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2D Structure
Also known as: Pentobarbitone, Nembutal, Mebubarbital, Mebumal, Ethaminal, Pentobarbituric acid
Molecular Formula
C11H18N2O3
Molecular Weight
226.27  g/mol
InChI Key
WEXRUCMBJFQVBZ-UHFFFAOYSA-N
FDA UNII
I4744080IR

A short-acting barbiturate that is effective as a sedative and hypnotic (but not as an anti-anxiety) agent and is usually given orally. It is prescribed more frequently for sleep induction than for sedation but, like similar agents, may lose its effectiveness by the second week of continued administration. (From AMA Drug Evaluations Annual, 1994, p236)
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
5-ethyl-5-pentan-2-yl-1,3-diazinane-2,4,6-trione
2.1.2 InChI
InChI=1S/C11H18N2O3/c1-4-6-7(3)11(5-2)8(14)12-10(16)13-9(11)15/h7H,4-6H2,1-3H3,(H2,12,13,14,15,16)
2.1.3 InChI Key
WEXRUCMBJFQVBZ-UHFFFAOYSA-N
2.1.4 Canonical SMILES
CCCC(C)C1(C(=O)NC(=O)NC1=O)CC
2.2 Other Identifiers
2.2.1 UNII
I4744080IR
2.3 Synonyms
2.3.1 MeSH Synonyms

