Anticholinergics

Question 1

Example of an Anticholinergic

Answer 1

Tiotropium

Question 2

How do Anticholinergics work?

Answer 2

Antimuscarinic drugs bind to the muscarinic receptor, where they act as a competitive inhibitor of acetylcholine. Stimulation of the muscarinic receptor brings about a wide range of parasympathetic ‘rest and digest’ effects. In blocking the receptor, antimuscarinics have the opposite effects: they increase heart rate and conduction; reduce smooth muscle tone, including in the respiratory tract; and reduce secretions from glands in the respiratory and gastrointestinal tracts. In the eye they cause relaxation of the pupillary constrictor and ciliary muscles, causing pupillary dilatation and preventing accommodation, respectively.

Question 3

Indications for Anticholinergics

Answer 3

In chronic obstructive pulmonary disease (COPD), short-acting antimuscarinics are used to relieve breathlessness, e.g. brought on by exercise or during exacerbations. Long-acting antimuscarinics (LAMAs) are used to prevent breathlessness and exacerbations.

In asthma, short-acting antimuscarinics are used as adjuvant treatment for relief of breathlessness during acute exacerbations (added to a short-acting β2 agonist, e.g. salbutamol). Long-acting antimuscarinics are added to high-dose inhaled corticosteroids and long-acting β2 agonists at ‘step 4’ in the treatment of chronic asthma.

Question 4

Contraindications for Anticholinergics

Answer 4

Antimuscarinics should be used with caution in patients susceptible to angle-closure glaucoma, in whom they can precipitate a dangerous rise in intraocular pressure. They should be used with caution in patients with or at risk of arrhythmias. However, in practice, most patients can take these drugs by inhalation without major problems.

Question 5

Side effects of Anticholinergics

Answer 5

When antimuscarinic bronchodilators are taken by inhalation, there is relatively little systemic absorption. Adverse effects, apart from dry mouth, are uncommon.

Question 6

Interactions of Anticholinergics

Answer 6

Interactions are not generally a problem due to low systemic absorption.

Question 7

Elimination of Anticholinergics

Answer 7

Renal

Question 8

Patient information on Anticholinergics

Answer 8

Long-acting antimuscarinics (e.g. tiotropium, glycopyrronium) are prescribed for regular administration, generally once daily.

Explain that you are offering a treatment to make their airways relax, which should therefore improve their breathing. They should understand that this treats the symptoms, not the disease. Ensure they are clear on how and when to take the inhaler (e.g. for acute symptoms, pre-emptively before exercise or regularly for long-acting medication). Discuss possible side effects, such as dry mouth, and advise them to chew gum or suck sweets (which should be sugar-free; see Antimuscarinics, genitourinary uses), or keep a bottle of water with them to relieve these.