Sustained-release tablet based on isosorbide 5-mononitrate and process for preparing it

Sustained-release tablet, characterized in that it comprises as active principle, isosorbide 5-mononitrate (5-ISMN) in the form of a powder having the following particle size profile:

• 40 to 60% of isosorbide 5-mononitrate of particle size larger than 80 .mu.m and smaller than 100 .mu.m,
• 20 to 50% of isosorbide 5-mononitrate of particle size larger than 100 .mu.m and smaller than 250 .mu.m,
• approximately 5% of isosorbide 5-mononitrate of particle size larger than 250 .mu.m and smaller than 500 .mu.m,
• approximately 0.5% of isosorbide 5-mononitrate of particle size larger than 500 .mu.m,
• approximately 0% to 34.5% of isosorbide 5-mononitrate having a particle size smaller than 80 .mu.m,
• in a homogeneous dispersion in a hydrophilic matrix comprising at least one swelling agent and at least one diluent, at a swelling agent to diluent weight ratio of between 0.2 and 0.7, said swelling agent containing a hydrophilic polymeric substance of apparent viscosity between about 0.1 and 100 Pa.s.