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Anticholinergics (aka antimuscarinic agents) are usually inhaled, but can be given IV in hospital. They are used in respiratory conditions as adjuncts to steroids and β2 receptors agonists.

  • It is also worth remembering that many other medications – particularly drugs that affect the nervous system and brain have many anticholinergic side effects. These are discussed in the relevant medication articles. 


  • 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 asthma, and far more commonly used in COPD. They 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 of anticholinergics

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


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 atropine is associated with far greater side-effects.

Clinical uses of anticholinergics

  • 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

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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