CPT1: ANS2

Question 1

What mechansims of action can parasympathomimetic drugs have?

Answer 1

• direct
• indirect

Question 2

What general effects do parasympathomimetic drugs have?

Answer 2

• Bradycardia - decreased HR
• hypotension - Low bp
• increased secretions: salivary, bronchial
• smooth muscle contraction
• Bronchoconstriction
• nausea/ vommitting, diaohrea
• increased peristalisis

Question 3

What do large doses of parasympathomimetic drugs do?

Answer 3

Stimulate then block

Leads to desensitisation of receptors and depolarising block (loss of electrical excitability at the end plate)

Question 4

What are examples of Muscarinic receptor agonists?

Answer 4

• Pilocarpine
• Bethanechol

Question 5

What does pilocarpine do?

Answer 5

• Partional agonist selective for MAchR
• Pilocarpine eye drops cross conjuctival membranes (ocular and systemic side effects)
• Causes pupilary ocnstriction and reduction of intraocular pressure

Question 6

What are side effects of pilocarpine?

Answer 6

Local:

• allergic conjuctivitis
• blurred vision
• cilary spasm
• lid twitching

Systemic

• Nausea,vomitting
• bradycardia (M2)
• Bronchoconstriction (M3)
• Hypotension

Question 7

What does Bethanechol do?

Answer 7

• Selective MAchR. Doesn’t cross BBB
• Used to alter urinary and GI tract motilty

GI:

• Stimulant laxative (Enhances parasympathetic activity

Bladder:

• Increases tone/ contractility of detrusor muscles and facilitaes voiding (smooth muscle of bladder wall)

Question 8

What are side effects of bethanechol

Answer 8

• Nausea, Vommitting, bradycardia, hypotension, increased salivation/ secretion/ sweating, bronchoconstriction, increased GI motiltiy

Question 9

What are general muscularinic agonist side effects?

Answer 9

CVS

• Bradycardia
• Decreased CO
• Decreased force of contraction
• Generalised vasodilation

Smooth Muscle:

• Non-vascular smooth muscle contracts
• GI
• Utrerine
• Detrusor
• Airway

Gland Secretion:

• Salivary
• Sweat glands
• Bronchial
• Pancreatic
• Gastric

Question 10

What are examples of indirect parasympathomimetic drugs?

Answer 10

Anticholinesterases/ Cholinesterase inhibitors

• Short acting: Edrophonium
• Medium acting: Neostigmine, Donepezil, Rivastigmine
• Long acting:

Galantamine

Question 11

How do Anticholinesterases work?

Answer 11

Acetylcholinesterases normally break down Acetylcholine. Anticholinesterases inhibit cholinesterases and prevent them form breaking Ach down so it is rounf dor longer to have an effect

Question 12

Describe the mechanism of action of Edrophonium

Answer 12

• Binds to anionic site of the enzyme
• Readily reversible and short acting
• Administered IV
• used as a diagonstic tool

Question 13

What is the mechanism of action of Neostigmine, rivastigime and donepezil

Answer 13

• BInds to anionic site of enzyme
• Carbamylates the enzyme which takes minutes to hydrolysis/ reverse
• slow recovery of carbamaylated enzyme means the drug action is prolonged

Question 14

What drugs are used to treat patients with alzheimers?

How?

Answer 14

RIvastigmine and donepezil

stop Ach being degrades so increase Ach avilability which helps alevate symptoms. Limites use due to adverse effects so these must out weigh benefit.

Question 15

What are side effects of AchE inhibitors?

What are cautions?

Answer 15

• Nausea, vomitting
• increased GI motility
• Urinary incontinece
• bradycardia
• Asthma
• hepatoxic
• sick sinus syndrome

Question 16

What are general side effects of Muscularinic antagonists?

