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Pharmacology > Cholinergics- Muscarinics > Flashcards

Cholinergics- Muscarinics Flashcards

1
Q

Cholinergics

A

Agents that bind nicotinic and/or muscarinic receptors and mimic effects of ACh, can be both excitatory and inhibitory

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2
Q

Giving exogenous ACh

A

M3 release endothelial nitric oxide to vasodilate, M2 reduce heart rate

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3
Q

Atropine with cholinergics

A

Blocks muscarinic receptors, ACh can only bind to nicotinic receptors, release of NE, NE acts on alpha-receptors to vasoconstrict

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4
Q

Direct-acting muscarinic cholinergics

A

Agonists- Cholinomimetics

Antagonists- Antimuscarinics

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5
Q

Direct-acting nicontinic cholinergics

A

Agonists- Cholinomimetics

Antagonists

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6
Q

Indirect-acting cholinomimetics

A

Choline esterase inhibitors (ChEI)

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7
Q

Muscarinics

A

Compounds that selectively bind and activate/inactivate muscarinic receptors, actions similar to alkaloid muscarine

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8
Q

Muscarinic actions

A

Correpond to parasympathetic stimulation through release of ACh at parasympathetic postganglionic sites

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9
Q

Exceptions to muscarinic actions

A

ACh vasodilate blood vessels but no parasympathetic innervation to blood vessels, ACh released at sweat glands by sympathetic innervation

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10
Q

Muscarinic receptors

A

G-protein coupled receptors, Gq, Gi, G0

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11
Q

Gq activation

A

Activated by M1, M3, M5

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12
Q

Gi activation

A

Activated by M2, M4

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13
Q

Action of G0

A

Increases opening probability of G-protein modified inwardly rectifying K channels, mediated by M2, M4, hyperpolarizes the cell, metabotropic

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14
Q

Alkaloids

A

Natural compounds, muscarine, pilocarpine

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15
Q

Muscarine

A

No clinical use, found in certain mushrooms, used as investigational tool to differentiate between agents with muscarinic or nicotinic activity

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16
Q

Pilocarpine

A

Tertiary cholinomimetic alkaloid, well absorbed, partial agonist

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17
Q

Choline esters

A

Agents with modified ACh structure for more muscarinic receptor selectivity and less susceptibility to cholinesterase inactivation, charged, little CNS penetration

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18
Q

Methyl group of choline esters

A

Makes drug more selective for muscarinic receptors

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19
Q

Acetyl to carbamol substitution on choline esters

A

Confers resistance to cholinesterase hydrolysis

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20
Q

Muscarinic effects on eye

A

Muscarinic agonists contract both iris sphincters and ciliary muscles through M3, iris pulled away from anterior chamber, trabecular meshwork at base of ciliary muscle opened, both facilitate aqueous humor outflow into canal of Schlemm

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21
Q

Cardiovascular effects of muscarinics

A

M2 mediates an increase in K current in cardiac cells to cause hyperpolarization, reduce action potential duration, decrease contractility of the heart

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22
Q

Cardiovascular effects of low concentrations of muscarinics

A

Activation of M3 on endothelial cells release NO, diffuses to adjacent vascular smooth muscle to activate guanylyl cyclase, increase cGMP, causes vasodilation, will stimulate reflex to return blood pressure to normal

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23
Q

Cardiovascular effects of high concentrations of muscarinics

A

Activation of M3 on vascular smooth muscle stimulates IP3 production, releases intracellular calcium, causes vasoconstriction

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24
Q

Muscarinic effects on lungs

A

M3, contraction of bronchial muscle (bronchoconstriction), stimulation of bronchial glands

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25
Q

Muscarinic effects on GI

A

M3, increase motility, relax sphincters, stimulates secretion

26
Q

Muscarinic effects on bladder

A

M2, M3, contraction of detrusor, relaxation of trigone and sphincter

27
Q

Muscarinic effects on glands

A

M3, stimulates sweat, salivary, lacrimal, nasopharyngeal secretion

28
Q

Muscarinic effects in CNS

A

M1 expressed in areas involving cognition, M2 mediates tremor, hypothermia, antincociception, M3 in hypothalamus, reduces appetitie and dimishes body fat mass

29
Q

Clinical uses of acetylcholine

A

Direct-acting choline ester, miosis induction for eye surgery

30
Q

Clinical uses of metacholine

A

Direct-acting choline ester, asthma diagnosis

31
Q

Clinical uses of carbachol

A

Direct-acting choline ester, miosis induction for eye surgery, glaucoma

32
Q

Clinical uses of bethanechol

A

Direct-acting choline ester, urinary retention, agent of choice for post-op, postpartum, and drug-related urinary retention, used to increase tone of the lower esophageal sphincter in patients with reflux esophagitis

