Introduction
The long-used method of intranasal medication delivery is currently regaining popularity. It is a useful method for administering medications such as proteins and peptides that require very little and do not dissolve well in the mouth. Because it eliminates several issues that arise when drugs or medicine are taken through the mouth. The nose is a convenient way to administer medication. It is quick to operate, easily accessible, and self-sufficient. It also does not hurt, requires no extra preparation, and is simple to perform even in an emergency.
What Is the Anatomy of the Nose?
The nasal vestibule is the front aperture of the nasal cavity, which is separated from the throat by the nasal septum. It is divided into three areas: the respiratory area for breathing, the olfactory area for smelling, and the vestibule where air enters. A lot of surface area is available for absorption since the nasal cavity walls are folded. Turbinates in these folds aid in warming and filtering the air. The mucus, primarily water, is secreted by the mucous membrane lining the nasal cavity to trap particles and guard against germs.
What Is the Mechanism of Nasal Absorption?
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First Mechanism: In this mechanism, medicines are slowly transported through tiny spaces between cells using water. Since it is passive, no energy is needed for it. Drug molecules vary in size; larger molecules, particularly those with more than 1000 Daltons, do not absorb as well.
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Second Mechanism: Here, medications pass via lipids, the oily portions of cells. This is a more active process influenced by the drug's affinity for fat. Additionally, drugs can cross cell walls with the aid of transporters or apertures, occasionally utilizing energy.
What Are the Advantages and Limitations of Intranasal Drug Delivery?
Benefits of Nasal Drug Administration:
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It prevents the liver from breaking it down first.
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Drugs take effect soon after absorption.
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Enhancers facilitate better absorption of larger medicines.
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Smaller medications are easily absorbed through the nose.
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Even medications that are ineffective when taken orally can nonetheless enter the body.
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It can take on the role of injections, particularly for peptides and proteins.
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It is more practical for long-term care than injections.
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It is effective for medications that pass quickly through the stomach.
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Excellent for substances that are poorly absorbed when ingested.
Limitation of Nasal Drug Administration:
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The safety of absorption enhancers is unknown.
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It may cause nasal irritation, which makes it less convenient than ingesting the medication.
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Regarding drug absorption, the nose has a smaller area than the stomach.
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Drug delivery can harm the cilia, or microscopic hairs, found in the nose.
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Certain substances used to aid in absorption may cause nasal irritation.
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Medication may go up in the lungs rather than the nose if not properly utilized.
What Are the Factors That Influence Intranasal Drug Delivery?
The following factors influence intranasal drug delivery:
Physicochemical Properties:
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Molecular Size: Molecular size plays a critical role in absorption. Larger molecules may find it difficult to get through the nose, whereas smaller molecules can.
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Lipophilic-Hydrophilic Balance: This refers to the drug's dissolution in water rather than fat. Medications dissolved in fats usually enter the body more easily through the nose.
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Enzymatic Degradation: Peptides and proteins, frequently employed in pharmaceuticals, can be broken down by enzymes in the nasal cavity. These enzymes may lessen the amount of these medications that enter the bloodstream when administered via the nose, decreasing their efficacy. The drug may undergo this breakdown process within the nasal cavity or crosses the nasal epithelial barrier, the layer of cells that divides the nasal cavity from the bloodstream. In either case, the amount of intact medication that is accessible for absorption is decreased by this enzymatic breakdown.
Effects on the Nasal passages:
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Membrane Permeability: The ease with which medications can flow through the nasal membrane is known as membrane permeability. Large molecules like proteins, peptides, and medications that dissolve in water have low membrane permeability. They are mostly taken up by a process known as endocytosis, which occurs in trace levels.
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Environmental pH: The nasal cavity's pH level impacts how well medications are absorbed. Certain medications are better absorbed when not charged or in a non-ionized state. Others that are slightly ionized are better absorbed. The path a medicine takes to pass through the nasal epithelial barrier depends on its shape.
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Mucociliary Clearance: Mucus and any other dissolved materials in the nasal cavity are removed by a process known as mucociliary clearance (MCC). This clearance is critical for keeping dangerous toxins out of the lungs. Because medications dissolved in mucus may be taken away before they are absorbed, the rate of this clearance influences drug absorption.
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Cold and Rhinitis: Drug absorption can be impacted by conditions such as rhinitis, which is characterized by inflammation of the nasal mucous membrane and increased production of mucus.
Factors Affecting Delivery:
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Formulation (Concentration, pH, Osmolarity): The nasal surface's pH and the drug's formulation can affect the absorption of the medication. Preventing irritation and enhancing drug penetration can be achieved by adjusting the pH to a certain range. Absorption is also influenced by the concentration gradient or variation in drug concentration across the nasal membrane.
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Viscosity: The drug's thickness impacts how long it adheres to the nasal mucosa. Formulations with a higher viscosity lengthen the contact time, enhancing medication penetration. However, highly viscous formulations can obstruct regular processes like mucociliary clearance.
What Are the Applications of Intranasal Drug Delivery?
The following are the applications of intranasal drug delivery:
Delivery of Regular Medications:
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Enhancers are unnecessary for the nasal mucosa to absorb many tiny, non-peptide medicines. This is because features like nasal turbinates give the nasal membrane a vast surface area and strong vascularization.
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Progesterone, estrogen, and other medications can enter the bloodstream virtually instantly by swiftly passing through the nasal mucosa. Compared to ingesting these medications, this may be quicker and more effective.
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Corticosteroids, hormones, vitamins, cardiovascular medications, and other medications can be administered through the nose.
Transport of Peptide-Based Medications:
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Proteins and peptides, such as insulin and hormones, are poorly absorbed through the stomach. Nasal administration is preferable because it can carry the medication straight into the bloodstream and avoid the stomach.
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However, enhancers, which may consist of specific chemicals or substances that improve the drug's absorption, are often required for these medications to promote absorption.
Drug Administration to the Brain:
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Drugs for diseases like Parkinson's and Alzheimer's must be delivered to the brain precisely and swiftly. Because the olfactory part of the nose offers a direct path to the brain, nasal administration can aid in this.
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Nasal delivery of medications such as neurotrophic factors or specific proteins can effectively treat brain-related disorders.
Delivery of Vaccines:
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Nasal vaccination delivery is successful due to the abundance of immunological tissue in the nasal passages. This indicates that the vaccination can promote both local and systemic (whole-body) immune responses.
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Nasal vaccinations can provide immunity against diseases such as measles, anthrax, influenza, and others. They do not require needles, are affordable, and are pleasant for patients.
Delivery of Diagnostic Agents:
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Nasal medication delivery is employed not only for therapeutic purposes but also for diagnostic purposes. Diagnostic chemicals such as secretin for pancreatic problems or phenolsulfonphthalein for kidney function can be delivered through the nose for quicker findings and less toxicity.
Conclusion
Intranasal medication distribution is a useful and developing strategy in contemporary medicine that combines efficiency, practicality, and patient-centeredness. Nasal drug absorption is influenced by membrane permeability, environmental pH, mucociliary clearance, and formulation characteristics. These factors affect drug delivery efficiency through the nasal cavity, impacting bioavailability and therapeutic efficacy.
Understanding and optimizing these variables are essential for developing effective nasal drug delivery systems across various pharmaceutical applications. Researchers expect more discoveries to maximize therapy results and change standards of care across various medical illnesses as research and development in this field continue to grow.
