Copaiba oil enhances in vitro/in vivo cutaneous permeability and in vivo anti‐inflammatory effect of celecoxib

OBJECTIVES: The aim of this article was to use copaiba oil (C.O) to improve skin permeability and topical anti-inflammatory activity of celecoxib (Cxb). METHODS: Formulations containing C.O (1-50%) were associated with Cxb (2%). In vitro skin permeability studies were conducted using porcine ear skin. Histological analysis of the hairless mice skin samples after application of formulations was achieved with the routine haematoxylin/eosin technique. The anti-inflammatory activity was assessed using the AA-induced ear oedema mice model. KEY FINDINGS: The formulation containing 25% C.O promoted the highest levels of in vitro Cxb permeation through pig ear skin, retention in the stratum corneum (SC) and epidermis/dermis of pig ear skin in vitro (~5-fold) and hairless mice skin in vivo (~2.0-fold), as compared with the control formulation. At 25%, C.O caused SC disorganization and increased cell infiltration and induced angiogenesis without clear signs of skin irritation. The formulation added to 25% C.O as adjuvant inhibited ear oedema and protein extravasation by 77.51 and 89.7%, respectively, and that it was, respectively, 2.0- and 3.4-fold more efficient than the commercial diethylammonium diclofenac cream gel to suppress these inflammatory parameters. CONCLUSIONS: 25% C.O is a potential penetration enhancer for lipophilic drugs like Cxb that can improve cutaneous drug penetration and its anti-inflammatory activity.