Fenobarbitaliin

Fenobarbitaliin, commonly known in English as phenobarbital, is a long-acting barbiturate with anticonvulsant and sedative-hypnotic properties. It is one of the oldest antiepileptic drugs still in routine clinical use, particularly in settings where long-term stability and low cost are important.

Phenobarbital exerts its effects primarily by potentiating GABA at the GABA-A receptor. By increasing the duration of chloride channel opening, it enhances inhibitory neurotransmission, reducing neuronal excitability and helping to prevent seizures. Its sedative action also makes it effective for preoperative sedation and, historically, as a sleep medication, though confidence in its use for insomnia has declined because of tolerance and safety concerns.

Indications include various seizure disorders, such as generalized tonic-clonic seizures and focal seizures, and sometimes neonatal seizures. It may be used when other anticonvulsants are ineffective or unsuitable. It is not typically a first‑line treatment for chronic insomnia in modern practice due to concerns about dependence and cognitive side effects.

Pharmacokinetics: Phenobarbital can be given orally or by injection. It is absorbed and distributed widely, with a long elimination half-life in adults (approximately 2 to 7 days, depending on age and health). It is extensively metabolized by the liver and is a potent inducer of hepatic enzymes, which can decrease the effectiveness of other drugs such as anticoagulants and oral contraceptives. Drug interactions and cumulative sedation are important considerations.

Safety: Common adverse effects include drowsiness, dizziness, and impaired coordination. Overdose can cause profound CNS and respiratory depression and can be fatal. Long-term use carries risks of tolerance, dependence, and withdrawal symptoms. Contraindications include porphyria and certain other conditions; use in pregnancy is associated with fetal risk and neonatal sedation.

Regulatory status: Phenobarbital is a prescription medication and is controlled in many jurisdictions because of its potential for misuse and dependence. It was introduced in the early 20th century and remains in use in many countries, though newer anticonvulsants have supplemented or replaced it in many indications.