The present disclosure relates to solid oral compositions of silodosin or its pharmaceutically acceptable salt thereof. More particularly capsule compositions of silodosin with one or more pharmaceutically acceptable excipients and process for their preparation.

The invention relates to a process for preparing silodosin. The invention relates to the preparation of substantially pure silodosin. The invention also relates to silodosin solid particles wherein 90 volume-percent of the particles (D90) are less than 10 microns and a process for achieving the particle size (D90) less than 10 microns.

Provided is a percutaneous absorption type formulation of a drug such as imidafenacin and silodosin, wherein stable absorption through the skin is realized. The percutaneous absorption type formulation containing a drug such as imidafenacin and silodosin further contains a transdermal absorption promoting agent, and fatty acid ester and/or fatty acid amide that further improve(s) the function of the transdermal absorption promoting agent.