Carisoprodol (Soma) is often not given its due credit. A lot gets lost in translation, I feel with this drug specifically. First off, it's a pro-drug. Like how we know Codeine is metabolized into Morphine in the body, Carisoprodol is metabolized into a drug called Meprobamate (Miltown). To further confuse things, Meprobamate is known as a "non-Barbiturate" drug.
A non-Barbiturate is in fact, any drug that is basically identical in effects to a Barbiturate, while still being chemically distinct from actual Barbiturates.
Furthermore, a lot of the younger folks, including myself (I know all of this from reading, not from experience) don't really know what Barbiturates are. They are potent sedative drugs, euphoric, addictive and extremely dangerous when used in large dose and/or polypharmacy.
So many people have died from Barbiturates that it's impossible to even begin to list them. They were notorious for taking people out in combination with Alcohol and if you're talking about using Barbiturates with say, powerful Opioids, you're really taking your life into your own hands.
The answer is that Carisoprodol is essentially a Barbiturate, very dangerous, capable of killing and at its worst when combined with other sedatives. My advice is to learn how the shit works before going on the laundry list of potential combinations. Don't underestimate the danger of these. I know they're readily available, but it's what I would call a pretty extreme loophole as a result of knowledge that these are so readily available