A citrate salt of (S) -4- (4-chloro-phenyl) -1- {3- [7- (1-hydroxy-1-methyl-ethyl) -11H-110-oxa-1-azadibenzo [a , d] cyclohepten-5-ylidene] -propyl} -3,3-dimethyl-piperidin-4-ol having the structural formula (III): in which at least 70% by weight of the citrate salt is a monocrystalline form, selected from the crystalline form A and the crystalline form B, in which the crystalline form A is characterized by one or more of the characteristics (i) - (iii) :( i) at least one of the diffraction peaks of X-ray powder at 2θ angles of 9.8, 11.7, 12.6, 15.5, 15.7,15.9, 17.3, 17.5, 18.2, 19.0 and 19, 7； (ii) an X-ray powder diffraction pattern substantially similar to that of FIG. 1； (iii) a DSC profile characterized by an endothermic transition that starts at 169oC with a Tmax at176oC, with a heating rate of 5oC / min； and in which crystalline form B is characterized by one or more of the characteristics (iv) - (vi) :( iv) at least one of the powder X-ray diffraction peaks at angles 2θ of 10.6, 11.6 , 12.3, 14.8, 15.8,16.1, 16.7, 18.8, 20.6, 21.7 and 24.5； (v) a substantially X-ray powder diffraction pattern similar to that of FIG. 6； (vi) a DSC profile characterized by an endothermic transition that starts at 184oC with a Tmax at 189oC with a heating rate of 5oC / min.Una sal de citrato de (S)-4-(4-cloro-fenil)-1-{3-[7-(1-hidroxi-1-metil-etil)-11H-110-oxa-1-azadibenzo[a,d]ciclohepten-5-iliden]-propil}-3,3-dimetil-piperidin-4-ol que tiene la formula estructural (III):en la que al menos el 70% en peso de la sal de citrato es una forma monocristalina, seleccionada de la formacristalina A y la forma cristalina B, en la que la forma cristalina A se caracteriza por una o mas de las caracteristicas(i)-(iii):(i) al menos uno de los picos de difraccion de rayos X en polvo a angulos 2&theta； de 9,8, 11,7, 12,6, 15,5, 15,7,15,9, 17,3, 17,5, 18,2, 19,0 y 19,7；(ii) un patron de difraccion de rayos X en polvo sustancialmente similar al de la FIG. 1；(iii) un perfil de DSC caracterizado p
