The use of benzodiazepines has increased sharply since they were first synthesised in the 1950s, and they have gradually replaced barbiturates and other hypnotic and anti-anxiety drugs (1). In 2008, 6 % of the Norwegian population was prescribed at least one benzodiazepine (2). Since the 1990s, z-hypnotics such as zopiclone (Imovane, Zopitin) and zolpidem (Stilnoct), have taken over for insomnia (3).
Benzodiazepines and z-hypnotics are chemically dissimilar, but both act by increasing the effect of the neurotransmitter gamma-aminobutyric acid (GABA) on GABAA receptors in the brain. This reduces neuronal excitability, with a hypnotic, anxiolytic and anticonvulsive effect as a result (4, 5).
Benzodiazepines can also be used as intoxicants, and have adverse long-term effects in the form of impaired cognitive abilities and risk of dependence. Overdosing results in altered level of consciousness, impaired coordination, amnesia and respiratory depression. The risk of an overdose is greatest in combination with other intoxicants with depressant effects. Flumazenil is an antidote, but has a short half-life and may cause seizures (4, 5).
Z-hypnotics cause less intoxication and entail less risk of inducing dependence (5), but the mechanism is otherwise so similar to benzodiazepines that we have chosen to include them in this study. In the following we use benzodiazepines as a collective term.
12 % of benzodiazepine users account for 59 % of prescribed use in Norway (6). A Swiss study found that heavy users often alternate between legal and illegal strategies to acquire benzodiazepines (7). In an anonymous British questionnaire survey (8), sources of benzodiazepines were general practitioners (55 %), friends and family (40 %), online purchasing (27 %), street sales (20 %) and abroad (11 %). Multiple sources were used by 31 %.
We describe acute poisonings treated by the main A&E clinic in Oslo, due to substance abuse of benzodiazepines, with emphasis on the type of benzodiazepine and other intoxicants they were taken in combination with.