The hydrolysis reaction of Pen-K in the CTAB/n-C5H11OH/H2O O/W microemulsion has been studied by UV-vis spectra. The results show that the microemulsion can inhibit the hydrolysis of Pen-K, which indicates the lower charge density of the polar group of Pen-K and the decreased concentration of H^+ in the place where Pen-K locates.

Key words: INHIBITION, PENTANOL, MICROEMUSION, STABILITY, HYDROLYSIS, PENICILLIN G, ULTRAVIOLET SPECTROPHOTOMETRY