Naso -Pulmonary drug Delivery Systems: A novel and emerging platform for Targeted Respiratory and systemic Therapy

In ancient times the Indian Ayurvedic system of medicines used nasal route for administration of drug and the process is called as “Nasya” Intranasal drug delivery is now recognized to be a useful and reliable alternative to oral and parenteral routes. Undoubtedly, the intranasal administration of medicines for the symptomatic relief and prevention or treatment of topical nasal conditions has been widely used for a long period of time. [2] The medication being given and The intended place of action determine the kind of device that is used Breath old dilation, Leukotriene inhibitors and inhaled corticosteroid are among the several treatment that are Frequently given utilizing NPPDS for treatment of asthma Nasal Decongest: you can use Nasal spray that contain decongestant to treat nasal congestion brought on by allergies or Other like common cold; prescription drug for migranes such as the nasal spray, harmone Replacement therapy such as the administration of estrogen and testosterone is used for Harmone replacement therapy in the form of nasal spray . It has been suggested that using the nasal mucosa as an administration route could Increase and speed drug absorption. The reason for this is Because of its big surface area, porous endothelium membrane, high blood flow overall, ability to evade first pass metabolism, and convenient accessibility. Recent year have seen a significant amount of research on the nasal delivery of medication for systemic treatment, including peptide and protein medicines, among many other molecules [1] Nasal administration is a route of administration in which drugs are insufflated through the nose .It can be a form of either topical administration or systemic  ,administration, as the drugs thus locally delivered can go on to have either pirely local or systemic effects. In general, among the primary targets for intranasal administration are pharmacologically active compounds with poor stability in gastrointestinal fluids, poor intestinal absorption and/or extensive hepatic first-pass elimination, such as peptides, proteins and polar drugs. The nasal delivery seems to be a favorable way to circumvent the obstacles for blood-brain barrier (BBB) allowing the direct drug delivery in the bio phase of central nervous system (CNS)-active compounds. It has also been considered to the administration of vaccines. Pulmonary drug delivery is the inhalation of drug formulation through mouth and the further deposition of inhaled pharmacological agents in lower airways. Pulmonary delivered drugs are rapidly absorbed except large macromolecules drugs, which may yield low bioavailability due to enzymatic degradation and/or low mucosal permeability. Pulmonary bioavailability of drugs could be improved by including various permeation enhancers such as surfactants, fatty acids, and saccharides, chelating agents and enzyme inhibitors such as protease inhibitors. The most important issue is the protein stability in the formulation: the dry powder formulation may need buffers to maintain the pH, and surfactants such as Tween to reduce any chance of protein aggregation. The stabilizers such as sucrose are also added in the formulation to prevent denaturation during prolonged storage. The pulmonary route has gained increasing importance in the recent times due to its unique properties such as large absorptive area of up to 100m[2] extremely thin 0.1 μm absorptive mucosal membranes and good blood supply. The respiratory tract is one of the oldest routes used for the administration of drugs. Over the past decades inhalation therapy as established itself as a valuable tool in the local therapy of pulmonary diseases such as asthma or COPD (Chronic Obstructive Pulmonary Disease [3,4] A layer of mucus covers the nasal tube epithelium, this layer is replaced ever ten to fifteen minutes. In adult, the PH of mucosal secretion ranges from 5.5- 6.5, while in children it ranges from 5.0 to 6.7. Particular are caught in mucus layer and subsequently expelled from the nasal cavity by the cilia. Every 20 minutes, the mucus in the nose clear the particle moving through the pace of about 5-6mm/min. Numerous enzymes are also found in nasal cavity. These isoforms of cytochrome P450 enzyme have been found in human-CYPIA, CYP2A, CYP2E Additional enzyme found in human nose include glutathione s-transferase and carboxylesterase. In recent years, a workable solution for administering drugs through the nose has emerged: the Naso pulmonary drug delivery system. This comprehensive review looks into the potential applications and benefits of the drug delivery system as well as its future prospects [5] [6]

ADVANTAGES

Intranasal Delivery:

