AUTHOR=Sulimai Nurul H. , Ko Jeff C. , Jones-Hall Yava L. , Weng Hsin-Yi , Deng Meng , Breur Gert J. , Knipp Gregory T. 

TITLE=Evaluation of 25% Poloxamer As a Slow Release Carrier for Morphine in a Rat Model

JOURNAL=Frontiers in Veterinary Science

VOLUME=5

YEAR=2018

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2018.00019

DOI=10.3389/fvets.2018.00019

ISSN=2297-1769

ABSTRACT=<p>The objectives of this study were to evaluate poloxamer as a slow release carrier for morphine (M) and potential tissue irritation after subcutaneous poloxamer–morphine (PM) injection in a rat model. Based on the result of a previous <italic>in vitro</italic> work, 25% poloxamer, with and without morphine, and saline were administered in 14 rats’ flanks. Blood for morphine concentrations was automatically sampled at multiple preprogrammed time points using the Culex™ unit for 48 h. Skin tissues from the injection sites were harvested and evaluated for histopathological changes. Following M or PM administration, it was determined that the half-life (<italic>t</italic><sub>1/2</sub>) was significantly longer in the PM (5.5 ± 7.2 h) than M (0.7 ± 0.8 h) indicated a slow dissolution of poloxamer with morphine. The <italic>t</italic><sub>max</sub> was within 15 min and <italic>C</italic><sub>max</sub> was approximately three times higher with M than with PM, reaching 716.8 (±153.7 ng/ml) of plasma morphine concentrations. There was no significant difference in total area under the curve and clearance of M versus PM. Histology inflammatory scores were similar between M, PM, and poloxamer but were significantly higher than saline control. We concluded that 25% poloxamer was capable of increasing the <italic>t</italic><sub>1/2</sub> of morphine, without a significant tissue irritation.</p>