Case studies in autonomic pharmacology

Question 1

Patient A had CV disease so was treated with B- blocker (atenolol). Explain its mode of action and why this was prescribed not propranolol
Also explain side effects

Answer 1

• Antagonist of B1 adrenoceptor
  (therefore agonist- adrenaline/ noradrenaline)
• Choose atenolol as cardio-selective B1 receptor whereas propranolol is a non-selective b- blocker so binds to B1/B2/B3 receptors causing bronchoconstriction and peripheral vasoconstriction (cold periphery)
• Side effects: dizziness upon standing constipation/ indigestion and trouble breathing (bronchoconstriction), cold periphery
• Bradycardia

Question 2

Glaucoma- what could be used to treat this (2)
If asthmatic which one should be avoided and if he did take this and suffered bronchospasm what could be taken to contradict this

Answer 2

1) beta blocker- as these would reduce the amount of fluid produced by the eye- hence reducing intraocular pressure
2) M3 agonist- promotes construction of circular muscle opening up drainage channel so XS fluid is drained

However the beta blocker can act on the B2 receptors causing bronchial constriction- hence salbutamol (b agonist needs to be used causing vasodilation)
OR muscarinic antagonist (as causes relaxation)

Question 3

Anaphylactic episode caused by massive release of histamine- causing drop in blood pressure and bronchoconstriction so treated with adrenaline as emergency treatment- why? Problems?

Answer 3

non-selective B- agonist

Causes vasodilation in bronchiole (B2) and increase in heart rate and force of contraction (B1)

Question 4

If accidently poisoned with organophosphorus insecticide- explain mode of action and useful drug to combat this and its type?

Answer 4

• Inhibits acetyl cholinesterase, covalently modifying by adding P (so in inactive form)
• Muscarinic, nicotinic and CNS symptoms
• causing overstimulation of parasympathetic nervous system- miosis, salvation sweating bradycardia, nicotinic effects include fasciculation (twitching SkM) and paralysis, CNS symptoms include anxiety, restlessness and dizziness
• Atropine= Anti- muscarinic or parasympatholytic (antagonist for muscarinic receptors reducing availability of mAChR and alleviating )
• Palidoxime- to reactivate by dephosphorylating AChE

Question 5

Woman presecribed antidepressant amitriptyline- neuronal transport reuptake inhibitor (indirect sympathomimetic) and has range side effects as muscarinic receptor antagonist (antimuscarinic activity) - what might side effects include and what neurotransmitter channel is blocked?

Answer 5

• dry mouth, constipation, pupil dilation (so blurred vision due to lack of accommodation), urinary retention, increased heart rate (due to block M2 receptors which decrease heart rate)
• Serotonin and NA- neurotransmitters effect

Question 6

If child accidently swallowed atropine tablets- what symptoms would we expect and what drugs can treat this?

Answer 6

• Muscarinic receptor antagonist
• Pupils dilate (photophobia- sensitive to light), tachycardia, dry mouth constipation, urinary retention
• so need muscarinic agonist- pilocarpine
• Or Acetlycholine esterase inhibitor - to increase amount ACh in synapse encouraging activity of parasympathetic NS