Mechanism of lidocaine release from carbomer-lidocaine hydrogels

ALVARO FEDERICO JIMENEZ KAIRUZ; DANIEL ALLEMANDI,; RUBEN MANZO,

JOURNAL OF PHARMACEUTICAL SCIENCES

Año: 2001 vol. 91 p. 267 - 267

0022-3549

heology, acid-base behavior, and kinetics of lidocaine release of carbomer±lidocaine (C-L) hydrogels are reported. A series of (C-L)x (x = mol% of L = 25, 50, 75, 100) that covers a pH range between 5.33 and 7.96 was used. Concentrations of ion pair ([R-COO-LH+]) and free species (L) and (LH+) were determined by the selective extraction of (L) with cyclohexane (CH) together with pH measurements, i.e., CH in a ratio CH/hydrogel 2:1 extracted 48% of the whole concentration of lidocaine [LT] of a (CÿL)100, {[LT] = ([R-COO-LH+]) + (L) + (LH+)}. The remaining species in the aqueous phase were distributed as: (L) 3.82%, (LH+) 14.5%, and [R-COO-LH+] 81.7%. Rheology and pH as a function of (CÿL) concentration are also reported. Delivery rates of free base L were measured in a Franz-type bicompartmental deviceusing water and NaCl 0.9% solution as receptor media. (CÿL) hydrogels behave as areservoir that releases the drug at a slow rate. pH effects on rate suggest that, under the