We describe an integrated microdosage system for controlled drug delivery to the human buccal mucosa, with emphasis on the microfluidic components. The system is designed to be part of a dental prosthesis and can thus be inserted, worn, removed, and re-inserted in the oral cavity enabling refill without the need for surgery. An additional advantage is the high bioavailability obtained by trans-mucosal drug administration. The challenges for such a system are the limited space requirement (volume of two back teeth) and the harsh environment in the oral cavity regarding chemical stability and mechanical loads up to 250 N. The main target application is the treatment of chronic diseases and addiction. In-vitro testing resulted in a delivery rate of 8 µl/h of the anti-addiction drug naltrexone solution. In the first human study for oral drug delivery devices, simplified systems without valve have been tested in-vivo. The bioavailability showed to be up to 25 times higher after delivery with the microsystem compared to swallowing of standard tablets.