Coated minispheres of salmon calcitonin target rat intestinal regions to achieve systemic bioavailability: Comparison between intestinal instillation and oral gavage

摘要

Achieving oral peptide delivery is an elusive challenge. Emulsion-based minispheres of salmon calcitonin (sCT) were synthesized using single multiple pill (SmPill (R)) technology incorporating the permeation enhancers (PEs): sodium taurodeoxycholate (NaTDC), sodium caprate (C-10), or coco-glucoside (CG), or the pH acidifier, citric acid (CA). Minispheres were coated with an outer layer of Eudragit (R) L30 D-55 (designed for jejunal release) or Surelease (R)/Pectin (designed for colonic release). The process was mild and in vitro biological activity of sCT was retained upon release from minispheres stored up to 4 months. In vitro release profiles suggested that sCT was released from minispheres by diffusion through coatings due to swelling of gelatin and the polymeric matrix upon contact with PBS at pH 6.8. X-ray analysis confirmed that coated minispheres dissolved at the intended intestinal region of rats following oral gavage. Uncoated minispheres at a dose of similar to 2000 I.U. sCT/kg were administered to rats by intra-jejunal (i.j.) or intra-colonic (i.c.) instillation and caused hypocalcaemia. Notable sCT absolute bioavailability (F) values were: 5.5% from minispheres containing NaTDC (i.j), 17.3% with CG (i.c.) and 18.2% with C-10 (i.c.). Coated minispheres administered by oral gavage at threefold higher doses also induced hypocalcaemia. A highly competitive F value of 2.7% was obtained for orally-administered sCT-minispheres containing CG (45 mu mol/kg) and coated with Eudragit (R). In conclusion, the SmPill (R) technology is a potential dosage form for several peptides when formulated with PEs and coated for regional delivery. PK data from instillations over-estimates oral bioavailability and poorly predicts rank ordering of formulations. (C) 2016 Elsevier B.V. All rights reserved.