Aerosols in Medicine
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Aerosols in Medicine

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Questions and Answers

What is the recommended particle size for an insoluble solid active in a suspension for aerosol formulation?

  • 50 - 100 µm
  • 1 - 5 µm
  • 10 - 20 µm
  • 5 - 10 µm (correct)

    • How does an increase in the viscosity of a formulation affect the spray characteristics?

  • It has no effect on the spray.
  • It produces a finer spray.
  • It results in larger droplet sizes. (correct)
  • It leads to increased evaporation.

    • What impact does increasing the propellant to product ratio have on droplet characteristics?

  • It results in a finer and drier spray. (correct)
  • It decreases the vapor pressure.
  • It leads to larger particle sizes.
  • It produces a more viscous spray.

    • Which method is used to measure particle size in aerosol testing?

    <p>Cascade impaction test</p> Signup and view all the answers

    What does an internal pressure measurement of an aerosol container help determine?

    <p>The spray pattern</p> Signup and view all the answers

    What is one of the primary uses of therapeutic aerosols?

    <p>Application to external surfaces of the body</p> Signup and view all the answers

    What is the primary effect of temperature changes on aerosol formulations?

    <p>It alters the vapor pressure.</p> Signup and view all the answers

    Why is moisture determination important in aerosol testing?

    <p>It affects degradation of active ingredients.</p> Signup and view all the answers

    Which of the following is NOT an advantage of using therapeutic aerosols?

    <p>High cost of production</p> Signup and view all the answers

    What characteristic of aerosols ideally results in better drug delivery?

    <p>Monodisperse particles</p> Signup and view all the answers

    What does the flame extension test evaluate in aerosol formulations?

    <p>The flammability of the contents</p> Signup and view all the answers

    What is a significant disadvantage of aerosol products?

    <p>Cannot be subjected to heat</p> Signup and view all the answers

    Aerodynamic diameter of aerosol particles is crucial because it influences what aspect?

    <p>Motion within a gas stream</p> Signup and view all the answers

    What might be a consequence of using propellants in aerosol formulations?

    <p>Potential toxicity with long-term use</p> Signup and view all the answers

    How does the exclusion of light contribute to the benefits of therapeutic aerosols?

    <p>It protects photolabile drugs from degradation.</p> Signup and view all the answers

    Which of the following factors is NOT typically considered in the size distribution of aerosols?

    <p>Volume of the aerosol container</p> Signup and view all the answers

    What criteria are important for selecting containers for nitrous oxide?

    <p>Mechanical strength, chemical inertness, and cost</p> Signup and view all the answers

    Which type of container is not suitable for low-pressure packages?

    <p>Aluminium containers</p> Signup and view all the answers

    What is a notable characteristic of stainless steel containers?

    <p>Expensive but can withstand high pressures and is virtually non-corrosive</p> Signup and view all the answers

    For an aerosol formulation where the active ingredient is not soluble in the propellant but soluble in a co-solvent, what should be done?

    <p>Dissolve the active in ethanol and add to the propellant mixture</p> Signup and view all the answers

    What prevents proper emptying of an aerosol container's product?

    <p>Polyethylene or polypropylene dip tubes not reaching the valve</p> Signup and view all the answers

    What is the primary function of valve actuators in aerosol containers?

    <p>To break-up the stream and control droplet size</p> Signup and view all the answers

    Which of the following materials is known to be light and low-cost for aerosol containers?

    <p>Tin plated steel</p> Signup and view all the answers

    In aerosol formulations, what factor is crucial when adjusting the proportions of propellants?

    <p>Desired pressure of the aerosol</p> Signup and view all the answers

    What is necessary for the active ingredient to dissolve directly in the propellant mixture in aerosol formulations?

    <p>A combination of propellants must be used.</p> Signup and view all the answers

    Which type of dip tube is preferred to ensure complete product emptying from an aerosol container?

    <p>Polyethylene or polypropylene dip tubes.</p> Signup and view all the answers

    What is a key aspect for selecting containers for nitrous oxide?

    <p>Mechanical strength and chemical inertness are crucial.</p> Signup and view all the answers

    What is a major limitation of glass containers in aerosol systems?

    <p>They can only withstand low pressures.</p> Signup and view all the answers

    In aerosol formulations, what is the impact of the ratio of co-solvent to propellant?

    <p>It is critical for ensuring proper solubility.</p> Signup and view all the answers

    Which type of valve actuator is designed to control the application of aerosol products?

    <p>An actuator shaped to facilitate depression of the valve stem.</p> Signup and view all the answers

    What defines the chemical reactivity of tin-plated steel containers?

