Effect of receptor solution specific conductivity on iontophoresis of tetracaine hydrochloride.
OBJECTIVE
To examine the quantitative relationship between solution specific conductivity and the permeability of tetracaine HCl, and to investigate the effect of receptor solution specific conductivity on the iontophoretic transport.


METHODS
An in vitro study was carried out to determine the iontophoretic permeability of tetracaine hydrochloride through rat skin. Iontophoretic flux of tetracaine hydrochloride through excised rat skin was determined using Valia-Chien two-chamber diffusion cells with a constant d.c. current and Ag/AgCl electrodes. The specific conductivities of donor and receptor solution were also measured.


RESULTS
Iontophoretic flux of tetracaine hydrochloride increased with a decrease of anion (chloride ion) concentration in receptor. And the iontophoretic permeability (ER, ER is the enhancement ratio, and ER = iontophoretic flux/passive flux) for tetracaine hydrochloride was directly related to the conductivity of receptor solution when other conditions were held constant. Linear regressions confirmed that ER was related to inverse of overall specific conductivity of donor and receptor solution [1/(ks.d + ks.r), ks.d and ks.r are the specific conductivity of donor and receptor solution].


CONCLUSIONS
The results suggest that specific conductivity of receptor solution may be a important factor for the iontophoretic permeability of a solute.
Xu
Dong-hang
DH
Department of Pharmacy, Second Affiliated Hospital, College of Medical Sciences, Zhejiang University, Hangzhou 310009, China.
Hu
Qiao-hong
QH
Liang
Wen-quan
WQ
D000279:Administration, Cutaneous; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D007478:Iontophoresis; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012869:Skin Absorption; D013748:Tetracaine / Q000008:administration & dosage / Q000493:pharmacokinetics*
D000779:Anesthetics, Local; D013748:Tetracaine