Phenobarbital (INN) or phenobarbitone (BAN) is a long-acting barbiturate and the most widely used anti-seizure medication globally. It has sedative properties, but as with other barbiturates, benzodiazepines are more commonly used for this purpose.The World Health Organization recommends phenobarbital as a first-line medication for partial and generalized tonic–clonic seizures in developing countries. In the more developed world, it is no longer recommended as a first- or second-line choice for most seizure types, though it is still commonly used to treat neonatal seizures. The injectable form is mostly used to control status epilepticus, while by mouth it is used to prevent seizures in people with epilepsy. It is occasionally used to treat an inability to sleep, anxiety and to help with drug withdrawal as well as surgery.Side effects include a decreased level of consciousness along with a decreased effort to breath. There is concern of both abuse and withdrawal following long term use. It may also increase the risk of suicide. It is pregnancy category B or D in the United States and category D in Australia, meaning that it is may cause harm when taken by pregnant women. A lower dose is recommended in those with poor liver or kidney function, as well as those who are older.It is a core medicine in the WHO Model List of Essential Medicines, which is a list of minimum medical needs for a basic health care system. It is the oldest still commonly used anti-seizure medication having first been sold in 1912.