The present invention related to the administration of bioactive agents via oral fast dispersing/dissolving drug delivery systems for treating illnesses of patient with critical buccal condition, leading to difficulties in swallowing oral medicine forms and thus difficulties in treating said illnesses. Particularly, the present invention discloses the administration of bioactive agents via oral fast dispersing/dissolving drug delivery systems for treating illnesses of patient with dysphagia and/or odynophagia and/or aspiration risk. Another aspect of the present invention is the administration of bioactive agents via oral fast dispersing/dissolving drug delivery systems for the treatment of dysphagia and/or odynophagia and/or aspiration risk.