title: Omeprazole absorption from a compounded transdermal formulation in healthy volunteers.
abstract: OBJECTIVE
  To evaluate the plasma concentration versus time profile of omeprazole following the administration of a compounded transdermal gel formulation in healthy volunteers.
  
  
  METHODS
  Single-dose transdermal pharmacokinetic (PK) study including a comparison with historical data from an oral PK study.
  
  
  METHODS
  Academic clinical research center.
  
  
  METHODS
  Eight healthy volunteers between 18 and 50 years of age.
  
  
  METHODS
  Omeprazole gel 40 mg (0.8 mL) was applied to the ventral surface of the forearm covering an area of 7 x 15 cm without an occlusive dressing. Blood samples were collected just before application and then at 1, 2, 3, 4, 6, and 8 hours. Plasma concentrations of omeprazole were determined using a validated liquid chromatography tandem mass spectrometry method.
  
  
  METHODS
  PK parameters (maximal plasma concentration [C(max)], the time of C(max), [T(max)], the area under the omeprazole concentration versus time curve from 0 to 8 hours, the elimination rate constant, and the half-life of the elimination phase) following transdermal administration, compared with historical controls who had received an oral omeprazole 40 mg dose during a previous study.
  
  
  RESULTS
  Of the eight volunteers, five had undetectable plasma omeprazole concentrations throughout the 8-hour study, precluding a complete PK analysis. For the three volunteers with detectable plasma omeprazole concentrations, the values ranged from 0.204 to 0.552 ng/mL. Including values of 0 for the patients with undetectable levels, the mean (+/- SD) C(max) was 0.153 +/- 0.241 ng/mL, and the T(max) in patients with detectable levels occurred at approximately 6 hours. The plasma concentrations following transdermal administration were approximately 1,000-fold lower than those observed with oral dosing.
  
  
  CONCLUSIONS
  Transdermal absorption from a single dose of the omeprazole gel formulation used in this study was poor. This transdermal gel formulation is clearly not bioequivalent to the oral capsule.
authors.affiliation: Department of Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, NY 14260-1200, USA. haas@buffalo.edu
authors.forename: Curtis E
authors.initials: CE
authors.lastname: Haas
authors.forename: Lydia
authors.initials: L
authors.lastname: Lin
authors.forename: Denise
authors.initials: D
authors.lastname: Cloen
authors.forename: Thomas
authors.initials: T
authors.lastname: Kufel
authors.forename: Richard
authors.initials: R
authors.lastname: Moon
authors.forename: Valerie
authors.initials: V
authors.lastname: Frerichs
mesh_terms: D000279:Administration, Cutaneous; D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000897:Anti-Ulcer Agents / Q000008:administration & dosage / Q000493:pharmacokinetics; D019540:Area Under Curve; D002214:Capsules; D002853:Chromatography, Liquid / Q000379:methods; D005260:Female; D005782:Gels; D006207:Half-Life; D006801:Humans; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008875:Middle Aged; D009853:Omeprazole / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D012867:Skin / Q000378:metabolism*; D012869:Skin Absorption; D013997:Time Factors
chemical_list: D000897:Anti-Ulcer Agents; D002214:Capsules; D005782:Gels; D009853:Omeprazole