Bimatoprost-loaded ocular inserts as sustained release drug delivery systems for glaucoma treatment: in vitro and in vivo evaluation.

The purpose of the present study was to develop and assess a novel sustained-release drug delivery system of Bimatoprost (BIM). Chitosan polymeric inserts were prepared using the solvent casting method and characterized by swelling studies, infrared spectroscopy, differential scanning calorimetry, drug content, scanning electron microscopy and in vitro drug release. Biodistribution of 99mTc-BIM eye drops and 99mTc-BIM-loaded inserts, after ocular administration in Wistar rats, was accessed by ex vivo radiation counting. The inserts were evaluated for their therapeutic efficacy in glaucomatous Wistar rats. Glaucoma was induced by weekly intracameral injection of hyaluronic acid. BIM-loaded inserts (equivalent to 9.0 µg BIM) were administered once into conjunctival sac, after ocular hypertension confirmation. BIM eye drop was topically instilled in a second group of glaucomatous rats for 15 days days, while placebo inserts were administered once in a third group. An untreated glaucomatous group was used as control. Intraocular pressure (IOP) was monitored for four consecutive weeks after treatment began. At the end of the experiment, retinal ganglion cells and optic nerve head cupping were evaluated in the histological eye sections. Characterization results revealed that the drug physically interacted, but did not chemically react with the polymeric matrix. Inserts sustainedly released BIM in vitro during 8 hours. Biodistribution studies showed that the amount of 99mTc-BIM that remained in the eye was significantly lower after eye drop instillation than after chitosan insert implantation. BIM-loaded inserts lowered IOP for 4 weeks, after one application, while IOP values remained significantly high for the placebo and untreated groups. Eye drops were only effective during the daily treatment period. IOP results were reflected in RGC counting and optic nerve head cupping damage. BIM-loaded inserts provided sustained release of BIM and seem to be a promising system for glaucoma management.

[Circadian rhythm variations of intraocular pressure and therapeutic decisions: interpretation of clinical trial results based on a statistical model]. / Variations nycthémérales de la pression intraoculaire et décisions thérapeutiques: Interprétation des résultats d'essais cliniques à partir d'un modèle statistique.

Therapeutic decisions (treatment initiation, continuation, change, combination, etc.) based on intraocular pressure (IOP) monitoring require knowledge of both circadian IOP fluctuations and the pharmacological circadian rhythm of the active ingredients. A simple model was applied to data from two clinical trials to estimate the consequences of circadian IOP fluctuations on (1) ocular hypertension diagnosis, (2) therapeutic adjustments, and (3) the daily cumulative effect of marginally low therapeutic differences. A grid for clinical interpretation of the average IOP differences is presented. The probability of an IOP that exceeds the target value for the diagnosis or therapy varied to a large extent throughout the day. IOP was higher in the morning than in the evening. The IOP variance (measured by standard deviation) was an important factor in decision-making, regardless of the IOP value itself. Regular IOP monitoring over the entire day allowed minimization of the time spent above a target value. IOP differences that seemed low when expressed in average values in therapeutic trials could have clinically significant consequences in the practitioner's decisions. The data presented suggest that ocular hypertension diagnosis and therapeutic decisions should be made early in the morning, at least for most patients. In any case, the time of the measurement should be considered in the therapeutic approach.