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Renin Angiotensin Mechanism.

Nasal Sprays.

 

Introduction.

  • Metered-dose pump sprays are used to administer the majority of pharmaceutical nasal preparations on the market that contain solutions, emulsions, or suspensions. 

  • Nasal sprays or nasal mists are used to deliver a drug or drugs through the nose, either locally to relieve cold or allergy symptoms such as nasal congestion or systemically. 

  • Although there are different delivery methods, most nasal sprays work by pumping a fine mist into the nostril with a hand-operated mechanism. 

  • Antihistamines, corticosteroids, and topical decongestants are the three primary classes that can be used locally. Sprays with metered doses come with a container, a pump with a valve, and an actuator. 

  • Metered-dose pump sprays' dose accuracy is influenced by the formulation's viscosity and surface tension. 

  • There are specific pump and valve combinations available for solutions with higher viscosities. 

Excipients Used in Nasal Spray Formulations:

  • There are various types of excipients used in nasal formulations. Commonly used and frequently added excipients are as follows,

  1. Buffers: 

    • Nasal secretions may alter the pH of the administered dose, which can affect the concentration of un-ionized drugs available for absorption. 

    • Therefore, an adequate formulation buffer capacity may be required to maintain the pH in-situ. 

    • Examples of buffers used in nasal spray sodium phosphate, Sodium citrate and citric acid. 

  2. Solubilizers: 

    • Aqueous solubility of a drug is always a limitation for nasal drug delivery in solution. 

    • Conventional solvents or co-solvents such as glycols, small quantities of alcohol, Transcutol (diethylene glycol monoethyl ether), medium chain triglycerides and Labrasol (saturated polyglycolyzed C8-C10 glyceride) can be used to enhance the solubility of drugs. 

  • Other compounds can be used like, the use of surfactants or cyclodextrins such as HP–sCyclodextrin that serve as a biocompatible solubilizer and stabilizer in combination with lipophilic absorption enhancers. 

  • In these cases, their impact on nasal irritancy should be considered. 

  1. Preservatives: 

    • Most nasal formulations are aqueous based so need preservatives to prevent microbial growth. Parabens, phenyl ethyl alcohol, benzalkonium chloride, EDTA and benzoyl alcohol are some of the commonly used preservatives in nasal formulations. 

  2. Antioxidants: 

    • A small quantity of antioxidants may be required to prevent drug oxidation. 

  • Commonly used antioxidants are sodium bisulfite, butylated hydroxytoluene, sodium metabisulfite and tocopherol.

  •  Usually, antioxidants do not affect drug absorption or cause nasal irritation. 

  1.  Humectants; 

    • Because of allergic and chronic diseases there can be crusts and drying of mucous membrane. 

    • Certain preservatives/ antioxidants are also likely to cause nasal irritation especially when used in higher quantities. 

    • Adequate intranasal moisture is essential for preventing dehydration. 

    • Therefore, humectants can be added especially in gel-based nasal products. 

    • Humectants avoid nasal irritation and do not affect drug absorption. Common examples include glycerin, sorbitol and mannitol. 

  2. Surfactants: 

  • Surfactant incorporation into nasal dosage forms can modify the permeability of nasal membranes, which may facilitate the nasal absorption of drugs. 

  • It also increases stability of suspension. 

  • Common examples include Polysorbate. 

  1. Bioadhesive polymers: 

    • Compounds that are capable of interacting with biological material through interfacial forces and being retained on such material for prolonged periods is called a bioadhesive polymer. 

    • They are also called as mucoadhesive if biological material is mucus membrane. 

    • The bioadhesive force of a polymer material is dependent on the nature of the polymer, the surrounding medium (pH), swelling and physiological factors (mucin turnover, disease state). 

    • From a safety (nasal irritancy) point of view use of a combination of carriers is often recommended. 

  2. Penetration enhancer: 

    • Chemical penetration enhancers are widely used in nasal drug delivery.

Characterization of Nasal Spray: 

  • pH 

  •  Osmolality 

  •  Viscosity 

  •  Impurities and Degradation Products 

  •  Preservatives and Stabilizing Excipients Assay 

  •  Pump Delivery 

  •  Spray Content Uniformity (SCU) 

  •  Spray Pattern and Plume Geometry 

  •  Droplet Size Distribution 

  •  Particle Size Distribution

Commonly Asked Questions:

  1. What are nasal sprays? Describe its formulation.

  2. Enlist different parameters for characterization of Nasal sprays.
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