A compound of formula I ##STR1## or a pharmaceutically acceptable salt thereof in which R.sub.1 and R.sub.2 are independently H or methyl, including individual enantiomers or racemates thereof, (for example N,N-dimethyl-1-[1-(4-chlorophenyl)cyclobutyl]-3-methylbutylamine hydrochloride optionally in the form of its monohydrate) is used for treating sleeping disorders including sleep apnoea and snoring.