International Journal of Pharmaceutics 219 (2001) 61 – 72 Effect of liposomes and niosomes on skin permeation of enoxacin Jia-You Fang a, *, Chi-Tzong Hong b , Wen-Ta Chiu c , Ying-Yue Wang a,d a Graduate Institute of Pharmaceutical Sciences, Taipei Medical Uniersity, 250 Wu -Hsing Street, Taipei, Taiwan b Department of Neurology, Taipei Municipal Wan Fang Hospital, Taipei Medical Uniersity, Taipei, Taiwan c Department of Neurosurgery, Taipei Municipal Wan Fang Hospital, Taipei Medical Uniersity, Taipei, Taiwan d Department of Pharmaceutics, Mackay Memorial Hospital, Taipei, Taiwan Received 6 December 2000; received in revised form 12 February 2001; accepted 19 February 2001 Abstract The skin permeation and partitioning of a fluorinated quinolone antibacterial agent, enoxacin, in liposomes and niosomes, after topical application, were elucidated in the present study. In vitro percutaneous absorption experi- ments were performed on nude mouse skin with Franz diffusion cells. The influence of vesicles on the physicochemical property and stability of the formulations were measured. The enhanced delivery across the skin of liposome and niosome encapsulated enoxacin had been observed after selecting the appropriate formulations. The optimized formulations could also reserve a large amount of enoxacin in the skin. A significant relationship between skin permeation and the cumulative amount of enoxacin in the skin was observed. Both permeation enhancer effect and direct vesicle fusion with stratum corneum may contribute to the permeation of enoxacin across skin. Formulation with niosomes demonstrated a higher stability after 48 h incubation compared to liposomes. The inclusion of cholesterol improved the stability of enoxacin liposomes according to the results from encapsulation and turbidity. However, adding negative charges reduced the stability of niosomes. The ability of liposomes and niosomes to modulate drug delivery without significant toxicity makes the two vesicles useful to formulate topical enoxacin. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Enoxacin; Liposomes; Niosomes; Skin permeatiom www.elsevier.com/locate/ijpharm 1. Introduction Liposomes, prepared from a variety of natural and synthetic phospholipids, are being considered as drug-carrying structures or vesicles. They may serve as a solubilization matrix, as local depot for sustained release of dermally active compounds, as permeation enhancers, or as a rate-limiting membrane barrier for the modulation of systemic absorption of drugs via the skin (Schreier and Bouwstra, 1994). Niosomes, non-ionic surfactant vesicles, are now widely studied as an alternative to liposomes. These vesicles appear to be similar * Corresponding author. Tel.: +886-2-27361661; fax: + 886-2-27074804. E-mail address: fajy@ms9.tisnet.net.tw (J.-Y. Fang). 0378-5173/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0378-5173(01)00627-5