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Pharm I > Muscarinic Antagonists > Flashcards

Muscarinic Antagonists Flashcards

1
Q

Naturally occurring alkaloids

A

Atropine

Scopolamine

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2
Q

Semisynthetic/synthetic antagonists

A
  1. Different duration:
    Homatropine and tropicamide
    (shorter duration of action than atropine)
  2. Receptor subtype selectivity:
    Darifenacin and solifenacin (M3 selective but not complete)
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3
Q

4h Half-life
Hepatic metabolism accounts for the elimination of about half a dose.

  1. No CNS effect (preferred to scopolamine). Central excitation at toxic doses.
  2. Mydriasis and loss of accommodation of considerable duration (7-12 days)
  3. Tachycardia, larger doses cause progressively increasing tachycardia by blocking vagal effects on M2 receptors on the SA nodal pacemaker. (may fail in adults)
A
  • Competitive antagonist
  • Causes only mild vagal excitation
  • Therapeutic dose 0.5-1 mg.
  • Symptoms varies as dose changes. (Table 2. P17)
    • Small doses: salivary and bronchial, sweating inhibition.
    • Larger doses: pupil dilation, blockade of vagal effects on heart, increase HR, UT& GI inhibition
    • Still larger doses of atropine: paralysis and coma; circulatory collapse and respiratory failure.
  • Modulate gastrin-elicited histamine release and gastric acid secretion.
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4
Q

Scopolamine (3)

  1. CNS depression, euphoria (substance abuse)
  2. Mydriasis and loss of accommodation of considerable duration (7-12 days)
  3. Less vagal blocking effect than atropine.
A

.

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5
Q

Belladonna alkaloids

  1. treatment of parkinsonism (effective with levodopa)
  2. treat side effects of conventional antipsychotic drug therapy
A

Atropine, scopolamine

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6
Q

Quaternary Derivatives

A

Ipratropium
Tiotropium
——————
Both: given by **Inhalation*
(almost exclusive effect to mouth and airways, systemic absorption is minimal!!)
1. Lack appreciable action on the CNS
2. More potent than atropine (greater inhibitory effects on ganglionic transmission)
3. Minimal inhibitory effect on mucosilary clearance relative to atropine; lessens increased accumulation of lower airway secretions to patients with airway diseases compared to atropine.

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7
Q 
Ipratropium bromide (4)
-----------------------
Inhalation, COPD, Asthma
max response over 30-90min
last for 4-6h
  1. FDA approved for perennial and common cold-associated rhinorrhea鼻涕溢
  2. Treat chronic obstructive pulmonary disease
    (less effective in most asthmatic patients)
A

-block all subtypes of muscarinic receptors

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8
Q 
Tiotropium bromide (4)
----------------------------
SLOWER ONSET
persist for 24h
Administered as a dry powder.
(Inhalation??
max response over 30-90min)

-Treat chronic obstructive pulmonary disease

A
  • Longer duration of action
  • Selectivity for M1 and M3 receptors (low selectivity for M2 minimizes its presynaptic effect on ACh release)
  • Bronchialdilation, tachycardia, and inhibition of secretion (similar to atropine)
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9
Q

Absorption

A
  1. Belladonna alkaloids and the tertiary synthetic and semisynthetic derivatives: absorbed rapidly from the GI tract, enters circulation when applied locally to the mucosal surfaces, absorption from intact skin is limited
  2. Belladonna alkaloids quaternary ammonium derivatives: penetrate the conjunctiva less readily, central effect are lacking.
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10
Q

Atropine and related belladonna alkaloids and other derivatives

Umeclidinium
Aclidinium

A
  1. Atropine, related belladonna alkaloids and synthetic analogs:
    reduce secretion in both upper and lower RT. Antihistamine.
  2. Treat bronchial asthma or chronic obstructive pulmonary diseases

Disadvantage: reduce bronchial secretions. material hard to be removed => obstruction/infection
Note: Ipratropium and tiotropium administered by inhalation do not produce adverse effects on mucociliary clearance. They are used with inhalation of long-acting adrenergic receptor agonists.

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11
Q

Long acting, antimuscarinic agent recently approved for oral inhalation.

NONSELECTIVE for M1-M5. COMPETITIVE and REVSERSIBLE antagonism.

