Background The risk for acidic reflux is mainly determined by the position of the gastric acid pocket. It was hypothesised that compounds affecting proximal stomach tone might reduce gastro-oesophageal reflux by changing the acid pocket position.

Objective To study the effect of azithromycin (Azi) on acid pocket position and acid exposure in patients with gastro-oesophageal reflux disease (GORD).

Methods Nineteen patients with GORD were included, of whom seven had a large hiatal hernia (≥3 cm) (L-HH) and 12 had a small or no hiatal hernia (S-HH). Patients were randomised to Azi 250 mg/day or placebo during 3 days in a crossover manner. On each study day, reflux episodes were detected using concurrent high-resolution manometry and pH-impedance monitoring after a standardised meal. The acid pocket was visualised using scintigraphy, and its position was determined relative to the diaphragm.

Results Azi reduced the number of acid reflux events (placebo 8.0±2.2 vs Azi 5.6±1.8, p<0.01) and postprandial acid exposure (placebo 10.5±3.8% vs Azi 5.9±2.5%, p<0.05) in all patients without affecting the total number of reflux episodes. Acid reflux occurred mainly when the acid pocket was located above, or at the level of, the diaphragm, rather than below the diaphragm. Treatment with Azi reduced hiatal hernia size and resulted in a more distal position of the acid pocket compared with placebo (below the diaphragm 39% vs 29%, p=0.03). Azi reduced the rate of acid reflux episodes in patients with S-HH (38% to 17%) to a greater extent than in patients with L-HH (69% to 62%, p=0.04).

Conclusion Azi reduces acid reflux episodes and oesophageal acid exposure. This effect was associated with a smaller hiatal hernia size and a more distal position of the acid pocket, further indicating the importance of the acid pocket in the pathogenesis of GORD.

clinical trial registration http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=1970 NTR1970.