STATISTICAL INTERPRETATION OF THE ANTISECRETORY EFFECT OF FAMOTIDINE MEASURED BY INTRAGASTRIC PH-METRY

Objective: Intragastric pH-metry is widely used to evaluate the effica cy of antisecretory drugs, but statistical interpretation of the measu rements has not yet been standardised. Methods: The effects of single morning (N = 9) or evening (N = 7) doses of the H-2-receptor antagonis t famotidine, 20 mg (QUAMATEL(R), Gedeon Richter, Hungary) were compar ed by 24-hour intragastric pH-metry in hyperacid patients, in a prospe ctive, controlled clinicopharmacological study. Intragastric pH was re peatedly measured with or without administration of famotidine, and {1 } the minute to minute median pH values were calculated, Results: {2} Both treatments significantly reduced gastric acidity according to the ''traditional'' parameters of the time at pH greater than or equal to 3, or median pH in the first 12 hours. Famotidine treatment in the ev ening was more effective than in the morning (634 vs 463 min or 5.22 v s 3.10). The morning and evening treatment groups did not differ from each other in these parameters when compared on the days without famot idine. {3} After demonstration of the significant differences between the treatment vs control days, and morning vs evening administrations we applied the Pattern Recognition by Independent Multicategory Analys is (PRIMA) method to select the most sensitive parameters for evaluati on of the H-2-receptor antagonist drug effect. The PRIMA method was de veloped to determine the sensitivity of each statistical parameter ana lysed in a comparison of different groups (discriminating power), and to determine the separability of groups using several parameters conco mitantly (separation of groups). The mean pH, the period at pH greater than or equal to 3, and the duration of pH-increase greater than or e qual to 1 on the day of treatment compared to the control day were fou nd to be the most sensitive parameters both in demonstrating H-2-recep tor antagonist effect and in differentiation of morning and evening do ses. (4) High separability of morning and evening treatment groups was achieved using these three parameters concomitantly according to the PRIMA method. Conclusion: This method may be of value in other clinica l or clinicopharmacological trials to standardise the statistical anal ysis of data by selection of the most sensitive parameters for compari son of the patient groups. In subsequent studies it might also increas e the sensitivity of discrimination by concomitant analysis of differe nt parameters using the smallest appropriate number of patients.