i wouldn't advise it. i tried looking around to see some of the effects but could only find cases on the gas form of butane, rather than liquid ingestion. not sure if there's a difference there, but the gas form in very high concentrations seems pretty lethal with you ending up having a seizure then ventricular fibrillation before death.
plenty of things have that warning, but don't have great odds of killing you and usually just cause you a ton of suffering. rule of thumb is, if you don't know how much you have to ingest, what effects you'll experience, the odds of a fatal outcome, aftermath of a failure, then i'd say no. there are much better methods out there with actual in-depth info and numerous success stories. some methods are tried and true for thousands of years like hanging, others are relatively new like SN. but they both have plenty of info to research and that's key in making a informed decision. CTB should never be done uninformed and on a whim, imo.