• Bypasses blood-brain barrier
• Suitable for CNS-active compounds
• Ideal for poor oral bioavailability compounds

Pulmonary Delivery:

• Rapid absorption, Good blood supply
• Large absorptive area (up to 100m²),Thin mucosal membranes (0.1 μm)
• Suitable for respiratory diseases (asthma, COPD),Requires permeation enhancers for large macromolecules

DISADVANTAGES

• Pathological conditions such as allergies and cold may alert      significantly the nasal bioavailability
• The histological toxicity of absorption enhancers used in nasal drug delivery system is not yet early established
• Relative inconvenient to patient when compared to oral delivery systems since they possibility of some irritation

Anatomy and Physiology of nose and pulmonary system

Nasal passages the intricate anatomical structure is situated between the nasopharynx and nostrils. It performs multiple activities including as breathing olfaction (smell perception) and airborne particles filtration. When it comes to nasal medicine administration its content and structure are particularly important [7]

5. The nasal cavity consists three main regions:

  1.Nasal vestibule

 2.Respiratory region

• Major drug absorption.
• 15-20 % of the respiratory cells covered by layer of long
• Cilia size 2-4 μm

3. Olfactory region

• Small area in the roof of the nasal cavity of about 10 cm2
• Drug is exposed to neurons thus facilitate it across the cerebro-spinal fluid.
• Normal pH of the nasal secretions in adult 5.5-6.5.
• Infants and young children 5.0-6.7.
• Nasal cavity is covered with a mucous membrane. Mucussecretion is
• composed of 95%-water,2%-mucin,1%-salts,1%-of other proteins

• Such as albumin, lysozyme and lactoferrinand 1%-lipids

{Fig: 2 Human respiratory system}

Vestibule:-

The first part of the respiratory tract to contact the external environment is the vestibule. Unlike the remaining nasal cavity, the vestibule is lined

with stratified squamous epithelium. [9]

 Nasal Valve and Airflow:-   

The nasal valve lies just posterior to the nasal vestibule. It is bounded laterally by the caudal end of the upper lateral cartilage, medially by the septum, and inferiorly by the lower rim of the pyriform aperture.

Nasal Septum:-

The nasal septum divides the nasal cavity into two separate compartments, increasing the total mucosal surface area. It consists of an anterior cartilaginous portion, which provides support for the nasal tip, and a posterior bony portion formed by the perpendicular plate of the ethmoid and the vomer.

Turbinates:-

The turbinate’s are three, rarely four, scroll-like projections from the lateral nasal wall. The lower two, referred to as the inferior and middle turbinate’s, are functionally the most significant. Each turbinate consists of a bony frame with overlying respiratory epithelium. Like the nasal septum, these aid in increasing the mucosal surface area of the nasal cavity to approximately 100 to 200 cm

Lungs:-

The lungs are the primary organs of the respiratory system in humans. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange

Nasopharyngeal region: -

This is also referred to as the “upper airways”, which involves the   respiratory airways from the nose down to the larynx. Trachea-bronchial region: -This is also referred to as the “central” or “conducting airways”, which starts at the larynx and extends via the trachea, bronchi, and bronchioles and ends at the terminal bronchioles.

Alveolar region: -

This is also referred to as the “respiratory airways”, “peripheral airways” or “pulmonary region”, Comprising the respiratory bronchioles, alveolar ducts and alveoli.

Pulmonary epithelium: -The lung contains more than 40 different cell types, of which more than six line the airways. The diversity of pulmonary epithelia can be illustrated by examining itsstructure at three principal levels.

The bronchi: -

These are lined predominantly with ciliated and goblet cells. Some serous cells, brush cells and Clara cells are also present with few Kulchitsky cells.

The bronchioles: -

These are primarily lined with ciliated cuboidal cells. The frequency of goblet and serous cells decreases with progression along the airways while the number of Clara cells increases.

The alveolar region: -This is devoid of mucus and has a much flatter epithelium, which becomes the simple squamous type, 0.1–0.5 μm thick.

