|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|
|RIDADR：||UN 2811 6.1/PG 3|
|by mouth (PO), rectal (PR), parenteral (intramuscular and intravenous)|
|Protein binding||20 to 45%|
|Metabolism||Hepatic (mostly CYP2C19)|
|Onset of action||within 5 min (IV) and 30 min (PO)|
|Biological half-life||53 to 118 hours|
|Duration of action||4 hrs to 2 days|
|Excretion||Renal and fecal|
|Chemical and physical data|
|Molar mass||232.235 g/mol|
|3D model (JSmol)||
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. In the developed world it is commonly used to treat seizures in young children, while other medications are generally used in older children and adults. It may be used intravenously, injected into a muscle, or taken by mouth. The injectable form may be used to treat status epilepticus. Phenobarbital is occasionally used to treat trouble sleeping, anxiety, and drug withdrawal and to help with surgery. It usually begins working within five minutes when used intravenously and half an hour when administered orally. Its effects last for between four hours and two days.
Side effects include a decreased level of consciousness along with a decreased effort to breathe. There is concern about both abuse and withdrawal following long-term use. It may also increase the risk of suicide. 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. If used during breastfeeding it may result in drowsiness in the baby. A lower dose is recommended in those with poor liver or kidney function, as well as elderly people. Phenobarbital is a barbiturate that works by increasing the activity of the inhibitory neurotransmitter GABA.
Phenobarbital was discovered in 1912 and is the oldest still commonly used anti-seizure medication. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is the least expensive anti-seizure medication at around $5 USD a year in the developing world. Access however may be difficult as some countries label it as a controlled drug.
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