Effect of the buffer system on stability of tetracaine hydrochloride 0.5% eyedrops

The effect of the buffer system on the stability of tetracaine hydrochloride in eyedrop formulation was evaluated. Eyedrop formulations containing tetracaine hydrochloride 0.5%(w/v) were prepared using different buffer systems (acetate, phosphate and borate buffer) under a constant pH of 5.4, and a buffer concentration of 0.06M. Long-term tests at 26 o C and accelerated stability tests at elevated temperature (45, 50, 60 oC) over a period of 168 days were carried out by following the macroscopic view, pH, sterility, content of tetracaine hydrochloride and detection of the degradation products. Also, values of the constant of degradation rate at different temperatures and t90% were calculated. The phosphate and acetate buffers provided satisfactorystability of tetracaine hydrochloride eyedrops, while borate buffer was not sufficient to maintain the pH value of the solution

Biopharmaceutical characterization of topical liposome formulations bearing 5-fluorouracil

Liposome dispersions and liposome gel formulations for topical administration were evaluated as modified release delivery systems for 5-fluorouracil. Drug substance has been entrapped in the internal aqueous compartment of liposomes during the preparation. The concentration of 5-fluorouracil in the hydration medium was varied and the effect on the liposome characteristics was considered. Liposome gel formulations were prepared by incorporation of liophylized liposomes into a structured vehicle of chitosan. The decrease of the amount of aqueous phase bearing total drug quantity (drug/aqueous phase ratio from 1:100, 1:60, 1:40) led to an increase of the percentage of liposome-entrapped drug, and decreased percentage of drug release, while particle size analysis showed no changes in vesicle size. Liposome gel formulations showed initially a higher drug release rate in comparision with liposome dispersions, which could be related to the release of “free” 5-fluorouracil, leaked from liposomes due to the process of liophylization. This was followed by slower release (after 1.5 hour) as a result of the influence of the viscosity of the gel matrix