Enhancement of transdermal delivery of phenylbutazone from liposomal gel formulations through deer skin.

Phenylbutazone (PBZ) is a nonsteroidal anti-inflammatory drug used in the treatment of chronic pain and arthritis. Topical and transdermal administration of PBZ would be beneficial in large animals in terms of minimizing gastro-intestinal ulcerations and other side effects, easy administration to legs and joints and minimizing the dose to reduce systemic toxicity of the drug. A topical liposomal preparation with different concentrations of a mono-substituted alkyl amide (MSA) and PBZ was formulated. The formulations were evaluated by in vitro skin-permeation kinetics through deer skin using Franz diffusion cells. By increasing drug loading from 1% to 5% w/w, the steady-state flux (microg/cm(2)/h) of PBZ was increased twofold (P < 0.001). Similarly, by increasing the MSA concentration from 0% to 4%, the steady-state flux (microg/cm(2)/h) of PBZ was increased twofold (P < 0.001). Overall, by increasing the drug load and the use of an appropriate amount of the penetration enhancer, the steady-state flux of PBZ through skin was increased fourfold (P < 0.001). MSA at both 2% and 4% w/w concentrations significantly increased the skin levels of PBZ as compared with control (P < 0.05). In conclusion, MSA served as an effective skin-penetration enhancer in the liposomal gel of PBZ for deer.