Amy, what did they say the cost was for the NAC and shipping. Have u ever thought about getting your GSH levels tested to see where they r at. We did GSH almost 18 months ago for about 2 months, I did not see any negitve side effects, nor did I see any benefit, but not sure at this point if it would be noticible with his good health. It is an expensive treatment not covered by insurance, by reading some of the articles I have, I do think there is a cellular conection to GSH and CF. I would consider starting him back on a daily regimine, but first I want to see what his GSH levels are and retest after being on NAC.