BACKGROUND: Non ulcer dyspepsia is an important health problem with a very high prevalence in the general population, being its pathophysiology still unclear and its association with H. pylori highly controversial. Many trials have been carried out assessing the effects of different drugs on the symptoms in dyspeptic patients, being one of the most common the use of H2 antagonist, even though the results have shown conflicting as far as efficacy is concerned. The goal of the present study is to determine the efficacy of famotidine (administered in three different regimens) as compared to placebo in relieving the symptoms of non ulcer dyspepsia.METHODS: Patients with chronic non ulcer dyspepsia were included and were selected by random in four groups; group I received famotidine 40 mg before breakfast, placebo before dinner and at bedtime; group II received famotidine 20 mg before breakfast and dinner and placebo at bedtime; group III received famotidine 40 mg at bedtime, placebo before breakfast and dinner; group IV received placebo before breakfast, dinner and at bedtime. A four week treatment period was completed. Endoscopy, measure of the gastric juice pH, and biopsy (including study for H.p) was done at the beginning of the study, at week 4 and at week 8. The patient was asked for a global assessment of improvement in the overall symptoms of dyspepsia at the end of weeks 1,4 and 8.RESULTS: Forty-eight patients (12 men and 36 women) participated in the study. There was not statistical difference between any of the four schemes of treatment and the effect over the pain and the symptoms during the study. Nevertheless there was a highly statistically difference (p<0.01) of the well being of the patient with all the groups of treatment received. There was a significant difference (p<0.05) between the pH of the groups II, III, IV, being the pH at fourth week, the one with a high mean value. There was not statistical difference in the pH value between patients that improve its symptoms and those that not H.p. presence was the same along the study in the group that showed improvement of pain and related symptoms and the group that did not improve. There was no significant changes in the histological pattern and the grade of inflammatory activity in relation to symptoms improvement. During the study there was not any clinical laboratory adverse experience.CONCLUSIONS: Non of the three schemes with famotidine used in this trial has proven to have any therapeutical benefit in non ulcer dyspepsia compared to placebo, even though patients improved their symptoms in all the four groups. It seems that gastric juice does not play a rol in the genesis of non ulcer dyspepsia. In this study, nor the presence of H.p. neither inflammatory activity are associated with the symptoms of non ulcer dyspepsia. More studies carefully designed are required not only to understand pathophysiological mechanism, also to identify effective treatments for this frequent entity.