Effect of hydroxypropyl-beta-cyclodextrin on the solubility, stability and in-vitro release of ciprofloxacin for ocular drug delivery.

Eye drops in the form of an aqueous solution with a lower viscosity are preferred for local administrations in ophthalmology. In ophthalmic formulations, cyclodextrins (CDs) are frequently used in recent years in order to increase water solubility, stability and bioavailability of an active substance and decrease an irritation to the eye. The scope of the present study was to investigate the influence of hydroxypropyl-beta-cyclodextrin (HPCD) on the solubility, stability and in vitro release of ciprofloxacin (CIP). According to the phase solubility studies, A(L) type solubility curve was obtained. HPCD improved the solubility of CIP 3 times at pH 5.5 and 2 times at pH 7.4. The two month stability studies indicated that CIP was more stable at pH 5.5 than at pH 7.4 and the stability of CIP was significantly increased by HPCD. The stability constant of the HPCD:CIP complex was increased further by a-ddition of 0.1% (w/v) polymer (HPMC and PVP) to the aqueous medium including HPCD. Stability constant of solutions prepared in an ultrasonic water bath was higher than solutions prepared by heating in an autoclave. The results indicated that the CIP:HPCD complex increased in vitro release of CIP and the addition of polymer promoted this increase even more.