{Cross-sectional view}

Site of drug spray & absorption

Pathways For Nasal Absorption

• Absorption through the olfactory neurons, transneuronal absorption. Olfactory epithelium is considered as a portal for substances to enter CNS.
• Absorption through the supporting cells & the  surrounding capillary bed.
• Venous drainage: a rich venous plexus is found under the mucous membrane which is drained by veins accompanying the arteries.
• Absorption into the cerebrospinal fluid 

Nose Brain Pathway:

• The olfactory mucosa (smelling area in nose) is in direct contact with the brain and CSF.
• Medications absorbed across the olfactory mucosa directly enter the brain.
• This area is termed the nose brain pathway and offers a rapid, direct route for drug delivery to the brain

{Nose Brain Pathway}

Mechanism of Drug Delivery in Nasal Drug Delivery System

Medium of Drug Delivery in the Nasal Drug Delivery System-medicines are absorbed through the nasal route by passing through the nasal mucosa, largely passable and vascularized membrane that lines the nasal depression. The nasal mucosa is a endearing route surface area and direct access to the bloodstream. To effectively transfer specifics from the nasal depression into the systemic rotation or to specifics locales within the respiratory tract, the medium of medicine   administration in nasal medicine delivery systems entails a number of pivotal process. The medicinal expression is generally scattered into the nasal as a liquid or as a greasepaint when administered. After that, the comes into contact with the nasal mucosa, which has a lot of blood vessels and a lot of area available for medicine penetration [10.11]

There are two introductory styles that the medicine’s patch can pass through the nasal mucosa

Transcellular pathway: -

lipophilic medication preferentially take up space in lipid bilayer of cell membrane  where they breakdown path. They go straight through the nasal mucosa lining epithelial cell

Paracellular pathway: -

This pathway is mainly used by hydrophilic medicine, which have difficulty passing through the cell membrane. They traverse the gap in between epithelial [12.13]

Two mechanisms have been considered predominantly out of several mechanisms that have been proposed.

The first involves an aqueous route of transport, which is also known as the paracellular route. Key feature of this mechanism involves

• This route is slow and passive.
• There is an inverse log-log correlation between intranasal absorption and the molecular weight of water-soluble compounds.
• Poor bioavailability was observed for a drug with a molecular weight greater  

The second involves transport through a lipoidal route is also known as the transcellular process and is responsible for the transport of lipophilic drugs that show a rate dependency on their lipophilicity. For examples, chitosan, a natural biopolymer from shellfish, opens tight junctions between epithelial cells to facilitate drug transport.[14.15.16]

Pathway For Drug Delivery Via Nasal Route

• ?Nasal cavity: The initial entry point for the drug.
•  Olfactory route: Pathway for drugs to reach the brain directly.
• Brain tissue: Target organ for certain drugs.
• Cerebrospinal fluid (CSF): Another potential pathway for drugs to reach the   
• Circulation: Drugs entering the bloodstream for systemic distribution.
• Tissues/Organs: Target sites for the drug's action.
• Elimination: Routes through which the drug is removed from the .[17.18.19]

Dosage forms in naso-pulmonary drug delivery system

1. Nasal drops

They are the most convenient and simple system developed for nasal drug delivery. Nose drops can be delivered with a squeezy or by a pipette a bottle. These pharmaceuticals formulations are often recommended for treating local conditions, which include suffering some challenges such as microbial growth, mucosal dysfunction, and non-specific loss of the nose or lower back. The featured disadvantage of this system is the lack of the dose precision, and therefore, nasal drops may not be useful for prescription products. It has been reported that nasal drops deposit human serum albumin in the nostrils more efficiently than nasal sprays.[20.21]  

2. Nasal sprays

Solution and suspension are formulated into nasal sprays. Availability of metered dose pumps and actuators, a nasal spray can deliver an exact dose from 25 to 200 μm. The morphology particles size (for suspensions) of the drug and viscosity of the formulation determine the choice of pump and actuator assembly.[22,23,24,25,]

