MAINTENANCE OF INTRAGASTRIC PH GREATER-THAN-4 WITH FAMOTIDINE IN DUODENAL-ULCER PATIENTS - FACTORS INFLUENCING DRUG REQUIREMENTS

The gastrojet, a closed loop pH feedback infusion pump capable of main taining intragastric pH at a target value by infusing ii, blockers at variable rates, was used to assess factors influencing the quantity of famotidine required to maintain intragastric pH above 4 for 24 hours in 34 fed patients with duodenal ulcers. The following factors were co nsidered: sex, age, duration of the disease, previous bleeding, previo us poor response to H-2 blockers (ulcer unhealed at six weeks, or recu rrence within three months during maintenance treatment), activity of the ulcer disease, smoking habits, cirrhosis. The patients had taken n o antisecretory drugs for the 15 days before the study. Two standardis ed meals were given during the study period (from 1000 to 1000). Fifty mi of famotidine (4 mg/ml) was loaded into infusion bags and the pump was programmed to deliver the drug intravenously at 11 rates varying from 0 to 40 mu l/min. The target pH was 4. Mean famotidine use was 11 1 mg (range 33 to 200), the 23 hour median pH was 5.3, and the mean ti me during which pH was above 4 was 75.4%. There was a negative correla tion (p < 0.001) between famotidine delivery and the inhibition of gas tric acidity. Statistical analysis showed that only cirrhosis signific antly influenced drug delivery, median pH, and the time during which p H was above 4. Mean drug delivery in the cirrhotic and non-cirrhotic p atients was 135 v 97 mg (p < 0.04), 23 hour median pH was 4.7 v 5.6 (p < 0.01), and the mean time at pH > 4 was 65.9 v 81.6% (p < 0.01). The re were large interindividual variations in famotidine requirements, b ut only cirrhosis was predictive of high dose requirement. These resul ts suggest that the appropriate amount of famotidine to treat duodenal ulcer in cirrhotic patients is probably higher than the usually recom mended dose.