1. A pharmaceutical formulation which comprises in addition to at least one carrier diluent or adjuvant at least one neuroleptic compound in an amount effective to exert a neuroleptic effect in a patient requiring such treatment and melatonin in an amount effective to ameliorate or prevent symptoms of tardive dyskensia developing in the patient. 2. A pharmaceutical formulation according to claim 1 characterized by at least one of the following features: it is adapted for oral rectal parenteral o...