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The rheological profiles of commercial corticosteroid nasal spray suspensions (Beconase, Nasacort, Flixonase, and Nasonex) were compared using shear and extensional techniques. Thixotropy/shear thinning was investigated (Carri-Med CSL100, concentric cylinder geometry) by (a) the generation of flow curves at low (100 sec-1) and high (1200 sec-1) maximum shear rates and (b) determination of equilibrium shear viscosities at constant shear rates of 10 sec-1, 100 sec-1, or 1200 sec-1. Extensional properties, on which droplet breakup and size depend, were examined using digital camera photography of droplet evolution and the length any trailing filament formed when the suspension was extruded from a 10-ml syringe at 500 microliters/min. All the nasal suspensions were shear thinning and were also thixotropic to varying degrees. The absence of significant thixotropic recovery at short times (5 min) for all the sprays implies that thixotropy is not necessarily the controlling factor for prolonged residence of the spray in the nasal cavity, but rather that it is the high viscosities present in all four sprays, even after structure breakdown. Preliminary extensional flow data identified differences among the four sprays, with extensional filament lengths increasing in the same rank order as the lowest shear rate (10 sec-1) equilibrium viscosities.

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Captopril has been administered to eight healthy male subjects by means of a pulsatile delivery system that was designed to release the drug in the colonic region of the intestine. The gastrointestinal transit and pulsatile release were followed using gamma scintigraphy. A pulsatile capsule system with release after a nominal 5-hr period was found to perform reproducibly in vitro and in vivo. In six of the eight subjects, the drug was delivered to the colon, and in the remaining two subjects, to the terminal ileum. Measurable blood levels of free captopril were found in three subjects. Variable instability of the drug in the distal intestine is suggested as a possible reason for the lack of absorption of the drug in the majority of subjects.

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