Muscarinic Receptor Blocking Drugs Flashcards
What are muscarinic receptor blocking drugs?
Anticholinergic drugs
Parasympatholytics
What is the mechanism of action of parasympatholytics?
They remove PSY stimulation on effector cells — SY stimulation will dominate
Name the tertiary tropines?
Atropine
Scopolamine
Homatropine
Benztropine
How long is the duration of effect of atropine?
7-10 days
What are the clinical uses of atropine?
Antispasmodic Anti-secretory Antidiarrheal Ophthalmology (but has a long half life) Management of AchE inhibitor OD
Is atropine a tertiary tropine or a quaternary?
Tertiary
Can atropine enter the CNS?
Why?
Yes
Because it is a tertiary tropine
Does atropine have central or peripheral effects?
Both central and peripheral effects
What is atropine competitive to?
Ach
What are the CNS effects of atropine?
Antimimetic effect Restlessness Hallucinations Epileptiform convulsions Coma Death
What are the peripheral effects of atropine?
Decreased secretions Dry mouth Decreased gastric secretion Dry skin Mydriasis (wide pupils) Cyclopegia (blurred vision) Hyperthermia Bronchodilator Tachycardia - TdP and V-fib Relaxation of abdominal smooth muscle which leads to decreased secretions in the intestine, urinary bladder, uterus and the Choledochus Constipation Dysuria Urinary retention
What is the treatment of acute intoxication with atropine?
Physostigmine
Why is physostigmine used in the treatment of atropine intoxication
Atropine is a competitive inhibitor of muscarinic receptors. The only way to overcome the effects of a competitive antagonist is to increase the concentration of the ligand for those receptors (Ach). Therefore we use an AchE inhibitor to increase the concentration of Ach at the synapse
What is mydriasis?
Dilation of the pupils
What is cyclopegia?
Loss of accommodation (blurred vision)
What are the clinical uses of parasympatholytics?
Mydriasis Bronchial asthma COPD (ipratropium spray) Bradycardia 1st degree AV blocks Peptic ulcer Incontinence Diarrhoea Abdominal cramps Parkinson’s syndrome Organophosphate poisoning
Which parasympatholytic is used to treat COPD and how is it administered?
Ipratropium spray
How long is the duration of effect of scopolamine?
3-7 days
What are the clinical uses of scopolamine?
Motion sickness
Post-operative nausea and vomiting
To block short term memory
‘Truth serum’
How is scopolamine administered to treat motion sickness?
Topical patch
Can scopolamine enter the CNS?
Yes because it is a tertiary tropine
What are the clinical uses of Homatropine?
Ophthalmology
What is the duration of effect of Homatropine?
1-3 days