Dexilant

The first PPI was omeprazole, closely followed by lansoprazole.

After some years, as Astra Zeneca foresaw their profits from omeprazole likely to drop as the drug went out of patent, they introduced esomeprazole (Nexium) which was refined from omeprazole. Basically, it is exactly the same. Omeprazole is a mix of of two mirror image molecules (known as enantiomers to chemists). Both right handed "S" enantiomers and left handed "R" enantiomers inhibit the ability of the parietal cells to produce gastric acid .

AZ separated the enantiomers and, through clever marketing, persuaded customers their S-omeprazole was superior, The R enantiomer is less active but converts to the S enantiomer in use.

AZ sponsored studies comparing 20mg omeprazole with 40mg esomeprazole showing their Nexium worked better. It worked better because there was twice as much. (AZ used flawed logic to claim 40mg esomep was equivalent to 20mg omep because they only used half the enantiomers. Of course, the dose will have had the same numbers so equivalence should have been equal weight.) But they succeeded with their marketing and raked in profits from their new drug until it went out of patent a few years ago when they started targeting other markets, including UK.

Meanwhile, Takeda, seeing their patent on lansoprazole running out, tried the same trick as AZ. They separated their enantiomers, levolansoprazole and dexlansoprazole, marketing the latter as Dexilant. However when they ran advertising campaigns to claim it was superior to lansoprazole, the FDA intervened and banned them as there was no evidence – they'd been fooled once by AZ and weren't going to fall for it again. So Takeda have had to employ other measures. One of those measures is providing free initial doses for doctors to provide to patients in some cases. After all, patients believe it is the drug they need.