I propose a message that arrives at a certain time, depending on the drug, to give a hint of how your character is feeling that could help you properly roleplay being high as a kite.
An example for marcy:
10 seconds after use: You feel your pulse jump up.
1 minutes after use: You taste something acidic in the back of your throat.
5 minutes after use: You're feeling really driven to do...something. Maybe some more marcy?
And then, towards the end of the ride, something to note that you feel yourself coming down. Drugs in real life tend to have a cycle in the same way, and you feel it as you move through the experience. You take them. It builds. It builds more. It peaks. It falls. It falls some more. You eventually sober up. You feel hungover/withdrawals from the experience.
Just a jumping off point, maybe the community could come together to write these as inspiration for the staff to finish off?