Background : Some patients with gastro-oesophageal reflux disease continue to experience symptoms despite therapy with proton pump inhibitors. One recently proposed cause is the occurrence of nocturnal acid breakthrough.

Aim : To investigate the relationship between acid breakthrough occurrence (nocturnal and daytime) and refractory symptoms among patients with gastro-oesophageal reflux disease on proton pump inhibitors.

Methods : Fifty-two consecutive patients with persistent symptoms of gastro-oesophageal reflux disease despite proton pump inhibitor therapy underwent 24-h pH study at the Mayo Clinic between January 1 and November 10, 1999. Relevant data were extracted and analysed.

Results : Fifty-two patients, 18 males and 34 females, were eligible for the study. The mean age was 53 ± 2.2 years. Thirty-seven patients (71%) had nocturnal acid breakthrough, and 36 (69%) had daytime acid breakthrough. Sixty per cent of patients experienced both nocturnal and daytime acid breakthrough, whereas 19% had neither. Among those with nocturnal and daytime acid breakthrough, only 36% and 33% of symptoms, respectively, were associated with gastro-oesophageal reflux episodes. The proportion of patients with symptoms and the mean symptom scores were not significantly different between those with and without acid breakthrough.

Conclusions : Gastric acid breakthrough occurs nocturnally and during the daytime in patients on proton pump inhibitor therapy. With less than 36% of refractory symptoms associated with gastro-oesophageal reflux, gastric acid breakthrough cannot explain symptom refractoriness to proton pump inhibitor therapy in a significant majority of patients evaluated by 24-h pH study.