Updated: 4/1/2018

Muscarinic Antagonists

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Topic
Therapeutic Actions for Muscarinic Antagonists

Drug
Organ System
Application and Comments
Atropine, homatropine, tropicamide

Eye and Cardiac

• Causes mydriasis and cycloplegia
• Used for ophthalmologic exams
• Can be used for post-MI bradyarrythmias 
Benztropine  CNS • Parkinson's disease
Scopolamine  CNS • Motion sickness
• Fast onset
Ipratropium  Respiratory • Asthma
• COPD
• Tiotropium produces a longer bronchodilator effect
• Relief of rhinorrhea with common cold, allergic and nonallergic rhinitis
Oxybutynin, trospium, glycopyrrolate Genitourinary • Reduce urgency in mild cystitis
• Reduce bladder spasms after urologic surgery
Methscopolamine, pirenzepine, propantheline Gastrointestinal • Peptic ulcer treatment

 

Atropine
  • Muscarinic antagonist
    • blocks effects of cholinesterase inhibitor poisoning
  • Organ system
    • eye: ↑ pupil dilation and cycloplegia
    • lungs: ↓ secretions
    • GI and GU: ↓ stomach acid secretion, ↓ gut motility, and ↓ urgency in cystitis
  • Toxicity
    • CNS: ↑ body temperature, disorientation, hyperthermia in infants
    • Cardiovascular: tachycardia and flushing
    • Dermatologic: anhidrosis and urticaria
    • GI and GU: dry mouth, constipation, urinary retention 
    • Ocular: cycloplegia, acute angle-closure glaucoma, dry eyes
  • The atropine adage: "hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter, the bowel and bladder loser their tone, and the heart runs alone" 
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(M1.PH.15.75) A 29-year-old farm hand is brought into the emergency department by his friends because he passed out while working in the field and was not able to be aroused. His friends state they thought he had a stomach bug as he was sweating profusely and had diarrhea and vomiting prior to losing consciousness. On exam, the patient's vitals are: T: 36 deg C, HR: 60 bpm, BP: 100/60 mmHg, RR: 12, SaO2: 99%. Diaphoresis, lacrimation, and increased salivation are appreciated. The patient's eyes are shown in Figure A. Which of the following medications should be administered to this patient? Tested Concept

QID: 106850
FIGURES:
1

Pyridostigmine only

2%

(4/195)

2

Atropine only

10%

(20/195)

3

Pyridostigmine and Physostigmine

6%

(12/195)

4

Atropine and Pralidoxime

76%

(149/195)

5

Sodium Bicarbonate and Pralidoxime

3%

(6/195)

M 1 D

Select Answer to see Preferred Response

(M1.PH.14.44) A 5-year-old boy is brought to the ED with fever and altered mental status. The boy was in his normal state of health until a few hours ago when he began to "not feel good" while on a deep-sea fishing trip as part of his family vacation. By the time that the family made it back to shore, the boy was experiencing blurred vision and confusion. In the ED his vitals were 101.6F, HR160, RR18, and O2 99% on room air. On exam, his skin is dry and flushed, and his abdomen is covered in small, round, stickers similar to that in Figure A. What gastrointestinal and urinary symptoms would you expect in this patient? Tested Concept

QID: 101708
FIGURES:
1

Incontinence of stool; urine retention

5%

(12/236)

2

Incontinence of stool and urine

12%

(29/236)

3

Constipation; urine retention

69%

(163/236)

4

Constipation; incontinence of urine

9%

(21/236)

5

Incontinence of stool; no urinary symptoms

3%

(6/236)

M 3 C

Select Answer to see Preferred Response

Evidence (3)
Topic COMMENTS (19)
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