Maybe this is an attempt to find a combination of drugs that will confuse the fuck out of any pathologist who eventually examines him, which drug out of twenty do you put on the death certificate, or do you just put down death by misadventure.
The harm reduction answer is simple, if you are so concerned about drug interactions and safety quit the long term methadone use and then taper and quit the benzo dependence then you can take whatever you like without having to second guess what is and isn't safe interaction-wise. Or don't its your choice, statistically Russian roulette is fine on average 5 times out of 6. If you get it wrong you're dead. You don't get another go because some random on the interwebs said it was OK.
The harm reduction answer is simple, if you are so concerned about drug interactions and safety quit the long term methadone use and then taper and quit the benzo dependence then you can take whatever you like without having to second guess what is and isn't safe interaction-wise. Or don't its your choice, statistically Russian roulette is fine on average 5 times out of 6. If you get it wrong you're dead. You don't get another go because some random on the interwebs said it was OK.