Radiotelemetry capsule

C. S. Chaw, E. Yazaki, D. F. Evans. The effect of pH change on the gastric emptying of liquids measured by electrical impedance tomography and pH-sensitive radiotelemetry capsule. Int. J. Pharm. 2001, 227, 167-175. 

Figure 6.2. pH profile in the GI tract of a healthy subject, measured with a radiotelemetry capsule. Modified from reference [5]. 

Mojaverian P (1996) Evaluation of gastrointestinal pH and gastric residence time via the Heidelberg Radiotelemetry Capsule Pharmacological application. Drug Development Research 38 73-85... 

Very few data are available on gastrointestinal pH in children. In 12 healthy subjects aged 8-14 years, the mean gastric pH was 1.5 and duodenal pH was 6.4, but this gradually rose in the small intestine reaching a peak value of 7.4 in the distal ileum.The pH dropped to 5.9 as the pH radiotelemetry capsule entered the caecum but increased to 6.5 in the rectum. The median gastric residence time of the telemetry capsule was 1.1 h, small intestinal transit time was 7.5 h, and colonic transit time was 17.2 h. 

Hie major site of bacterial activity is the caecum where the anaerobic bacteria ferment substrates (e.g. soluble fibre) in a liquid mixture. The fermentation in the caecum produces a marked drop in the pH of the luminal contents. Hie low oxygen tension in the colonic lumen encomages reductive conditions and this principle has been used to deliver dmgs specifically to the colon in the treatment of ulcerative colitis. pH studies using a pH-sensitive radiotelemetry capsule in normal, ambulatory volunteers have shown that the mean pH in the colonic lumen is 6.4 0.6 in the ascending colon, 6.6 0.8 in the transverse colon and 7.0 0.7 in the descending colon. The azo-bond of sulfasalazine is cleaved by bacteria] azo-reductase activity to release the active component 5-aminosalicylic add (Fig. 8.54). 

Mojaverian, P., Chan, K., Desai, A. and Vivian, J. (1989). Gastrointestinal transit of a solid indigestible capsule as measured by radiotelemetry and dual gamma scintigraphy. Pharm. Res. 6 717-722. 

---