Drug delivery through nose: A noninvasive technique for brain targeting

Majority of drugs are usually introduced through oral or intra-venous route for fast action, better patient compliance and ease of drug administration. However, the low bioavailability and limited brain exposure of orally administered drugs pose a huge challenge to treat neurodegenerative and psychiatric disorders. So, the situation demands for targeting the drug to brain. For brain targeting, a number of factors are considered viz. molecular weight, route of administration, lipophilic character of drug and blood brain barrier (BBB). These factors limit the movement of drug into brain tissue through BBB. To overcome these problems, intranasal drug administration is one of the promising routes that bypasses BBB and cuts down the dose to be administered with better brain exposure to drug. Nasal route has been used for the administration of antihistamines, local analgesics and corticosteroids intended for local drug delivery in nasal allergy, nasal congestion and nasal infection. However, systemic drug delivery through this route has also been explored in recent times. For nose to brain drug delivery, olfactory and respiratory region are utilized which also enable delivery of larger molecules to reach brain tissues. Such delivery systems are generally pH or temperature dependent. Certain diseases of nervous system like migraine, dementia, parkinsonism, epilepsy and Alzheimer’s disease can be successfully treated through this route. This review attempts to highlight the anatomy of nose, mechanisms of drug delivery from nose to brain, critical factors in the formulation of delivery systems, nasal formulations and applications of nasal route for delivery of various drugs.