title: Effect of stabilizer on the maximum degree and extent of supersaturation and oral absorption of tacrolimus made by ultra-rapid freezing.
abstract: OBJECTIVE
  Solid dispersions containing various stabilizers and tacrolimus (TAC) prepared by an Ultra-rapid Freezing (URF) process were investigated to determine the effect on their ability to form supersaturated solutions in aqueous media and on enhancing transport across biological membranes.
  
  
  METHODS
  The stabilizers included poly(vinyl alcohol; PVA), poloxamer 407 (P407), and sodium dodecyl sulfate (SDS). In vivo absorption enhancement in rats was also investigated. Dissolution studies were conducted at supersaturated conditions in both acidic media for 24 h and at delayed release (enteric) conditions to simulate intestinal transit.
  
  
  RESULTS
  The rank order of C/Ceq(max) in the dissolution studies at acidic conditions was URF-P407 > URF-SDS > Prograf (PRO) > URF-PVA:P407. For C/Ceq(max) under enteric conditions, the order was URF-SDS > PRO > URF-PVA:P407 > URF-P407, and for the extent of supersaturation (AUC) in acidic and pH shift conditions it was URF-SDS>PRO>URF-PVA:P407>URF-P407. The pharmacokinetic data suggests URF-P407 had the greatest absorption having higher C (max) with a 1.5-fold increase in AUC compared to PRO. All URF compositions had a shorter T (max) compared to PRO.
  
  
  CONCLUSIONS
  The nanostructured powders containing various stabilizing polymers formed by the URF process offer enhanced supersaturation characteristics leading to increased oral absorption of TAC.
authors.affiliation: College of Pharmacy, University of Texas at Austin, Austin, TX 78712-1074, USA.
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Overhoff
authors.forename: Jason T
authors.initials: JT
authors.lastname: McConville
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Keith P
authors.initials: KP
authors.lastname: Johnston
authors.forename: Jay I
authors.initials: JI
authors.lastname: Peters
authors.forename: Robert O
authors.initials: RO
authors.lastname: Williams
mesh_terms: D000143:Acids; D000818:Animals; D019540:Area Under Curve; D004339:Drug Compounding; D005079:Excipients / Q000737:chemistry*; D005615:Freezing; D006863:Hydrogen-Ion Concentration; D007166:Immunosuppressive Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics*; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D020442:Poloxamer / Q000737:chemistry; D011142:Polyvinyl Alcohol / Q000737:chemistry; D011208:Powders; D051381:Rats; D017207:Rats, Sprague-Dawley; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D012995:Solubility; D016559:Tacrolimus / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics*; D014961:X-Ray Diffraction
chemical_list: D000143:Acids; D005079:Excipients; D007166:Immunosuppressive Agents; D011208:Powders; D020442:Poloxamer; D012967:Sodium Dodecyl Sulfate; D011142:Polyvinyl Alcohol; D016559:Tacrolimus