The treatment of brain disorders is the greatest challenge because of a variety of formidable obstacles in effective drug delivery and maintaining therapeutic concentrations in the brain for a prolonged period. The brain is a delicate organ, and evolution built very efficient ways to protect it. The same mechanisms that protect it against intrusive chemicals can also frustrate therapeutic interventions. Approximately, 100% of large molecule drugs and > 98% of small molecule drugs do not cross the blood-brain barrier (BBB). Many advanced and effective approaches to brain delivery of drugs have emerged in recent years. Intranasal drug delivery is one of the important delivery options for brain targeting, as the brain and nose compartments are connected to each other via the olfactory/trigeminal route and via peripheral circulation. Realization of nose to brain transport and the therapeutic viability of this route can be traced from the ancient times and has been investigated for rapid and effective transport in the last two decades. Many patents have been filed in recent past, claiming enhanced delivery of intranasally administered therapeutics to the brain via olfactory/trigeminal neural pathways, use of novel devices for targeted delivery to olfactory region etc. Various models have been designed and studied by scientists to establish the qualitative and quantitative transport through nasal mucosa to brain. The development of nasal drug products for brain targeting is still faced with enormous challenges. A better understanding in terms of properties of the drug candidate, nose to brain transport mechanism, and transport to and within the brain is of utmost importance. A critical review of recent patents claiming different approaches for enhanced brain delivery through the nasal route will help in determining the focus of this promising area of research.
Keywords: Nose to brain transport, olfactory pathway, trigeminal pathway, CNS, BBB, intranasal delivery, brain disorders
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