The nasal route of drug delivery, a part of Novel Drug Delivery Systems (NDDS), offers a promising alternative to traditional routes by leveraging the nasal cavity's unique properties for effective drug administration.
It supports local, systemic, and even central nervous system (CNS) delivery of therapeutic agents.
Advantages
Bypassing First-Pass Effect: Avoids hepatic metabolism, enhancing bioavailability.
Rapid Onset: Rich vascularization allows for quick absorption.
Patient Compliance: Non-invasive and easy to use.
Potential CNS Delivery: Drugs can reach the brain via the olfactory and trigeminal nerve pathways.
Disadvantages
Limited Volume: Only small drug volumes can be administered.
Enzymatic Barrier: Nasal enzymes may degrade certain drugs.
Mucosal Irritation: Some drugs may irritate the nasal mucosa.
Mucociliary Clearance: Ciliary movement can clear drugs, reducing absorption time.
Mechanisms of Nasal Absorption
Transcellular Transport: Lipophilic drugs diffuse through epithelial cells.
Paracellular Transport: Hydrophilic drugs pass between epithelial cells via tight junctions.
Transcytosis: Larger molecules like peptides and proteins are transported in vesicles.
Neuronal Transport: Direct drug transport to the CNS via olfactory and trigeminal nerves.
Factors Influencing Nasal Drug Absorption
Drug Properties
Molecular Weight: Smaller molecules permeate more easily.
Lipophilicity: Balanced lipophilicity is crucial for efficient absorption.
Formulation Factors
pH and Ionic Strength: pH affects drug ionization and compatibility with the nasal mucosa.
Viscosity: Higher viscosity can enhance residence time but may complicate administration.
Absorption Enhancers: Surfactants, fatty acids, and chelating agents improve permeability but must be used cautiously to avoid irritation.
Physiological Factors
Nasal Pathology: Conditions like rhinitis can alter drug absorption.
Mucociliary Clearance: Reduces residence time by moving drugs towards the throat.
Blood Flow: Affects the rate of drug uptake.
Device-Related Factors
Device design impacts deposition and absorption efficiency within the nasal cavity.
Applications
Local Action: Allergic rhinitis, sinusitis.
Systemic Action: Drugs like peptides, proteins, and hormones (e.g., calcitonin, insulin).
Vaccination: Nasal delivery of vaccines for mucosal immunity.
Brain Delivery: Treatments for neurological disorders via the nose-to-brain pathway.
Nasal drug delivery systems offer versatile and effective options for both local and systemic therapies.
Their non-invasive nature, rapid onset, and potential for CNS delivery make them a cornerstone of emerging drug delivery technologies.