Antimuscarinics, bronchodilators

Question 1

Describe how different types of antimuscarinics are used for patients with COPD.

Answer 1

Short acting antimuscarinics are used to receive breathlessness brought on by exercise or during exacerbations.

Long acting antimuscarinics (LAMAs) are used to prevent breathlessness and exacerbations.

Question 2

Describe how different types of antimuscarinics are used for patients with asthma.

Answer 2

Short acting antimuscarinics are used as adjuvants for relief of breathlessness during acute exacerbations, usually in combination with Salbutamol.

Long acting antimuscarinics are added to high dose inhaled corticosteroids and long acting beta agonists at ‘step 4’ in the treatment of chronic asthma.

Question 3

1) Describe the action of antimuscarinic drugs at a molecule level.
2) What are the effects of the action of antimuscarinics?
3) What are the effects of antimuscarinic drugs on the eye?

Answer 3

1) Competitive inhibitor of acetylcholine.
2) Increase HR and conduction, reduce smooth muscle tone (incl. in respiratory tract) and reduce secretions from glands (in respiratory and GI tracts).
3) Relaxation of pupillary and ciliary constrictor muscles, causing pupillary dilatation and preventing accommodation.

Question 4

1) What is the main adverse effect of antimuscarinics?

2) Why are side effects from inhaled antimuscarinic drugs uncommon?

Answer 4

1) Dry mouth.

2) Because when antimuscarinic bronchodilators are taken by inhalation, there is very little systemic absorption.

Question 5

Which 2 groups of patients should antimuscarinic bronchodilators be used with caution in?

Answer 5

1) Patients susceptible to closed angle glaucoma.

2) Patients with or at risk of arrhythmias.

Question 6

Why should antimuscarinic bronchodilators be used with caution in patients at risk of closed angle glaucoma?

Answer 6

Because they can precipitate a dangerous rise in intraocular pressure.

Question 7

Why are interactions with antimuscarinic bronchodilators generally not a problem?

Answer 7

Due to the low systemic absorption.

Question 8

1) Name the main short acting muscarinic antagonist.

2) Give 2 examples of long acting muscarinic antagonists.

Answer 8

1) Ipratropium

2) Tiotropium and Glycopyrronium.

Question 9

1) How would Ipratropium be prescribed for stable patients?
2) How would Ipratropium be prescribed during an acute attack?
3) How would long acting muscarinic antagonists usually be prescribed?

Answer 9

1) Usually a standard dose of 40mcg by inhalation QDS or PRN.
2) 250-500mcg 6-hourly by nebulisation.
3) For regular administration, usually OD.