Pharmacology
PPIs are more potent at acid suppression than H2-receptor antagonists. They block the final common pathway of acid secretion by irreversibly binding to and inactivating the proton pump (H+/K+-ATPase exchange). This results in a greater proportion of healed erosive oesophagitis compared with the use of H2-receptor antagonists (84% ± 11% vs 52% ± 17%).15
PPIs have a short plasma half-life (mostly 1–2 hours) and are only effective when proton pumps are active (in the postprandial period). The timing of administration is therefore important, with the greatest efficacy being seen when PPI concentrations are maximal at the time of a meal. As the inactivation of the proton pump is irreversible, the biological half-life of the drug is considerably longer than its plasma half-life. Consequently, if an increase in acid suppression is required, a second dose taken later in the day (e.g. before the evening meal) is more effective than doubling the morning dose.
Start treatment with once-daily dosing 30–60 minutes before a meal. This is usually breakfast as the greatest amount of H+/K+-ATPase is present after a prolonged fast. Drug metabolism differs between individuals, and although some patients may respond better to one drug than another, overall symptom relief appears to be equivalent. The most important differences between individuals are largely related to adherence and the timing of a dose, as well as the amount of PPI per unit dose.
Maintenance therapy
Patients with typical symptoms of GORD who respond to 4–8 weeks of PPI therapy can reduce their dose to ‘when required’ while continuing lifestyle measures, antacids and, when required, H2-receptor antagonists as a less potent alternative to the PPI. There may be a period of acid hypersecretion following the withdrawal of PPI, but any symptoms will reduce over a period of about a month, after which recurring symptoms are most likely to be due to underlying reflux disease.16 Using a PPI when required will be adequate for some patients, however 75–90% will relapse over six months.5 This reflects the chronic nature of the condition rather than a failure of treatment. Surveillance gastroscopy is not required in patients with GORD.
An alternative approach is a more formal step-down of the PPI. The dose is reduced to determine the minimum needed to control symptoms. This may involve a gradual reduction in the dose or frequency with the aim of switching to ‘when required’ therapy. This approach allows patients to put lifestyle modifications into place and to find the lowest dose they need for adequate control of their symptoms.
Patients with evidence of significant erosive oesophagitis (Los Angeles Grades C, D), scleroderma oesophagus or Barrett’s oesophagus should remain on maintenance PPI therapy even if they are asymptomatic.17
Adverse effects
The potential adverse effects of PPIs include headache and diarrhoea (less than 2%). Other important but rare adverse events include interstitial nephritis, hypomagnesaemia, reduced vitamin B12 absorption, increased Clostridium difficile infection and possibly community-acquired pneumonia.7, 10 An association between PPIs and osteoporotic fractures is likely to be due to shared risk factors including increased age and medical comorbidity.18,19 A randomised trial found no evidence of an increased risk of cardiovascular events in patients taking PPIs and thienopyridines such as clopidogrel.10, 20 There was also no evidence that separating the doses of the two drugs changed cardiac risk.21 If there are major concerns about the interaction, a PPI with less cytochrome P450 (CYP) metabolism such as rabeprazole may be used.