The invention provides a method of assessing the appropriate therapeutic dose of 1-{4-[1-(4-cyclohexyl-3-trifluoromethyl-benzyloxyimino)-ethyl]-2-ethyl-benzyl}-azetidine-3- carboxylic acid to administer to a patient in need thereof, comprising the steps of: (i) testing whether or not the patient has the poor metabolizer genotype； and (ii) if the patient does not have the poor metaboliser genotype, administering 1-{4-[1-(4-cyclohexyl-3-trifluoromethyl-benzyloxyimino)-ethyl]-2-ethyl-benzyl}-azetidine-3-carboxylic acid, or a pharmaceutically acceptable salt thereof, to the patient at the standard therapeutic dose； and (iii) if the patient does have the poor metaboliser genotype, either (a) administering 1-{4-[1-(4-cyclohexyl-3-trifluoromethyl-benzyloxyimino)-ethyl]-2-ethyl-benzyl}-azetidine-3-carboxylic acid, or a pharmaceutically acceptable salt thereof, to the patient at a therapeutic dose below that of the standard therapeutic dose； or (b) not administering 1-{4-[1-(4-cyclohexyl-3-trifluoromethyl-benzyloxyimino)-ethyl]-2-ethyl-benzyl}-azetidine-3-carboxylic acid, or a pharmaceutically acceptable salt thereof, to the patient.
