Pentobarbital
Also called Pentobarbitone, Nembutal, Mebubarbital, Pentobarbituric acid, Ethaminal
Part of the metabolic pathway of Pentobarbital and Sodium thiopental. See the timeline on the metabolic highway.
Dosage
Oral bands as drawn from PsychonautWiki's ranges below. The table is the source of truth.
When sources disagree, both rows are shown as published. Nothing is averaged or merged.
Oral
| Source | Threshold | Light | Common | Strong | Heavy |
|---|---|---|---|---|---|
| PsychonautWiki | 25 mg PW | 50–100 mg PW | 100–200 mg PW | 200–300 mg PW | 300 mg+ PW⚠ The source's own markup is broken here, so this is how a reader of the source would see it. |
| TripSit | – | 50–100 mg TS | 100–200 mg TS | – | 200–300 mg TS |
Intramuscular
Intravenous
TripSit dose text
TripSit's factsheet also states its doses as text.
Oral Light: 50-100mg Common: 100-200mg Heavy: 200-300mg | IM Light: 100-150mg Common: 150-200mg Heavy: 200mg+ | IV Light: 50-60mg Common: 60-100mg Heavy: 100mg+ TS
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Duration
Oral, drawn at the midpoint of each PsychonautWiki range.
| Route · source | Onset | Come-up | Peak | Offset | Total | After-effects |
|---|---|---|---|---|---|---|
| Oral · PsychonautWiki | 15–60 minutes PW | – | 1–3 hours PW | 1–2 hours PW | 4–6 hours PW | 1–36 hours PW |
TripSit factsheet
Mixing
For best safety practice, don't mix this drug with other depressants.
Why: respiratory depression. PsychonautWiki says:
- “Respiratory depression (also known as hypoventilation) can be described as a reduced urge to breathe that can be fatal depending on its intensity.” (PsychonautWiki, Respiratory depression, revision 150612)
- “... otherwise safe dosages of these compounds can become fatal when combined with even small amounts of other classes of depressant. For example, benzodiazepines combined with opioids are an extremely common cause of fatal respiratory depression. It is therefore strongly discouraged to combine these depressants at any dosage range.” (PsychonautWiki, Respiratory depression, revision 150612)
- “The most common cause of substance-related deaths is the combination of depressants (such as opiates, benzodiazepines, or alcohol) with other depressants.” (PsychonautWiki, Responsible drug use, revision 168206)
- “This combination potentiates the muscle relaxation, amnesia, sedation, and respiratory depression caused by one another. At higher doses, it can lead to a sudden, unexpected loss of consciousness along with a dangerous amount of depressed respiration.” (PsychonautWiki, dangerous interactions table, "Depressants" row, revision 156847)
Quotes from PsychonautWiki, CC BY-SA 4.0.
Acute combinations: what happens when these are taken close together. Entries backed by a medical journal or agency are listed first.
Backed by medical journals
Other documented combinations
- Depressants (1,4-Butanediol, 2-methyl-2-butanol, alcohol, barbiturates, GHB/GBL, methaqualone, opioids) - This combination can result in dangerous or even fatal levels of respiratory depression. These substances potentiate the muscle relaxation, sedation and amnesia caused by one another and can lead to unexpected loss of consciousness at high doses. There is also an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should try to fall asleep in the recovery position or have a friend move them into it. Pentobarbital is deemed to have an increased incidence of serious adverse effects when used concurrently with other depressants than other depressants. PW⚠ PsychonautWiki lists this combination without a danger rating.
- Dissociatives - This combination can lead to an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it. PW⚠ PsychonautWiki lists this combination without a danger rating.
- Stimulants - It is unsafe to combine barbiturates with stimulants due to the risk of excessive intoxication. Stimulants decrease the sedative effect of barbiturates, which is the main factor most people consider when determining their level of intoxication. Once the stimulant wears off, the effects of barbiturates will be considerably increased, leading to intensified disinhibition as well as other effects. If combined, one should strictly limit themselves to only dosing a certain amount of barbiturates per hour. This combination can also potentially result in severe dehydration if hydration is not monitored. PW⚠ PsychonautWiki lists this combination without a danger rating.
