Preliminary brain-targeting studies on intranasal mucoadhesive microemulsions of sumatriptan

The aim of this investigation was to prepare microemulsions containing sumatriptan (ST) and sumatriptan succinate (SS) to accomplish rapid delivery of drug to the brain in acute attacks of migraine and perform comparative in vivo evaluation in rats. Sumatriptan microemulsions (SME)/sumatriptan succinate microemulsions (SSME) were prepared using titration method and characterized for drug content, globule size and size distribution, and zeta potential. Biodistribution of SME, SSME, sumatriptan solution (SSS), and marketed product (SMP) in the brain and blood of Swiss albino rats following intranasal and intravenous (IV) administrations were examined using optimized technetium-labeled (^99mTc-labeled) ST formulations. The pharmacokinetic parameters, drug targeting efficiency (DTE), and direct drug transport (DTP) were derived. Gamma scintigraphy imaging of rat brain following IV and intranasal administrations were performed to ascertain the localization of drug. SME and SSME were transparent and stable with mean globule size 38±20 nm and zeta potential between -35 to -55 mV. Brain/blood uptake ratios at 0.5 hour following IV administration of SME and intranasal administrations of SME, SMME, and SSS were found to be 0.20, 0.50, 0.60, and 0.26, respectively, suggesting effective transport of drug following intranasal administration of microemulsions. Higher DTE and DTP for mucoadhesive microemulsions indicated more effective targeting following intranasal administration and best brain targeting of ST from mucoadhesive microemulsions. Rat brain scintigraphy endorsed higher uptake of ST into the brain. Studies conclusively demonstrated rapid and larger extent of transport of microemulsion of ST compared with microemulsion of SS, SMP, and SSS into the rat brain. Hence, intranasal delivery of ST microemulsion developed in this investigation can play a promising role in the treatment of acute attacks of migraine.