Inhalation drug administration involves delivering medications directly to the respiratory tract through breathing. This route allows both local treatment of respiratory conditions and systemic drug delivery through the large surface area of the lungs. It’s particularly valuable for respiratory diseases and offers rapid absorption for some systemic medications.
Forms of Inhalation Devices
- Metered-Dose Inhalers (MDIs): Pressurized devices delivering measured doses
- Dry Powder Inhalers (DPIs): Breath-activated powder delivery devices
- Nebulizers: Devices converting liquid medication to fine mist
- Soft Mist Inhalers: Mechanical devices producing slow-moving aerosol
- Spacers/Chambers: Auxiliary devices improving MDI delivery
Advantages
- Direct delivery to airways
- Rapid onset for local effect
- Lower systemic drug exposure
- Smaller doses needed
- Non-invasive administration
- Self-administration possible
- Adjustable dosing
- Minimal systemic side effects
Disadvantages
- Technique-dependent
- Device maintenance required
- Coordination needed
- Local irritation possible
- Complex instructions
- Cost of devices
- Storage requirements
- Variable absorption
Best Practices
- Proper device technique
- Regular device cleaning
- Correct breathing pattern
- Proper timing of inspiration
- Device maintenance
- Spacer use when indicated
- Mouth rinsing after use
- Regular technique review
Special Considerations
- Patient coordination ability
- Respiratory function
- Age-specific factors
- Device preferences
- Cost implications
- Environmental factors
- Storage conditions
- Emergency situations
Device Types and Particle Size Requirements
Metered-dose inhalers (MDIs) deliver the drug as a pressurized aerosol from a canister containing a propellant (typically hydrofluoroalkane). They require coordination between actuation and inhalation — many patients struggle with this, making spacers or valved holding chambers essential add-ons. Dry powder inhalers (DPIs) are breath-activated: the patient’s inhalation pulls powder from a capsule or blister (e.g., Diskus, Turbuhaler). DPIs require a minimum inspiratory flow rate of 30–60 L/min, limiting use in young children and severe COPD. Nebulizers convert liquid drug solutions into a fine mist using compressed air (jet nebulizer) or ultrasound (ultrasonic or mesh nebulizer) over 5–15 minutes, requiring no patient coordination. Particle size determines lung deposition: particles > 10 µm deposit in the oropharynx, 5–10 µm reach the trachea and bronchi, 1–5 µm reach the bronchioles and alveoli (the therapeutic range), and < 1 µm are exhaled. Salbutamol (albuterol) MDI delivers 100 µg/puff and is used for acute asthma relief — proper technique requires a slow, deep inhalation (30 L/min) followed by a 10-second breath hold. Inhaled corticosteroids (e.g., fluticasone propionate 250 µg) are used for daily asthma control; mouth rinsing after use prevents oral thrush and hoarseness. Spacer devices holding 60–100 mL reduce oropharyngeal deposition by 50–80% and double lung deposition.
Conclusion
Inhalation drug administration provides an effective route for both respiratory and systemic medications. Success depends on proper device selection, patient education, and consistent technique to ensure optimal drug delivery to the intended site.
