Enhancing Mechanism of Enhancers as a Basis for Delivery of Bioactive Peptides

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When lidocaine is dissolved in an aqueous gel, the drug is absorbed well, and decreased pain when a needle is inserted through the skin for injection of human growth hormone.Al though diltiazem is absorbed through the gastrointestinal tract well, formulations which enable to absorb the drug fast through oral mucosa is required since absorption of diltiazem through the oral mucosa is not very efficient. High concentrations in the mouth caused by fast dissolution of the drug in the mouth are required to increase absorption from the mouth and to give enough concentrations in the blood.Amphotericin B with molecular weight of 924 is a large molecule and is poorly absorbed from the gastrointestinal tracts. In order to absorb the drug in a predictable fashion, some modification in formulation is necessary. Concentrations of the drug in the blood were measured both in adults and children and low in both.Effect of chitosan, a polysaccaride with amino groups, on nasal absorption of hydrophilic drugs was studied as a representative of basic polymers. Aqueous solubility is limited in high molecular weight chitosan, and moderately soluble chitosan samples weer examined. Riboflavin phosphate was used as a model of peptides because of its hydrophilic nature and its easy assay. Chitosan samples were obtained from several companies and four samples with high aqueous solubility were employed in the study. Effect of chitosan on absorption of riboflavin phosphate through nasal mucosa in rabbits was studied. Effect of concentrations of chitosan on enhancing absorption of riboflavin phosphate was studied in Chitosan C-9 because other samples were less soluble than this in water. Maximal enhancing effect was noted at 0.5% among 0.5,1, and 2%. Bioavailability of insulin was increased by chitosan.Egualen, a delivative of azulene was effective in increasing bioavailability of insulin and salmon calcitonin.