Are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They have addiction potential, both physical and psychological. Barbiturates have now largely been replaced by benzodiazepines in routine medical practice - for example, in the treatment of anxiety and insomnia – mainly because benzodiazepines are believed to be less dangerous. Some examples of Barbiturates are: hexobarbital (Evipal®), thiamyl (Surital®). (Secinal®), butabarbital (Butisol®), and metharbital (Gemonil®). If physical dependency occurs, withdrawal symptoms occur if the drug is abruptly stopped. Withdrawal form these drugs produce anxiety, tremors, nightmares, insomnia, vomiting and seizures.