Amphoteric drugs

Tam, K. Y. Multiwavelength spectrophotometric resolution of the micro-equilibria of a triprotic amphoteric drug methacycline. Mikrochim. Acta 2001, 136, 91-97. 

Takacs-Novak, K., Tam, K. Y. Multiwavelength spectrophotometric determination of add dissodation constants. Part V. Microconstants and tautomeric ratios of diprotic amphoteric drugs./. Pharm. Eiomed. Anal. 2000, 17, 1171-1182. 

Rifampin is an amphoteric drug substance theoretical concentration ratio was based on its behavior as an organic acid. pKa value given for aminoglycosides is unconfirmed. 

Mixed mode Reverse-phase (C ) cmd cation-exchange phase Isolation of basic and amphoteric drugs from serum, plasma, and urine... 

Figure 8.4. Four-step process for the isolation of basic and amphoteric drugs using mixed-mode sorbents.

Lipophilicity profiles of amphoteric drugs are more complicated than partitioning of simple acids and bases. A comprehensive review of the issues encountered in the determination of logF/Z) of amphoteric compounds has been published by Pagliara et al. ... 

An ammonia diffusion system is applicable to amphoteric drug substances. In this method, the mixture of three partially immiscible solvent i.e. acetone, ammonia water, dichloromethane was used as crystallization system. In this system ammonia water acted as bridging liquid as well as good solvent, acetone as the water miscible but poor solvent, thus drug precipitated by solvent change without forming ammonium salt. Water immiscible solvent such as hydrocarbon or halogenated hydrocarbons e.g. dichloromethane induced liberation of ammonia water. 

Figure 4.11 Morphine, an amphoteric drug. The pi is the isoelectric pH at which the positive and negative charges are balanced. 

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