Purification process of crude terbinafine from non-metal contaminants

Process for the purification from non-metal contaminants of the allylamine pharmaceutical terbinafine of formula (I) in free base form or acid addition salt form, by distilling crude terbinafine base, preferably by short path distillation, e.g. at a temperature above 100~C and reduced pressure, e.g. 0.2 mbar (method A), optionally together with salt formation of the resultant product under simultaneous precipitation of pure trans isomer (method B), and recovering the pure product in free base or acid addition salt form. Detection of non-metal contaminants such as substance A of formula (II) is preferably effected by RP HPLC analysis with UV detection.