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In vitro characterization of a formulation of butorphanol tartrate in a poloxamer 407 base intended for use as a parenterally administered slow-release analgesic agent.

In vitro characterization of a formulation of butorphanol tartrate in a poloxamer 407 base intended for use as a parenterally administered slow-release analgesic agent. Lainesse D, Smith DA, Kynch HK, et al. Am J Vet Res. 2017;78:677-687.

Objective--To assess rheological properties and in vitro diffusion of poloxamer 407 (P407) and butorphanol-P407 (But-P407) hydrogels and to develop a sustained-release opioid formulation for use in birds.

Sample--P407 powder and a commercially available injectable butorphanol tartrate formulation (10 mg/mL).

Procedures--P407 and But-P407 gels were compounded by adding water or butorphanol to P407 powder. Effects of various concentrations of P407 (20%, 25%, and 30% [{weight of P407/weight of diluent} X 100]), addition of butorphanol, and sterilization through a microfilter on rheological properties of P407 were measured by use of a rheometer. In vitro diffusion of butorphanol from But-P407 25% through a biological membrane was compared with that of a butorphanol solution.

Results--P407 20% and 25% formulations were easily compounded, whereas it was difficult to obtain a homogenous P407 30% formulation. The P407 was a gel at avian body temperature, although its viscosity was lower than that at mammalian body temperature. The But-P407 25% formulation (butorphanol concentration, 8.3 mg/mL) was used for subsequent experiments. Addition of butorphanol to P407 as well as microfiltration did not significantly affect viscosity. Butorphanol diffused in vitro from But-P407, and its diffusion was slower than that from a butorphanol solution.

Conclusions and Clinical Relevance--But-P407 25% had in vitro characteristics that would make it a good candidate for use as a sustained-release analgesic medication. Further studies are needed to characterize the pharmacokinetic and pharmacodynamic properties of But-P407 25% in vivo before it can be recommended for use in birds.

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Title Annotation:Selected Abstracts from the Literature
Publication:Journal of Avian Medicine and Surgery
Article Type:Report
Date:Sep 1, 2017
Words:284
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