it is a well-known fact that AF took drugs like barbiturates. Felix Yusupov in his memories on the murder of Rsputin also mentions that Nickolay II took drugs as well. Yusupov decided to murder Rasputin so he decided to establish a closer relation with him through Munya Golovina, Rasputin`s admirer and adherer. When Rasputin and Yusupov became a sort of "friends", the former boasted about his influence on N and A. At that time a famous doctor Badmaev was also admitted to Aleksandra Fedorovna`s ( it was during WW1), and Rasputin boasted that the Tzar is given some "herbs" that make hhim "calm" and make him "obey". I guess , these were some herbs which, taken in bigger doses, could have produced such an effect. I will try to find an appropriate passage in Yussupov1s book