Benzodiazepines became the most widely prescribed and often misused drugs. They are well absorbed when given orally and act mostly for many hours. In overdose, benzodiazepines cause prolonged sleep, without serious depression of respiration or cardiovascular function. In the presence of other CNS depressants, particularly alcohol, they can cause severe, even life threatening, respiratory depression. The effects can be counteracted by a receptor antagonist, flumazenil. Chronic intoxication by misuse of higher doses causes inhibition, disturbances of memory, speech, emotional instability. Tolerance occurs to the sleep-inducing and euphoric effects, but not to the anxiolytic one. Stopping benzodiazepine treatment after weeks or months ca uses anxiety, insomnia, tremor, dizziness, nausea, vomiting. Many of these signs can be explained as rebound phenomena, but confusion, delusions, convulsions, hyperpyrexia leading to the lethal end in severe cases cannot be explained that way. The withdrawal syndrome is slower in onset and less intense than with barbiturates, probably because of the long plasma half-life of most benzodiazepines. The effects of long-acting benzodiazepines tend to increase with age, causing drowsiness and confusion. Benzodiazepines cross placenta and enter breast milk.

Key words: benzodiazepines – acute poisoning – abuse – withdrawal syndrome