1. Diabutal

2. Etaminal

3. Ethaminal

4. Mebubarbital

5. Mebumal

6. Monosodium Salt Pentobarbital

7. Nembutal

8. Pentobarbital Sodium

9. Pentobarbital, Monosodium Salt

10. Pentobarbitone

11. Sagatal

2.3.2 Depositor-Supplied Synonyms

1. Pentobarbitone

2. Nembutal

3. Mebubarbital

4. Mebumal

5. Ethaminal

6. Pentobarbituric Acid

7. Neodorm

8. 76-74-4

9. Dorsital

10. Nebralin

11. Rivadorm

12. Pentobarbiturate

13. Pentabarbitone

14. Neodorm (new)

15. Pentabarbital

16. Pentobarbitalum

17. 5-ethyl-5-(sec-pentyl)barbituric Acid

18. 5-ethyl-5-(1-methylbutyl)barbituric Acid

19. 5-ethyl-5-(1-methylbutyl)malonylurea

20. 5-ethyl-5-(1-methylbutyl)-2,4,6(1h,3h,5h)-pyrimidinetrione

21. 2,4,6(1h,3h,5h)-pyrimidinetrione, 5-ethyl-5-(1-methylbutyl)-

22. Nsc 28708

23. Sodium Pentobarbital

24. Pentobarbital Cii

25. Pentobarbital Calcium

26. Barbituric Acid, 5-ethyl-5-(1-methylbutyl)-

27. Nsc-28708

28. 5-ethyl-5-(pentan-2-yl)pyrimidine-2,4,6(1h,3h,5h)-trione

29. Chembl448

30. 5-ethyl-5-pentan-2-yl-1,3-diazinane-2,4,6-trione

31. Chebi:7983

32. Aethaminalum

33. I4744080ir

34. Nembutal (van)

35. Neodorm (van)

36. Ncgc00096074-01

37. Pentobarbitale

38. Pentobarbital (van)

39. Pentobarbitone (van)

40. Pentobarbitale [dcit]

41. 5-ethyl-5-(1-methyl-butyl)-pyrimidine-2,4,6-trione

42. Pentobarbitalum [inn-latin]

43. 5-ethyl-5-(pentan-2-yl)-1,3-diazinane-2,4,6-trione

44. Phetobarbitone

45. 5-ethyl-2-hydroxy-5-(1-methylbutyl)pyrimidine-4,6(1h,5h)-dione

46. Nembutal (tn)

47. Ethyl-propylmethylcarbinylbarbituric Acid

48. Ccris 7089

49. Pentobarbital [inn]

50. Hsdb 3151

51. Einecs 200-983-8

52. Pentobarbital (usp/inn)

53. Brn 0087067

54. Barbituric Acid, 5-ethyl-5-(2-pentyl)-

55. Pentobarbital [usp:inn:ban]

56. Sr-01000317092

57. Unii-i4744080ir

58. (+-)-5-ethyl-5-(1-methylbutyl)barbituric Acid

59. (rs)-pentobarbital

60. Continal (salt/mix)

61. (plusmn)-pentobarbital

62. Sedalixir (salt/mix)

63. Spectrum_001783

64. 57-33-0

65. Spectrum2_001991

66. Spectrum3_001783

67. Spectrum4_000574

68. Spectrum5_001705

69. Dsstox_cid_3435

70. Pentobarbital [mi]

71. Ec 200-983-8

72. (.+/-.))-pentobarbital

73. Dsstox_rid_77026

74. Pentobarbital [hsdb]

75. Dsstox_gsid_23435

76. Oprea1_143902

77. Oprea1_775730

78. Schembl24966

79. Bspbio_003305

80. Kbiogr_001008

81. Kbioss_002267

82. Pentobarbital [vandf]

83. 5-24-09-00168 (beilstein Handbook Reference)

84. Divk1c_000992

85. Pentobarbital [mart.]

86. Spectrum1900006

87. Spbio_002201

88. Pentobarbital [who-dd]

89. Gtpl5480

90. Dtxsid7023435

91. Schembl11114711

92. Component Of Emesert (salt/mix)

93. Component Of Synirin (salt/mix)

94. Hms503g05

95. Kbio1_000992

96. Kbio2_002266

97. Kbio2_004834

98. Kbio2_007402

99. Kbio3_002807

100. Ninds_000992

101. Hms2094e21

102. Hms3713b10

103. Pentobarbital [green Book]

104. Pharmakon1600-01900006

105. Pentobarbital [orange Book]

106. Pentobarbital Cii [usp-rs]

107. Nsc28708

108. Pentobarbital [ep Monograph]

109. Tox21_111555

110. Bdbm50055935

111. Ccg-39476

112. Nsc760434

113. Pentobarbital [usp Monograph]

114. Stl367899

115. Pentobarbital 0.1 Mg/ml In Methanol

116. Pentobarbital 1.0 Mg/ml In Methanol

117. 2,4,6(1h,3h,5h)-pyrimidinetrione, 5-ethyl-5-(1-methylbutyl)-, (+-)-

118. Akos000277861

119. Wln: T6vmvmv Fhj Fy3&1 F2

120. Ccg-220564

121. Db00312

122. Nsc-760434

123. Cas-76-74-4

124. Idi1_000992

125. Ncgc00096074-02

126. Ncgc00344563-01

127. Sbi-0052713.p002

128. Db-056119

129. C07422

130. D00499

131. 057p561

132. Q409632

133. Sr-05000001789

134. Thiopental Sodium Impurity B [ep Impurity]

135. Sr-01000317092-2

136. Sr-05000001789-1

137. Brd-a44448661-001-01-4

138. (+/-)-5-ethyl-5-(1-methylbutyl)barbituric Acid

139. 2,6(1h,3h,5h)-pyrimidinetrione, 5-ethyl-5-(1-methylbutyl)-

140. 5-ethyl-5-(1-methylbutyl)-2,6(1h,3h,5h)-pyrimidinetrione

141. Pentobarbital, European Pharmacopoeia (ep) Reference Standard

142. Pentobarbital, United States Pharmacopeia (usp) Reference Standard

143. 2,4,6(1h,3h,5h)-pyrimidinetrione, 5-ethyl-5-(1-methylbutyl)-, (+/-)-

144. Pentobarbital Solution, 1.0 Mg/ml In Methanol, Ampule Of 1 Ml, Certified Reference Material

2.4 Create Date
2005-03-25
3 Chemical and Physical Properties
Molecular Weight 226.27 g/mol
Molecular Formula C11H18N2O3
XLogP32.1
Hydrogen Bond Donor Count2
Hydrogen Bond Acceptor Count3
Rotatable Bond Count4
Exact Mass226.13174244 g/mol
Monoisotopic Mass226.13174244 g/mol
Topological Polar Surface Area75.3 Ų
Heavy Atom Count16
Formal Charge0
Complexity305
Isotope Atom Count0
Defined Atom Stereocenter Count0
Undefined Atom Stereocenter Count1
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Drug Information
1 of 2  
Drug NameNembutal sodium
Drug LabelThe barbiturates are nonselective central nervous system depressants which are primarily used as sedative hypnotics and also anticonvulsants in subhypnotic doses. The barbiturates and their sodium salts are subject to control under the Federal Contro...
Active IngredientPentobarbital sodium
Dosage FormInjectable
RouteInjection
Strength50mg/ml
Market StatusPrescription
CompanyOak Pharms

