Pentobarbital abuse

Barbiturates. The hrst barbiturate, barbital, was introduced in 1903 and was followed a few years later by phenobarbital. The barbiturates effectively relieve anxiety, but they are never used as anxiolytics today due to toxicity and abuse concerns. However, several barbiturates, including phenobarbital (Luminal), secobarbital (Seconal), and pentobarbital (Nembutal), remain available and are occasionally used to treat epilepsy and rarely to manage acute alcohol withdrawal. 

Before the introduction of the benzodiazepines, a number of drugs from different chemical and pharmacological classes were used in the treatment of anxiety and insomnia. However, these drugs are more toxic and produce more serious side effects than do the benzodiazepines. Many also have signihcant abuse potential. Consequently, most of these compounds are no longer widely used. These drugs include the barbiturates (e.g., pentobarbital, amobarbital), carbamates (e.g., meprobamate), piperidinediones (e.g., glutethimide), and alcohols (e.g., ethchlorvynol). 

The CNS depressants include barbiturates, nonbarbiturate sedatives, and the benzodiazepines. As the medical use of barbiturates decreased, primarily because of their high addiction liability and the danger of acute lethality, the use of the benzodiazepine anxiolytics increased. The most commonly abused barbiturates are secobarbital, pentobarbital, and amobarbital. Pheno-barbital is not generally abused, because of its slow onset of action. The most commonly abused anxiolytics include diazepam, chlordiazepoxide, midazolam, lo-razepam, and flurazepam. These drugs are readily attainable from illicit sources. 

Schedule II drags have a high potential for abuse. They are accepted for medical use with restrictions. These drugs may lead to severe psychological or physical dependence. Barbiturates in this category are amo-barbital (Amytal), pentobarbital (Nembutal), and secobarbital (Seconal, 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. 

Several classes of pharmacologic agents are available for insomnia. Barbiturates are the oldest agents that have been used for insomnia and include pentobarbital, secobarbital, and amobarbital. Barbiturates are currently not recommended because of their high abuse potential (due to rapid development of tolerance) and lethal potential in overdose situations. Barbiturates potentiate the GABAergic-induced increase in chloride ion conductance at low doses, and at high doses they depress calcium-dependent action potentials. Caution should be exercised in patients with marked renal or liver dysfunction, severe respiratory disease, suicidal tendencies, or history of alcohol/drug abuse. 

Mintzer, M. Z., Guarino, J., Kirk, T, Roache, J. D., 8c Griffiths, R. R (1997). Ethanol and pentobarbital Comparison of behavioral and subjective effects in sedative drug abusers. Experimental and Clinical Psychopharmacolo y, 5, 203-215. 

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. 

Roache, J. D., Griffiths, R. R. (1985). Comparison of triazolam and pentobarbital Performance impairment, subjective effects and abuse liability. The Journal of Pharmacology and Experimental Therapeutics, 234, 120-133. 

Sullivan JT, Jasinski DR, Johnson RE. 1993. Single-dose pharmacodynamics of diazepam and pentobarbital in substance abusers. Clinical Pharmacology and Therapeutics 54 645-653. 

Schedule 11 drugs have an accepted medical use in the United States and a high rate of abuse, with either severe psychological or physical dependence potential. These drugs include morphine, codeine, cocaine, amphetamine, and most barbiturate preparations containing amobarbital, secobarbital, and pentobarbital. 

---