Muscarinic Antagonists Flashcards
Give an example of a short acting muscarinic antagonist
Ipratropium bromide
Give an example of a long-acting muscarinic antagonist
Tiotropium bromide
What is the mechanism of action of muscarinic antagonists?
They compete with acetylcholine to bind to muscarinic receptors
What is acetylcholine?
A neurotransmitter involved in generating action potentials and activating the sympathetic and parasympathetic nervous systems
What are the routes of delivery of muscarinic antagonists?
- Inhaled
- Nebulised
- Intranasal
When might intranasal muscarinic antagonists be used?
For rhinitis
What are the indications for muscarinic antagonists?
- 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
What muscarinic antagonist is used in overactive bladder and urge incontinence?
Solifenacin
What muscarinic antagonist is used in irritable bowel syndrome?
Mebeverine
When should muscarinic antagonists be used with caution?
- Bladder outflow obstruction
- Paradoxical bronchospasm
- Prostatic hypertrophy
- Susceptibility to closed angle glaucoma
When should tiotropium bromide specifically be used with caution?
- Arrhythmias or heart failure requiring hospitalisation in the past 12 months
- MI within past 6 months
What might muscarinic antagonists interact with?
TCAs
What can happen if muscarinic antagonists are given with TCAs?
Adverse effects are more pronounced
When do drug interactions for muscarinic antagonists generally not apply?
In anti-muscarinics administered by inhalation
How often should people on muscarinic antagonists be reviewed?
6-monthly
What should be included in the review of patients on muscarinic antagonists?
- Confirm inhaler technique is correct
- Ask about symptomatic improvement and side effects
What are the common side effects of muscarinic antagonists?
- Constipation, diarrhoea, and GI motility disorders
- Dry mouth
- Cough
- Headache and sinusitis
What are the less common side effects of muscarinic antagonists?
- Angle-closure glaucoma, blurred vision, mydriasis
- Palpitations, tachycardia, dizziness
- Urinary retention
What are the rare side effects of muscarinic antagonists?
Dental caries
What counselling needs to be provided when starting muscarinic antagonists?
- Inhaler technique
- Written asthma action plan
- Side-effects
- When to stop
What should you counsel the patient about regarding inhaler technique with muscarinic antagonists?
Teach patient correct inhaler technique and review this during follow-up appointments
What is a written asthma action plan?
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
What should you warn patients to do if they are using increased doses of muscarinic antagonists?
Seek medical help
What should you counsel the patient about regarding side effects of muscarinic antagonists?
Warn patients that the use of muscarinic antagonists can cause unpleasant side effects
What should you counsel the patient about regarding when to stop muscarinic antagonists?
Advise patient to stop if they experience excessive drowsiness and confusion
