The composition contains an indirect sympathomimetic compound (Ia) and tyrosine or a tyrosine precursor such as phenylalanine. (Ia) is selected from ephedrine amphetamine phenylpropanolamine pseudoephedrine norpseudoephedrine diethylpropione benzphetamine phendimetrazine phenmetrazine phentermine chlorphentermine aminorex or mixtures of these. Phenylpropanolamine amphetamine and ephedrine are preferred. The weight ratio of the tyrosine or its precursor to (Ia) is 1.5:1-5000:1. Daily dose is e.g....