A placebo-controlled trial of an oral capsaicin load in patients with functional dyspepsia

The pathophysiology of functional dyspepsia is poorly understood. Visceral hypersensitivity may play a key role. We studied a previously validated test to assess chemical hypersensitivity in functional dyspepsia by applying an oral capsaicin load.

A total of 116 outpatients with upper gastrointestinal (GI) symptoms participated in this double-blind, placebo-controlled trial of which 73 patients received a final diagnosis of functional dyspepsia. Patients swallowed a capsule containing 0.75 mg capsaicin or placebo. A graded questionnaire evaluated the severity of nine upper GI symptoms before and after capsule ingestion and an aggregate symptom score was calculated. A final score of >9 was considered as a positive test.

In functional dyspepsia, median perception scores were 10.8 (interquartile range: 4.5-18.8) after ingestion of capsaicin and 0.5 (0.0-2.5) after placebo (P < 0.001). Thirty-seven functional dyspepsia patients (54%) had a positive test after capsaicin ingestion, whereas only four (11%) patients with upper GI symptoms but without functional dyspepsia were capsaicin positive [median perception score: 1.5 (0.0-5.0)]. After placebo, symptom scores were low and not significantly different among patient groups (P > 0.05). Clinical characteristics, age, and gender distribution was similar in capsaicin positive and capsaicin negative functional dyspepsia patients (P > 0.05). The value of patient blinding was good.

Half of functional dyspepsia patients had chemical hypersensitivity, determined with an oral capsaicin load. Placebo response was negligible. The results of the capsaicin test were not associated with specific dyspepsia symptoms or Rome subgroups.