Question 1

A patient has developed muscarinic antagonist toxicity from ingestion of an unknown chemical. The nurse should prepare to administer which medication?&#10;A) Atropine (Sal-Tropine) IV&#10;B) Physostigmine (Antilirium)&#10;C) An acetylcholinesterase activator&#10;D) Pseudoephedrine (Ephedrine)

Accepted Answer

Physostigmine is indicated for muscarinic antagonist toxicity. Atropine is a drying agent and would only complicate the drying action that arises from the muscarinic antagonist. An acetylcholinesterase activator would only contribute to dryness that arises from the muscarinic antagonist. Ephedrine is not indicated for muscarinic antagonist toxicity.

Question 2

A patient receives topical atropine to facilitate an eye examination. The nurse will tell the patient to remain in a darkened room or to wear sunglasses for several hours until the effects of the medication wear off. This teaching is based on the nurse's knowledge that muscarinic antagonists cause:

A) elevation of intraocular pressure.
B) miosis and ciliary muscle contraction
C) paralysis of the iris sphincter.
D) relaxation of ciliary muscles.

Accepted Answer

By blocking muscarinic receptors in the eye, atropine causes paralysis of the iris sphincter, which prevents constriction of the pupil; consequently, the eye cannot adapt to bright light. This also causes an elevation in intraocular pressure, which increases the risk of glaucoma. However, it is not an indication for wearing darkened glasses. Muscarinic agonists cause miosis; atropine causes mydriasis. The effect of relaxing ciliary muscles focuses the eye for far vision, causing blurred vision.

Question 3

An older adult patient who lives alone and is somewhat forgetful has an overactive bladder and reports occasional constipation. Which treatment will the nurse anticipate for this patient?&#10;A) Behavioral therapy&#10;B) Oxybutynin (Ditropan XL) extended-release tablets&#10;C) Oxybutynin (Oxytrol) transdermal patch&#10;D) Percutaneous tibial nerve stimulation (PTNS)

Accepted Answer

The transdermal patch is applied weekly and may be the best option for a patient who is more likely to forget to take a daily medication. The transdermal preparation has fewer side effects than the systemic dose so is less likely to increase this patient's constipation. Behavioral therapy should be tried first in patients who can participate. However, it is not the best option for a forgetful patient who lives alone, because it requires scheduled voiding and timing of fluid intake. The extended-release tablets must be given daily, and this patient may not remember to take them. PTNS is used after behavioral and drug therapies have failed.

Question 4

A patient will begin using a transdermal preparation of a muscarinic antagonist for overactive bladder (OAB). The nurse teaches the patient what to do if side effects occur. Which statement by the patient indicates the need for further teaching?

A) "I can use sugar-free gum for dry mouth."
B) "I may need laxatives for constipation."
C) "I should keep the site covered to prevent other people from getting the medicine."
D) "I will take Benadryl for any itching caused by a local reaction to the patch."

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Accepted Answer

Benadryl is an antihistamine, and even though it is not classified as a muscarinic antagonist, it has anticholinergic effects. Giving it with a muscarinic antagonist greatly enhances these effects, so it should not be used. Muscarinic antagonists cause dry mouth, and patients should be taught to use sugar-free gum or candies to help with this. Muscarinic antagonists can cause constipation, and laxatives may be used. Medication applied topically can be transferred to others who come in contact with the skin, so the site should be covered.

Question 5

A patient received atropine intravenously before surgery. The recovery room nurse notes that the patient is delirious upon awakening, has a heart rate of 96 beats per minute, a respiratory rate of 22 breaths per minute, and a blood pressure of 110/78 mm Hg. The nurse notifies the anesthesiologist, who will order:

A) activated charcoal to minimize intestinal absorption of the antimuscarinic agent.
B) an acetylcholinesterase inhibitor to compete with the antimuscarinic agent at receptors.
C) an antipsychotic medication to treat the patient's central nervous system symptoms.
D) ipratropium bromide (Atrovent) to counter the respiratory effects of the antimuscarinic agent.

Accepted Answer

This patient is showing signs of antimuscarinic toxicity, caused by the atropine given during surgery. The most effective antidote is physostigmine, which inhibits acetylcholinesterase, allowing acetylcholine to build up at cholinergic junctions and compete with the antimuscarinic agent for receptor binding. Activated charcoal is only useful if an antimuscarinic agent has been ingested, because it impedes absorption from the GI tract. Because this patient's psychotic symptoms are caused by an antimuscarinic agent, physostigmine should be given to treat the cause; an antipsychotic medication would only treat the symptom. Ipratropium bromide is an antimuscarinic agent and would only compound the effects. This patient's respiratory rate is only mildly elevated.

Question 6

Bethanechol (Urecholine) is used to treat urinary retention but is being investigated for use in which other condition?&#10;A) Gastric ulcers&#10;B) Gastroesophageal reflux&#10;C) Hypotension&#10;D) Intestinal obstruction

Accepted Answer

Bethanechol is being investigated for treatment for gastroesophageal reflux disease (GERD) because of its effects on esophageal motility and the lower esophageal sphincter. Bethanechol stimulates acid secretion and could intensify ulcer formation. Bethanechol can cause hypotension. Because bethanechol increases the motility and tone of intestinal smooth muscle, the presence of an obstruction could lead to bowel rupture.

Question 7

A prescriber has ordered pilocarpine (Pilocar). A nurse understands that the drug stimulates muscarinic receptors and would expect the drug to have which action?&#10;A) Reduce excessive secretions in a postoperative patient&#10;B) Lower intraocular pressure in patients with glaucoma&#10;C) Inhibit muscular activity in the bladder&#10;D) Prevent hypertensive crisis

Accepted Answer

Pilocarpine is a muscarinic agonist used mainly for topical therapy of glaucoma to reduce intraocular pressure. Pilocarpine is not indicated for the treatment of excessive secretions and mucus; in fact, pilocarpine is used to treat dry mouth. Pilocarpine does not inhibit muscular activity in the bladder. Pilocarpine is not used to prevent hypertensive crisis.

Question 8

A prescriber has ordered bethanechol (Urecholine) for a postoperative patient who has urinary retention. The nurse reviews the patient's chart before giving the drug. Which part of the patient's history would be a contraindication to using this drug?

A) Asthma as a child
B) Gastroesophageal reflux
C) Hypertension
D) Hypothyroidism

Accepted Answer

Bethanechol is contraindicated in patients with active or latent asthma, because activation of muscarinic receptors in the lungs causes bronchoconstriction. It increases the tone and motility of the gastrointestinal (GI) tract and is not contraindicated in patients with reflux. It causes vasodilation and would actually lower blood pressure in a hypertensive patient. It causes dysrhythmias in hyperthyroid patients.

Deck 14: Muscarinic Agonists and Antagonists