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Pharmacology > Cholinergic Drugs > Flashcards

Cholinergic Drugs Flashcards

1
Q

What is a cholinergic drug?

A

-substance that produces the same effect as Acetylcholine

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2
Q

Direct acting cholinergic drugs?

A

-stimulate cholinergic receptors

  1. synthetic- esters of choline (Bethanechol, Carbachol)
  2. natural- acetylcholine (eyes), alkaloids (nicotine, pilocarpine), marijuana
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3
Q

Indirect acting cholinergic drugs?

A

-function to elevate endogenous levels of ACh

  1. inhibition of acetylcholinesterase
    - prevents ACh breakdown
    - reversible, competitive, short acting
    - irreversible, noncompetitive
  2. enhanced release of ACh
    - done via Guanidine
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4
Q

Acetylcholine as a drug?

A

Clinical use:

  • short duration of action
  • non specific cholinergic drug, affects all receptors muscarinic and nicotinic
  • highly susceptible to acetylcholinesterase

Miochol:

  • ACh for intraocular use
  • causes smooth muscle of iris to contract (pupil constriction)
  • duration of action 10-20 mins

ADR:
-burning and itching eyes along with headache

-some ACh makes it to systemic circulation when injected into eyes

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5
Q

Methacholine?

A
  • somewhat susceptible acetylcholinesterase
  • acts on muscarinic receptors only
  • longer duration of action
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6
Q

Carbachol?

A
  • synthetic choline ester, direct acting cholinergic
  • acts on muscarinic and nicotinic receptors
  • not degraded by acetylcholinesterase

Clinical use:

  • treat open angle glaucoma (intraocular pressure)
  • duration is up to 8 hours

Mechanism:
-pupillary constriction causes opening, allowing aqueous humor to exit via Canal of Schlemm

ADR:

  • flushing
  • sweating
  • cramping
  • increased GI activity (urination)
  • severe headache
  • systemic effects
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7
Q

Bethanechol?

A
  • synthetic choline ester, direct acting cholinergic
  • acts only on muscarinic receptors
  • not degrade by acetylcholinesterase

Effects:

  • increases GI peristalsis and defecation
  • increases detrusor muscle tone
  • stimulates urination

Clinical use:

  • non obstructive urinary retention
  • neurogenic atony of urinary bladder (loss of muscle tone)
  • post op abdominal distention

ADR:

  • flushing
  • sweating
  • cramping
  • increased GI activity
  • urinary urgency
  • severe headache
  • salivation

When not to use drug (contraindication):

  • asthma like attacks (those with asthma are given anticholinergic drugs)
  • parksonism (increasing ACh, diminishes the balance between Dopamine)
  • usual ANS responses to systemic ACh (ADR above)
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8
Q

Pilocarpine?

A
  • natural, direct acting cholinergic
  • cholinomimetic alkaloid, precursor of ACh

Effects:

  • contraction of ciliary muscle, pupil constriction
  • decreases intraocular pressure
  • systemic salivation, sweating
  • bradycardia

Clinical use:

  • treat open and narrow angle glaucoma
  • reversal of mydriatics (dilation) after eye exam
  • ocular therapeutic system- unit inserted into conjunctival sac for continuous release of pilocarpine to open angle glaucoma (for elderly patients, could cause infections)
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9
Q

Nicotine?

A
  • natural, direct acting cholinergic
  • cholinomimetic alkaloid

Effects:

  • activates receptors in ANS ganglia, neuromuscular junctions, adrenal medulla, and brain
  • causes people to become physically dependent, not carcinogenic
  • stimulates cerebral cortex (alertness, cognition increase)
  • stimulates limbic system (reward and pleasure)
  • Tachycardia
  • peripheral vasoconstriction (net effect of sym and parasym)

Clinical use:
-helps someone quit smoking (could OD if smoking still)

ADR:

  • hypertension from tachycardia
  • Buergers disease- interference of circulation due to vasoconstriction
  • diarrhea
  • insomnia
  • increase cognition
  • dysmenorrhea
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10
Q

Varenicline (Chantix)?

A
  • partial agonist of nicotinic receptors, weaker than nicotine
  • increases cholinergic system
  • blocks nicotine, releases Dopamine
  • could cause schizophrenia, bipolar disorder, depression
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11
Q

Cholinergic crisis?

