The in-vivo evaluation of an osmotic device (Osmet) using gamma scintigraphy

Abstract

The release of a radiolabelled marker from an orally administered osmotic pump device (Osmet) has been evaluated in-vivo in a group of 6 subjects, using the technique of gamma scintigraphy. The duration of residence of the pump in the stomach was greatly influenced by food intake. However, the release of the marker from the device was independent of food and position within the gastrointestinal tract. Furthermore, the material released from the osmotic pump was well distributed in the gastrointestinal tract. Good agreement between in-vitro and in-vivo release rates was obtained.

Oral absorption profile of nitrendipine in healthy subjects: a kinetic and dynamic study.

“…Since the in vitro performance of the Osmets in different media has been established to be quite independent of the release medium (Davis et al, 1984;Eckenhoff et al, 1981), the present observation can best be explained by diminished absorption of nitrendipine in the lower parts of the G.I. tract.…”

“…With scintigraphic methods it has been shown that Osmet-type dosage forms reach the colon between approximately 4-10 h after intake when administered after a light breakfast (Davis, 1983). The presence of food is important in causing longer transit times by delaying the emptying of the stomach (Davis et al, 1984;O'Reilly et al, 1987). Our subjects however had eaten only a light breakfast, which makes longterm retention of the Osmet in the stomach unlikely.…”

“…Since the ratio of the plasma concentrations of nitrendipine and its pyridine metabolite remained unchanged, it is likely that the amount of drug entering the circulation increased, hence the rate of input of nitrendipine into the body increased. The influence of food on the in vivo release rate from Osmets has shown to be minimal for Osmets loaded with other compounds (Davis et al, 1984) and it is therefore more likely that the intake of food accelerates the dissolution rate of nitrendipine from the suspension that has already been pumped out of the Osmet and thus enhancing the absorption rate of nitrendipine.…”

“…In fact, the blood pressure lowering effect could be dissociated from its accompanying reflex tachycardia by choosing a low rate of increase of the nifedipine plasma concentration (Kleinbloesem et al, 1987). The same principle may apply to other vasodilating agents, including nitrendipine, and therefore in the present study the kinetic and haemodynamic effect profile of this drug was investigated when given by a tablet formulation and by an osmotic pumping device from which nitrendipine is released at zero-order rate for 13 h. Such a device has been used in previous studies both orally and rectally in man (Davis, 1983;Davis et al, 1984;de Leede et al, 1982de Leede et al, , 1984Kleinbloesem etal., 1984a) and its usefulness as an experimental tool in clinical pharmacology has been reviewed Urquhart, 1985).…”

Chitosan–Chondroitin Sulfate Based Matrix Tablets for Colon Specific Delivery of Indomethacin

“…Most of the previous literature reports on colonic targeting have focused on the development of a colonic delivery system based on time-and pH-dependent delivery systems as well as systems that utilize bacteria, which colonizes the colon or enzymes produced by these bacteria to affect drug release (2,3). The poor site specificity problem occurs with time release dosage form due to large variation in gastric emptying time (4) and passage across the ileocecal junction. In addition, poor site specificity of pH-dependent system was very well established due to large variation in pH of the gastrointestinal tract (GIT) (5,6).…”