Intermediate-acting barbiturate

Intermediate-acting (eg, amobarbital [Amytal], aprobarbital [Alurate], butabarbital [Butisol]). The average duration of action of die intermediate-acting barbiturates is 6 to 8 hours. 

Short and intermediate-acting barbiturates take effect within 15 to 40 minutes. The effects of these barbiturates last from five to six hours. These medications are prescribed for sedation or to help people sleep. The barbiturates in this category are amobarbital, pentobarbital, secobarbital, bubalbital, butabarbital, talbutal, and aprobarbital. 

According to the United States Drug Enforcement Agency (DEA), drug abusers favor short and intermediate-acting barbiturates. Barbiturate users often refer to the pills they take in terms of the color of the capsule. These street names include blues or blue devils for Amytal reds, red birds and red devils for Seconal yellow jackets for Nembutal purple hearts for Luminal and rainbows and Christmas trees for Tuinal. 

Long-acting barbiturates include phenobarbital (Luminal) and mephobarbital (Mebaral). These drugs, which take effect in about one hour and last for about 12 hours, are used primarily for daytime sedation and the treatment of seizure disorders or mild anxiety. Generally, these are not drugs of abuse rather the short- and intermediate-acting barbiturates—such as amobarbital (Amytal), pentobarbital (Nembutal), and secobarbital (Seconal)—are among those most commonly abused. 

The barbiturates have a low therapeutic index and a relatively high abuse potential. Because of their rapid onset and short duration of action, the short- to intermediate-acting barbiturates are used as sedative-hypnotics (amobarbitai, butabarbital, butalbital, pentobarbital, and secobarbital) and are those most commonly abused. The longer acting barbiturates (mephobarbital and phenobarbital), used primarily for their anticonvulsant properties, are rarely abused. 

These positional isomers (I) and (II) belong to the barbiturate family. However, these positional isomers speeifically diifer only in the formation of the 5-carbon side chain attached to the C-5 position to the barbiturate ring system. Thus, eompound (I) is a short-acting barbitnrate whereas, eompound (II) is an intermediate-acting barbiturate. 

The onset of action for intermediate acting barbiturates is 30 minutes and their hypnotic effect last for 2 to 6 hours. Most of them are first degraded by the liver and the metabolised product subsequently excreted by the kidney. They are generally used in insomnia and also as a pre-operative sedative. They also find their use in the treatment of convulsions when administered intravenously. 

Its hypnotic action is similar to the intermediate-acting barbiturate which may be enhanced when administered along with an antihistaminic agent like diphenylhydramine. It may be used as a sedative at lower dose levels. 

It is safely used for indueing sleep in all types of insomnia without causing depression of respiration. Its hypnotic action is parallel to intermediate-acting barbiturates. 

A. Specific levels of phenobarbital are usually readily available from hospital clinical laboratories concentrations greater an 60-80 mg/L are usually associated with coma and those greater than 150-200 mg/L with severe hypotension. For short- and intermediate-acting barbiturates, coma is likely when the semm concentration exceeds 20-30 mg/L. Barbiturates are easily detected in routine urine toxicologic screening. 

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