2 of 2  
Drug NameNembutal sodium
Drug LabelThe barbiturates are nonselective central nervous system depressants which are primarily used as sedative hypnotics and also anticonvulsants in subhypnotic doses. The barbiturates and their sodium salts are subject to control under the Federal Contro...
Active IngredientPentobarbital sodium
Dosage FormInjectable
RouteInjection
Strength50mg/ml
Market StatusPrescription
CompanyOak Pharms

4.2 Therapeutic Uses

Adjuvants, Anesthesia; GABA Modulators; Sedatives, Barbiturate

National Library of Medicine's Medical Subject Headings online file (MeSH, 1999)


/Pentobarbital sodium is indicated for use as a/ sedative. /Included in US product label/

US Natl Inst Health; DailyMed. Current Medication Information for Nembutal sodium (pentobarbital sodium) injection (November 2006). Available from, as of March 19, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2563


/Pentobarbital sodium is indicated for use as a/ hypnotic, for the short-term treatment of insomnia, since they appear to lose their effectiveness for sleep induction and sleep maintenance after 2 weeks. /Included in US product label/

US Natl Inst Health; DailyMed. Current Medication Information for Nembutal sodium (pentobarbital sodium) injection (November 2006). Available from, as of March 19, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2563


/Pentobarbital sodium is indicated for use as a/ preanesthetic. /Included in US product label/

US Natl Inst Health; DailyMed. Current Medication Information for Nembutal sodium (Pentobarbital sodium) injection (November 2006). Available from, as of March 19, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2563


For more Therapeutic Uses (Complete) data for Pentobarbital (10 total), please visit the HSDB record page.


4.3 Drug Warning

Barbiturates may be habit forming. Tolerance, psychological and physical dependence may occur with continued use. Patients who have psychological dependence on barbiturates may increase the dosage or decrease the dosage interval without consulting a physician and may subsequently develop a physical dependence on barbiturates. To minimize the possibility of overdosage or the development of dependence, the prescribing and dispensing of sedative-hypnotic barbiturates should be limited to the amount required for the interval until the next appointment. Abrupt cessation after prolonged use in the dependent person may result in withdrawal symptoms, including delirium, convulsions, and possibly death. Barbiturates should be withdrawn gradually from any patient known to be taking excessive dosage over long periods of time.

US Natl Inst Health; DailyMed. Current Medication Information for Nembutal sodium (pentobarbital sodium) injection (November 2006). Available from, as of March 19, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2563


Nembutal Sodium capsules contain the dye tartrazine (FD&C yellow No. 5), which may cause allergic reactions including bronchial asthma in susceptible individuals. Although the incidence of tartrazine sensitivity is low, it frequently occurs in patients who are sensitive to aspirin.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


IV administered pentobarbital sodium may cause respiratory depression, apnea, laryngospasm, bronchospasm, or hypotension, particularly if the drug is administered too rapidly. When administered IV, the drug must be administered slowly, and personnel and equipment should be readily available for administration of artificial respiration. Too rapid administration may cause respiratory depression, apnea, laryngospasm, or vasodilation with fall in blood pressure.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


Barbiturates should be administered with caution, if at all, to patients who are mentally depressed, have suicidal tendencies, or a history of drug abuse.

US Natl Inst Health; DailyMed. Current Medication Information for Nembutal sodium (pentobarbital sodium) injection (November 2006). Available from, as of March 19, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2563


For more Drug Warnings (Complete) data for Pentobarbital (34 total), please visit the HSDB record page.


4.4 Minimum/Potential Fatal Human Dose

The toxic dose of barbiturates varies considerably but, in general, a severe reaction is likely to occur when the amount ingested is more than 10 times the usual oral hypnotic dose. Potentially lethal blood concentrations are those in excess of 80 ug/mL for phenobarbital, 50 ug/mL for amobarbital or butabarbital, and approximately 30 ug/mL for secobarbital or pentobarbital; however, some patients have survived much higher blood concentrations. /Barbiturates General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2578


4.5 Drug Indication

For the short-term treatment of insomnia.


