Barbiturates are CNS depressants used therapeutically as sedatives, hypnotics and anticonvulsants . Short to intermediate acting barbiturates may generally be detected for 1 to 4 days following use. Long acting barbiturates, such as Phenobarbital, may be detected for several weeks after chronic use. False positive results may be seen with Aminoglutethimide, Dezocine, Glutethimide, Primidone & Retinoic acid.