I was prescribed cyclobenzaprine for severe neck and shoulder tightness. The PA along with the pharmacist cautioned about it's effects and recommended starting with half pills etc. As I did this, I found that even with a full dose I found zero affect on my muscles and zero affect on my state of mind (drowsiness, "buzzed" etc). I could have saved money and taken Tic Tacs. I now am taking Soma twice a day which does seem to minimize the pain and tightness. I only take Crestor and Niaspan for cholesterol and occasional Lodine for my back. Other than the miscellaneous Tylenol-3 for a root canal or something, I do not have any history of drug use with myself or my family. My question is this: being an athletic 185# male, full doses of the above have minimal affects with my muscles where as my co-worker who is 250#-275# is floored with even half does. What are the stats on resistance to these types of medication and what would cause this? Being a well-degree'd radiochemist be as technical as you want.