title: In vitro/in vivo correlation of transdermal naltrexone prodrugs in hairless guinea pigs.
abstract: OBJECTIVE
  The purpose of this investigation was to evaluate the in vitro and in vivo percutaneous absorption of the following prodrugs of naltrexone (NTX): 2'-ethylbutyryl-3-O-ester-NTX (ETBUT-ester), methyl-3-O-carbonate-NTX (ME-carbonate), ethyl-3-O-carbamate-NTX (ET-carbamate), and N,N-dimethyl-3-O-carbamate-NTX (DME-carbamate) in hairless guinea pigs.
  
  
  METHODS
  In vitro fluxes of NTX and its prodrugs through guinea pig skin were determined using a flow-through diffusion cell system. The pharmacokinetics of NTX prodrugs were determined after topical application of transdermal patches in guinea pigs.
  
  
  RESULTS
  All the prodrugs hydrolyzed to NTX on passing through the skin, and ME-carbonate provided the highest NTX flux and had the highest apparent permeability coefficient (K(p)). ME-carbonate and ET-carbamate underwent the highest extent of bioconversion to NTX upon passing through the skin as compared to ETBUT-ester and DME-carbamate. The results of the in vivo studies indicated that a significant amount of NTX was delivered after the application of transdermal patches of NTX prodrugs. A mean steady-state plasma concentration of 7.1 ng/ml was obtained after the application of transdermal patches of ME-carbonate. A good correlation was obtained between the in vitro and in vivo results.
  
  
  CONCLUSIONS
  The results of the in vivo studies indicated that the ME-carbonate prodrug of NTX was the most promising drug candidate for transdermal delivery.
authors.affiliation: Department of Pharmaceutical Sciences, University of Kentucky College of Pharmacy, Lexington, KY, USA.
authors.forename: Satyanarayana
authors.initials: S
authors.lastname: Valiveti
authors.forename: Kalpana S
authors.initials: KS
authors.lastname: Paudel
authors.forename: Dana C
authors.initials: DC
authors.lastname: Hammell
authors.forename: Mohamed O
authors.initials: MO
authors.lastname: Hamad
authors.forename: Jianhong
authors.initials: J
authors.lastname: Chen
authors.forename: Peter A
authors.initials: PA
authors.lastname: Crooks
authors.forename: Audra L
authors.initials: AL
authors.lastname: Stinchcomb
mesh_terms: D000279:Administration, Cutaneous; D000465:Algorithms; D000818:Animals; D019540:Area Under Curve; D004058:Diffusion; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009271:Naltrexone / Q000008:administration & dosage / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D010539:Permeability; D011355:Prodrugs / Q000008:administration & dosage / Q000494:pharmacology*; D012869:Skin Absorption
chemical_list: D009292:Narcotic Antagonists; D011355:Prodrugs; D009271:Naltrexone