5 Pharmacology and Biochemistry
5.1 Pharmacology

Pentobarbital, a barbiturate, is used for the treatment of short term insomnia. It belongs to a group of medicines called central nervous system (CNS) depressants that induce drowsiness and relieve tension or nervousness. Little analgesia is conferred by barbiturates; their use in the presence of pain may result in excitation.


5.2 MeSH Pharmacological Classification

GABA Modulators

Substances that do not act as agonists or antagonists but do affect the GAMMA-AMINOBUTYRIC ACID receptor-ionophore complex. GABA-A receptors (RECEPTORS, GABA-A) appear to have at least three allosteric sites at which modulators act: a site at which BENZODIAZEPINES act by increasing the opening frequency of GAMMA-AMINOBUTYRIC ACID-activated chloride channels; a site at which BARBITURATES act to prolong the duration of channel opening; and a site at which some steroids may act. GENERAL ANESTHETICS probably act at least partly by potentiating GABAergic responses, but they are not included here. (See all compounds classified as GABA Modulators.)


Hypnotics and Sedatives

Drugs used to induce drowsiness or sleep or to reduce psychological excitement or anxiety. (See all compounds classified as Hypnotics and Sedatives.)


Adjuvants, Anesthesia

Agents that are administered in association with anesthetics to increase effectiveness, improve delivery, or decrease required dosage. (See all compounds classified as Adjuvants, Anesthesia.)


5.3 ATC Code

N - Nervous system

N05 - Psycholeptics

N05C - Hypnotics and sedatives

N05CA - Barbiturates, plain

N05CA01 - Pentobarbital


5.4 Absorption, Distribution and Excretion

Absorption

Barbiturates are absorbed in varying degrees following oral, rectal, or parenteral administration.


Route of Elimination

Barbiturates are metabolized primarily by the hepatic microsomal enzyme system, and the metabolic products are excreted in the urine, and less commonly, in the feces. Approximately 25 to 50 percent of a dose of aprobarbital or phenobarbital is eliminated unchanged in the urine, whereas the amount of other barbiturates excreted unchanged in the urine is negligible.


Nearly all of an oral or rectal dose of pentobarbital is absorbed from the GI tract. Following oral administration of pentobarbital, peak plasma concentrations are usually reached in 30-60 minutes.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


When pentobarbital is administered orally or rectally, the onset of action occurs within 15-60 minutes. The onset of action is within 1 minute following iv administration and within 10-25 minutes following im administration. Like secobarbital, pentobarbital probably has a duration of hypnotic effect of 1-4 hours following oral or rectal administration and about 15 minutes following iv administration.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


Plasma pentobarbital concentrations of 1-5 ug/mL generally produce sedation, and plasma concentrations of 5-15 ug/mL produce sleep in most patients; however, plasma concentrations of greater than 10 ug/mL may produce deep coma, and those in excess of 30 mcg/mL are potentially lethal.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


Approximately 35-45% of pentobarbital is bound to plasma proteins.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


For more Absorption, Distribution and Excretion (Complete) data for Pentobarbital (15 total), please visit the HSDB record page.


5.5 Metabolism/Metabolites

by hepatic microsomal enzyme system


Pentobarbital is metabolized by the liver chiefly by penultimate oxidation of the 1-methylbutyl substituent to a secondary alcohol, 5-ethyl-5-(3'-hydroxy-1'-methylbutyl) barbituric acid (hydroxypentobarbital) which is an inactive metabolite. Approximately 40-50% of an oral hypnotic dose of pentobarbital is excreted in urine as hydroxypentobarbital. The 1-methylbutyl substituent of pentobarbital can also be oxidized to form pentobarbital carboxylic acid, and small quantities of this metabolite have been found in urine.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


The liver biotransforms most ... short acting barbiturates (90%-99%). Short-acting compounds /eg, pentobarbital & secobarbital/ are oxidized to more polar & inactive compounds (alcohols, ketones, phenol, or carboxylic acid). /Barbiturates/

Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology - Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier Science Publishing Co., Inc. 1988., p. 575


Pentobarbital contains an asymmetric carbon atom in butyl side chain. Main route of metabolism is (omega-1)-oxidation to yield 5-ethyl-5-(3'-hydroxy-1'-methylbutyl)barbituric acid. This process creates a new center of asymmetry, thus giving rise to 4 possible diastereoisomeric metabolites.

