Intranasal administration of peptides: nasal deposition, biological response, and absorption of desmopressin.

The nasal administration of desmopressin [1-(3-mercaptopropionic acid)-8-D-arginine-vasopressin] in humans was investigated. Desmopressin solutions containing 99mTc-labeled human serum albumin were administered intranasally as a spray, using two metered-dose pumps, or as drops, using a rhinyle catheter or a single-dose pipet. Images of the sites of deposition and rates of clearance were monitored quantitatively by gamma scintigraphy. Plasma levels of desmopressin were measured using a highly sensitive and specific radioimmunoassay. The biological response was determined by measuring circulating levels of F VIII, the antihemophilia factor. The sprays were deposited mainly anteriorly, from which small portions were cleared slowly into the nasal pharynx. In contrast, the drops were deposited mostly posteriorly and cleared very rapidly in large portions; some were swallowed immediately. Plasma levels showed that desmopressin was absorbed to a greater extent after administration of the spray with a 2 to 3-fold increase in the relative bioavailability compared with the drops. The biological response was clearly enhanced after spray administration and produced similar increases in F VIII activity. A linear correlation was observed between maximum plasma desmopressin levels and maximum F VIII activity. The use of an intranasal spray device can deposit well-controlled doses within the nasal cavity, which remain there sufficiently long to provide a clear enhancement in absorption and bioavailability.