Until the recent development of precise dosing device, there was not a lot of interest during this system. Nasal gels are high viscosity thickened solutions or suspensions. The benefits ofa nasal gel include the reduction of post-nasal drip due tohigh viscosity, reduction of taste impact due to reduced swallowing, reduction of anterior leakage of the formulation, reduction of irritation using soothing/emollient excipients, and target to mucosa for higher absorption.[26]

4. Nasal powder

This dosage form may be formulated if solution and suspension dosage forms cannot be formulated, for example, due to lack of drug stability. The advantages to the nasal powder dosage form are the absence of superior stability and preservative of the formulation. However, the suitability of the powder formulation is dependent on the solubility, particles size, aerodynamic properties, and nasal irritancy of the active drug and excipients. Local application of the drug is another advantage of this system .[27.28.29.30.31]

These are phospholipid vesicles composed by bilayer enclosing one or more aqueous compartments, in these compartments drug can be entrapped or adsorbed.

Microsphere has an important role in nasal drug delivery with enhancing absorption, sustained release, and also has great importance because it protects the drug from enzymatic degradation.[32]

Catheters are used to deliver the drops to a specified region of nasal cavity easily. Place the formulation in the tube andkept tube one end was positioned in the nose, and the solution was delivered into the nasal cavity by blowing through the other end by mouth. Dosing of catheters is determined by the filling prior to administration and accuracy of the system and this is mainly used for experimental studies only.[33]

Nebulizer is a device used to administer medication in the form of a mist inhaled into the lungs. The compressed air is filling into the device, so it is called compressed air nebulizers. The common technical principal for all nebulizers, isto either use oxygen, compressed air or ultrasonic power, as means to break up medical solutions/ suspensions into small aerosol droplets, for direct inhalation from the mouthpiece of the device. Nebulizers accept their medicine in the form of a liquid solution, which is often loaded into the device upon use. Corticosteroids and Bronchodilators such as salbutamol (Albuterol USAN) are often used, and sometimes in combination with ipratropium. The reason these pharmaceuticals are inhaled instead of ingested is in order to target their effect to the respiratory tract, whichspeeds onset of action of the medicine and reduces side effects, compared to other alternative intake routes This device is not suitable for the systemic delivery of drug by patient himself.[34.35]

smooth plastic bottle with a simple jet outlet. While pressing the plastic bottle the air inside the container is pressed out of the small nozzle, thereby atomizing a certain volume. By releasing the Squeezed nasal bottles are mainly used as delivery de-vice for decongestants. They include a pressure again air is drawn inside the bottle. This procedure often results in contamination of the liquid by microorganisms and nasal secretion sucked inside. Dose accuracy and deposition of liquids delivered via squeezed nasal bottles are strongly de-pendent on the mode of administration. The differences between vigorously and smoothly pressed applications influence the dose as well as the droplet size of the formulation. Thus the dose is hard to control. Therefore squeezed bottles with vasoconstrictors are not recommended to be used by children .[36]

10. Insufflators

Insufflators are the devices to deliver the drug sub-stance for inhalation; it can be constructed by using a straw or tube which contains the drug substance and sometimes it contains syringe also. The achieved particle size of these systems is often increased compared to the particle size of the powder particles due to insufficient deaggregation of the particles and results in a high coefficient of variation for initial deposition areas. Many insufflator systems work with pre-dosed powder doses in capsules.[37]

11.Dry powder inhalers (DPIs):-

Dry powder inhalers (DPIs) fall into two main types, passive or active, based on the airflow source for powder aerosolization. They are also classified into single-dose reusable, multidose, and single-use devices. DPIs are categorized based on dose capacity, patient involvement in powder aerosolization, and the mechanism of powder dispersion. Concerning dose capacity, they are classified into single-unit dose, multi-unit dose, and multi-dose reservoirs such as asthma, bronchitis, emphysema and COPD and have also been used in the treatment of diabetes mellitus. The medication is commonly held either in a capsule for manual loading or a proprietary form from inside the inhaler. Once loaded or actuated, the operator puts the mouthpiece of the inhaler into their mouth and takes a deep inhalation, holding their breath for 5-10 seconds. There are a variety of such devices. The dose that can be delivered is typically less than a few tens of milligrams in a single breath since larger powder doses may lead to provocation of cough.[38]

