Microcrystals of (E)-8-(3,4-dimethoxystyryl)-1,3-diethyl-7-methyl-3,7-dihydro-1H-purine-2,6-dione having an average particle size of less than 50 µm； microcrystals of (E)-8-(3,4-dimethoxystyryl)-1,3-diethyl-7-methyl-3,7-dihydro-1H-purine-2,6-dione having an average particle size of less than 50 µm and a crystallinity of 20% or more or the like, which possess excellent solubility, stability, bioavailability, dispersing property in a pharmaceutical formulation； and the like are provided. A solid pharmaceutical formulation which is characterized by comprising the same is also provided.