A

-see sawing between cholinergic and anticholinergic drugs

Effects:

  • sweating
  • increased bronchial and salivary secretions
  • bradycardia
  • muscle weakness (overstimulation)
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12
Q

Physostigmine (Antilirium)?

A
  • short acting, reversible, indirect acting cholinergic
  • inhibit acetylcholinesterase
  • topical, systemic
  • highly lipid soluble, tertiary structure, can cross BBB

Clinical use:

  • treat open angle glaucoma
  • reverse myadriasis from anticholinergic
  • antidote to toxic neurological effects caused by having central anticholinergic activity (Scopolamine, antidepressants)
  • clinical trials in treatment of alzheimers, short half life, slight increase in memory performance

ADR:

  • typical systemic reactions
  • bradycardia
  • diaphoresis
  • bronochospasm
  • respiratory paralysis (overstimulation of muscles and too much ACh, can’t get repolarization and relaxation)
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13
Q

Edrophonium?

A
  • short acting, reversible, indirect acting cholinergic
  • inhibit acetylcholinesterase
  • given by IV

Clinical use:

  • diagnose Myasthenia Gravis (autoimmune disease)
  • treat poisoning of non depolarizing skeletal muscle relaxants
  • test for cholinergic OD in those with Myasthenia
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14
Q

Neostigmine?

A
  • short acting, reversible, indirect acting cholinergic
  • inhibit acetylcholinesterase
  • quaternary compound, does not cross BBB

Clinical use:

  • treat Myasthenia Gravis
  • treat poisoning of nondepolarizing skeletal muscle relaxants
  • reverse neuromuscular blocking agent used for surgeries
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15
Q

Pyridostigmine?

A
  • short acting, reversible, indirect acting cholinergic
  • inhibit acetylcholinestase

Clinical use:

  • treat myasthenia gravis
  • treat poisoning of non depolarizing skeletal muscle relaxants
  • occupies receptors so irreversible nerve gas does not damage

ADR:

  • increased salivary secretions
  • sweating
  • GI and urinary functions increase
  • may lose ability to control GI and urinary
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16
Q

How do indirect acting irreversible cholinergic drug work?

A
  • cause permanent inactivation of acetylcholinesterase via phosphorylation
  • remains impaired until new enzymes are synthesized (weeks or months)
  • chemical warfare, pesticides
  • very lipid soluble, must wear gloves
17
Q

Echothiophate?

A
  • irreversible, indirect acting cholinergic
  • inactivate acetylcholinesterase
  • long duration of action, may persist weeks

Clinical use:

  • treat glaucoma
  • pupillary constriction, miosis
  • angle closure after an iridectomy (remove part of iris)
18
Q

Isoflurophate?

A
  • irreversible, indirect acting cholinergic
  • inactivate acetylcholinesterase
  • similar to echothiophate
  • water insoluble, readily absorbed into skin, systemic effects

Clinical use:
-maintenance therapy for glaucoma applied every 8-72 hours

19
Q

Pralidoxine?

A

-cholinesterase inhibitor antidote

Mechanism:
-disrupts bond between phosphorous group of irreversible enzyme inhibitor and binding site of cholinesterase enzyme

Clinical use:
-treat OD of irreversible cholinesterase inhibitor due to insecticide poisoning

20
Q

Guanidine?

A
  • indirect acting cholinergic
  • stimulates release of endogenous ACh
  • relatively high toxicity

Clinical use:

  • alleviate muscle weakness in myasthenia gravis
  • alleviate symptoms of Eaton Lambert syndrome (muscle cancer)

ADR:

  • diarrhea
  • abdominal cramping
  • tachycardia
  • rash and bone marrow depression
  • anemia
21
Q

What changes occur to cholinergic neurons as people age?

A
  • reduced activity of choline acetylcholine transferase
  • reduced synthesis of ACh
  • reduced responsiveness of post synaptic M1 receptors in frontal cortex and hippocampus
  • loss of cortical neurons
22
Q

How does a person reduce risk of losing memory/alzheimers?

A

-keep brains active and engaged to strengthen synapses

23
Q

Additional neuronal changes seen in patients with alzheimers?

