis on the Nurse Specialist Archives of the American Association of Nurse Anesthetists. 1953