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3047334 
Journal Article 
On iontophoretic delivery enhancement: Ionization and mobility of lidocaine hydrochloride in propylene glycol 
Karami, K; Beronius, P 
1998 
Yes 
International Journal of Pharmaceutics
ISSN: 0378-5173
EISSN: 1873-3476 
IPA/99/1163189 
168 
1 
85-95 
English 
WOS:000074504900011 
IPA COPYRIGHT: ASHP To optimize conditions in iontophoretic delivery, the ionization and mobility of 0.4-10 mM lidocaine hydrochloride in propylene glycol were studied at 25DGC using precision conductometry and the conductance equation of Fuoss-Hsia and Fernandez-Prini. Using a 2 parameter analysis of the equilibrium, lidocaine H+ lidocaine+H+, an acid dissociation constant of 2.5x10-7 was obtained; pKa was 6.6 and the limiting molar conductivity was 0.2675 sq cm/mol. For concentrations above 1.2 mM, there was strong evidence of formation of ion pairs, lidocaine H+Cl-. The ion pair association constant was estimated to be about 40, indicating that about 15% of the electrolyte was in the form of lidocaine H+Cl- at the highest concentration (10 mM). 
iontophoresis; lidocaine hydrochloride; propylene glycol; enhancer; molar conductivity; ionic conductivity; ion pairs