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The effects of polyacrylic acid gel on the nasal absorption of insulin and [Asu1,7]-eel calcitonin were investigated in rats. The nasal administration of insulin (1 IU kg-1) in polyacrylic acid gel at 0.1 and 1% w/v showed maximum hypoglycaemic effects at 30 min and 1 h after administration, respectively. However, the nasal administration of insulin in carboxymethyl cellulose (1% w/v) solution had no hypoglycaemic effect at the same dose. When [Asu1,7]-eel calcitonin (10 U kg-1) was administered nasally in polyacrylic acid gel (0.1% w/v), a prominent hypocalcaemic effect was observed during the first 30 min. Nasal administration of [Asu1,7]-eel calcitonin in saline had no hypocalcaemic effect at the same dose. The results indicate that the polyacrylic acid gel base significantly enhanced the absorption of insulin and [Asu1,7]-eel calcitonin via the nasal cavity.

The effects of viscous solutions of hyaluronate-sodium of various average molecular weights (MW) on the nasal absorption of vasopressin (AVP) and its analogue, 1-deamino-8-D-arginine vasopressin (1-d-8-DAVP), were examined in rats. Solutions of hyaluronate with MW greater than 3 x 10(5) daltons enhanced the nasal absorption of AVP; solutions of MW 5.5 x 10(4) daltons were not effective. The enhancing effects on the nasal absorption of AVP and 1-d-8-DAVP were dependent on the concentration in the range of 0-1.5% (w/v) hyaluronate (MW 1.4 x 10(6) daltons). The nasal absorption of AVP was increased with this solution at lower pH. Bioavailabilities after nasal administration of AVP and 1-d-8-DAVP in hyaluronate solutions (MW 1.4 x 10(6) and 2 x 10(6) daltons) increased more than 2-and 1.6-fold as compared to nasal administration of AVP and 1-d-8-DAVP in buffer solutions (pH 7.0), respectively. Hyaluronate solution (MW 1.4 x 10(6) daltons) did not affect the ciliary beat frequency of rabbit nasal mucosal membranes in vitro. Therefore, hyaluronate solution may be useful as a vehicle for nasal delivery of AVP and 1-d-8-DAVP.

In order to evaluate an indomethacin polyvinyl alcohol (PVA) hydrogel for rectal administration, the in vitro release characteristics of indomethacin from the hydrogel and indomethacin plasma concentrations after rectal administration were examined. The PVA hydrogel containing indomethacin was prepared by a low-temperature crystallization method. The release of indomethacin from the PVA hydrogel agreed with the Fickian diffusion model for 10 hr. Rectal administration of indomethacin hydrogels to rats yielded high indomethacin plasma concentrations, without producing a sharp peak, and a sustained-release effect. In dogs, the indomethacin hydrogel produced a similar sustained-release effect; however, the indomethacin plasma concentration was relatively low compared with that of an indomethacin suppository.

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