Drug classes are not always filled with equivalent drugs. The first ACE inhibitor – captopril – has a shorter half life than the rest of the available class, and thus is more difficult to use. One could find many such examples of the first being the least useful. However, when it comes to proton pump inhibitors, it appears that they all work similarly. That is why the release of generic omeprazole (Prilosec) is so exciting. And physicians are responding predictably and prescribing the generic! Generic Drug Prilosec Off to Strong Start in U.S.