Different Techniques for Intranasal Delivery of Insulin to the Olfactory Cleft in Management of Anosmia: A Comparative Review

Anosmia means inability to recognize odors at an accurate level and is considered one of the serious health conditions. The pathophysiology has not been yet fully understood, and depends on the underlying cause, most commonly post-viral. Different treatment regimens have been used as auxiliary therapy for improving olfaction but have not been approved as final treatments. Currently, intranasal insulin has been developed as a treatment of anosmia and there are various methods for its local delivery to the olfactory epithelium (nasal sprays, gel foam, fast dissolving films, and air pump) with different doses. The aim of this review is to summarize the different methods of insulin delivery to the olfactory cleft and to evaluate the current literature assessing which method is the most effective. This systematic review study involved a literature search of various electronic databases, including PubMed, Google Scholar, Embase and Cochrane Library using a combination of keywords related to "intranasal insulin, olfactory dysfunction and anosmia". Seven articles followed the inclusion criteria and were included in the current review. The findings showed different variations in the observed effects on olfactory detection and discrimination based on different methods of insulin administered. Based on current review results, direct application of insulin into olfactory cleft (Gelfoam, Fast- dissolving films) has been reported to be more effective in management of anosmia over other forms of insulin delivery such as intranasal spray and air pump.