Left-Right Difference in Brain Pharmacokinetics Following Nasal Administration Via One-Site Nostrils.

The olfactory and trigeminal pathways are direct delivery pathways between the nose and brain. To determine the effect of direct delivery on drug distribution in the brain, two model drugs with different physical properties, antipyrine (ANP), with high membrane permeability, and ranitidine (RNT), with low membrane permeability, were selected. For ANP, direct delivery from the nose to the brain was observed only in the olfactory bulb beside the nasal cavity, with a direct transport percentage (DTP) of approximately 45 %, whereas in the frontal and occipital brains, the contribution from the systemic circulation to the brain was observed as the primary route of brain distribution.