Solid composition for the oral administration of dyes and diagnostic use thereof

A solid composition for oral administration containing at least one dye in association with at least one physiologically acceptable excipient, said composition comprising:

• (a) at least one dye selected from among methylene blue, congo red, carmine indigo, toluidine blue or mixtures thereof;
• (b) a first matrix in which said at least one dye is incorporated, wherein said first matrix comprises at least one lipophilic compound having a melting point below 90° C. and at least one amphiphilic compound;
• (c) a second matrix comprising at least one hydrophilic compound, wherein the first matrix is dispersed in the second matrix;
• (d) optionally other physiologically acceptable excipients;
• and
• (e) optionally a gastro-resistant coating.