Do the tutorials to learn how to work with lists and TinyDB
The simple solution would be to use the alarmmanager extension App Inventor Extensions: Alarm Manager | Pura Vida Apps it is just to use one method to set a repeating alarm...
However you said earlier
So let me suggest you to reduce the requirements and simplify your project.. just use the free alarm extension App Inventor Extensions: Alarm | Pura Vida Apps and set an alarm to take the next medicament... and after getting the alarm, opem the app and set the alarm to take the next medicament, etc
A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook http://www.appinventor.org/book2 ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here http://www.appinventor.org/content/CourseInABox/Intro and the aia files for the projects in the book are here: http://www.appinventor.org/bookFiles
How to do a lot of basic things with App Inventor are described here: http://www.appinventor.org/content/howDoYou/eventHandling .
Also do the tutorials Our Tutorials! to learn the basics of App Inventor, then try something and follow the Top 5 Tips: How to learn App Inventor
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.