On iontophoretic delivery enhancement: ionization and transport properties of lidocaine hydrochloride in aqueous propylene glycol.
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)=1.5x10(-8) for the acid dissociation constant of LidH(+), i.e. pK(a)=7.82, and the limiting ionic conductivity, lambda(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.
Karami
K
K
Physical Pharmaceutical Chemistry, Uppsala University, Uppsala Biomedical Center, P.O. Box 574, SE-751 23, Uppsala, Sweden.
Merclin
N
N
Brounéus
F
F
Beronius
P
P
D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004553:Electric Conductivity; D007478:Iontophoresis; D008012:Lidocaine / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D011409:Propylene Glycols; D012995:Solubility
D000779:Anesthetics, Local; D011409:Propylene Glycols; D008012:Lidocaine