barbiturate sodium thiopental used for capital punishment by lethal injection in the United States when that drug became unavailable. In 2011 the U.S. manufacturer of sodium thiopental stopped production, and importation of the drug proved impossible. Pentobarbital was used in an U.S. execution for the first time in December 2010 in Oklahoma, as part of a three-drug protocol. In March 2011 pentobarbital was used for the first time as the sole drug in a U.S. execution, in Ohio. Since then several states as well as the federal government have used pentobarbital for lethal injections; some use three-drug protocols and others use pentobarbital alone. Pentobarbital is produced by the Danish company Lundbeck. Use of the drug for executions is illegal under Danish law, and when this was discovered, after public outcry in Danish media, Lundbeck stopped selling it to US states that impose the death penalty and prohibited US distributors to sell it to any customers, such as state authorities, that practice or participate in executions of humans. Texas began using the single-drug pentobarbital protocol for executing death-row inmates on July 18, 2012, because of a shortage of pancuronium bromide, a muscle paralytic previously used as one component of a three-drug cocktail. In October 2013, Missouri changed its protocol to allow for pentobarbital from a compounding pharmacy to be used in a lethal dose for executions. It was first used in November 2013. According to a December 2020 ProPublica article, by 2017 the federal 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 was aware that the use of pentobarbital as their "new drug choice" would be challenged in the courts because some lawyers had said that "pentobarbital would flood prisoners’ lungs with froth and foam, inflicting pain and terror akin to a death by drowning." BOP claimed that these concerns were unjustified and that their two expert witnesses asserted that the use of pentobarbital was "humane". On July 25, 2019, US Attorney General William Barr directed the federal government to resume capital punishment after 16 years. The federal protocol provides for intravenous administration of 2x2.5 grams of pentobarbital sodium. Metabolism Pentobarbital undergoes first-pass metabolism in the liver and possibly the intestines. Drug interactions Administration of ethanol, benzodiazepines, opioids, antihistamines, other sedative-hypnotics, and other central nervous system depressants will cause possible additive