Muscarinic Antagonists

Question 1

Give an example of a short acting muscarinic antagonist

Answer 1

Ipratropium bromide

Question 2

Give an example of a long-acting muscarinic antagonist

Answer 2

Tiotropium bromide

Question 3

What is the mechanism of action of muscarinic antagonists?

Answer 3

They compete with acetylcholine to bind to muscarinic receptors

Question 4

What is acetylcholine?

Answer 4

A neurotransmitter involved in generating action potentials and activating the sympathetic and parasympathetic nervous systems

Question 5

What are the routes of delivery of muscarinic antagonists?

Answer 5

• Inhaled
• Nebulised
• Intranasal

Question 6

When might intranasal muscarinic antagonists be used?

Answer 6

For rhinitis

Question 7

What are the indications for muscarinic antagonists?

Answer 7

• Acute bronchospasm and severe/life threatening asthma
• Management of reversible obstructive airways disease (asthma and COPD)
• Rhinorrhoea
• Overactive bladder (OAB) and urge incontinence
• Irritable bowel syndrome

Question 8

What muscarinic antagonist is used in overactive bladder and urge incontinence?

Answer 8

Solifenacin

Question 9

What muscarinic antagonist is used in irritable bowel syndrome?

Answer 9

Mebeverine

Question 10

When should muscarinic antagonists be used with caution?

Answer 10

• Bladder outflow obstruction
• Paradoxical bronchospasm
• Prostatic hypertrophy
• Susceptibility to closed angle glaucoma

Question 11

When should tiotropium bromide specifically be used with caution?

Answer 11

• Arrhythmias or heart failure requiring hospitalisation in the past 12 months
• MI within past 6 months

Question 12

What might muscarinic antagonists interact with?

Answer 12

TCAs

Question 13

What can happen if muscarinic antagonists are given with TCAs?

Answer 13

Adverse effects are more pronounced

Question 14

When do drug interactions for muscarinic antagonists generally not apply?

Answer 14

In anti-muscarinics administered by inhalation

Question 15

How often should people on muscarinic antagonists be reviewed?

Answer 15

6-monthly

Question 16

What should be included in the review of patients on muscarinic antagonists?

Answer 16

• Confirm inhaler technique is correct

- Ask about symptomatic improvement and side effects

Question 17

What are the common side effects of muscarinic antagonists?

Answer 17

• Constipation, diarrhoea, and GI motility disorders
• Dry mouth
• Cough
• Headache and sinusitis

Question 18

What are the less common side effects of muscarinic antagonists?

Answer 18

• Angle-closure glaucoma, blurred vision, mydriasis
• Palpitations, tachycardia, dizziness
• Urinary retention

Question 19

What are the rare side effects of muscarinic antagonists?

Answer 19

Dental caries

Question 20

What counselling needs to be provided when starting muscarinic antagonists?

Answer 20

• Inhaler technique
• Written asthma action plan
• Side-effects
• When to stop

Question 21

What should you counsel the patient about regarding inhaler technique with muscarinic antagonists?

Answer 21

Teach patient correct inhaler technique and review this during follow-up appointments

Question 22

What is a written asthma action plan?

Answer 22

A written plan given to all patients with asthma which describes the appropriate course of action if their asthma symptoms worsen, or if they become severely short of breath

Question 23

What should you warn patients to do if they are using increased doses of muscarinic antagonists?

Answer 23

Seek medical help

Question 24

What should you counsel the patient about regarding side effects of muscarinic antagonists?

Answer 24

Warn patients that the use of muscarinic antagonists can cause unpleasant side effects

Question 25

What should you counsel the patient about regarding when to stop muscarinic antagonists?

Answer 25

Advise patient to stop if they experience excessive drowsiness and confusion