Preparation of morphine compounds with low content of ~a-~b unsaturated compounds, comprises: contacting crude morphine compound with a base in conditions allowing Michael addition reaction on the ~a-~b unsaturated compounds； separating morphine compound of the reaction mixture； and optionally separating the addition product formed from the morphine compound. An independent claim is included for a composition comprising at least 99% in dry weight of morphine compound or its salt and ~a-~b unsaturated compound having a content of less than 100 ppm. ACTIVITY : Analgesic. MECHANISM OF ACTION : None given.
