*Article* **Intranasal Zolmitriptan-Loaded Bilosomes with Extended Nasal Mucociliary Transit Time for Direct Nose to Brain Delivery**

**Mai M. El Taweel \*, Mona H. Aboul-Einien, Mohammed A. Kassem and Nermeen A. Elkasabgy**

Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Cairo University, Kasr El-Aini Street, Cairo 11562, Egypt; mona.abouleinien@pharma.cu.edu.eg (M.H.A.-E.); mohamed.kassem@pharma.cu.edu.eg (M.A.K.); nermeen.ahmed.elkasabgy@pharma.cu.edu.eg (N.A.E.) **\*** Correspondence: mai.eltaweel@pharma.cu.edu.eg

**Abstract:** This study aimed at delivering intranasal zolmitriptan directly to the brain through preparation of bilosomes incorporated into a mucoadhesive in situ gel with extended nasal mucociliary transit time. Zolmitriptan-loaded bilosomes were constructed through a thin film hydration method applying Box–Behnken design. The independent variables were amount of sodium deoxycholate and the amount and molar ratio of cholesterol/Span® 40 mixture. Bilosomes were assessed for their entrapment efficiency, particle size and in vitro release. The optimal bilosomes were loaded into mucoadhesive in situ gel consisting of poloxamer 407 and hydroxypropyl methylcellulose. The systemic and brain kinetics of Zolmitriptan were evaluated in rats by comparing intranasal administration of prepared gel to an IV solution. Statistical analysis suggested an optimized bilosomal formulation composition of sodium deoxycholate (5 mg) with an amount and molar ratio of cholesterol/Span® 40 mixture of 255 mg and 1:7.7, respectively. The mucoadhesive in situ gel containing bilosomal formulation had a sol-gel temperature of 34.03 ◦C and an extended mucociliary transit time of 22.36 min. The gelling system possessed enhanced brain bioavailability compared to bilosomal dispersion (1176.98 vs. 835.77%, respectively) following intranasal administration. The gel revealed successful brain targeting with improved drug targeting efficiency and direct transport percentage indices. The intranasal delivery of mucoadhesive in situ gel containing zolmitriptan-loaded bilosomes offered direct nose-to-brain drug targeting with enhanced brain bioavailability.

**Keywords:** zolmitriptan; intranasal; bilosomes; sodium deoxycholate; mucoadhesive gel; brain targeting
