Anti-Asthma Drugs

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Drug Delivery[edit]

  • Preferred mode of delivery of many drugs with a direct effect on airways, particularly for asthma and COPD
  • Only way to deliver some drugs such as cromolyn sodium and anticholinergic drugs
  • The preferred route of delivery for beta-2 agonists and corticosteroids to reduce systemic side effects, as well as reducing onset of action
  • Inhalation is also used to facilitate systemic drug delivery in other diseases eg. insulin in diabetics
  • Particle Size is of critical importance in determining the site of deposition in the respiratory tract
  • Optimal size for inhaled particles to settle in airways is 2-5μm
  • Larger particles are deposited in upper airways, while smaller particles remain suspended and are exhaled
  • Only 10-20% of total drug delivered enters lower airways with a conventional MDI
  • Drugs act directly on target cells in the airway, as well as being absorbed into bronchial circulation to act more distally on peripheral airways
  • Pressurised MDIs: HFA propellant, required coordination of inhalation with device activation
  • Spacer Chambers: Reduce the velocity of particles entering the upper airways and the size of the particles by allowing propellant to evaporate
  • Reduces drug deposition onto oropharynx and therefore reduction of local side effects - especially corticosteroids
  • Does not require inhalation coordination - can be used in young children
  • Dry Powder Inhalers:
  • Scatter a fine powder dispersed by air turbulence on inhalation.. Can cause airway irritation.
  • Nebulisers:
  • Either jet (driven by stream of gas) or ultrasonic (driven by rapidly vibrating piezo-electric crystal)
  • The drug is inhaled during normal tidal breathing, therefore much higher doses can be delivered
  • Useful in acute illness, small children, extreme airway obstruction
  • Oral Administration:
  • 20x more medication required for oral dosing.
  • Theophylline is ineffective when inhaled and must be given orally/IV
  • Corticosteroids may also have to be given orally/IV


  • β2 adrenergic agonists - most widely used bronchodilators as they are the most effective and have minimal side effects