title: In-vitro and in-vivo characteristics of a modified-release double-pulse formulation for a water soluble drug.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the in-vitro dissolution and in-vivo pharmacokinetic profile of a novel two-phase modified-release formulation for diltiazem hydrochloride, as a water-soluble drug.
  
  
  METHODS
  The delivery system consisted of two tablets inserted into a capsule. Both tablets comprised a coated drug core-matrix. The coating of the first tablet was intended to produce a first phase with a relatively fast release profile, while that of the second tablet included a unique controlling membrane designed to achieve a delayed controlled-release profile. Three different formulations were tested for their dissolution profiles both in water media and in buffer with a pH of 6.8. These formulations were also evaluated for their pharmacokinetic profile in healthy volunteers after single administration of a 240 mg dose. Serial venous blood samples were collected over 36 h post administration to measure diltiazem levels by HPLC. In addition the in-vivo /in-vitro correlation (IVIVC) was calculated for these formulations.
  
  
  RESULTS
  The in-vitro characteristics of these formulations demonstrated a controlled release profile in both media but with different characteristics, as in Formulation 3 where faster dissolution profile obtained in water but slower one in pH 6.8 buffer. In-vivo the pharmacokinetic profile of these formulations showed that arabinogalactan containing formulations achieved plasma levels which allow a once daily administration. IVIVC calculation demonstrated that dissolution tested in buffer 6.8 media better correlates with the percent absorbed in-vivo and the best results were achieved with the formulation containing the highest amount of polysaccharide in the coating.
  
  
  CONCLUSIONS
  It is concluded that the developed formulations achieved a controlled release profile both in-vitro and in-vivo which are suitable for once-daily administration.
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel. avi.avramoff@dexcel.com
authors.forename: A
authors.initials: A
authors.lastname: Avramoff
authors.forename: A J
authors.initials: AJ
authors.lastname: Domb
mesh_terms: D000328:Adult; D019540:Area Under Curve; D002121:Calcium Channel Blockers / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D002214:Capsules; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D018592:Cross-Over Studies; D003692:Delayed-Action Preparations; D004110:Diltiazem / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D004311:Double-Blind Method; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D008297:Male; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013607:Tablets; D055815:Young Adult
chemical_list: D002121:Calcium Channel Blockers; D002214:Capsules; D003692:Delayed-Action Preparations; D013607:Tablets; D004110:Diltiazem