He could be telling the truth. Although I never thought about doing that mixture, it would be possible if he was extracting his DXM. Or in other words, not being a fucking jack ass and just taking a shit load of cough medicine. Its also probably the only way he wouldnt die... lol
I've built up quite a tolerance taking drugs over the past 10 years. I normally just take the gels now, but I used to do ammonia/petroleum ether extractions.