Activated carbon as a biological model: comparison between activated carbon adsorption and oil-water partition coefficient for drug activity correlation.
Octanol-water partition coefficients have been used as a principal parameter for the analysis of quantitative structure-activity relationships (QSAR). With ionized drugs, however, the correlation is not impressive. Although clinical local anesthetics exist mainly in the ionized form at physiological pH, the nerve-blocking potency is correlated with the oil-water partition coefficients of the un-ionized species. In the present report, the adsorption of 18 local anesthetics onto activated carbon surfaces was compared with oil-water partition coefficients for correlation with the minimum nerve-blocking (MBC) potency. The log octanol-water partition coefficients showed large differences between the charged and uncharged species (lidocaine: 0.49 and 1.82, procaine: -0.56 and 1.74, respectively), whereas the log carbon surface adsorbabilities showed much smaller differences (lidocaine: 3.00 and 3.04, and procaine 2.95 and 3.00, respectively). An excellent correlation was found between the log carbon surface adsorption and the log MBC values in both ionized and un-ionized drugs.
Abe
I
I
Department of Anesthesia, University of Utah School of Medicine, Salt Lake City 84132.
Kamaya
H
H
Ueda
I
I
D000327:Adsorption; D002606:Charcoal; D008954:Models, Biological; D009821:Oils; D013329:Structure-Activity Relationship; D014867:Water
D009821:Oils; D014867:Water; D002606:Charcoal