4.8 Muscarinic Antagonists

Atropine is a muscarinic antagonist.

Mechanism of Action: Specific anticholinergic responses are dose-related. Small doses of atropine inhibit salivary and bronchial secretions and sweating. Moderate doses dilate the pupil, inhibit accommodation, and increase the heart rate (vagolytic effect). Large doses decrease motility of the gastrointestinal and urinary tracts, and very large doses will inhibit gastric acid secretion.

Indications for Use: Varying dosages are used preoperatively to diminish secretions, to stimulate the heart rate in conditions causing bradycardia, or to treat muscarinic symptoms of insecticide (organophosphorus or carbamate) poisoning or mushroom poisoning.

Nursing Considerations Across the Lifespan: As with all anticholinergics, use with caution with the elderly, because elderly clients may react with agitation or drowsiness. Heat stroke may occur in the presence of high temperatures. Immediately report symptoms of overdose: urine retention, abnormal heartbeat, dizziness, passing out, difficulty breathing, weakness, or tremors. Physostigmine has been used to reverse anticholinergic effects.

Atropine can be given to pediatric clients, with doses adjusted according to the child weight.

Patient Teaching & Education: Advise clients that use of these medications may cause dizziness and drowsiness, so clients should be aware of potential impact on their level of alertness.  Additionally, use of medications may cause dry mouth, and frequent oral hygiene is encouraged.  The use of atropine may cause urinary retention in males with benign prostatic hypertrophy (BPH).^[1]

Now let’s take a closer look at the medication card on atropine in Table 4.8.^[2][3] Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication.

Table 4.8 Atropine Medication Card