Figure 5.
Examples of charged-species aggregation. (a) Brequinar appears to form a negatively-charged dimer above pH 7, as indicated by a slope of +2 in the log S-pH plot. Sodium-drug salt precipitates above pH 9 [34]. (b) 3-(4-Heptyl-benzoyl)-benzoic acid appears to form an 8-monomer aggregate above pH 7, as indicated by the slope of +8 in the plot [35]. (c) Ciprofloxacin cation appears to form a pentameric aggregate below pH 6, as well as a phosphate salt for pH < pHmax [36]. The possibility of drug-phosphate complexation has not been ruled out.