[Oral medication via feed and water -- pharmacological aspects]. 
By treatment of single animals or a live stock a treatment regimen has to be chosen, which guarantees a sufficient concentration of the administered drug in the target tissue.  On the other hand, particular care has to be taken to avoid that single animals get a too high, intolerable dose of the administered drug.  These elementary requirements must be met by the attending veterinarian. The treatment schedule must be in line with the current phamaceutical law.  Some of the most outstanding problems associated with application via feed and water are discussed.  Crucial factors apart from practicability are the bioavailability depending on pharmaceutical form and the avoidance of displacements of drugs.  Future efforts should focus on the optimization of oral medication.