Miscellaneous Central Nervous System Depressants

Abstract

Central nervous system (CNS) depressants remain a frequently encountered class of drugs in forensic toxicology. The most commonly encountered group, the benzodiazepines are discussed in Chap. 20. The oldest group of CNS depressants, the barbiturates, are still used therapeutically, principally as anesthetic agents and anticonvulsants. Barbiturates are classified based on their chemical structure, duration of action, and pharmacological properties. Gamma-hydroxybutyric acid (GHB) is a simple hydroxylated, short-chain fatty acid with a very short duration of action. However, its detection in biological specimens is complicated by the fact that it is also produced endogenously from the metabolism of the neurotransmitter gamma-aminobutyric acid (GABA) and is produced in postmortem blood specimens. Zolpidem, zopiclone, and zaleplon, collectively known as “z-drugs,” all interact with the GABA receptor in different ways to produce their CNS depressant effects. Some of the newer CNS depressants that are used to manage sleep disorders include melatonin agonists such as ramelteon and tasimelteon, and dual orexin receptor antagonists such as suvorexant. Other sedative-hypnotics, muscle relaxants, and drugs with CNS depressant activity are also discussed.