1.没错,又是所谓的状语从句的省略或非谓语从句语法：当状语从句的主语为it或和主句主语相同时,且从句的谓语以be动词开头,则可以省略状语从句的主语和be动词.
即：when taken = when (the drug) is taken
2.to be discussed是不定式的被动结构,做后置定语,修饰the problems.
the problems to be discussed意思是“将要被讨论的问题”.
另附三种后置定语形式如下：
被修饰词 + to be done“将要被...的...”,如：the meeting to be held 将要被举行的会议；
被修饰词 + being done “正在被...的...”,如：the meeting being held 正在举行的会议
被修饰词 + done “已经被...的...”,如：the meeting held 已经举行了的会议