What Is Phenobarbital?

Jillian O Keeffe

The medical drug phenobarbital has a sedative and anti-convulsant effect. The drug is prescribed for people who have trouble sleeping, for those who suffer from anxiety and to control epileptic seizures. It is available as an oral medication.

Phenobarbital is prescribed to patients on a temporary basis to treat insomnia.
Phenobarbital is prescribed to patients on a temporary basis to treat insomnia.

Phenobarbital affects the central nervous system, which is why it has an effect on anxiety levels. At low doses, the drug produces drowsiness and slows down body movement. It also can produce a hypnotic state in the person taking it. At higher doses, the drug causes the body to sleep, but this type of sleep differs from normal sleep. Phenobarbital can take an hour to have an effect, but the effects can last for as long as 12 hours. Of the entire barbiturate group of medicines, phenobarbital has the longest-lasting effects.

Moderate side effects of phenobarbital include bad dreams.
Moderate side effects of phenobarbital include bad dreams.

The drug is available as a capsule, a tablet or a liquid that is sometimes known as an elixir. A typical regimen of the drug involves taking a dose one to three times per day. The medication can be habit-forming, despite the likelihood that the beneficial effects of the drug might lessen over time.

People who take phenobarbital to control epileptic seizures should follow a doctor's instructions closely. If an epileptic patient finds that his or her seizures are not controlled properly, the doctor might raise the dosage of the drug. All barbiturates have anti-convulsant properties, but only phenobarbital, metharbital and mephobarbital have these beneficial effects at low doses.

The drug is only a temporary solution to insomnia and should be taken for only two weeks. After this time, the drug might become less effective at encouraging sleep. Even during the two-week regimen, phenobarbital does not allow patients to fall into a natural sleep cycle. The dream portions of the sleep cycle usually are reduced. Some patients might find that they experience more nightmares or insomnia than before.

Side effects of the drug include stomach problems, headaches and dizziness. Moderate side effects include bad dreams, constipation and pains in muscles or joints. Severe side effects, which are a reason for a patient to notify his or her doctor straight away, include allergic reaction, bleeding episodes and seizures. An overdose of phenobarbital can be fatal.

Pregnant or breastfeeding women as well as people who have previously had organ disease or anemia should ask their doctor before taking phenobarbital. The drowsiness produced by the drug can be exacerbated by the effects of other medications, including common painkillers such as acetaminophen, antidepressants or even vitamins. Someone taking the drug should be careful of operating heavy machinery or driving until it is known how the drug affects him or her. The drug also can interfere with oral contraceptives.

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