In vitro study on tamsulosin release kinetics from biodegradable PLGA in situ implants

The objective of this study was to evaluate the effect of drug loading and the effect of excipients on the release pattern of tamsulosin tydrochloride from in situ PLGA implants formed in vitro in gelatin gel. This system is prepared by dissolving a biodegradable polymer (DL-PLGA 70K) in biocompatible solvent, dimethyl sulfoxide (DMSO). Then either the drug or drug with excipients was added to it. The drug solution was poured into the hollow of gelatin gel, the solvent dissipated into the surrounding gelatin base through diffusion leading phase separation and subsequent coagulation of the polymer. The drug formed a rod like implant in situ. Two types of implants were prepared such as implants containing tamsulosin hydrochloride and implants containing tamsulosin hydrochloride with biocompatible excipients such as Tween 20, Tween 60, Span 20, Span 80, Chremophore EL, or Chremophore RH 40. In vitro dissolution studies were performed in static condition using phosphate buffer (pH 7.4) to observe the release of drugs from these implants for 10 days. Formulation containing only tamsulosin hydrochloride showed that drug loading was 83.54%, 90.23%, 86.72%, 89.17% and 94.08% against the actual drug content of 9.09%, 13.04%, 16.67%, 20% and 23.08% respectively. The release rate of drug was 64.51%, 70.64%, 74.08%, 76.12% and 80.05% accordingly. It can be concluded that the release rate of drug increases with increasing drug concentrations. The other formulation containing tamsulosin with excipients showed that the release rate was 74.70%, 75.14%, 60.03%, 63.83%, 70.82% and 76.43% against same conc. of drug (8.7% of drug) but different excipients such as tween 20, tween 60, span 20, span 80, chremophore EL and chremophore RH 40 respectively. The loading efficiency was 79.33%, 87.34%, 91.91%, 94.19%, 88.48% and 95.34% respectively. It can be concluded that excipient lowers the release rate of the drug and may prolong the activity and overall release kinetics.