I keep 0.5mg alprazolam in my psychedelic kit specifically for emergencies. During an LSD trip (150ug) that turned dark around the 4-hour mark — thought loops, paranoia, feeling trapped in eternity — I decided to use the abort switch.
T+0:00 placed the tablet under my tongue for faster absorption. T+0:10 the first hint of relief. The anxious edge of the trip started softening. T+0:20 the thought loops broke. I could think linearly again. T+0:30 the trip was still present but defanged. Visuals continued mildly but the psychological distress was completely gone.
Important notes: it doesn't end the trip, it removes the anxiety and panic. You'll still have mild residual effects. The dose should be low — 0.25-0.5mg is sufficient. You don't need a full bar and you don't want one.
Having this available actually makes me less likely to need it. Knowing I have an exit reduces pre-trip anxiety, which reduces the chance of a difficult experience. I've used it once in about 15 trips.
Every psychonaut should have a trip killer on hand. Alprazolam, trazodone, or a similar anxiolytic. It's a seatbelt — you hope you never need it, but you always wear one.