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. more...
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.
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 maintence of anesthesia in surgical procedures. Maintainence of anesthesia is maintained by the inhaled anesthetics/flourinated 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 for induction of 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 ben shown to be superior to pentobarbital 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 and maintains coma for about 55-130 hours. In the Netherlands, it is used 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. in Pakistan and Abu Salem in India.
Read more at Wikipedia.org