['The rapid onset and symptomatic response to histamine-2 receptor antagonists prior to the pharmacological effect on acid secretion suggests a different mechanism of action.', 'To determine if ranitidine decreases oesophageal sensitivity to chemical and mechanical stimulation, potentially via oesophageal histamine receptors.', 'A total of 18 patients with functional heartburn received oral ranitidine 150 mg b.d. or placebo for 7 consecutive days in a double-blind randomized crossover design and underwent Barostat balloon distention and Bernstein acid infusion on study day 1 (90 min postdose) and study day 7. First sensation and pain were recorded and pain severity was rated on a 5-point Likert scale and a 100 mm visual analogue scale. Least square mean values were generated and one-tailed t-tests were performed.', 'After a single dose of ranitidine 150 mg, time to pain with oesophageal acid infusion was increased by 29% (P < 0.05) and visual analogue scale and Likert scores were decreased by 20% (P < 0.06) and 23% (P < 0.02), respectively compared with placebo. After 1 week of ranitidine, positive alterations in sensory parameters persisted. Balloon distention sensory parameters were not altered by ranitidine.'] Does a single dose of ranitidine 150 mg modulate oesophageal acid sensitivity in patients with functional heartburn?