Drug Guide

Barbiturates

By Anthony McDaniel, M.D.

Barbiturates are drugs that act as central nervous system depressants, and, by virtue of this, they produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants. They have addiction potential, both physical and psychological. Barbiturates have now largely been replaced by benzodiazepines in routine medical practice - for example, in the treatment of anxiety and insomnia – mainly because benzodiazepines are significantly less dangerous in overdose. However, barbiturates are still used in general anesthesia, as well as for epilepsy. Barbiturates are derivatives of barbituric acid. Barbiturates like pentobarbital and phenobarbital were long used as anxiolytics and hypnotics. Today, benzodiazepines have largely supplanted them for these purposes, because benzodiazepines have less potential for lethal overdoses. Barbiturates are classified as ultrashort-, short-, intermediate-, and long-acting, depending on how quickly they act and how long their effects last. Barbiturates are still widely used in surgical anesthesia, especially to induce anesthesia, though their use during induction of anesthesia has largely been supplanted. Ultrashort barbiturates such as thiopental (Pentothal) produce unconsciousness within about a minute of intravenous (IV) injection. These drugs may be used to induce general anesthesia. Volatile anesthetics are then used to maintain general anesthesia until the end of the operation. Because thiopental and other ultrashort-acting barbiturates are typically used in hospital settings, they are not very likely to be abused, noted the DEA.

Phenobarbital is used as an anticonvulsant for people suffering from seizure disorders such as febrile seizures, tonic-clonic seizures, status epilepticus, and eclampsia. Long-acting barbiturates such as phenobarbital (Luminal) and mephobarbital (Mebaral) are prescribed for few reasons. When taken at bedtime, they help treat insomnia, and when taken during the day they have sedative effects that can aid in the treatment of tension and anxiety. However, prescription for the treatment of these conditions is now rare due to the risks of physical dependence and fatal overdose. These drugs are more often prescribed in the treatment of convulsive conditions like epilepsy. Phenobarbital has also been used in the treatment of delirium tremens during alcohol detoxification, although benzodiazepines have a more favorable safety profile and are more often used. Long-acting barbiturates take effect within one to two hours and last 12 hours or longer. Like ethanol, barbiturates are intoxicating and produce similar effects during intoxication. The symptoms of barbiturate intoxication include respiratory depression, lowered blood pressure, fatigue, fever, unusual excitement, irritability, dizziness, poor concentration, sedation, confusion, impaired coordination, impaired judgment, addiction, and respiratory arrest which may lead to death. Recreational users report that a barbiturate high gives them feelings of relaxed contentment and euphoria. The main risk of acute barbiturate abuse is respiratory depression. Physical and psychological dependence may also develop with repeated use. Other effects of barbiturate intoxication include drowsiness, lateral and vertical nystagmus, slurred speech and ataxia, decreased anxiety, a loss of inhibitions. Barbiturates are also used to alleviate the adverse or withdrawal effects of illicit drug misuse.

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