Answer 16

inhibition of secretions:

• Salivary and sweat glands
• Gastric secretions- slightly reduced (M1)
• Bronchial glands

Heart Rate:

• Trachycardia (M2)
• Arterial blood pressure unaffected

Smooth Muscle

• Reduced GI motility
• Bronchodilation
• Urinary tract dilation

Question 17

Examples of muscarinic antagonists

Answer 17

• Atropine and Hyosine: naturally occuring plant compound, readily absorbed in GUT and crosses BBB
• Atropine methonitrate: Atropine derivative, doesnt cross BBB (reduced central side effects)
• Pirenzepine - M1 antagonist. Reduces Gastric acid secretion
• Darifenacin - M3 selective. Reduces bladder contraction

Question 18

What can muscarinic antagonists be used for?

Answer 18

1. Motion sickness - hyosine
2. Asthma - short term relief of symptoms (dilation). B2 agonist preferred
3. Parkinsons

Question 19

What is an example of an agonist for both a and b receptors?

What can it be used for?

Answer 19

Adrenaline

• anaphylatic shocks - IM first choice but Iv in emergancy
• decongestant
• cardiac arrest - IV administered
• With local anaesthetics - local anaesthetics cause dilation of blood vessels so adminsistering vasoconstrictor slows rate of absorption and prolongs action

Question 20

What are systemic effects of a adrenoagonists?

Answer 20

• Vascular smooth muscle contraction (a1)
• skin and splanchnic vacular bed contraction
• large veins, arteries and arterioles vasoconstriction
• Decreased vacular compliance (ability for blood vessels to expand/ relax)
• increased centeral venous pressure
• Increased peripheral resistance
• increased BP intiates bsroreceptor reflex
• cerebral/ conary/ pulmonsry beds unaffected
• increased cardiac work

Question 21

What are examples of a agonists?

Answer 21

• Phenylephrine - a1 (decongestant)
• clonidine - a2 (acts centerally)

Question 22

What effects do phenylephrine have?

Side effects?

Answer 22

• constriction of blood vessels
• constriction of nasal passage ways
• reduction in swelling

Question 23

What effects does clonidine have?

side effects?

Answer 23

• Hypertension and migrane
• centerally acting hypertensive
• decreases CO and peripheral resistance
• cant withdrawl suddenly

Causes blood vessels to relax and treats hypertension

• Sedatative
• depression
• fluid retention
• constipation

Question 24

What are general actions of B adrenoagonists?

Answer 24

Smooth muscle:

• Relaxation of smooth muscle B2
• Vaso dilation B2 (mainly endothelium dependent). Relaxation not just mediated by cAMP but also BKCa channels
• B3 mediated signalling not just by cAMP but also by delayed rectifier K+ channels

Nerve terminals:

• a2 - inhibitory (inhibits NT release)
• B2 - facilitates NT release

Heart:

• B1 - increase force and rate
• increased CO and O2 consumption

Metabolism

• Encourages conversion of energy stores to fuels. B1/2 - liver and muscle carbohydrate metabolism. B3 - lipolysis. a2 - insulin secretion decreased

SKeletal

• Tremor or shaking

Question 25

What are examples of B agonists?

Answer 25

• b1 - dobutamine - septic shock. Increased contractility. Iv administration
• B2 - salbutamol - bronchodilation. Uterine smooth muscle dilation

Question 26

Clinical effects of adrenoreceptor antagonists

Answer 26

• MI
• Angina
• heart failure
• hypertension
• dysrhymias

Anxiety

migranes

Question 27

Examples of a antagonists

effects?

Answer 27

• a1 - prazosine, doxazosine
• vasodilation and fall in arterial pressure
• blockage of a1 mediated vasoconstriction
• increased CO as drop in BP detected by baroreceptors which increase sympatheitc response
• Smooth muscle relaxation
• additional blockage of a2 - increases #NT release

Question 28

b antagonist examples

Answer 28

• Propranolol: B1/2
• Oxprenolol: non selective
• Nebivilol: B1/ NO
• Atenalol: B1
  *

Question 29

What are the exceptions to effects of propanolol?

Answer 29

• at rest propranol doesnt effect HR, CO, atria pressure
• depends on degree of sympathetic activity

Question 30

Effects of B antagonists

Answer 30

• Bronchoconstriction
• cardiac depression
• bradycardia
• hypoglycemia
• fatigue - reduced CO/ muscle perfusion
• cold extremitoes - reduced B vasodilation