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Rapid onset, smaller doses → fewer side effects
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Bypasses first-pass metabolism
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Effective for poorly absorbed oral drugs
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Factors Influencing Deposition
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Breath-holding
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Particle aerodynamic diameter
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Humidity & formulation properties
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Reduce throat deposition (down to 15%
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Improve lung delivery (~20%)
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Eliminate need for timing coordination
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Require cleaning; bulky
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Drug particle:
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~5 µm
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Carrier particle:
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30–60 µm
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Must balance adhesion (mixing) with desorption (release)
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General Info:
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Converts liquid into inhalable mist
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Used for large doses, severe attacks
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Suitable for children and elderly
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Inhaled during normal breathing
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Types of Nebulisers:
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Jet:
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Uses compressed air; most common
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Ultrasonic:
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Vibrates crystal → liquid mist
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Mesh:
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Liquid pushed through vibrating mesh → fine spray
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Mesh Nebulizers offer finer droplets & faster delivery
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Air pathway:
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Nasal cavity → pharynx → trachea → bronchi → bronchioles → alveoli
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Bronchi:
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Cartilage rings, cilia for clearing particles
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Bronchioles:
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<1 mm diameter; end in alveoli for gas exchange
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Release dose during inhalation (e.g. Easi-Breathe, Autohaler)
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Ideal for patients with coordination difficulties
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Single Dose (e.g., Cyclohaler):
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Capsule pierced manually
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Multidose – Foil-based (Diskhaler, Accuhaler):
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Blister packs
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Reservoir-based (Turbohaler, Easyhaler):
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Multiple doses, drug stored inside
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Thermal Inhalers:
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Thin film drug heated (~400°C), vaporized, and condensed into 1–3 µm particles
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Triggered by breath; compact and efficient
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Mucociliary clearance:
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removes particles
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Pathologies:
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inflammation, obstruction, reduced elasticity
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Deposition affected by particle size and breathing pattern
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Inhalations:
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Vapors from volatile substances or hot water
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Examples: eucalyptus oil, propylhexedrine
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Vitrellae:
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Crushed glass capsules releasing vapors
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Example: amyl nitrite for angina
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Overview:
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Breath-activated → no propellants needed
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Drug in dry powder form, usually with a carrier (e.g., lactose)
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Requires deep, strong inhalation to disperse powder
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Advantages:
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Larger doses possible
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No need for coordination
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Disadvantages:
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Performance depends on user’s inspiratory effort
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Drug exposed to humidity
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Generally more expensive
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Inertial Impaction (>5 µm):
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Upper airways
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Sedimentation (~1–5 µm):
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Bronchi/bronchioles
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Diffusion (<0.5–1 µm):
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Alveoli or exhaled
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Features:
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Pressurized canister delivers metered dose
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Propellants: HFA (replaced CFCs)
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Dose reliability decreases near empty
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Formulation:
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Mostly suspensions due to poor solubility in propellants
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Evaporation affects particle size
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Advantages
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Only 10–15% of dose reaches lungs
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High velocity = throat deposition (up to 80%)
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Requires coordination; poor compliance
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Disadvantages
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Only 10–15% of dose reaches lungs
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High velocity = throat deposition (up to 80%)
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Requires coordination; poor compliance
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