A
  1. In the airways it inhibits M3 receptor in the smooth muscle => bronchodilation.
  2. Long-term, once-daily
  3. For maintenance treatment of airflow obstruction in patients with COPD, including chronic bronchitis and/or emphysema.
  4. SHOULD NOT BE USED FOR ACUTE SYMPTOMS.
  5. Avoid coadministration with other anticholinergic-containing drugs.
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12
Q

Long acting, antimuscarinic agent recently approved for oral inhalation.

NONSELECTIVE for M1-M5. COMPETITIVE and REVSERSIBLE antagonism.

A
  1. In the airways it inhibits M3 receptor in the smooth muscle => bronchodilation.
  2. Long-term, twice-daily
  3. For maintenance treatment of airflow obstruction in patients with COPD, including chronic bronchitis and/or emphysema.
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13
Q 
Genitourinary Tract
-----------------
Tolterodine, fesoterodine, trospium chloride
oxybutynin
solifenacin
darifenacin
A

Muscarinic antagonists to treat overactive urinary bladder diseases.

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14
Q 
Treat overactive urinary bladder disease:
----------------------------
Tolterodine
Fesoterodine
Trospium chloride
(synthetic substitutes of atropine)
---------------------------
Other drugs:
Darifenacin
Solifenacin
Flavoxate
A
  • Lower intravesicular pressure and increase capacity in the bladder.
  • Reduce the frequency of contractions by antagonizing parasympathetic bladder control.

Side effects:
-dry mouth and eyes limited the tolerability of these drugs.

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15
Q

Oxybutynim
(marked as a transdermal system)

A

Lower incidence of side effects than oral immediate- or extended-release preps.

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16
Q

Trospium (4)
(Long used in Europe and recently approved for use in the US)

A

Effective as oxybutynin with better tolerability.

17
Q

Solifenacin

A

Newly approved with a favorable efficacy: side effect ratio.

??

18
Q

Darifenacin
(Selective antagonists for M2 and M3 muscarinic receptors respectively)

A

Potential utility

19
Q 
Treat overactive urinary bladder disease:
----------------------------
Tolterodine
Fesoterodine (recently approved)
(Convert to active 5-HMT)
POTENT
A

Shows selectivity for the urinary bladder but NO SUBTYPE SELECTIVITY

20
Q

For management of peptic ulcer (they can reduce gastric motility and the secretion of gastric acid)

A

Belladonna alkaloids and sedative combinations.
(to treat irritable bowel and increased tone/spasticity or motility of the GI tract), DICYCLOMINE can be used

Also produce pronounced side effects => alternative agents are now used

21
Q 
GI Tract
--------------------
Belladonna alkaloids:
1. Atropine
2**. 1-Hyoscyamine sulfate
3. Scopolamine
A

-Reduce tone and motility when administered in maximal tolerated doses.
-Expected to be useful in conditions involving excessive smooth muscle contraction, but this may not be the case due to M3’s higher selectivity.
(major effects on salivation, bronchiolar secretion/contraction and bladder motility)
-Used in combination with other sedatives/antianxiety agents/Ergotamine.
-Used for diarrhea treatment associated with irritative conditions of the lower bowel. (dysenteries and diverticulitis, salmonella dysentery, ulcerative colitis and Crohn’s disease).
-They are effective in reducing excessive salivation.

22
Q

Ophthalmology

Limited effects to the eye

A

Produce mydriasis and cycloplegia

23
Q 
Ophthalmology
---------------------------
Atropine
Scopolamine
(preferred to tropicamide/short acting)
A

Instances in which complete cycloplegia is required

24
Q

Homatropine (semisynthetic derivative of atropine)
Cyclopentolate hydrochloride (often used in pediatric formulations)
Tropicamide

A

Agents preferred to topical atropine and scopolamine used in ophthalmologic practices

Preferred because of their shorter duration of action

25
Q

Cardiovascular System

A
  • limited clinical application

- used in coronary care units for short-term interventions of in surgical settings.

