Pentobarbital

Pentobarbital (previously known as pentobarbitone in Britain and Australia) is a short-acting barbiturate typically used as a sedative, a preanesthetic, and to control convulsions in emergencies.[1] It can also be used for short-term treatment of insomnia but has been largely replaced by the benzodiazepine family of drugs.

Not to be confused with phenobarbital or sodium pentothal.

Pentobarbital
Clinical data
Trade namesNembutal
AHFS/Drugs.comMonograph
MedlinePlusa682416
License data
Pregnancy
category
  • AU: C
Routes of
administration		By mouth, IV, IM, rectal; also intraperitoneal & intracardiac (for animal euthanasia)
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability70–90% (oral); 90% (rectal)
Protein binding20–45%
MetabolismLiver
Elimination half-life15–48 hours
ExcretionKidney
Identifiers
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.895
Chemical and physical data
FormulaC11H18N2O3
Molar mass226.276 g·mol−1
3D model (JSmol)
  (verify)

In high doses, pentobarbital causes death by respiratory arrest. It is used for veterinary euthanasia and is used by some U.S. states and the U.S. federal government for executions of convicted criminals.[2]

Pentobarbital was widely abused and known on the streets as "yellow jackets" due to the yellow capsule of the Nembutal brand. Pentobarbital in pill form is no longer available. The death of Marilyn Monroe in 1962 was ruled as probable suicide due to an overdose of pentobarbital.[3]

Uses

Medical

Typical applications for pentobarbital are sedative, short term hypnotic, preanesthetic, insomnia treatment, and control of convulsions in emergencies.[1] Abbott Pharmaceutical discontinued manufacture of their Nembutal brand of Pentobarbital capsules in 1999, largely replaced by the benzodiazepine family of drugs. Pentobarbital was also widely abused, known on the street as "yellow jackets".[4] They were available as 30, 50, and 100-milligram capsules of yellow, white-orange, and yellow colors, respectively.[5]

It is also used as a veterinary anesthetic agent.[6]

Pentobarbital also has an application in reducing intracranial pressure in Reye's syndrome, traumatic brain injury and induction of coma in cerebral ischemia patients.[7] Pentobarbital-induced coma has been advocated in patients with acute liver failure refractory to mannitol.[8]

Euthanasia

Pentobarbital can cause death when used in high doses. It is used for euthanasia for humans as well as animals. It is also used by itself, or in combination with complementary agents such as phenytoin, in commercial animal euthanasia injectable solutions.

Pentobarbital Sodium (CAS No. 57-33-0)

In the Netherlands, it is part of the standard protocol for physician-assisted suicide for self-administration by the patient.[9]

It is also used by mouth for physician-assisted death in the United States states of Oregon, Washington, Vermont, and California (as of January, 2016).[10][11]

The oral dosage of pentobarbital indicated for physician-assisted suicide in Oregon, US is typically 10 g in liquid form.[12][11]

Execution

Pentobarbital has been used or considered as a substitute for other drugs traditionally used for capital punishment in the United States when they are in short supply.[13] Such use however is illegal under Danish law, and when this was discovered, after public outcry in Danish media, Lundbeck, the owner of the drug, stopped selling it to US states that impose the death penalty. US distributors of the drug are forbidden by the owner to sell it to any customers, such as several state authorities, that practice or participate in executions of humans.[14]

Texas began using pentobarbital for executing death-row inmates by lethal injection on July 18, 2012.[15] The use of pentobarbital has been considered by several states, including Ohio, Arizona, Idaho, and Washington; those states made the decision to switch following shortages of pancuronium bromide, a muscle paralytic previously used as one component in a three-drug cocktail.[15]

In October 2013, Missouri changed its protocols to allow for a compounded pentobarbital to be used in a lethal dose for executions[16] and it was first used in November 2013.[17][18]

According to a December 2019 ProPublica article, by 2017, the Bureau of Prisons (BOP) in discussion with then Attorney General Jeff Sessions, had begun to search for suppliers of pentobarbital to be used in lethal injections. The BOP were aware that courts would challenge the use of pentobarbital as their "new drug choice" as some lawyers have said that "pentobarbital would flood prisoners’ lungs with froth and foam, inflicting pain and terror akin to a death by drowning." BOP said that these concerns were not justified and that their two expert witness said that the use of pentobarbital was "humane".[19] On July 25, 2019, US Attorney General William Barr directed the federal government to resume capital punishment after 16 years. The drug of choice for these executions is pentobarbital.[20]

Metabolism

Pentobarbital undergoes first-pass metabolism in the liver and possibly the intestines.[21]

Drug interactions

Administration of ethanol, benzodiazepines, opioids, antihistamines, other sedative-hypnotics, and other central nervous system depressants will cause possible additive effects.[7]

Chemistry

Pentobarbital is synthesized by methods analogous to that of amobarbital, the only difference being that the alkylation of α-ethylmalonic ester is carried out with 2-bromopentane in place of 1-bromo-3-methylbutane to give pentobarbital.[22][23][24]

Society and culture

Names

Pentobarbital is the INN, AAN, BAN, and USAN while pentobarbitone is a former AAN and BAN.

