Which action is an action of Cholinergic drugs?

Raj. CHO - 2023

Pharmacology

Easy

Appeared in: Raj. CHO - 2023

Explanation

Cholinergic drugs mimic the neurotransmitter acetylcholine, stimulating the parasympathetic nervous system ('rest and digest').
A primary action is on the eye's iris sphincter muscle, causing it to contract.
This muscle contraction leads to pupil constriction, also known as miosis.
This effect is therapeutically important in managing conditions like glaucoma, as it facilitates the drainage of aqueous humor.

Option B: This is also a correct action of cholinergic drugs. They stimulate glands, leading to increased secretions, including saliva. However, the question is flawed as it presents multiple correct options in a single-choice format.
Option C: This statement is incorrect. Cholinergic drugs increase the tone and motility of smooth muscles, especially in the gastrointestinal tract and urinary bladder, leading to effects like increased urination and bowel movements.
Option D: This is also a correct action of cholinergic drugs. They act on the heart's sinoatrial node to slow the heart rate (bradycardia). The question is flawed as it presents multiple correct options.

Visual 1: Diagram: A visual comparing a constricted pupil (miosis) due to parasympathetic/cholinergic stimulation with a dilated pupil (mydriasis) from sympathetic/anticholinergic action.
Visual 2: Infographic: The 'SLUDGE' mnemonic (Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis) to help remember the common effects of cholinergic stimulation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Actions of Cholinergic Drugs (Parasympathomimetics) as background academic context rather than a clinical decision trigger.
Nurses must be able to identify signs of cholinergic crisis (overdose), which can be remembered by the mnemonic DUMBELS: Diarrhea, Urination, Miosis, Bradycardia, Emesis, Lacrimation, Salivation. This is a medical emergency requiring immediate intervention, often with atropine.
Cholinergic drugs have important therapeutic uses, such as pilocarpine for glaucoma and bethanechol for non-obstructive urinary retention.
What if? If a patient is taking an anticholinergic drug like atropine, the nurse should monitor for the opposite effects: pupil dilation, dry mouth, tachycardia, and urinary retention.

How to Approach the Question

First, identify the key term in the question: 'Cholinergic drugs'.
Recall that 'cholinergic' relates to acetylcholine and the parasympathetic nervous system, which controls 'rest and digest' functions.
Systematically evaluate each option based on the known effects of parasympathetic stimulation.
A. Pupil constriction (miosis): Yes, this is a classic parasympathetic effect.
B. Increase salivation: Yes, 'rest and digest' involves increasing digestive secretions.
C. Decrease smooth muscle tone: No, the parasympathetic system increases tone in the gut and bladder.

Concept Tested & Keywords

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