 Formulation Of Inhalers: -

1.Dry power inhalers:

• The dry-powder-inhalers are designed to deliver drug/excipients powder to the lungs.
• Dry powder inhalers (DPls) are devices through which a dry powder formulation of an   active drug is delivered for lo cal or systemic effect via the pulmonary route
• Dry powder inhalers are bolus drug delivery devices that contain solid drug, suspended or dissolved in anon polar volatile propellant or in dry powder inhaler that is fluidized when the patient inhales.
• These are commonly used to treat respiratory diseases such as asthma, bronchitis, emphysema and COPD
• and have also been used in the treatment of diabetes mellitus.

• Excipients used in DPI are used as carrier for Active Pharmaceutical Ingredient (API). Most commonly used carrier is Lactose Monohydrate. [39.40]

Formulation of DPI mainly includes following three steps;

1. API Production

The important requirement of API in case of DPI is particle size. Particle size of drug should be less than 5 um. / It should be in the range of 2-5 pm.

2. Formulation of API with or without carriers.

The part of carrier in DPI is enhancing the flow property of powder. After drug and carrier have separately been brought to their desired forms, they are combined in the blending

4.Integration of the formulation into device

• After the formulation has been blended, it is filled into capsules.
• Currently there are two types:
• Unit dose devices: * Multi dose Devices

Unit-Dose Devices :

Single dose powder inhalers are devices in which a powder containing capsule is placd in a holder. The capsule is opened within the device and the powder is inhaled.

Multidose Devices:

This device is truly a metered-dose powder delivery system. The drug is contained within a storage reservoir and can be dispensed into the dosing chamber by a simple back and forth twisting action on the base of the unit.

A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs, in the form of a short burst of aerosolized medicine that is inhaled by the patient. It is the most commonly used delivery system for treating asthma, chronic obstructive pulmonary disease (COPD) and other respiratory diseases. The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of both for the treatment of asthma and COPD. Other medications less commonly used but also administered by MDI are mast cell stabilizers, such as (cromoglicate or nedocromil).The advantages of MDIs are their portability and small size, availability over a wide do-sage range per actuation, dose consistency, dose accuracy, protection of the contents and that they are quickly ready for use.[41.42]

?Metered Dose Inhalers (MDI) :-

A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs in the form of a short burst of aerosolized medicine that is usually self-administered by the patient via inhalation.  Meter Dose Inhaler (MID) has a pressurized container of medication that fits into a mouthpiece. A dose of medication is released into lungs by pushing the container into the mouthpiece

• A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs. It is the most commonly used delivery system for treating asthma, chronic obstructive pulmonary disease(COPD) and other respiratory diseases.
• The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of both for the treatment of asthma and COPD.
• Pressurized metered aerosols may be formulated as either solutions or suspensions of drug in the liquefied propellant.
• Compared with suspension formulations, solution MD0s offer the benefits of homogenous formulation.
• The basic requirements for formulation of MD0s are containers, propellants, and metering valve.
• Filling Metered Dose inhaler : filled by propellant pressure. liquefying at reduced temperature or elevated pressure .
• Additional propellants is then added at the same temperature. [43]

There are two types of nebulizers, jet and ultrasonic, that differ in the force used to generate the aerosol from the respective liquid. Depending on the model and the manufacturer, nebulizers generate 1–5 μm droplets. Nebulizers do not require patient coordination between inhalation and actuation, thus they are useful for pediatric, elderly, ventilated, non-conscious patients, or those who are unable to use pMDIs or DPIs.

Example: -

1. Peptide and Protein Drugs

Insulin (nasal or pulmonary delivery)

Transported via transcytosis or paracellular routes.

Calcitonin (nasal spray)

Delivered across the nasal epithelium via paracellular pathways with absorption enhancers.

