Anticholinergics

Question 1

Commonly used drugs

Answer 1

Ipratropium - inhaled

Tiotropium - longer acting

Question 2

What are they used for?

Answer 2

• 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

Question 3

How do they work?

Answer 3

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.

Question 4

Side effects

Answer 4

• Dry mouth
• Nausea
• Constipation
• Headache
• Urinary retention in men (triotropium – tends to occur in men who already have a large prostate)
• Can contribute to angle-closure glaucoma

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.