Comparative efficacy of esomeprazole and omeprazole: Racemate to single enantiomer switch

Both omeprazole and its S enantiomer (esomeprazole) have been available and used to treat symptoms of gastroesophageal reflux disease (GERD) and conditions associated with excessive stomach acid secretion for more than a decade. Controversy exists over improved efficacy of S enantiomer (esomeprazole) over parent racemate (omeprazole). However, a comparison of the clinical outcomes of these products may reveal the rationale for switching from the racemate to single enantiomer. Since enantiomers of omeprazole are equipotent, we compared the outcomes of equal doses of each product to see if both actually differ in their efficacy's or the reported superiority of S enantiomer is just a dose effect.

A web search was carried out for randomized controlled trials with head-to-head comparisons of omeprazole and S-omeprazole. The data were abstracted and after calculating the odd ratios (OR) for the outcomes reported in each study, the combined overall odd ratios (OR') were estimated. The random effect inverse variance method with omeprazole as the reference (OR" = 1) was used.

Out of 1171 studies, 14 were deemed eligible. There was no significant difference in the therapeutic success between omeprazole and S-omeprazole as a part of triple therapy for the treatment of H. pylori in both intention-to-treat (OR', 1.06; CI, 0.83, 1.36; p = 0.63) as well as per-protocol analysis (OR', 1.07; CI, 0.84, 1.36; p = 0.57). For the treatment of gastro-oesophageal reflux disease, S-omeprazole was significantly but marginally superior to the racemate (OR', 1.18; CI, 1.01, 1.38; p = 0.04). The two products were equipotent in all metrics used to assess intragastric pH except for the % patients maintaining a 24 h gastric pH above 4 (1.57; CI, 1.04, 2.381; p = 0.03).

The therapeutic benefit of chiral switch of omeprazole is questionable considering the substantially greater economic burden involved.