Copaiba Oil: Chemical Composition and Influence on In-vitro Cutaneous Permeability of Celecoxib

Background: Use of topical or transdermal administration of Celecoxib (Cxb) is an interesting strategy in cutaneous treatments since it reduces or avoids side effects of the oral route. However, Cxb´s high lipophilicity and the stratum corneum (SC) barrier impair cutaneous penetration. Objective: Evaluation of copaiba oil (C.O) as a potential skin penetration enhancer (P.E) for Cxb. Methods: The chemical composition of C.O was evaluated by GC-MS. Both in-vitro release and permeability assay of Cxb in Polyethylene glycol 400/ propylene glycol (PEG 400/PG) vehicle associated to C.O (1-50% w/w) were determined in a modified diffusion cell fitted with a synthetic hydrophobic membrane and pig ear skin as model, respectively. Results: GC-MS analysis of C.O showed that it is composed of sesquiterpenes (68.65%) and diterpenes (22.26%). Formulations containing 25% C.O (F4) and 50% C.O (F5) have shown in-vitro burst release in the first 2 h, but only F4 released 100% of drug after 24 h. The highest Cxb permeation across skin was obtained from F4 and the highest skin retentions for F4 and F5 in the stratum corneum and epidermis plus dermis. Conclusion: The increased Cxb permeability through skin and its retention for an extended time (24h) at 25% C.O suggest that it could be a promising adjuvant for the development of transdermal formulations of Cxb.