26
Q

Atropine

A

-considered in the initial treatment of patients with acute myocardial infarction
-may be used in cases of high vagal tone or AV block
(restore HR to a level sufficient to maintain adequate hemodynamic status, eliminates AV nodal block)
-need careful dose control

27
Q

Parkinonism & dystonias
Motion sickness drugs

A
  • Belladonna alkaloids and synthetic substitutes were the only agents helpful in the treatment of Parkinsonism for many years.
  • Levodopa or levodopa along with carbidopa now is the treatment choice.
  • Alternative or concurrent therapy with muscarinic receptor antagonists may be required in some patients.
28
Q 
CNS
--------------------------------
Tertiary-amine antagonists:
Benztropine mesylate
Procyclidine
Trihexyphenidyl hydrochloride
A
  • Efficacious in preventing dystonias or parkinsonism symptoms.
  • Drugs gain access to the CNS
29
Q

Motion sickness drugs

A
  • Belladonna alkaloids were the first drugs to be used for prevention.
  • Scopolamine is the most effective prophylactic agent (short (4-6h) exposure to severe motion sickness, transdermal preparation.
  • Needs to be given prophylactically (prevention).
  • Side effects of scopolamine: dry mouth, drowsiness, blurred vision, mydriasis and cycloplegia, rare psychotic episodes.
30
Q

Scopolamine to produce tranquilization 镇静 and amnesia 记忆衰退 in many cases

A

Example: Labor
-Use is declining and of questionable value

Untoward effects
-given alone in the presence of pain or severe anxiety may induce outbursts of uncontrolled behavior.

31
Q

Atropine (block vagal reflex response induced by surgical manipulation of visceral organ)

Atropine or glycopyrrolate is used with neostigmine
(block parasympathomimetic effects of neostigamine when neostigamine is used to reverse skeletal muscle relaxation after surgery. Serious cardiac arrhythmias have occasionally occurred.)

A
  • Relatively nonirritating to the bronchi
  • Eliminated the need for prophylactic use of muscarinic receptor antagonists
    • Atropine used to antagonize the parasympathomimetic effects of pyridostigmine or anticholinesterase agents such as neostigamine (drugs administered in treatment of MYASTHENIA GRAVIS)
  • will not interfere with salutary effects at the skeletal neuromuscular junction. Most useful earily in therapy before tolerance to muscarinic side effects has developed. **
32
Q

Other Muscarinic Antagonists

A 
Methscopolamine
Homatropine
Glycopyrrolate
Mepenzolate
Propantheline
33
Q

Methscopolamine bromide (4)

A
  • Quaternary ammonium derivative of scopolamine. (lacks the central actions of scopolamine)
  • limited to GI diseases
  • Less potent than atropine and is poorly absorbed
  • Action is more prolonged than atropine
34
Q

Homatropine methylbromide (4)

A
  • Quaternary derivative of homatropine
  • Less potent than atropine in antimuscarinic activity
  • 4x more potent than atropine as a ganglionic blocking agent.
  • Available in combination with hydrocodone as an antitussive combination.

Uses: 1. relief of GI spasm. 2. Adjunct in peptic ulcer disease.

35
Q

Glycopyrrolate

A
  • Employed orally to inhibit GI motility.
  • Used parentally to block the effects of vagal stimulation during anesthesia and surgery. (used in combination with formoterol fumarate, long-acting beta2 agonist for COPD)

Other antispasmodic drugs:
Tertiary amines: Dicyclomine hydrochloride, Flavoxate hydrochloride, Oxybutynin chloride, Tolterodine tartrate.

Quaternary amine: Trospium chloride

All agents are used for their antispasmodic properties, decrease spasm of the GI tract, biliary tract, ureter and uterus.

36
Q

Mepenzolate Bromide (4)

A

Quaternary amine with peripheral actions similar to those of atropine.

Indications: adjunctive therapy of peptic ulcer disease. Has been used as an antispasmodic for the relief of GI disorders.

37
Q

Propantheline bromide

A
  • More widely used of the synthetic NONSELECTIVE muscarinic receptor antagonist.
  • High doses produce the symptoms of ganglionic blockade.
  • Toxic doses block the skeletal neuromuscular junction.
  • It’s duration of action is comparable to that of atropine (repeated doses may be needed)
  • Treatment of marked excitement
  • Support respiration and control of hyperthermia may be necessary.

Pharm I (6 decks)

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