Phenobarbital was synthesized by the German organic chemist Emil Fischer in 1911. It is approved and marketed in the Czech Republic as an antiepileptic in tablet and injection form. Although phenobarbital as a hypnosedative has been outdated for decades, it is still available as a substance and used for the individual compounding of various obsolete mixtures. It is likely that prescribers are unaware of the risks associated with their use. The article presents a brief pharmacological profile of phenobarbital, lists the most often used mixtures, substance consumption and risks associated with its use.