Int J Pharm. 2006 Feb 3;308(1-2):8-13. Epub 2005 Dec 9.
The use of citric acid to prolong the in vivo gastro-retention of a floating dosage form in the fasted state.
Stops F1, Fell JT, Collett JH, Martini LG, Sharma HL, Smith AM.Author informationAbstract
Gastro-retentive dosage forms have the potential to improve local therapy and decrease the variation in bioavailability that is observed with a number of commercially available immediate and modified release preparations. In this study, a dosage form has been developed, utilising freeze-dried calcium alginate beads, designed to float on the surface of the stomach contents thus prolonging the retention time. The aim of the study was to also assess the in vivo behaviour of the radio-labelled calcium alginate beads when they were administered under fasting conditions with either water or an aqueous solution of citric acid, a potential gut transit delaying substance. The study was performed in healthy male volunteers who swallowed the radio-labelled calcium alginate beads after a 10h overnight fast. Gamma scintigraphy was selected as the method to monitor the movement of the calcium alginate beads. The volunteers consumed no further food or drink until gastric emptying of the calcium alginate beads was complete. The results indicated that prolonged gastric retention was achieved when the dosage form was administered with the citric acid solution when compared to retention in the absence of citric acid. Citric acid, therefore, has the potential to delay the gastric emptying of the calcium alginate beads when administered to fasted volunteers.
Aliment Pharmacol Ther. 1999 Aug;13(8):1057-62.
Citric acid or orange juice for the 13C-urea breath test: the impact of pH and gastric emptying.
There is an ongoing debate about the optimal test drink to be used in the 13C-urea breath test (13C-UBT). We recently reported that a citric acid solution is the optimal test drink in the 13C-UBT, because it provides a high 13CO2 recovery and the excellent accuracy of the test appears optimal compared to other test meals. Orange juice, because of a better taste, is also propagated as a test drink in the 13C-UBT.
To compare the diagnostic accuracy of the 13C-UBT with either orange juice or citric acid solution as a test drink. Furthermore, the effect of these test drinks on the gastric emptying rate was determined.
H. pylori status was assessed by histology, rapid urease test and culture in 50 consecutive dyspeptic patients. A 13C-UBT was performed on two consecutive days by giving 75 mg of 13C-urea randomly dissolved in 200 mL 0.1 M citric acid solution or 200 mL orange juice. The 13CO2/12CO2 ratio was measured in breath samples taken before and 15, 30, 45 and 60 min after administration of the test drink. The gastric emptying rate of orange juice and citric acid solution was compared to that of water in 10 healthy subjects on three consecutive days by means of a 13C-sodium acetate breath test; 50 mg of 13C-sodium acetate was dissolved in 200 mL of each solution and breath samples were collected before and every 10 min for 90 min after administration of the test drink.
RESULTS:Twenty-six out of 50 patients (52%) were infected with H. pylori. Significantly higher values over baseline (35.7+/-5.2 per thousand vs. 23.2+/-3.4 per thousand, P < 0.001) and higher area under the curve (1507+/-198 vs. 927+/-128, P < 0.001) were observed in H. pylori-positive patients when citric acid solution was administered compared with orange juice. Sensitivity of the 13C-UBT was 100% when citric acid was used as a test drink and 88% with orange juice. Specificity was 100% with both test drinks. Gastric emptying of citric acid solution (t1/2 = 60.9+/-3.5 min) was significantly slower than that of orange juice (t1/2 = 49.7+/-3.1 min, P < 0.001).
13C-UBT loses diagnostic accuracy when orange juice instead of citric acid is used as a test drink. The faster gastric emptying of orange juice might be responsible for the lower diagnostic accuracy of the 13C-UBT.