A
  1. increased deposition of beta amyloid protein
  2. reduced number of synapses
  3. reduced activity of acetylcholinesterase
  4. possible genetic factors
    - can also develop due to head trauma
  5. exposure to excessive aluminum
24
Q

Lecithin (phosphatidylcholine)?

A
  • drug to try to increase synthesis of ACh
  • precursor of ACh
  • 26 mg daily PO

Effects:

  • increase levels of ACh in central synapses
  • reduces tardive dyskinesia
  • increase in plasma choline levels
  • no improvement in memory or cognition in alzheimers patients, presynaptic uptake of choline may be impaired
  • therapeutic only when combined with Physostigmine or Tacrine
25
Q

4-Aminopyridine (4-AP)?

A
  • drug to try to increase release of ACh
  • used in clinical trials for treatment of alzheimers

Mechanism:

  1. blocks K+ channels
  2. reduces K+ exiting the cell
  3. longer time to repolarize the cell
  4. increased calcium influx, increased vesicle fusion
  5. increased release of ACh

Effects:

  • could improve memory and cognition
  • placebo effect

ADR:

  • xerostomia (dry mouth)
  • disorientation
  • confusion
26
Q

Treatments to reduce alzheimers?

A

Enhance cholinergic activity

  1. increase synthesis of ACh
  2. increase release of ACh
  3. reduce catabolism of ACh (primary method)
27
Q

Tacrine (tetrahydroaminoacridine, THA, Cognex)?

A
  • centrally acting reversible cholinesterase agent
  • inhibits acetylcholinesterase
  • short half life (2-4 hours)
  • dose 40-120 mg daily PO

Effects:
-increase cognitive performance

ADR:
-HEPATOTOXIC (increase bilirubin)

28
Q

Donepezil (Aricept)?

A
  • centrally acting reversible anti cholinesterase agent
  • inhibits acetylcholinesterase
  • long half life (70 hours), less frequent dosing, lower rate of ADR
  • first product approved by FDA for treatment of dementia and alzheimers

Effects:

  • cognitive improvement (disappears when drug therapy is withdrawn)
  • NOT HEPATOTOXIC

ADR:

  • diarrhea
  • anorexia
  • muscle cramps
  • insomnia
29
Q

Rivastigmine?

A

Effects:
-inhibits acetylcholinesterase and butyrylcholinesterase

Clinical use:
-treats mild to moderate dementia of alzheimers

30
Q

Galantamine?

A

Effects:

  • inhibits acetylcholinesterase
  • stimulates nicotinic receptors at sites different from those of acetylcholine
  • enhances action of nicotinic receptors in presence of acetylcholine
  • stimulates central cholinergic sites without causing concomitant desensitization

Clinical use:
-treat alzheimers, dementia

31
Q

Memantine?

A
  • Glutamate is excitatory and acts as NMDA receptor
  • in some alzheimers, there is over activity of NMDA which may be tearing down receptors
  • this promotes excess calcium influx which cause synaptic or dendritic damage, necrosis or apoptosis

Mechanism:
-Memantine binds to NMDA receptor and noncompetitively blocks it

Effects:

  • slows progression of alzheimers
  • may reduce pain
32
Q

Deferoxamine?

A

Effects:

  • approved as iron chelator to treat acute iron intoxication and chronic iron overload
  • may reduce aluminum levels in bones of patients presenting with renal failure, patients with dialysis induced encephalopathy

Clinical use:

  • drug to treat alzheimers
  • use parenteral form
  • could slow rate of cognitive deterioration

ADR:

  • hearing loss
  • impaired vision
  • diarrhea
  • leg cramps
  • tachycardia
  • reversible upon discontinuation
33
Q

1-Deprenyl?

A

Effects:

  • irreversible inhibitor of MAO-B
  • stops degradation of ACh in presynaptic membrane
  • slows degeneration in patients with Parkinson’s
  • improves cognition
  • additive with cholinesterase inhibitors

Clinical use:

  • help treat alzheimer’s
  • alzheimers may be caused by free radicals
  • combine with Tacrine or Physostigmine
  • dose 10mg daily PO

Pharmacology (9 decks)

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