Until the late 1960s, the symptoms of anxiety and insomnia were mainly treated with barbiturates. The barbiturates are known to cause dependence, and severe withdrawal effects were sometimes reported following the abrupt termination of their administration. Furthermore, their efficacy in the treatment of anxiety disorders was limited. The discovery of the benzodiazepine anxiolytic chlordiazepoxide some 30 years ago, and the subsequent development of numerous analogues with an essentially similar pharmacological profile, rapidly led to the replacement of the barbiturates with a group of drugs that have been widely used for the treatment of anxiety disorders, insomnia, muscle spasm and epilepsy and as a preoperative medication. The benzodiazepines have also been shown to have fewer side effects than the barbiturates, to be relatively safe in overdose and to be less liable to produce dependence than the barbiturates. They have now become the most widely used of all psychotropic drugs; during the last 25 years it has been estimated that over 500 million people worldwide have taken a course of benzodiazepine treatment.
In recent years there has been growing concern among members of the public and the medical profession regarding the problem of dependence and possible abuse of the benzodiazepines, and the recent decrease in the number of prescriptions of these drugs for the treatment of anxiety reflects this concern. And yet, despite the decline in the short-term use of benzodiazepine drugs to treat anxiety, their use as hypnotic sedatives is largely unchanged. Furthermore, their long-term use for the treatment of anxiety and/or insomnia continues. Thus in the UK approximately 1.5% of the adult population have taken benzodiazepines continuously for 1 year or more, while nearly half of these have taken the drugs for at least 7 years. It has been variously estimated that approximately 0.25 million people have
Fundamentals of Psychopharmacology. Third Edition. By Brian E. Leonard © 2003 John Wiley & Sons, Ltd. ISBN 0 471 52178 7
Table 9.1. Benzodiazepines on the ''selected list'' for the NHS
Half-life (range in hours)
Drugs used for anxiety Chlordiazepoxide*
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