Drugs affecting the Respiratory System

Drugs affecting the Respiratory System

  1. Anti-Cholinergics
  2. Anti-Histamines
  3. Beta-Agonists
  4. Cromones
  5. Different types of Inhaler
  6. Inhaled Corticosteroids
  7. Leukotriene Antagonists
  8. Xanthines

 

Anti-Cholinergics

Anti-cholinergics (aka antimuscarinics agents)
These are also usually inhaled, but can be given IV in hospital.
 

Mechanism

  • They essentially bind to and block ACh receptors. ACh is the main neurotransmitter involved in muscle contraction thus by blocking its action you prevent muscle contraction.
  • They are mainly used as an adjuvant to β2 agonists – they are not very effective on their own.
  • They also reduce mucous secretion
  • There are 3 types of muscarinic receptor, and these drugs act on them all – thus they are not selective.
  • They are virtually never used in asthmaand far more commonly used in COPDThey may be used in asthma during severe exacerbations where β2 agonists are not having the desired effect.
  • They have a slow onset of action (30-60m) compared to salbutamol, probably because they are poorly absorbed from the respiratory tract.
  • The half-life is short (about 15 minutes) – and the half-life is due to the removal of the drug from its receptor, and not due to removal of the drug from the blood.
  • Triatropium has a much longer half life of up to 3.5 hours. 
 

Examples

  • Ipratropium – this is the main drug that it used, and it is usually inhaled
  • Tiotropium – this is longer acting
 

Pharmacokinetics

They are given again by inhalation. They are poorly absorbed into the blood stream and so have very little systemic effect.
 

Unwanted effects

 
However – generally there are few side effects due to the localised nature of administration – for example, the systemic drug atropineis associated with far greater side-effects.
 

Clinical use recommendations

  • In asthma – as an adjunct to steroids and β2-receptor agonists
  • In COPD – tiotropium (longer acting) tends to be used
  • In bronchospasm –brought about by β2 receptors agonists

 

Anti-Histamines

 

Histamine H1-receptor antagonists 
These are not used in the management of respiratory conditions. They are mostly effective against mast cell activated inflammatory reactions. In asthma, mast cells are involved in the early stages of the reaction, but their role is not great enough to respond to therapeutic modification.
These drugs are useful in patients with very mild atopic asthma, such as in cases of hay fever.

- See more at: http://almostadoctor.co.uk/content/systems/drugs/respiratory-medications/anti-histamines#sthash.Jtc19a3D.dpuf

 

Cromones

 

Cromones – e.g.Sodium cromoglicate, nedocromil sodium
This is often described as a mast cell stabilizer. It prevents the release of inflammatory mediators (such as histamine) from mast cells.
These drugs have no bronchidilator activity, and thus are of no use in an asthma attack; thus they are preventative. They are usually less effective than inhaled corticosteroids.
Their main use is in mild-to-moderate, antigen induced and exercise induced asthmaThey are also used as an inhalant to treat seasonal rhinitis, and as an ophthalmic agent to treat conjunctivitis.
 

Mechanism

  • It enhances phosphorylation of a specific protein in mast cells. this protein interferes with signal transduction pathways to cause a reduction in the release of inflammatory mediators by mast cells.
  • It also affects sensory C-fibres, and this can help reduce bronchoconstriction as a result of direct irritation (e.,g. by sulphur dioxide)
  • If used long-term, they reduce chemotaxis of, and thus accumulation of eosinophils, neutrophils and macrophages in the lung, thus reducing the effect of any late phase reaction
  • They act on B cells, to reduce IgE production
 

Use

The very first dose will protect against the early phase reaction. Treatment may be required for 1-2 months to provide protection against the late phase reaction

 

Different types of Inhaler