Development of patch and spray formulations for enhancing topical delivery of sinomenine hydrochloride

The purpose of this work was to investigate feasibility of a promising topical drug delivery system (TDDS) for sinomenine hydrochloride (SMH), extracted from the Chinese medicinal plant sinomenine acutum and currently used for the treatment of rheumatoid arthritis. It was found that SMH was a weak base (pKa, 7.98 ± 0.04) with pH‐dependent solubility and partition coefficient. The result of in vitro permeation studies demonstrated that the permeation enhancer azone was the most effective. In contrast, spray had higher accumulative permeated amounts of SMH than patch, but permeated duration of spray was shorter than that of patch. The efficacy on Freund's complete adjuvant‐induced arthritis suggested that there was near arthritis index for SMH spray with medium dose (i.e., 15 mg/rat) and oral solution at a dose of 12 mg/rat, indicating that topical SMH delivery system could achieve the similar anti‐inflammatory efficacy with oral administration. Pharmacokinetic parameters including Cmax and AUC for both topical preparations were lower than those for oral preparation, which hinted that systemic side effect could be ignored. Therefore, the spray and patch were promising formulations for successful topical delivery of SMH through the skin instead of oral administration with side effects. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1790-1799, 2010