CAS No.50-06-6 Phenobarbital


Name Phenobarbital
CAS Registry Number 50-06-6
Synonyms 2,4,6(1H,3H,5H)-Pyrimidinetrione, 5-ethyl-5-phenyl-;5-Ethyl-5-phenyl-2,4,6(1H,3H,5H;5-ethyl-5-phenyl-2,4,6-(1h,3h,5h)pyrimidinetrione;5-ethyl-5-phenyl-barbituricaci;5-Phenyl-5-ethylbarbituric acid;5-phenyl-5-ethylbarbituricacid;6(1h,3h,5h)-pyrimidinetrione,5-ethyl-5-phenyl-4;acido5-fenil-5-etilbarbiturico
Molecular Structure Phenobarbital   50-06-6
Molecular Formula C12H12N2O3
Molecular Weight 232.24
mp: 174℃
Hazard Codes: Details
Risk Statements: 61-25-40-43-39/23/24/25-23/24/25-11
Safety Statements: 53-36/37-45
RIDADR: UN 2811 6.1/PG 3

CAS 50-06-6 Wiki / 50-06-6 MSDS

2D chemical structure of phenobarbital
3D ball-and-stick model of phenobarbital
Clinical data
Trade names Luminal
AHFS/ Monograph
MedlinePlus a682007
  • AU: D
  • US: D (Evidence of risk)
Routes of
by mouth (PO), rectal (PR), parenteral (intramuscular and intravenous)
ATC code
  • N05CA24 (WHO) N03AA02 (WHO)
Legal status
Legal status
  • AU: S4 (Prescription only)
  • CA: Schedule IV
  • DE: Prescription only (Anlage III for higher doses)
  • UK: Class B
  • US: Schedule IV
Pharmacokinetic data
Bioavailability >95%
Protein binding 20 to 45%
Metabolism Hepatic (mostly CYP2C19)
Onset of action within 5 min (IV) and 30 min (PO)[1]
Biological half-life 53 to 118 hours
Duration of action 4 hrs[1] to 2 days[2]
Excretion Renal and fecal
CAS Number
  • 50-06-6 YesY
PubChem CID
  • 4763
  • 2804
  • DB01174 YesY
  • 4599 YesY
  • YQE403BP4D
  • D00506 YesY
  • CHEBI:8069 YesY
  • CHEMBL40 YesY
ECHA InfoCard 100.000.007
Chemical and physical data
Formula C12H12N2O3
Molar mass 232.235 g/mol
3D model (JSmol)
  • Interactive image

Phenobarbital, also known as phenobarbitone or phenobarb, is a medication recommended by the World Health Organization for the treatment of certain types of epilepsy in developing countries.[3] In the developed world it is commonly used to treat seizures in young children,[4] while other medications are generally used in older children and adults.[5] It may be used intravenously, injected into a muscle, or taken by mouth.[1] The injectable form may be used to treat status epilepticus.[1] Phenobarbital is occasionally used to treat trouble sleeping, anxiety, and drug withdrawal and to help with surgery.[1] It usually begins working within five minutes when used intravenously and half an hour when administered orally.[1] Its effects last for between four hours and two days.[1][2]

Side effects include a decreased level of consciousness along with a decreased effort to breathe.[1] There is concern about both abuse and withdrawal following long-term use.[1] It may also increase the risk of suicide.[1] It is pregnancy category B or D (depending on how it is taken) in the United States and category D in Australia, meaning that it may cause harm when taken by pregnant women.[1][6] If used during breastfeeding it may result in drowsiness in the baby.[7] A lower dose is recommended in those with poor liver or kidney function, as well as elderly people.[1] Phenobarbital is a barbiturate that works by increasing the activity of the inhibitory neurotransmitter GABA.[1]

Phenobarbital was discovered in 1912 and is the oldest still commonly used anti-seizure medication.[8][9] It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.[10] It is the least expensive anti-seizure medication at around $5 USD a year in the developing world.[11] Access however may be difficult as some countries label it as a controlled drug.[11]