Novel Liposome Aggregate Platform (LAP) system for sustained retention of drugs in the posterior ocular segment following intravitreal injection.

A novel Liposome Aggregate Platform (LAP) system for prolonged retention of drugs in the posterior eye segment after intravitreal injection (IVT) was developed and evaluated. Calcein, FITC-dextran-4000 (FD4) and Flurbiprofen (FLB), were encapsulated in negatively charged liposomes, and mixed with protamine to produce the LAP. The lipid/protamine ratio was fixed, in order to have a convenient aggregation rate permitting IVT injection and also a sustained release of liposome-entrapped molecules (in vitro) from LAP. In vitro release studies confirmed the potential of LAP system consisted of HPC/DPPG/Chol liposomes and protamine (at 1:1 w/w to lipid), to delay calcein, FD4 and FLB release, compared to free liposomes. In vivo studies demonstrated increased vitreous retention of liposomes and LAP for all molecules, compared to the corresponding solutions; however the retention of FD4 is similar for non-aggregated liposomes and LAP, and calcein retention is only slightly increased by LAP compared to liposomes. The later result may be connected with the visible ocular inflammation caused by both dyes; interestingly inflammation was moderately reduced when dyes were entrapped in liposomes and even more when in LAP. No visible inflammation was demonstrated for FLB, and the LAP system significantly increased the retention of FLB in the ocular tissues (compared to non-aggregated liposomes). Taking into account the capability of the novel LAP system to decrease inflammatory reactions towards calcein and FD4, and prolong the retention of FLB in ocular tissues, it is concluded that such systems, after further optimization, may be considered as promising effective and safe approaches for treatment of posterior segment ocular pathologies.

Pharmacokinetics and efficacy of intraocular flurbiprofen.

PURPOSE: Intravitreal delivery of non-steroidal anti-inflammatory drugs could be an effective way to treat macular edema caused by posterior segment inflammation. In this study, we evaluated the intravitreal bioavailability and anti-inflammatory efficacy of flurbiprofen in rabbit eyes. METHODS: For pharmacokinetics, 0.1 ml of 7.66 mg/ml flurbiprofen solution was injected intravitreally and vitreous drug levels were analyzed at specific time points using LC-MS technique. For efficacy, 100 ng lipopolysaccharide of E.coli was injected intravitreally in rabbits to induce inflammation. The animals were separated in three groups and received intraocular flurbiprofen, dexamethasone and PBS to serve as control. Complete ocular examination and total cell count in aqueous fluid were determined to evaluate the extent of inflammation. Eyes were then enucleated for histopathology analysis. The efficacy in the uveitis model was determined by clinical signs of inflammation, total leukocyte count and histology findings. RESULTS: No adverse events were observed during pharmacokinetic assessment. No signs of inflammation, hemorrhage or retina detachment were detected. The recovery of flurbiprofen from vitreous samples was 92.6%. The half-life of flurbiprofen was estimated to be 1.92 h with an elimination constant rate (K) of 0.36. Treatment with intraocular injections of flurbiprofen and dexamethasone significantly reduced total leukocyte count in a manner comparable to dexamethasone [reduction of 96.84% (p < 0.05) and 97.44% (p < 0.05), respectively]. Histologic studies demonstrated significantly less signs of ocular inflammation after flurbiprofen injection compared to control eyes. CONCLUSIONS: Flurbiprofen is effective in suppressing inflammation in this experimental uveitis model. In our experimental setting, intravitreal flurbiprofen seem to have a therapeutic result comparable to dexamethasone. However, the half-life of the drug remains short, necessitating further research to prolong its presence in the vitreous cavity.

Sustained release of intravitreal flurbiprofen from a novel drug-in-liposome-in-hydrogel formulation.

A novel Flurbiprofen (FLB)-in-liposome-in-hydrogel formulation was developed, as a method to sustain the release and increase the ocular bioavailability of FLB following intravitreal injection. For this, FLB loading into liposomes was optimized and liposomes were entrapped in thermosensitive hydrogels consisted of Pluronic F-127 (P). FLB solution, liposomes, and FLB dissolved in hydrogel were also used as control formulations. Actively loaded liposomes were found to be optimal for high FLB loading and small size, while in vitro studies revealed that P concentration of 18% (w/v) was best to retain the integrity of the hydrogel-dispersed liposome, compared to a 20% concentration. The in vitro release of FLB was significantly sustained when FLB-liposomes were dispersed in the hydrogel compared to hydrogel dissolved FLB, as well as the other control formulations. In vivo studies were carried out in pigmented rabbits which were injected through a 27G needle with 1mg/mL FLB in the different formulation-types. Ophthalmic examinations after intravitreal injection of all FLB formulations, revealed no evidence of inflammation, hemorrhage, uveitis or endophthalmitis. Pharmacokinetic analysis results confirm that the hybrid drug delivery system increases the bioavailability (by 1.9 times compared to solution), and extends the presence of the drug in the vitreous cavity, while liposome and hydrogel formulations demonstrate intermediate performance. Furthermore the hybrid system increases MRT of FLB in aqueous humor and retina/choroid tissues, compared to all the control formulations. Currently the potential therapeutic advances of FLB sustained release formulations for IVT administration are being evaluated.