Risks and toxicity
Pentobarbital likely has moderate toxicity relative to dose. However, pentobarbital is potentially lethal when mixed with depressants like alcohol or opioids. Pentobarbital has a higher risk of death or serious adverse effects associated with concurrent depressant use than other drugs such as benzodiazepines. There have been studies linking the use of barbiturates, particularly phenobarbital, with the development of cancer.[8] PW
It is strongly recommended that one use harm reduction practices when using this drug. PW
Tolerance and addiction potential
Pentobarbital is extremely physically and psychologically addictive. Barbiturate withdrawal is medically serious and can potentially cause a life-threatening withdrawal syndrome that can cause seizures, psychosis, and death. Drugs which lower the seizure threshold such as tramadol and amphetamine should be avoided during withdrawal. If an individual is addicted to a short-acting barbiturate such as pentobarbital, switching to a longer acting drug such as phenobarbital may be of some benefit. PW
Tolerance will develop to the sedative-hypnotic effects of pentobarbital after prolonged use. It is unknown exactly how long it takes for tolerance to reach baseline. Pentobarbital presents cross-tolerance with all barbiturates, meaning that after its consumption all barbiturates will have a reduced effect. PW
Dangerous interactions
Although many drugs are safe on their own, they can become dangerous and even life-threatening when combined with other substances. The list below contains some common potentially dangerous combinations, but may not include all of them. Certain combinations may be harmless in low doses of each but still increase the potential risk of death. Independent research should always be done to ensure that a combination of two or more substances is safe before consumption. PW
Overdose
Barbiturate overdose may occur when a barbiturate is taken in extremely heavy quantities or concurrently with other depressants. This is particularly dangerous with other GABAergic depressants such as benzodiazepines and alcohol since they work in a similar fashion, but bind to distinct allosteric sites on the GABAA receptor, thus their effects potentiate one another. Benzodiazepines increase the frequency in which the chlorine ion pore opens on the GABAA receptor while barbiturates increase the duration in which they are open, meaning when both are consumed, the ion pore will open more frequently and stay open longer. Barbiturate overdose is a medical emergency that may lead to a coma, permanent brain injury or death if not treated promptly and properly. Barbiturate overdose has an increased frequency of serious adverse effects when compared to other depressants.[9] PW
Symptoms of a barbiturate overdose may include severe thought deceleration, slurred speech, confusion, delusions, respiratory depression, coma or death.[10] PW
TripSit factsheet
- Avoid
- All other CNS depressants, also avoid if you have respiratory issues or liver issues as barbiturates are harsh on the liver.[1] TS
Median lethal dose (LD50) in animals
Quoted from PubChem's Non-Human Toxicity Values, which come from the Hazardous Substances Data Bank (HSDB). PubChem describes them as: “Quantitative non-human toxicity values (e.g., lethal dose) for this compound. The data shown here are mostly for lab animals (e.g., rat, mouse, guinea pig, and rabbit).” and defines the “LD50 (median lethal dose, the estimated amount of a chemical expected to kill 50% of test animals in a single dose)”. PC
| LD50 (as the source gives it) | Reference |
|---|---|
| LD50 Rat oral 118 mg/kg PC | O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 1230 (via HSDB record 3151) |
| LD50 Rat oral 125 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 2611 (via HSDB record 3151) |
| LD50 Rat ip 108 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 2611 (via HSDB record 3151) |
| LD50 Rat sc 144 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 2611 (via HSDB record 3151) |
