Table 1.

Characteristics of selected microemulsions

Formulation	Original		pH = 5		With druga
	Size(nm)/P.I.	Zeta potential (mV)	Size(nm)/P.I.	Zeta potential (mV)	Size(nm)/P.I.	Zeta potential (mV)
ME-O	50.3/0.21	−1.1	—	—	53.5/0.22	−1.9
ME-W	43.4/0.20	−2.5	42.0/0.18	−2.7	47.8/0.22	−2.5
ME-Wphy	50.7/0.18	−4.3	53.2/0.21	+29.1	54.8/0.18	+20.1

P.I., polidispersity index. ^aSize and zeta potential for ME-O containing drug were determined at the original pH, whereas these parameters for ME-W and ME-Wphy were determined after pH adjustment to 5.