Nocturnal acid breakthrough: pH, drugs and bugs.

Nocturnal acid breakthrough (NAB) was defined by Peghini et al. in 1998 as the presence of at least 60 continuous minutes of intragastric pH < 4 during the overnight period (22:00-06:00 h) in patients taking a proton pump inhibitor (PPI) twice-daily before meals. NAB was shown to occur in more than 70% of patients on PPI therapy but can be decreased or eliminated by adding a histamine-2 receptor antagonist (H2RA) at bedtime. Helicobacter pylori status influences intragastric acid control on PPI therapy: H. pylori-positive patients having better gastric acid control compared with their H. pylori-negative counterparts. Recent data indicate that NAB might not occur in H. pylori-positive subjects on twice-daily PPI, suggesting there is no need for combined PPI twice-daily and H2RA therapy to control night-time gastric acid secretion in these individuals. The clinical importance of NAB has been debated ever since this concept was introduced. The importance of NAB in healthy subjects and asymptomatic, uncomplicated gastro-oesophageal reflux disease patients on PPI therapy may be low, but ignoring it in patients with poor oesophageal motility and Barrett's oesophagus may result in suboptimal treatment. Further studies are warranted to investigate whether leaving H. pylori to 'assist'acid suppression obtained by PPI twice-daily, adding bedtime H2RAs after successful H. pylori eradication or other approaches to eliminate NAB results in better clinical outcomes.