Does long-term medication with a proton pump inhibitor induce a tolerance to H2 receptor antagonist?

When does proton pump inhibitor treatment become long term? A scoping review

OBJECTIVE

Proton pump inhibitor (PPI) use has risen substantially, primarily driven by ongoing use over months to years. However, there is no consensus on how to define long-term PPI use. Our objectives were to review and compare definitions of long-term PPI use in existing literature and describe the rationale for each definition. Moreover, we aimed to suggest generally applicable definitions for research and clinical use.

DESIGN

The databases PubMed and Cochrane Library were searched for publications concerning long-term use of PPIs and ClinicalTrials.gov was searched for registered studies. Two reviewers independently screened the titles, abstracts, and full texts in two series and subsequently extracted data.

RESULTS

A total of 742 studies were identified, and 59 met the eligibility criteria. In addition, two ongoing studies were identified. The definition of long-term PPI use varied from >2 weeks to >7 years. The most common definition was ≥1 year or ≥6 months. A total of 12/61 (20%) of the studies rationalised their definition.

CONCLUSION

The definitions of long-term PPI treatment varied substantially between studies and were seldom rationalised.In a clinical context, use of PPI for more than 8 weeks could be a reasonable definition of long-term use in patients with reflux symptoms and more than 4 weeks in patients with dyspepsia or peptic ulcer. For research purposes, 6 months could be a possible definition in pharmacoepidemiological studies, whereas studies of adverse effects may require a tailored definition depending on the necessary exposure time. We recommend to always rationalise the choice of definition.

Effects of oral rehydration therapy on gastric volume and pH in patients with preanesthetic H2 antagonist

Recent preanesthetic fasting practice allows patients to take clear fluids up to 2 h before surgery without taking any antacid for the prophylaxis of aspiration pneumonia; this practice is defined as oral rehydration therapy (ORT). It has been reported that with ORT the gastric volume may be significantly lower than that with a standard fasting regimen, although in a standard fasting regimen without preanesthetic antacid, gastric pH and volume values could be critical for causing aspiration pneumonia. In this study we compared gastric fluid status in patients with ORT and those with a standard fasting regimen; patients in both groups received a preanesthetic H(2) antagonist. One hundred and four patients were randomly assigned to either the ORT or standard fasting group, and all were given roxatidine 75 mg 2 h before surgery. After the induction of anesthesia, the gastric contents were collected via a gastric tube to measure gastric volume and pH. Neither gastric volume nor pH differed between the groups (ORT 9.6 ± 8.2 ml and 5.6 ± 1.7, respectively, vs. standard fasting 8.5 ± 6.8 ml and 5.5 ± 1.7, respectively). These data suggest that ORT may not reduce gastric volume in patients receiving a preanesthetic H(2) antagonist.

A marked increase in gastric fluid volume during cardiopulmonary bypass

Major physiological stress occurs during cardiac surgery with cardiopulmonary bypass. This is related to hypothermia and artificial organ perfusion. Thus, serious gastrointestinal complications, particularly upper gastrointestinal bleeding, sometimes follow cardiac surgery. We have compared the antisecretory effects of a preanesthetic H(2) antagonist (roxatidine, cardiopulmonary bypass-H(2) group, n = 15) and a proton pump inhibitor (rabeprazole, cardiopulmonary bypass-PPI group, n = 15) in patients undergoing cardiac surgery with cardiopulmonary bypass, and also compared in patients undergoing a off-pump coronary artery bypass graft surgery (off-pump cardiopulmonary bypass-H(2) group, n = 15). Gastric pH (5.14 ± 0.61) and gastric fluid volume (13.2 ± 2.4 mL) at the end of surgery in off-pump cardiopulmonary bypass-H(2) groups was significantly lower and higher than those in both cardiopulmonary bypass-H(2) (6.25 ± 0.54, 51.3 ± 8.0 mL) and cardiopulmonary bypass-PPI (7.29 ± 0.13, 63.5 ± 14.8 mL) groups, respectively although those variables did not differ between groups after the induction of anesthesia. Plasma gastrin (142 ± 7 pg/mL) at the end of surgery and maximal blood lactate levels (1.50 ± 0.61 mM) in off-pump cardiopulmonary bypass-H(2) group were also significantly lower than those in both cardiopulmonary bypass-H(2) (455 ± 96 pg/mL, 3.97 ± 0.80 mM) and cardiopulmonary bypass-PPI (525 ± 27 pg/mL, 3.15 ± 0.44 mM) groups, respectively. In addition, there was a significant correlation between gastric fluid volume and maximal blood lactate (r = 0.596). In conclusion, cardiopulmonary bypass may cause an increase in gastric fluid volume which neither H(2) antagonist nor PPI suppresses. A significant correlation between gastric fluid volume and maximal blood lactate suggests that gastric fluid volume may predict degree of gastrointestinal tract hypoperfusion.