On iontophoretic delivery enhancement: ionization and transport properties of lidocaine hydrochloride in aqueous propylene glycol

• Published in: International journal of pharmaceutics 2000-05, Vol.201 (1), p.121-124
• Main Authors: Karami, Kiomars, Merclin, Nadia, Brounéus, Fredrik, Beronius, Per
• Format: Article
• Language: English
• Subjects: Anesthetics, Local - administration & dosage; Anesthetics, Local - chemistry; Anesthetics, Local - pharmacokinetics; Biological and medical sciences; Chemical Phenomena; Chemistry, Physical; Electric Conductivity; Enhancer; General pharmacology; Iontophoresis; Iontphoresis; Lidocaine - administration & dosage; Lidocaine - chemistry; Lidocaine - pharmacokinetics; Lidocaine hydrochloride; Medical sciences; Molar conductivity; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Propylene glycol (PG); Propylene Glycols; Solubility; Transport number
• ISSN: 0378-5173; 1873-3476
• DOI: 10.1016/S0378-5173(00)00400-2

The ionization and transport properties of lidocaine hydrochloride (LidHCl) in aqueous propylene glycol (PG) containing 20% PG by weight was studied by means of electrical precision conductometry. For drug concentrations exceeding about 1.7 mM a slight formation of LidH +Cl − ion-pairs is indicated; ion-pair association constant, K p=1.73 (molar scale). A two variable analysis of the experimental data yielded K a=1.5×10 −8 for the acid dissociation constant of LidH +, i.e. p K a=7.82, and the limiting ionic conductivity, λ o(LidH +)=21.73 cm 2 S mol −1. To enable evaluation of single ion conductivities the proton transport number of HCl in the present solvent mixture was determined using the moving boundary method.