It typically happens in about 5-10% of patients. It's not all that common as far as adverse reactions go. The frustrating part is that it can be easily avoided by adding a second drug like a proton pump inhibitor (Prilosec, Nexium), but doctors tend to not know that, and a lot of pharmacists are too...lazy, pathetic, etc....to step in and suggest it. Very frustrating that people have to go through it.
Yep, my wife is a Dietitian, it's surprising how little some Drs know about some things. Most of them that she works with are very good, but you get a few who know everything, yet know nothing.