Testing
Effects
Overview
Pentobarbital, also known as pentobarbitone in British English and by the brand name Nembutal, is a short-acting psychoactive drug of the barbiturate class which produces powerful anxiolytic, hypnotic, muscle relaxant and amnesic effects. Pentobarbital is used medically as a hypnotic for the short-term treatment of insomnia and as an anticonvulsant in emergency situations. Pentobarbital is also used to put patients into medically induced comas. Pentobarbital works in a similar fashion to benzodiazepines, however barbiturates bind to a distinct allosteric site on the GABAA receptor. PW
A CNS depressant drug that is of the barbituate class. Typically not used often as it is easier to OD on than benzodiazepines, the new alternative to barbituates. Used often for insomnia, to cause sedation.[1] TS
Pentobarbital is a short-acting barbiturate typically used as a sedative, a preanesthetic, and to control convulsions in emergencies. It can also be used for short-term treatment of insomnia but has been largely replaced by the benzodiazepine family of drugs.[2] WP
In high doses, pentobarbital causes death by respiratory arrest. It is frequently used for veterinary euthanasia, and is used by some US states and the United States federal government for executions by lethal injection. In some countries and states, it is also used for physician-assisted suicide.[3]
Pentobarbital was developed by Ernest H. Volwiler and Donalee L. Tabern at Abbott Laboratories in 1930. The drug was widely abused beginning in the late 1930s, and it is sometimes known as "yellow jackets" due to the yellow color of Nembutal-branded capsules.[6]
History
Legal status
- Internationally, pentobarbital is listed in Schedule III of the UN Convention on Psychotropic Substances.[11] PW
- Australia: Pentobarbital is a Schedule 8 controlled substance.[12] PW
- Canada: Pentobarbital is a Schedule IV controlled substance.[13] PW
- Germany: Pentobarbital is controlled under Anlage III BtMG (Narcotics Act, Schedule III) It can only be prescribed on a narcotic prescription form.[14] PW
- Russia: Pentobarbital is a Schedule II controlled substance.[15] PW
- Switzerland: Pentobarbital is a controlled substance specifically named under Verzeichnis B. Medicinal use is permitted.[16] PW
- United Kingdom: Pentobarbital is a Class B controlled substance.[17] PW
- United States: Pentobarbital is a Schedule II controlled substance.[18] PW
Society and culture
Pentobarbital is the INN, AAN, BAN, and USAN, while pentobarbitone is a former AAN and BAN. WP
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). Nembutal is trademarked and manufactured by the Danish pharmaceutical company Lundbeck (now produced by Akorn Pharmaceuticals), which is the only injectable form of pentobarbital approved for sale in the United States. However, European Union restrictions on the export of drugs used to impose the death penalty constrained the availability of the drug in the United States and Canada. Attempts by drug smugglers to transport pentobarbital from Mexico to the United States have been reported since 2018.[19–22] WP
Ernest H. Volwiler and Donalee L. Tabern developed pentobarbital at Abbott Laboratories in 1930. Abbott discontinued its Nembutal brand of pentobarbital capsules in 1999, largely replaced by the benzodiazepine family of drugs. Abbott's Nembutal, known on the streets as "yellow jackets", was widely abused. They were available as 30, 50, and 100 mg capsules of yellow, white-orange, and yellow colors, respectively.[6]
In the 2025 mystery film Wake Up Dead Man, lethal doses of pentobarbital are used as a slow-acting poison in the murder of two separate characters. WP
Pharmacology
Pharmacodynamics
Like other barbiturates, pentobarbital binds to the barbiturate-binding site on the GABAA receptor. This action increases the duration of ion-channel opening. At high doses, pentobarbital is capable of opening the ion channel in the absence of GABA.[26] WP