33
Q

Clinical uses of pilocarpine

A

Direct-acting alkaloid, glaucoma, Sjogren’s syndrome (xerostomia)- systemic autoimmune disease where immune cells destroy exocrine glands

34
Q

Clinical uses of cevimeline

A

Direct-acting muscarinic agonist for treatment of dry mouth associated with Sjogren’s syndrome

35
Q

Side effects of muscarinics

A

Diarrhea, urination, miosis/muscle weakness, bronchospasm, bradycardia, excitation, lacrimation, salivation/sweating/seizures (DUMBBELS)

36
Q

Contraindications of muscarinics

A

Coronary insufficiency (reduced blood pressure exacerbates decrease in coronary blood flow), hyperthyroidism (reduces AV conduction with increased heart rate- arrhythmia), asthma (bronchoconstriction), peptic ulcer disease (increased gastric acid secretion)

37
Q

Muscarinic antagonists

A

Sometimes called parasympatholytics- do not lyse parasympathetic neurons, exert effects not predictable from block of parasympathetic nervous system, better called antimuscarinics

38
Q

Classes of muscarinic antagonists

A

Naturally occuring alkaloids- atropine, scopolamine
Semisynthetic derivatives of alkaloids- ipratropium, tiotropium
Synthetic congeners with selectivity for muscarinic receptor subtypes- tolterodine

39
Q

Atropine

A

Alkaloid, used to dilate pupils

40
Q

Scopolamine

A

Alkaloid, used for prophylactic treatment of motion sickness

41
Q

Ipratropium, tiotropium

A

Quaternary compounds, do not cross the blood brain barrier, used for bronchial asthma and COPD

42
Q

Tolterodine

A

Treatment of urinary incontinence

43
Q

Pharmacokinetics of alkaloid and tertiary antimuscarinic

A

Well absorbed from the gut and conjunctival membranes, can get into CNS, scopolamine is rapidly distributed into the CNS, has greater effects than other antimuscarinics

44
Q

Pharmacokinetics of quaternary antimuscarinics

A

Only 10-30% of the drug is absorbed and are poorly taken up by the brain, less CNS effect, exhibit greater nicotinic blocking activity and more likely to interfere with ganglionic or neuromuscular transmission

45
Q

Pharmacodynamics of atropine

A

Reversible inhibitor of muscarinic receptors, receptors are active, most drugs that block actions of ACh are inverse agonists, atropine binds nicotinic receptors with low potency

46
Q

CNS effects of scopolamine

A

Low doses- produces CNS depression, drowsiness, amnesia

High doses- can cause excitement, agitation, hallucinations, delirium, coma

47
Q

CNS effects of atropine

A

Low doses- causes mild vagal excitement

High doses- can cause excitement, agitation, hallucinations, delirium, coma

48
Q

Effects of antimuscarinics on the eye

A

Cause unopposed sympathetic dilator activity and mydraisis, Weaken contraction of ciliary muscle, cycloplegia, which results in loss of accomodation and focus for near vision, may cause acute glaucoma

49
Q

Effects of antimuscarinics in the heart

A

Low doses- reduction in heart rate due to blockade of presynaptic M1 receptors (normally limit ACh release)
High dose- tachycardia

50
Q

Respiratory effects of antimuscarinics

A

Can cause bronchodilation and reduce secretion, not useful in asthma treatment, limited effectiveness in COPD due to blockade of parasympathetic postganglionic presynaptic M2 autoreceptors, frequently used before inhalant anesthetics to reduce secretions

51
Q

GI effects of antimuscarinics

A

Impaired tone and motility, prolonged gastric emptying time, induced intestinal paralysis is temporary

52
Q

Effects of antimuscarinics on urinary tract

A

Relaxes smooth muscle of ureters and bladder and slows voiding, may precipitate urinary retention in men with prostatic hyperplasia

53
Q

Effects of antimuscarinics on glands

A

Inhibit secretion of most glands, leading to dry mouth and dry skin

54
Q

Clinical uses of antimuscarinics

A

Inhibit effects of parasympathetic nervous system activity, have undesired side effects that are usually not serious, local administration to minimize systemic absorption

55
Q

Side effects of 0.5 mg atropine

A

Depress salivary and bronchial secretion and sweating

56
Q

Side effects of 1 mg atropine

A

Pupils dilate, accomodation of lens to near vision inhibited, vagal effects on heart are blocked (increases heart rate)

57
Q

Side effects of 2 mg atropine

A

Inhibit parasympathetic control of urinary bladder and GI tract, inhibit micturition and decrease tone and motility of the gut

58
Q

Side effects of 5 mg atropine

A

Gastric secretion and motility inhibited

59
Q

Side effects of >10 mg atropine

A

Excitement, hallucination, delirium, coma

60
Q

Contraindications of antimuscarinics

A

Patients with glaucoma, elderly men (increased incidence for prostatic hyperplasia), increase symptoms in patients with gastric ulcer

Pharmacology (15 decks)

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