Short answer: it is sometimes done, but both mirtazapine (Remeron) and lorazepam (Ativan) can blunt psilocybin’s effects. The impact varies with dose, how long and how often you use them, and the reasons they were prescribed. I cannot verify your specific situation.
Mirtazapine interacts with serotonin receptors, including 5-HT2A, which is central to classic psychedelic effects. Many people report a flatter experience with fewer visuals and less emotional depth. Stopping mirtazapine just to intensify a session can backfire with withdrawal, sleep disruption, or mood changes, so any adjustment should be discussed with your prescriber.
Lorazepam enhances GABA activity, often lowering anxiety and body tension. It can make the session feel calmer and less intense, though psychedelic qualities may still be present. Some people avoid lorazepam for a period before a session to limit interaction, but only if that is safe for you and agreed with your clinician.
If you are considering a guided session, do an intake and prepare carefully, especially when using medication. For an overview of preparation and integration in this context, see psilocybin therapy. Please discuss your plans with your own doctor before making changes.
Stay safe and take your time.