A pillbox with eight compartments. One for each weekday and one to be selected during transport. The lid snaps in permanently (you might have to press tightly to connect both parts).
A locking mechanism prevents unwanted opening of the compartments. To rotate the lid, pull it gently while turning.
[Update 2017-03-24] "Wochenspender V2.stl" is a modified version with the names of the weekdays (MO-DI-MI-DO-FR-SA-SO) written on the outside rim of the bottom part.
[Update 2017-04-16] There is now a spanish version, too (LU-MA-MI-JU-VI-SA-DO): "Wochenspender Espanol.stl"
The wall thickness is 1.2 mm. PLA is sufficient, as long as you keep the box away from heat and direct sunlight (which you should do anyway because of the medicine inside).