2.  Antidiabetic Drugs

Metformin (oral)

Absorbed via organic cation transporters (OCTs) on intestinal epithelium.

3.    Antiviral Drugs

Zidovudine (AZT)

Transported via carrier-mediated epithelial transporters

4   Anticancer Drugs

5   Fluorouracil (topical, GI)

Absorbed through passive diffusion and sometimes via nucleoside transportes

Several factors have an effect on the general bioavailability of medication that square measure administered through the nasal route. The factors may be touching to the physiochemical properties of the medication, the anatomical and physiological properties of the cavum and therefore the sort and characteristics of chosen nasal medication delivery system. These factors play key role for many of the medication so as to achieve therapeutically effective blood levels once nasal administration. The factors influencing nasal drug absorption square measure represented as follows.

1. Physiochemical properties of drug

• Molecular size.
• Lipophilic-hydrophilic balance.
• Enzymatic degradation in cavum.

2. Nasal result

• Membrane porosity.
• Environmental pH
• Mucociliary clearance
• Cold, rhinitis.

3. Delivery result

• Formulation (Concentration, pH, osmolality) Delivery effects
• Drugs distribution and deposition. Viscosity

1.Physiochemical properties of drug

Molecular size

The molecular size of the drug influence absorption of the drug through the nasal route. The oleo philic medication have direct relationship between the MW associated drug permeation whereas water- soluble compounds depict an inverse relationship. The speed of permeation is high-ly sensitive to molecular size for compounds with MW ≥ three hundred Daltons.[44]

Lipophilic-hydrophilic balance

The deliquescent and oleophilic nature of the drug additionally affects the method of absorption. By increasing lipophilicity, the permeation of the compound usually in-creases through nasal mucous membrane. though the nasal mu-cosa was found to possess some deliquescent character, it seems that these mucosae are primarily oleophilic in nature and also the lipid domain plays a very important role within the barrier operate of those membranes. Oleophilic medication like Narcan, buprenorphine, androgen and 17a-ethinyl- estrogen are nearly utterly absorbed once administered intranasal route.[45]

Enzymatic degradation in cavum

In case of peptides and proteins are having low bio-availability across the cavum, thus these medication might have chance to bear catalyst degradation of the drug molecule within the lumen of the cavum or throughout passage through the animal tissue barrier. These each sites are having exo-peptidases and endopeptidases, exo-peptidases are mono-amino peptidases and di-amino peptidases. These are having capability to cleave peptides at their N and C termini and endopeptidases like amino alkanoic acid and amino alkanoic acid, which may attack internal amide bonds.[46]

Nasal effect factors

Membrane permeability

Nasal membrane porousness is that the most significant issue, that have an effect on the absorption of the drug through the nasal route. The water soluble medication and particularly massive mass medication like peptides and proteins area unit having the low membrane porousness. That the compounds like peptides and proteins area unit main-ly absorbed through the endo cystic transport method in low amounts. Soluble high mass medication cross the nasal membrane principally by passive diffusion through the liquid pores (i.e. tight junctions.[47]

Environmental pH

Hydrogen ion concentration

The environmental hydrogen ion concentration plays a crucial role within the potency of nasal drug absorption. little soluble compounds like carboxylic acid, 2-hydroxybenzoic acid, and organic compound acid show that their nasal absorption in rat occurred to the best extent at those hydrogen ion concentration values wherever these compounds area unit within the unionized kind. However, at hydrogen ion concentration values wherever these compounds area unit partly ionized, substantial absorption was found. This implies that the unionized oleophilic kind crosses the nasal animal tissue barrier via transcellular route, whereas the additional oleophilic ionized kind passes through the liquid paracellular route.[48]

Mucociliary clearance

Mucociliary clearance may be a one among the functions of the higher tract is to forestall baneful sub-stances (allergens, bacteria, viruses, toxins etc.) from reaching the lungs. Once such materials adhere to, or dissolve in, the secretion lining of the cavum, they're transported towards the cavity for ultimate discharge into the epithelial duct. Clearance of this secretion and therefore the adsorbed/dissolved substances into the bum is named the MCC. This clearance mechanism influence the absorption method thanks to the dissolved medicine within the cavum square measure discharge by the each the secretion and therefore the cilia, that is that the motor of the MCC and therefore the secretion transport rate is half dozen mm/min. it's of utmost importance that the MCC isn't impaired so as to forestall lower tract infections.[49]

