Intranasal administration of melatonin starch microspheres

Using melatonin as model drug, starch microspheres for intranasal administration were prepared by an emulsification-crosslinking technique using a uniform design to optimize preparation conditions. The entrapment ratio of melatonin in the microspheres was 11.0% and particle sizes ranged from 30 to 60 mum. Melatonin was released from the microspheres in a sustained manner in vitro. Nasal clearance of Tc-99m labeled starch microspheres was investigated using gamma scintigraphy. It was revealed that >80% of the starch microspheres could be detected in the nasal tissue 2 h after administration, compared to 30% for a solution. The pharmacokinetics of melatonin starch microspheres was investigated after intranasal administration. The absorption rate was rapid (T-max = 7.8 min), and the absolute bioavailability was high, 84.07%. A good correlation was found between in vitro release and in vivo absorption data. (C) 2004 Elsevier B.V. All rights reserved.