    <p>Plastic coatings can create non-reactive surfaces.</p> Signup and view all the answers

    Which characteristic of aerosol containers allows them to withstand high pressures?

    <p>The material composition, like stainless steel or aluminum.</p> Signup and view all the answers

    What is an advantage of using therapeutic aerosols in medication delivery?

    <p>They offer high concentration of medicament over a limited area.</p> Signup and view all the answers

    What is a significant disadvantage of aerosol products?

    <p>They can be environmental hazards.</p> Signup and view all the answers

    What might be a consequence of using an insoluble drug in an aerosol formulation?

    <p>Formulation difficulties arise requiring emulsion or suspension systems.</p> Signup and view all the answers

    Which factor is NOT typically considered in the aerodynamic diameter of aerosol particles?

    <p>Color of the particles</p> Signup and view all the answers

    Which statement regarding propellants in aerosol formulations is true?

    <p>They may lead to toxicity with long-term use.</p> Signup and view all the answers

    What is an ideal characteristic of aerosol particles in terms of size distribution?

    <p>They should be monodisperse.</p> Signup and view all the answers

    Which of the following statements about the exclusion of air in aerosol products is correct?

    <p>It helps prevent oxidation of the product.</p> Signup and view all the answers

    What is the primary function of metered valves in aerosol systems?

    <p>To dispense a controlled and uniform dosage.</p> Signup and view all the answers

    What occurs when an aerosol formulation consists of an active that is not soluble in the propellant but is soluble in water?

    <p>Two liquid and one vapour phase is produced.</p> Signup and view all the answers

    How does increasing the vapour pressure of propellants affect aerosol spray characteristics?

    <p>It leads to a finer spray with smaller particle sizes.</p> Signup and view all the answers

    Which factor can lead to a decrease in the particle size of an aerosol spray?

    <p>Higher temperature of the propellant.</p> Signup and view all the answers

    What does the discharge rate in aerosol testing primarily indicate?

    <p>The expected number of operations needed to empty the container.</p> Signup and view all the answers

    What is the primary purpose of phase Doppler anemometry in aerosol analysis?

    <p>To measure the scattering of a laser beam by aerosol particles.</p> Signup and view all the answers

    What role does a dispersing agent play in aerosol formulations containing insoluble solids?

    <p>It enhances the wetting of particles by the liquid phase.</p> Signup and view all the answers

    What is indicated by the presence of solvents and co-solvents in an aerosol formulation?

    <p>They can affect the pressure which influences the spray characteristics.</p> Signup and view all the answers

    What does the flame extension test evaluate in aerosol formulations?

    <p>The flammability and safety of the aerosol product.</p> Signup and view all the answers

    Study Notes

    Aerosols

    • Aerosols are a fine dispersion of liquid or solid particles in a gas, where particle size is less than 50µm. Examples include mists and smoke.
    • Therapeutic aerosols are used for applying medication to external body surfaces, or accessible body cavities like the mouth and nose. They are also sprayed onto protective films for wounds and burns.
    • Common active ingredients include antiseptics, antibiotics, local anaesthetics, dermatological steroids, and bronchodilators.

    Advantages of Aerosols

    • Convenient, fast, and easy application.
    • Efficient dispersion of the medication.
    • Avoids direct manual contact with the medication, protecting both the medication and the patient.
    • Provides immediate, localized application.
    • High concentration of medication in a limited area is achieved.
    • Minimizes irritation to sensitive areas.
    • Rapid response to medication.
    • Controlled and uniform dosage via metered valves.
    • No product contamination from the environment.
    • Protects light-sensitive (photolabile) drugs.
    • Prevents oxidation and hydrolysis.
    • No first-pass effect when administered via oral inhalation.

    Disadvantages of Aerosols

    • Costly due to expensive containers, valves, propellants, and filling methods.
    • Can be difficult to dispose of properly.
    • Heat susceptibility; pressure build-up can occur.
    • If the drug in question exhibits insolubility when combined with the chosen propellant, it necessitates the use of co-solvent emulsions or suspensions to achieve an effective delivery system. This requirement increases the complexity of the formulation process, as careful consideration must be given to the compatibility and stability of all components involved.
    • Propellant toxicity, especially with long-term use, exists.
    • The cooling sensation produced by volatile propellants can cause discomfort or pain when applied to already injured or sensitive skin, potentially exacerbating the condition rather than providing relief.
    • Necessary to test formulation compatibility with all container and valve parts.
    • Aerosol systems can potentially pose an environmental hazard.
    • Faulty valves or spray systems can render the product useless.