Cold, rhinitis

Rhinitis may be a most often associated common malady, it influence the bioavailability of the drug. It’s chiefly classified into coryza and customary, the symptoms square measure hyper secretion, skin sensation and physiological reaction chiefly caused by the viruses, microorganism or irritants. coryza is that the allergic airway malady, that affects 100 percent of population. It’s caused by chronic or acute inflammation of the mucosa of the nose. These conditions have an effect on the absorption of drug through the secretion membrane due the inflammation.

Delivery effect factors

Factors that have an effect on the delivery of drug across nasal membrane like surfactants, dose pH, osmolarity, viscosity, particle size and nasal clearance, drug structure will be wont to advantage to boost absorption

Formulation (Concentration, pH, Osmolarity)

The pH of the formulation and nasal surface, will have an effect on a drug’s permeation. To avoid nasal irritation, the pH of the nasal formulation ought to be adjusted to four.5–6.5 as a result of muramidase is found in nasal secretions that is answerable for destroying sure microorganism at acidic pH. Below basic conditions, muramidase is inactivated and therefore the tissue is liable to microorganism infection. In addition to avoiding irritation, it ends up in getting efficient drug permeation and prevents the expansion of bacteria.[50]

Concentration gradient plays important role within the absorption / permeation method of drug through the nasal membrane thanks to nasal tissue layer injury. Examples for this are nasal absorption of L-Tyrosine was shown to extend with drug concentration in nasal introduction experiments. Another is absorption of hydroxy acid was found to say no with concentration. This decline is probably going thanks to nasal tissue layer injury by the permanent. [51]

The osmolarity of the indefinite quantity type affects the nasal absorption of the drug; it absolutely was studied within the rats by victimization model drug. The binary compound concentration of the formulation affects the nasal absorption. The maximum absorption was achieved by zero.462 M binary compound concentration; the upper concentration not solely causes augmented bioavailability however conjointly ends up in the toxicity to the nasal epithelial tissue[52]

Theories of Naso pulmonary Drugs Delivery System

The term “Naso pulmonary drug delivery” describes the administration of medications via the nasal canal, which targets the lungs and the upper respiratory system. This method has a number of benefits, including non-invasive delivery, a quick start of action, and avoidance of first-pass metabolism. The pulmonary medication delivery mechanism is the subject of five theories. For the pulmonary drug delivery route, the following 5 theories are taken into consideration for the delivery of the medication:

• Electronic Theory
• Adsorption Theory
• Wetting Theory
• Diffusion Theory
• Fracture Theory

Nasopulmonary drug delivery systems are based on a number of theories that optimize medication deposition, absorption, and effectiveness in the nasal and pulmonary areas. The idea of mucocilliary clearance, which controls the passage of mucus and other particles through the respiratory epithelium, is one well-known theory. While pulmonary drug delivery systems must take into consideration clearance mechanisms in the lungs to achieve optimal drug deposition and retention, nasal drug delivery systems must overcome application this clearance mechanism to ensure sufficient drug retention and absorption in the nasal cavity. Particle size and aerodynamic behavior are the focus of another hypothesis, which highlights the need of maximizing particle size distribution and aerodynamic characteristics to enable effective medication delivery to both the nasal and pulmonary areas. 13–16, There is discussion on these theories [53]

These are the five theories for medication distribution and absorption for treating a specific condition, along with a few commercially available drug items listed in Table 2 above. Furthermore, Nasopulmonary drug delivery is greatly influenced by theories of drug solubility, permeability, and formulation properties, which direct the creation of formulations that can improve drug solubility and penetration. Targeted distribution to particular respiratory tract areas and via mucosal barriers [63]

{The Theories of Naso-pulmonary Drugs Delivery System}