One brand name for this drug is Nembutal, coined by John S. Lundy, who started using it in 1930, from the structural formula of the sodium salt—Na (sodium) + ethyl + methyl + butyl + al (common suffix for barbiturates).[25] Nembutal is trademarked and manufactured by the Danish pharmaceutical company Lundbeck (now produced by Akorn Pharmaceuticals) and is the only injectable form of pentobarbital approved for sale in the United States. Abbott discontinued their Nembutal brand of Pentobarbital capsules in 1999, largely replaced by the Benzodiazepine family of drugs. Abbott's Nembutal brand of Pentobarbital capsules were widely abused and were known on the streets as "yellow jackets". They were available in 50 and 100 Mg.strength yellow capsules.[26]

Pentobarbital can occur as a free acid, but is usually formulated as the sodium salt, pentobarbital sodium. The free acid is only slightly soluble in water and in ethanol.[27][28]

Notable overdoses

The death of Marilyn Monroe in 1962 was ruled as probable suicide due to an overdose of pentobarbital.[29] Kenneth Halliwell's death is also attributed to an overdose of pentobarbital.

References
  1. "Nembutal sodium- pentobarbital sodium injection". DailyMed. 31 December 2016. Retrieved 29 January 2020.
  2. "Ohio says it will switch to new drugs for executions". Reuters. 28 October 2013.
  3. "Ohio says it will switch to new drugs for executions". Reuters. 28 October 2013.
  4. High Times Encyclopedia of Recreational Drugs. Aldrich, Michael R., Ashley, Richard, Horowitz, Michael. New York: Stonehill. 1978. p. 243. ISBN 0-88373-082-0. OCLC 4557439.CS1 maint: others (link)
  5. Physicians' Desk Reference (33rd ed.). Oradell, N.J.: Medical Economics Co. 1979. p. 403. ISBN 0-87489-999-0. OCLC 4636066.
  6. "International". Drugs.com.
  7. "Pentobarbital". Monograph. AHFS / Drugs.com.
  8. Stravitz RT, Kramer AH, Davern T, Shaikh AO, Caldwell SH, Mehta RL, Blei AT, Fontana RJ, McGuire BM, Rossaro L, Smith AD, Lee WM (2007). "Intensive care of patients with acute liver failure: Recommendations of the U.S. Acute Liver Failure Study Group". Critical Care Medicine. 35 (11): 2498–2508. doi:10.1097/01.CCM.0000287592.94554.5F. PMID 17901832. S2CID 11924124.
  9. "Euthanica". Euthanesia Dossier (in Dutch). NRC Webpagina's.
  10. Jennifer Fass; Andrea Fass (2011). "Physician-assisted Suicide: Ongoing Challenges for Pharmacists". Am J Health Syst Pharm. 68 (9): 846–849. doi:10.2146/ajhp100333. PMID 21515870.
  11. Philip Nitschke; Fiona Stewart (2006). The Peaceful Pill Handbook. Exit International US Ltd. p. 137. ISBN 0978878809.
  12. Jennifer Fass and Andrea Fass (2011). "Physician-assisted Suicide: Ongoing Challenges for Pharmacists". Am J Health Syst Pharm. 68 (9): 846–849. doi:10.2146/ajhp100333.
  13. "States urge feds to help import lethal injection drugs". CNN. 21 May 2012.
  14. "The Hidden Hand Squeezing Texas' Supply of Execution Drugs". Time. 7 August 2013.
  15. "Texas executes Yokamon Hearn with pentobarbitol". BBC News. 18 July 2012. Retrieved 9 December 2017.
  16. "Lethal injection: Secretive US states resort to untested drugs - BBC News". BBC News. Retrieved 17 March 2016.
  17. "Missouri executes serial killer Franklin". 20 November 2013.
  18. "Joseph Paul Franklin Executed; First MO Inmate Killed Using Pentobarbital". 20 November 2013.
  19. Arnsdorf, Isaac (23 December 2020). "Inside Trump and Barr's Last-Minute Killing Spree". ProPublica. Retrieved 11 January 2021.
  20. AG Barr orders reinstatement of the federal death penalty
  21. Knodell RG, Spector MH, Brooks DA, Keller FX, Kyner WT (1980). "Alterations in pentobarbital pharmacokinetics in response to parenteral and enteral alimentation in the rat". Gastroenterology. 79 (6): 1211–1216. doi:10.1016/0016-5085(80)90915-4. PMID 6777235.
  22. Volwiler, E. H.; Tabern, D. L. (1930). "5,5-Substituted Barbituric Acids1". Journal of the American Chemical Society. 52 (4): 1676–1679. doi:10.1021/ja01367a061.
  23. German imperial patent, D.R.P. 293163 (1916), Bayer
  24. GB patent 650354, Wilde, B. E. & Balaban, I. E., "Improvements in the manufacture of substituted barbituric and thiobarbituric acids", issued 1951-02-21, assigned to Geigy
  25. Fosburgh LC (1997). "From this point in time: Some memories of my part in the history of anesthesia--John S. Lundy, MD". AANA Journal. 65 (4): 323–328. PMID 9281913.
  26. Jolly, David (1 July 2011). "Danish Company Blocks Sale of Drug for U.S. Executions". The New York Times. Retrieved 20 November 2013.
  27. "Pentobarbital Compound summary (CID4737)". Pubchem. NCBI.
  28. "FR1972_08_25_17226" (PDF). Food and Drug Administration. Cite journal requires |journal= (help)
  29. "Ohio says it will switch to new drugs for executions". Reuters. 28 October 2013.
  • "Pentobarbital". Drug Information Portal. U.S. National Library of Medicine.
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