    Aerosol Systems

    • Two-phase systems: contain a liquid phase (propellant or propellant mixture with the active ingredient in solution - could form a foam), and a vapour phase (propellant vapor). Propellant vapor pressure is high, pressurizing the container. When the valve is depressed, the pressure forces the liquid into the atmosphere, causing the propellant to vaporize and disperse the active ingredient. If the active is insoluble, a co-solvent like ethanol can be used thus affecting the vapor pressure.
    • Three-phase systems: involves a solution of the active ingredient in a suitable solvent immiscible with the propellant. The system has distinct propellant liquid phase, solution liquid phase, and a vapour phase. The propellant's position (lighter or heavier than the solution) affects the necessary modifications to the dip-tube to avoid propellant spraying.

    Propellants

    • Propellants need specific properties: low toxicity, non-flammable and non-explosive, odorless and colorless, good solvents, non-irritating, and relatively inexpensive.
    • Propellant types include liquefied gases like fluorinated hydrocarbons (e.g., fluoromethanes) and hydrocarbons (e.g., propane), and compressed gases (insoluble, like nitrogen, and soluble, like nitrous oxide).

    Containers

    • Container selection criteria include mechanical strength, chemical inertness, and cost.
    • Glass containers, especially when reinforced with plastic films to enhance durability, are ideal for low-pressure applications. They offer excellent chemical resistance and transparency, allowing for easy monitoring of contents while minimizing contamination risks.
    • Stainless steel is expensive but withstands high pressures well; it's virtually non-corrosive.
    • Tin-plated steel is a cost-effective option that can be made non-reactive using suitable plastic coatings.
    • Steel containers typically consist of three distinct parts: a cylindrical body that holds the contents, a top that secures the container, and a bottom that provides stability and durability.
    • Aluminum containers, which are typically produced in two-piece or mono-bloc designs, are renowned for their ability to withstand high internal pressures. These containers are lightweight and highly resistant to corrosion, making them suitable for various applications, including those that involve storing gases or liquids under pressure, ensuring both safety and efficiency.
    • Glass containers are often molded to fit specific types of valves for low pressures.
    • Plastics, like acetal resins and polypropylene, are suited to high-pressure applications.

    Valves, Dip Tubes & Actuators

    • Valve type depends on the product's formulation and application.
    • Different valves exist for sprays, foams, and delivering individual doses.
    • Metering valves control the amount of product released into a chamber.
    • Precise product emptying employs polyethylene/polypropylene dip tubes which connect to the valve and extend the entire length of the container.
    • Valve actuators are specially shaped to facilitate easy application to specific body areas, providing a desired product and propellant droplet size.

    Basic Aerosol Formulation

    • Formulation depends on the active ingredient's solubility in the propellant.
      • If the active is soluble, it dissolves directly into the propellant or propellant mixture and propellant ratios are adjusted to achieve the desired pressure.
      • When dealing with active ingredients that are insoluble in water but can be dissolved in a co-solvent, it is essential to utilize solvents such as ethanol as an effective medium for solubilization. The ratio between the co-solvent and the propellant is crucial, as it directly impacts the formulation's stability, efficacy, and ability to deliver the active ingredient effectively when applied or sprayed. Careful adjustments to this ratio can lead to optimal performance.
      • If the active is insoluble in both propellant and co-solvent, but soluble in water (H₂O), it can be formulated in an aqueous solution with the propellant, which can also be introduced into the system, or it can be formulated as an emulsion.
    • If the active ingredient is an insoluble solid, it must be suspended in the propellant at a specific particle size, typically ranging from 5 to 10 micrometers (µm). This size range is crucial for ensuring that the particles remain evenly dispersed in the aerosol mixture, thus providing consistent delivery and optimal therapeutic effect upon application.

    Factors Affecting Spray Characteristics

    • Viscosity affects particle size; higher viscosity means larger particles and a wetter spray; lower viscosity means smaller particles and a finer spray.
    • Propellant vapour pressure impacts particle size; higher pressure result in finer sprays.
    • Propellant-product ratio: higher propellant ratio generally creates a finer, drier spray.
    • Solvents can affect pressure, influencing the spray.
    • Temperature changes affect vapor pressure and spray.

    Testing of Aerosols

    • Manufacturing processes use inline leakage testing - immersed in hot water to detect leaks.
    • Internal pressure measurement uses a pressure gauge.
    • Spray pattern assessment is based on pressure, viscosity, and product/propellant ratios, and visually examined.
    • Discharge rates inform on the number of operations to empty a container.
    • Flammability test is performed.
    • Particle size analysis utilizes cascade impaction tests.
    • Phase Doppler Anemometry may be used to measure laser beam scattering from particles.
    • Moisture content is checked for its impact on metal corrosion and degradation of certain drugs.
    • Propellant mixture analysis uses gas-liquid chromatography.

