BDZs, designer BDZs, and Z-drugs: pharmacology and misuse insights

Benzodiazepines (BZDs) are a widely prescribed class of sedative-hypnotics compounds for the treatment of a broad range of conditions as anxiety and obsessive-compulsive disorders, phobias, sleep related problems associated with insomnia and for the management of alcohol and GHB withdrawal. Zolpidem, zopiclone and zaleplon, commonly known as Z-drugs are non-benzodiazepine hypnotic drug with pharmacology similar to BDZs. Despite their usefulness, BDZs and Z-drugs present a potential for abuse and dependence. Moreover, the non-medical use of BDZs is a well-known phenomenon and represents an increasingly widespread public health problem since is associated with an elevated risk of serious health consequences or fatal overdose, especially among specific group of users. The spectrum of BDZs and Z-drugs misuse is extended by new synthetic BDZs, which may pose high risks to users, since the majority have never undergone clinical trials or tests and consequently their pharmacology and toxicology is largely unknown.

The clinical and forensic toxicology of Z-drugs

The Z-drugs zolpidem, zopiclone, and zaleplon were hailed as the innovative hypnotics of the new millennium, an improvement to traditional benzodiazepines in the management of insomnia. Increasing reports of adverse events including bizarre behavior and falls in the elderly have prompted calls for caution and regulation. Z-drugs have significant hypnotic effects by reducing sleep latency and improving sleep quality, though duration of sleep may not be significantly increased. Z-drugs exert their effects through increased γ-aminobutyric acid (GABA) transmission at the same GABA-type A receptor as benzodiazepines. Their pharmacokinetics approach those of the ideal hypnotic with rapid onset within 30 min and short half-life (1-7 h). Zopiclone with the longest duration of action has the greatest residual effect, similar to short-acting benzodiazepines. Neuropsychiatric adverse events have been reported with zolpidem including hallucinations, amnesia, and parasomnia. Poisoning with Z-drugs involves predominantly sedation and coma with supportive management being adequate in the majority. Flumazenil has been reported to reverse sedation from all three Z-drugs. Deaths from Z-drugs are rare and more likely to occur with polydrug overdose. Z-drugs can be detected in blood, urine, oral fluid, and postmortem specimens, predominantly with liquid chromatography-mass spectrometry techniques. Zolpidem and zaleplon exhibit significant postmortem redistribution. Zaleplon with its ultra-short half-life has been detected in few clinical or forensic cases possibly due to assay unavailability, low frequency of use, and short window of detection. Though Z-drugs have improved pharmacokinetic profiles, their adverse effects, neuropsychiatric sequelae, and incidence of poisoning and death may prove to be similar to older hypnotics.

Methods for the analysis of nonbenzodiazepine hypnotic drugs in biological matrices

Zopiclone, zolpidem and zaleplon (Z-drugs) are nonbenzodiazepine hypnotic drugs that are used for the treatment of insomnia. These drugs were developed with the intent to overcome some disadvantages of benzodiazepines, such as dependence and next day sedation. In general, the nonbenzodiazepine hypnotic drugs are administered in oral doses daily and are widely biotransformed in the body. A large number of analytical methods based on chromatographic and electrophoretic techniques for the quantification of Z-drugs and their metabolites in biological matrices have been reported. In this review, the bioanalytical methods for Z-drugs were reviewed with the focus placed on sample preparation procedures and the separation techniques used. Furthermore, as these drugs are also reported as drugs of abuse or in drug-facilitated crime, screening methods that simultaneously cover these drugs and also other drugs of abuse were included in this review.