Testa, B. and P. Jenner. Drug Metabolism: Chemical & Biochemical Aspects. New York: Marcel Dekker, Inc., 1976., p. 257


Metabolized by liver by ... oxidation of 1-methylbutyl substituent to ... 5-ethyl-5-(3-hydroxy-1-methylbutyl)barbituric acid (hydroxypentobarbital) /and/ pentobarbital carboxylic acid ... Glucuronide conjugates of alcohols /and further unidentified oxidation products also found in urine of /humans/.

American Society of Hospital Pharmacists. Data supplied on contract from American Hospital Formulary Service and other current ASHP sources., p. 1975


For more Metabolism/Metabolites (Complete) data for Pentobarbital (6 total), please visit the HSDB record page.


5.6 Biological Half-Life

5 to 50 hours (dose dependent)


Plasma concentrations of pentobarbital decline in a biphasic manner with a half-life of about 4 hours for the first phase and 35-50 hours for the second phase.

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2583


The plasma half-life for pentobarbital in adults is 15 to 50 hours and appears to be dose dependent.

US Natl Inst Health; DailyMed. Current Medication Information for Nembutal sodium (pentobarbital sodium) injection (November 2006). Available from, as of March 19, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2563


Following iv admin of pentobarbitone sodium 50 mg to 5 healthy subjects pentobarbitone was noted to have a distribution phase (alpha-phase) of about 4 hr, & elimination occurred with a harmonic mean beta-phase half-life of about 50 hr. This suggested that for pentobarbitone the body has a central plasma compartment & one or more extravascular compartments. ... /In another study/ findings of 7 healthy subjects /revealed/ an average beta-phase half-life of only 22.3 hr following iv admin of 100 mg pentobarbitone sodium. After oral admin the half-life was about the same. A more detailed knowledge of pentobarbitone pharmacokinetics was needed to explain the deviation ... /between these 2 different studies/. /Pentobarbitone sodium/

Reynolds, J.E.F., Prasad, A.B. (eds.) Martindale-The Extra Pharmacopoeia. 28th ed. London: The Pharmaceutical Press, 1982., p. 810


5.7 Mechanism of Action

Pentobarbital binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged. All of these effects are associated with marked decreases in GABA-sensitive neuronal calcium conductance (gCa). The net result of barbiturate action is acute potentiation of inhibitory GABAergic tone. Barbiturates also act through potent (if less well characterized) and direct inhibition of excitatory AMPA-type glutamate receptors, resulting in a profound suppression of glutamatergic neurotransmission.


The exact mechanism(s) by which barbiturates exert their effect on the CNS, has not been fully elucidated. However, it is believed that such effects are related, at least partially, to the drugs' ability to enhance the activity of gamma-aminobutyric acid (GABA), the principal inhibitory neurotransmitter in the CNS, by altering inhibitory synaptic transmissions that are mediated by GABAA receptors. /Barbiturates General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2579


Although the drugs act throughout the CNS, a site of particular sensitivity is the polysynaptic midbrain reticular formation which is concerned with the arousal mechanism. Barbiturates induce an imbalance in central inhibitory and facilitatory mechanisms influencing the cerebral cortex and the reticular formation. The significance of the effect of barbiturates on neurotransmitters is unclear. It appears that the drugs decrease the excitability of both presynaptic and postsynaptic membranes. It has not been determined which of the various actions of barbiturates at cellular and synaptic levels are responsible for their sedative and hypnotic effects. /Barbiturates General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2579


Relatively low doses of the barbiturates depress the sensory cortex, decrease motor activity, and produce sedation and drowsiness. In some patients, however, drowsiness may be preceded by a period of transient elation, confusion, euphoria, or excitement, especially after subhypnotic doses of aprobarbital, pentobarbital, or secobarbital. /Barbiturates General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2579


Larger doses distort judgment, cloud perception, suppress motor activity, and produce drowsiness and sleep. Still larger doses induce anesthesia. Barbiturate-induced sleep differs from physiologic sleep. Barbiturates reduce the rapid eye movement (REM) or dreaming stage of sleep. Stages III and IV sleep are also decreased. Although tolerance develops to the REM-suppressant effects during chronic administration, REM rebound occurs when the drugs are withdrawn, and the patient may experience markedly increased dreaming, nightmares, and/or insomnia. /Barbiturates General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2009. Bethesda, MD. (2009), p. 2579


For more Mechanism of Action (Complete) data for Pentobarbital (22 total), please visit the HSDB record page.