Drug poisonings of all forms are only effective in about 1.5% of cases. Just an FYI.
Besides barbiturates (e.g., pentobarbital AKA N) or inorganic salts (e.g., sodium nitrite), most pharmaceutical drugs are not fatal as they have been designed to be difficult to commit suicide with.
If they are fatal they will likely be very painful, damagimg certain organs or bodily systems in the process, potentially causing seizures or cognitive dysfunctions, painful heart palpitations/arythmias, or feelings of suffocation along the way.
I don't recommend drug poisonings asides from those recommended in the peaceful pill handbook (N, SN, cardiac switch, etc). For this reason.