Reverse iontophoresis as a noninvasive tool for lithium monitoring and pharmacokinetic profiling.
OBJECTIVE
Transdermal iontophoresis was investigated as a noninvasive tool for drug monitoring and pharmacokinetic profiling. Lithium, a frequently monitored drug, was used as a model. The objectives were a) to demonstrate the linear dependence of the iontophoretic extraction flux of lithium on the subdermal concentration of the drug, b) to evaluate the capacity of iontophoresis to monitor sudden changes in the subdermal level, c) to investigate the utility of reverse iontophoresis as a tool in pharmacokinetic studies, and d) to examine the validity of an internal standard calibration procedure to render the method completely noninvasive.


METHODS
Transdermal, iontophoretic extraction was performed in vitro using dermatomed pig-ear skin. The subdermal solution consisted of a physiological buffer containing lithium chloride at concentrations in the therapeutic range and two putative internal standards, sodium and potassium, at fixed physiological levels. The subdermal concentration of lithium was changed either in a stepwise fashion or by simulating one of two pharmacokinetic profiles.


RESULTS
Lithium was extracted via electromigration to the cathode. A excellent correlation between subdermal lithium concentration and iontophoretic extraction flux was observed. Iontophoresis tracked sudden concentration changes and followed kinetic profiles. In addition, the effective elimination rate constant could be directly, and noninvasively, estimated from the extraction flux data.


CONCLUSIONS
Reverse iontophoresis is a potentially useful and noninvasive tool for lithium monitoring.
Leboulanger
Benoît
B
School of Pharmacy, University of Geneva, Geneva, Switzerland.
Fathi
Marc
M
Guy
Richard H
RH
Delgado-Charro
M Begoña
MB
D000279:Administration, Cutaneous; D000818:Animals; D016903:Drug Monitoring / Q000379:methods*; D004423:Ear; D066298:In Vitro Techniques; D007478:Iontophoresis / Q000379:methods*; D018020:Lithium Compounds / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008954:Models, Biological; D012869:Skin Absorption; D013552:Swine; D013997:Time Factors
D018020:Lithium Compounds