title: Percutaneous absorption of flurbiprofen in the hairless rat measured in vivo using 19F magnetic resonance spectroscopy.
abstract: The objective of this investigation was to develop a new methodology using 19F-magnetic resonance spectroscopy (MRS) to measure the in vivo percutaneous absorption of flurbiprofen through hairless rat skin. A 2% W/V flurbiprofen gel (Klucel HF, hydroxypropyl cellulose 1.5% to 2% W/V) containing isopropyl alcohol, water, and propylene glycol (55:35:10 v/v/v) was prepared. A 2-mg dose (100 mg of gel) was applied to the skin of the lower back of an anesthetized hairless rat, contained with a rubber o-ring, and occluded with a lexan plastic cover slip. The animal was placed on an MR surface coil (3.5-cm diameter tuned to 19F) and measurements taken continuously over approximately 3 h in 10-min intervals with a 2-tesla GE CSI nuclear magnetic resonance (NMR) spectrometer. One measures the disappearance of MR signal intensity per interval, which directly relates to the percent of drug disappearance over time, which in turn was converted to a flux value. The flux of flurbiprofen in vivo was found to be 95 +/- 22 micrograms/cm2/h. This is approximately four times greater than the flux of flurbiprofen through excised human skin reported by Akhter and Barry (22 +/- 14 micrograms/cm2/h). This new in vivo method measures drug disappearance and can be readily transferred to man. This method may be adapted to study other fluorine compounds or other nuclei with magnetic properties. It avoids exposure of a patient or animal to the radiation used in x-ray fluorescence methods or to 14C- or 3H-radiolabeled drugs.
authors.affiliation: Department of Pharmaceutics, College of Pharmacy, University of Illinois, Chicago 60612.
authors.forename: D J
authors.initials: DJ
authors.lastname: Lee
authors.forename: C T
authors.initials: CT
authors.lastname: Burt
authors.forename: R L
authors.initials: RL
authors.lastname: Koch
mesh_terms: D000818:Animals; D005260:Female; D005461:Fluorine; D005480:Flurbiprofen / Q000493:pharmacokinetics*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D051381:Rats; D011923:Rats, Nude / Q000502:physiology*; D012869:Skin Absorption / Q000502:physiology
chemical_list: D005461:Fluorine; D005480:Flurbiprofen