Current Challenges
Rapid Metabolism of PPIs
High-dose PPI therapy is a key component of therapy for peptic ulcer healing. PPIs are metabolized by the cytochrome P450 system, which is comprised of multiple isoenzymes. CYP2C19, an isoenzyme involved in PPI metabolism, has 21 polymorphisms, which have variable effects leading to ultra-rapid, extensive, intermediate, or poor metabolism of PPIs.10 With rapid metabolism of PPIs, standard dosing can result in inadequate suppression of acid secretion. Despite this knowledge, routine testing of CYP2C19 phenotype is not recommended due to the cost of testing. Instead, inadequate ulcer healing should prompt consideration of increased PPI dosing to 80 mg orally twice daily, which may be sufficient to overcome rapid PPI metabolism.11
Relative Potency of PPIs
In addition to variation in PPI metabolism, the relative potency of various PPIs has been questioned. A review of all available clinical studies of the effects of PPIs on mean 24-hour intragastric pH reported a quantitative difference in the potency of 5 PPIs, with omeprazole as the reference standard. Potencies ranged from 0.23 omeprazole equivalents for pantoprazole to 1.82 omeprazole equivalents for rabeprazole.12 An additional study of data from 56 randomized clinical trials confirmed that PPIs vary in potency, which was measured as time that gastric pH is less than 4. A linear increase in intragastric pH time less than 4 was observed from 9 to 64 mg omeprazole equivalents; higher doses yielded no additional benefit. An increase in PPI dosing from once daily to twice daily also increased the duration of intragastric pH time less than 4 from 15 to 21 hours.13 Earlier modeling of the relationship between duodenal ulcer healing and antisecretory therapy showed a strong correlation of ulcer healing with the duration of acid suppression, length of therapy, and the degree of acid suppression. Additional benefit was not observed after intragastric pH rose above 3.14 Thus, as the frequency and duration of acid suppression therapy are more important than PPI potency, PPIs can be used interchangeably.13,14
Addressing Underlying Causes
Continued NSAID Use. Refractory peptic ulcers are defined as those that do not heal despite adherence to 8 to 12 weeks of standard acid-suppression therapy. A cause of refractory peptic ulcer disease that must be considered is continued NSAID use.1,15 In a study of patients with refractory peptic ulcers, 27% of patients continued NSAID use, as determined by eventual disclosure by the patients or platelet cyclooxygenase activity assay, despite extensive counseling to avoid NSAIDs at the time of the diagnosis of their refractory ulcer and at subsequent visits.16 Pain may make NSAID cessation difficult for some patients, while others do not realize that over-the-counter preparations they take contain NSAIDs.15
Another group of patients with continued NSAID exposure are those who require long-term NSAID therapy for control of arthritis or the management of cardiovascular conditions. If NSAID therapy cannot be discontinued, the risk of NSAID-related gastrointestinal injury can be assessed based on the presence of multiple risk factors, including age > 65 years, high-dose NSAID therapy, a history of peptic ulcer, and concurrent use of aspirin, corticosteroids, or anticoagulants. Individuals with 3 or more of the preceding risk factors or a history of a peptic ulcer with a complication, especially if recent, are considered to be at high risk of developing an NSAID-related ulcer and possible subsequent complications.17 In these individuals, NSAID therapy should be continued with agents that have the lowest risk for gastrointestinal toxicity and at the lowest possible dose. A meta-analysis comparing nonselective NSAIDs to placebo demonstrated naproxen to have the highest risk of gastrointestinal complications, including GIB, perforation, and obstruction (adjusted rate ratio, 4.2), while diclofenac demonstrated the lowest risk (adjusted rate ratio, 1.89). High-dose NSAID therapy demonstrated a 2-fold increase in risk of peptic ulcer formation as compared to low-dose therapy.18
In addition to selecting the NSAID with the least gastrointestinal toxicity at the lowest possible dose, additional strategies to prevent peptic ulcer disease and its complications in chronic NSAID users include co-administration of a PPI and substitution of a COX-2 selective NSAID for nonselective NSAIDs.1,9 Prior double-blind, placebo-controlled, randomized, multicenter trials with patients requiring daily NSAIDs demonstrated an up to 15% absolute reduction in the risk of developing peptic ulcers over 6 months while taking esomeprazole.19