Never, his ms does mess with his lungs and he gets bronchial infections, I've never given it to him when he has a cough, though LSD has worked wonders for us both when we've had coughs in the past, so I don't give him anything off yellow that might be harsh just the white crystals. Keep in mind this guy is one of the most spiritual people I know, It's pretty miraculous that he's kicking it as healthy as he is. IMO these substance should go in combo with spiritual practice especially if ones intent is to become well also keep in mind that everyone is different. Make surw your friend is honest about how he's doing physically, mentally and spiritually, if he's in good health and spirits say a prayer and if he's ready start him off slow. That's the best advice I can give.
One question though is your friend a smoker, tobacco or marijuana?