Pharmacokinetics
Pentobarbital undergoes first-pass metabolism in the liver and possibly the intestines.[27] WP
Chemistry
User reports
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References
- Other Information on summary duration onset and dosage: Page 930 - Nurse's drug handbook 14th edition Jones and Bartlett 2015
- Journal / agency Nembutal sodium- pentobarbital sodium injection. 31 December 2016
- Other Palmer K. Ohio says it will switch to new drugs for executions. 28 October 2013
- Other Chaar B, Sami Isaac S. Euthanasia drugs: What is needed from medications for assisted deaths?. 20 October 2017
- Other Martin H. Euthanasia referendum: What drugs are used in assisted dying, and how do they work?. 13 August 2020
- Other Saxon W. Ernest Volwiler, 99, Medicinal Chemistry Leader. October 7, 1992
- Journal / agency Cozanitis DA. One hundred years of barbiturates and their saint. Journal of the Royal Society of Medicine. December 2004. doi:10.1177/014107680409701214 · PMID 15574863 · PMC1079678
- Journal / agency Friedman, G. D., Habel, L. A. Barbiturates and lung cancer: a re-evaluation. International Journal of Epidemiology. 1 June 1999. doi:10.1093/ije/28.3.375
- Journal / agency Twyman, R. E., Rogers, C. J., Macdonald, R. L. Differential regulation of gamma-aminobutyric acid receptor channels by diazepam and phenobarbital. Annals of Neurology. March 1989. doi:10.1002/ana.410250302
- Journal / agency Barbiturate intoxication and overdose: MedlinePlus Medical Encyclopedia
- Harm reduction site UN Convention on Psychotropic Substances
- Other S8 Controlled Drugs
- Other Branch, L. S. Consolidated federal laws of Canada, Controlled Drugs and Substances Act. 2022
- Other Anlage III BtMG
- Other Постановление Правительства РФ от 01.10.2012 N 1002 (ред. от 09.08.2019) “Об утверждении значительного, крупного и особо крупного размеров наркотических средств и психотропных веществ, а также значительного, крупного и особо крупного размеров для растений, содержащих наркотические средства или психотропные вещества, либо их частей, содержащих наркотические средства или психотропные вещества, для целей статей 228, 228.1, 229 и 229.1 Уголовного кодекса Российской Федерации” - КонсультантПлюс
- Other Verordnung des EDI über die Verzeichnisse der Betäubungsmittel, psychotropen Stoffe, Vorläuferstoffe und Hilfschemikalien
- Other Drugs penalties
- Other DEA Schedule II Drugs
- Journal / agency Fosburgh LC. From this point in time: some memories of my part in the history of anesthesia--John S. Lundy, MD. AANA Journal. August 1997. PMID 9281913
- Other Sanburn J. The Hidden Hand Squeezing Texas' Supply of Execution Drugs. 7 August 2013
- Journal / agency Cooney K, Titcombe L. Lessons and Recommendations from a Pentobarbital Shortage: US and Canada 2021. Animals. February 2022. doi:10.3390/ani12030365 · PMID 35158688 · PMC8833479
- Journal / agency Palamar JJ, Fitzgerald ND, Goldberger BA, Cottler LB. Monitoring illicit pentobarbital availability in the United States: A National Drug Early Warning System briefing. Drug and Alcohol Dependence. October 2024. doi:10.1016/j.drugalcdep.2024.112402 · PMID 39173219 · PMC11384643
- Other Jolly D. Danish Company Blocks Sale of Drug for U.S. Executions. 1 July 2011
- Other Aldrich MR, Ashley R, Horowitz M. High Times Encyclopedia of Recreational Drugs. 1978
- Other Physicians' Desk Reference. 1979
- Journal / agency Baer AB, Holstege CP. Encyclopedia of Toxicology. January 2005. doi:10.1016/b0-12-369400-0/00104-6
- Journal / agency Knodell RG, Spector MH, Brooks DA, Keller FX, Kyner WT. Alterations in pentobarbital pharmacokinetics in response to parenteral and enteral alimentation in the rat. Gastroenterology. December 1980. doi:10.1016/0016-5085(80)90915-4 · PMID 6777235
Text and values on this page are quoted from PsychonautWiki (CC BY-SA 4.0), Wikipedia (CC BY-SA 4.0), TripSit factsheets, PubChem (public domain). Each value links to the exact revision it came from.