Design and evaluation of prednisolone acetate eye drops with prolonged effect

The potentiality of interaction of prednisolone acetate with six cyclodextrins [CyDs], namely alph-, beta-, gamma-, dimethyl-beta-CyD [DM-beta-CyD], trimethyl-beta-CyD [TM-beta-CyD] and hydroxypropyl-beta-cyclodextrin [HP-beta-CyD] was monitored by spectrophotometric measurements. The results revealed formation of equimolar complexes in these systems. The apparent solubility of prednisolone acetate in water was found to increase linearly with increasing CyD concentration or CyD combined with 0.25% polyvinylpyrrolidone [PVP] or hydroxyethylcellulose [HEC]. The partition coefficient of prednisolone acetate and its complexes between n-octanol and phosphate buffer of pH 6.7 was determined. The effect of CyDs on the permeation of prednisolone acetate through semi-permeable membrane was also investigated. The results revealed that all investigated CyDs increase the permeation of prednisolone acetate. The effect of CyDs or CyDs combined with 0.25% PVP or HEC on the bioavailability of prednisolone acetate eye drops was assessed by measuring the intraocular pressure [IOP] in rabbits. The results indicated the possibility of utilizing a formula containing beta-CyD together with 0.25% PVP or HEC for preparing prednisolone acetate eye drops characterized by an increased biological availability of the drug as well as a marked prolongation of its effect extending up to a period of 18 hr

Dissolution rate measurements as a predictory tool for assessing comparative bioavailability of generic ampicillin capsules

The dissolution rate of 12 batches of commercial ampicillin capsules manufactured by four leading pharmaceutical companies was determined by both closed and open dissolution systems. The most consistent results were those obtained by the USP method. The beaker as well as flow-through methods showed higher discriminating ability for differentiating the dissolution behavior of different batches of ampicillin capsules of the same brand. On the other hand, the flow- through method provided best discrimination of the dissolution characteristics of different brands. At the same time, the USP rotating basket method did not afford good discriminating ability for different lots belonging to the same brand or for different brands. The bioavailability of these products was assessed in human subjects according to a Latin square design

Interaction of xanthines with khellin

The potentiality of interaction of khellin with certain xanthine derivatives, viz, caffeine, theophylline, acepifylline and dyphelline was investigated. Differential ultraviolet spectrophotometry revealed a marked effect of xanthines on the exthinction coefficient of khellin. Applying continuous variation method on spectrophotometric measurements revealed the formation of 1: 1 complexes between khellin and caffeine or theophylline, 2: 1 khellin- acepifylline as well as 1: 2 khellin - dyphelline complexes. The results of determination of the stability constant of the complexes revealed that theophylline and caffeine exhibit the highest tendency to complex with khellin, while acepifylline and dyphelline show a more or less weak tendency. The dissolution of khellin as well as the investigated khellin complexes was found to follow first order kinetics during the first 30 min of the dissolution run. On the other hand, the solublizing power of the investigated xanthine derivatives was also calculated