Blockade of the gastric acid pump, hydrogen-potassium adenosine triphosphat
ase (H+,K+-ATPase), by proton pump inhibitors (PPIs) is one of the most eff
ective treatments for gastro-oesophageal reflux disease (GORD), In ideal te
rms, however, the inhibition of acid secretion should occur rapidly, on the
first dose, and remain virtually complete in a dose-dependent manner, Seve
ral aspects of PPI biochemistry prevent the achievement of this ideal. PPIs
target the final step of acid secretion and, due to the covalent nature of
their inhibition of H+,K(+-)ATPase, cause suppression of acid secretion lo
ng after the drug has been eliminated. Their disadvantages stem from their
mechanism of action: they require accumulation and activation in active par
ietal cells and have short plasma half-lives, hence a relatively slow onset
of action, An extension of PPI plasma half-lives is an obvious goal, possi
bly via exploitation of probable differences in the metabolism of the two e
nantiomers (structural mirror images) present in current PPI formulations:
e,g., clinical data on the S-enantiomer of omeprazole (esomeprazole) sugges
t some improvement in acid control, An alternative is to generate a pro-dru
g of a PPI; plasma levels of the PPI would thus depend on release of the ac
tive metabolite from the pro-drug, again extending drug half-life. Another
area of active investigation is the development of acid-pump antagonists to
inhibit acid secretion at its final step. Eur J Gastroenterol Hepatol 13 (
suppl 1):S35-S41 (C) 2001 Lippincott Williams & Wilkins.