    Dry Powder Inhalers (DPI)

    • Fine drug powder is mixed with an excipient (e.g. lactose). The mixture is housed in a hard gelatin capsule.
    • Excipient particle size is larger than the drug to prevent it from entering the airway.
    • When the capsule is opened, a turbulent airflow disperses the powder which is inhaled.

    Advantages and Disadvantages of DPI's

    • Advantages:*
    • No hand-breath coordination is needed.
    • Environmentally friendly.
    • Can deliver proteins/peptides.
    • Disadvantages:*
    • More expensive than Metered Dose Inhalers (MDIs) are widely used devices for delivering medication directly to the lungs through aerosolized sprays. They are commonly employed in the management of respiratory conditions, such as asthma and chronic obstructive pulmonary disease (COPD). MDIs allow patients to inhalatively receive precise doses of medication, ensuring optimal therapeutic outcomes. The design typically features a canister containing the drug formulation, combined with a propellant that helps to create a fine mist for inhalation. Proper technique is crucial for maximizing drug delivery and effectiveness.
    • Requires frequent refilling.
    • Loose powder makes the device messy and can cause coughing.
    • Reliance on inspiratory effect to disperse the aerosol.
    • Variable performance among patients and across different days.

    Nebulisers

    • Devices employed for aerosolizing drug solutions into inhalable mists include

    • Ultrasonic Nebuliser are an effective means of delivering aerosolized medication directly to the respiratory tract. These devices provide a method for patients who may struggle with puffs or sprays, ensuring deeper lung penetration.

    • Jet nebulizers are medical devices used to deliver medication in the form of a mist, allowing it to be inhaled directly into the lungs.

    • These devices operate by using a jet of compressed air or oxygen to create an aerosolized mist from a liquid medication solution. The mechanism involves a jet nozzle that draws in the liquid, and the energy from the air stream breaks the liquid into fine droplets suitable for inhalation. Jet nebulizers are commonly used for patients with respiratory conditions such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis, as they provide the ability to deliver larger doses of medication compared to metered-dose inhalers (MDIs).

      Advantages and Disadvantages of Jet Nebulizers

      • Advantages:

        • Effective for high doses of medication.
        • Can be used with a variety of medications, including those that are not suitable for MDIs.
        • Suitable for patients who may have difficulty using inhalers, such as children or the elderly.

      • Disadvantages:

        • May be less portable compared to inhalers.
        • Requires a power source, limiting use in certain settings.
        • Cleaning and maintenance are necessary to prevent contamination and ensure proper functioning.

      , which use compressed air to generate a mist for inhalation.

    Ultrasonic Nebuliser

    • An ultrasonic nebuliser utilizes an electrically powered transducer that generates high-frequency vibrations, effectively transforming the drug solution into tiny aerosolized droplets. These small particles are essential for efficient inhalation therapy, as they can easily penetrate deep into the lungs, ensuring maximum drug delivery and therapeutic effects. This type of nebuliser is particularly valuable in the treatment of respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD).
    • One significant advantage of ultrasonic nebulisers is their quiet operation, which makes them more comfortable for patients, especially children. However, they do rely heavily on an electric power source, which poses a risk of overheating during extended use and necessitates careful monitoring to prevent malfunction.

    Jet (Air-blast) Nebuliser

    • A compressed gas stream (jet) generates a negative pressure, inducing liquid from the reservoir into the jet, atomising it into smaller droplets.
    • Coarse droplets are collected while smaller droplets are inhaled.

    Advantages of Nebuliser Therapy

    • Large bronchodilator doses are possible.

    • Hand-breath coordination is not a requirement when using jet nebulizers. This feature enhances convenience, as patients do not need to synchronize their inhalation with the device's operation.

    • Issues concerning propellant sensitivity are avoided using solutions like Isotonic saline -is a sterile solution that contains 0.9% sodium chloride (NaCl) in water, which is equal in concentration to human body fluids. This makes it an essential component in various medical applications. It is commonly used for intravenous (IV) infusions and to maintain or restore fluid balance within patients.

      In the context of respiratory therapy, isotonic saline can be nebulized to help hydrate and thin mucus in patients with conditions such as asthma or cystic fibrosis, making it easier to expel mucus.

    • Vehicle solution (normal saline) has additional positive effects (soothing airways and liquifying secretions).

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    Description

    Explore the fascinating world of aerosols, their definitions, applications, and advantages in medicinal use. This quiz covers therapeutic aerosols and their active ingredients, focusing on how they facilitate medication delivery efficiently. Test your knowledge on this essential aspect of modern medicine.

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