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Renin Angiotensin Mechanism.

Introduction to Nasal drug delivery system.

 

Introduction.

  • For a very long time, nasal drug administration has been used to produce both topical and systemic effects. 

  • Congestion, rhinitis, sinusitis, and other related allergic or chronic conditions are all treated through topical administration. 

  • Due to the lack of pancreatic and gastric enzymatic activity, the neutral pH of nasal mucus, and less dilution by gastrointestinal contents, the nasal route of drug delivery has been considered as a potential administration route to achieve faster and higher levels of drug absorption. 

  • It is an effective way to deliver medications, such as proteins and peptides, which are active at low doses and have no minimal oral bioavailability. 

  • One of the reasons for the low degree of absorption of peptides and proteins via the nasal route is rapid movement away from the absorption site in the nasal cavity due to the muco-ciliary clearance mechanism. 

  • Decongestants for cold-related nasal symptoms and antihistamines and corticosteroids for allergic rhinitis are two prominent therapeutic classes of drugs administered.

  • In contrast to oral and intravascular routes of administration, intranasal drug administration effectively increases the availability of drugs in the body. 

  • Compared to parenteral and oral administration, it provided a faster and longer period of drug absorption. 

  • Drugs commonly given by this route includes,

    • Analgesics (such as morphine), 

    • medications for the heart, such as propranolol and carvedilol, 

    • hormones, such as levonorgestrel, progesterone, and insulin, 

    • anti‐inflammatory agents such as indomethacin and ketorolac, 

    • antiviral drugs (acyclovir).

Advantages of nasal drug delivery:

  1. Drug degradation observed in the gastrointestinal tract is absent. 

  2. First pass metabolism in the liver is prevented. 

  3. It is possible to achieve quick drug absorption and action. 

  4. By using an absorption enhancer or another method, it is possible to increase the bioavailability of larger drug molecules. 

  5. For smaller drug molecules, nasal bioavailability is good. 

  6. Nasal drug delivery is a method for delivering medications to the systemic circulation that are not orally absorbed. 

  7. Convenient for the patients on long term therapy, when compared with parenteral medication. 

  8. Drugs possessing poor stability in g.i.t. fluids can be given by nasal route.

  9. Very useful for administration of polar compounds exhibiting poor oral absorption.

Limitations 

  1. The toxicity of absorption enhancers used in nasal drug delivery systems is not yet clearly established. 

  2. Relatively inconvenient to patients when compared to oral delivery systems since it may cause nasal irritation. 

  3. Nasal cavity has a smaller absorption surface area when compared to GIT. 

  4. Risk of local side effects and irreversible damage of the cilia on the nasal mucosa. 

  5. Certain surfactants used as enhancers may break and even dissolve membranes in high concentration. 

Mechanisms of Absorption:

  • The absorbed drugs from the nasal cavity must pass through the mucus layer; it is the first step in absorption. Small, unchanged drugs easily pass through this layer but large, charged drugs are difficult to cross. 

  • The principal protein of the mucus is mucin, it has the tendency to bind to the solutes, hindering diffusion. Additionally, structural changes in the mucus layer are possible as a result of environmental changes (i.e. pH, temperature, etc.) 

  • Common mechanisms by which a drug gets absorbed from nasopulmonary areas are as follows,

  • Mechanism 1:

    • It involves an aqueous route of transport, which is also known as the  paracellular route but slow and passive. 

    • There is an inverse correlation between intranasal absorption and the molecular weight of water-soluble com-pounds. 

    • The molecular weight greater than 1000 Daltons having drugs shows poor bioavailability. 

  • Mechanism 2-

    •  It involves transport through a lipoidal route and it is also known as the transcellular process. 

    • It is responsible for the transport of lipophilic drugs that show a rate dependency on their lipo-philicity. 

    • Drugs also cross cell membranes by an active transport route via carrier-mediated means of transport through the opening of tight junctions for example: chitosan, a natural biopolymer, opens tight junctions between epithelial cells to facilitate drug transport. 

What Affects Nasal Drug Absorption?

  1. Physicochemical properties of drugs:

    1. Molecular size. 

    2.  Lipophilic-hydrophilic balance. 

    3.  Enzymatic degradation in nasal cavity. 

    4.  Stability 

    5.  Solubility 

    6.  Physical state of drug 

    7.  Chemical state of drug 

  2. Nasal Effect:

    1. Membrane permeability. 

    2.  Environmental pH 

    3.  Muco-ciliary clearance 

    4.  Cold, rhinitis. 

    5.  Blood flow 

  3. Effect of drug formulation 

    1. Formulation (Concentration, pH, osmolarity) 

    2.  Delivery effects 

    3.  Drugs distribution and deposition. 

    4.  Viscosity 

    5.  Pharmaceutical excipients. 

Commonly asked questions.

  1. What is Nasal drug delivery system? Give its advantages and disadvantages.

  2. Discuss mechanisms of drug absorption for Nasal drug delivery system and also write advantages and disadvantages.

  3. What is Nasal drug delivery system? Give its advantages and disadvantages. Enlist different factors affecting drug absorption via Nasal drug delivery system.
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