text: * Omeprazole (brand names Losec, Prilosec, Zegerid, Ocid, Lomac, Omepral, Omez, Ultop, Ortanol, Gastrozol)
  Omeprazole was the first PPI on the market, in 1988. It is a 1:1 racemate drug with a backbone structure of timoprazole, but substituted with two methoxy and two methyl groups. One of the methoxy group is at position 6 of the bensoimidazole and the other at position 4 of the pyridine and the methyl groups are at position 3 and 5 of the pyridine.
  Omeprazole is available as enteric-coated tablets, capsules, chewable tablets, powder for oral suspensions and powder for intravenous injection.
  * Lansoprazole (brand names: Prevacid, Zoton, Inhibitol, Levant, Lupizole, Lancid, Lansoptol, Epicur)
  Lansoprazole was the second of the PPI drugs to reach the market, being launched in Europe in 1991 and the US in 1995.
  It has no substitutions at the benzimidazole  but two substituents on the pyridine, methyl group at position 3 and a trifluoroethoxy group at position 4. The drug is a 1:1 racemate of the enantiomers dexlansoprazole and levolansoprazole. It is available in gastroresistant capsules and tablets as well as chewable tablets.
  * Pantoprazole (brand names: Protonix, Somac, Pantoloc, Pantozol, Zurcal, Zentro, Pan, Nolpaza, Controloc, Sunpras)
  Pantoprazole was the third PPI and was introduced to the German market in 1994.
  It has a difluoroalkoxy sidegroup on the benzimidazole part and two methoxy groups in position 3 and 4 on the pyridine.
  Pantoprazole was first prepared in April 1985 by a small group of scale-up chemists. It is a dimethoxy-substituted pyridine bound to a fluoroalkoxy substituted benzimidazole.
  Pantoprazole sodium is available as gastroresistant or delayed release tablets and as lyophilized powder for intravenous use.
  * Rabeprazole (brand names: Zechin, Rabecid, Nzole-D, AcipHex, Pariet, Rabeloc, Zulbex, Ontime, Noflux)
  Rabeprazole is a novel benzimidazole compound on market, since 1999 in USA. It is similar to lansoprazole in having no substituents on its benzimidazole part and a methyl group at site 3 on the pyridine, the only difference is the methoxypropoxy substitution at site 4 instead of the trifluoroethoxy group on lansoprazole.
  Rabeprazole is marketed as rabeprazole sodium salt. It is available as enteric-coated tablets.
  * Esomeprazole (brand names: Nexium, Esotrex, Emanera, Neo-Zext)
  In 2001 esomeprazole was launched in USA, as a follow-up of omeprazoles patent.
  Esomeprazole is the (S)-(−)-enantiomer of omeprazole and provides higher bioavailability and improved efficacy, in terms of stomach acid control, over the (R)-(+)-enantiomer of omeprazole. In theory, by using pure esomeprazole the effects on the proton pump will be equal in all patients, eliminating the "poor metabolizer effect" of the racemate omeprazole. It is available as delayed-release capsules or tablets and as esomeprazole sodium for intravenous injection/infusion. Oral esomeprazole preparations are enteric-coated, due to the rapid degradation of the drug in the acidic condition of the stomach. This is achieved by formulating capsules using the multiple-unit pellet system.
  Although the (S)-(−)-isomer is more potent in humans, the (R)-(+)-isomer is more potent in testings of rats, while the enantiomers are equipotent in dogs.
  * Dexlansoprazole (brand names: Kapidex, Dexilant)
  Dexlansoprazole was launched as a follow up of lansoprazole in 2009.
  Dexlansoprazole is an (R)-(+)-enantiomer of lansoprazole, marketed as Dexilant. After oral appliance of the racemic lansoprazole, the circulating drug is 80% dexlansoprazole. Moreover, both enantiomers have similar effects on the proton pump. Consequently, the main advantage of Dexilant is not the fact that it is an enantiopure substance. The advantage is the pharmaceutical formulation of the drug, which is based on a dual release technology, with the first quick release producing a blood plasma peak concentration about one hour after application, and the second retarded release producing another peak about four hours later.