Anticholinergics (Parasympatholytics)

Anticholinergics are drugs that oppose the effects of acetylcholine. In essence, they also lyse and block the effects of parasympathetic nervous system (PNS) so they are also called as parasympatholytics. Atropine is currently the only widely used anticholinergic drug. Other common examples include meclizine, scopolamine and ipratropium.

Table of Common Drugs and Generic Names


Here is a table of commonly encountered anticholinergic agents, their generic names, and brand names:

Classification Generic Name Brand Name
Anticholinergics atropine (generic)
ipratropium Atrovent
meclizine Bonine, Antivert
methscopolamine Pamine
scopolamine Transderm Scop
tiotropium Spiriva

Disease Spotlight: Gastrointestinal Ulcers


  • Anticholinergics were once very widely used to decrease GI activity and secretions. However, more specific and less toxic drugs are available now and the utilization of this drug class is now limited.
  • GI ulcers are basically erosions in the lining of the GIT caused by increased HCl production most commonly from H. pylori infection. Patients with GI ulcers suffer from burning abdominal pain, nausea, and acid reflux.

Therapeutic Action


The desired and beneficial actions of anticholinergics are as follows:

  • Competitively blocking the ACh receptors at muscarinic cholinergic receptor sites that are responsible for mediating the effects of the parasympathetic postganglionic impulses.
  • Atropine, the prototype drug, is derived from the plant belladonna. It is used to depress salivation and bronchial secretions and to dilate the bronchi, but it can thicken respiratory secretions (causing obstruction of airways).
  • Atropine and scopolamine work by blocking only the muscarinic effectors in the parasympathetic nervous system and the few cholinergic receptors in the SNS.

Indications


Anticholinergics are indicated for the following medical conditions:

  • Prevention of nausea, vomiting, and dizziness associated with motion sickness.
  • Adjunctive therapy for treatment of GI ulcers
  • Decrease secretions before anesthesia or intubation
  • Maintenance treatment of bronchospasm associated with COPD.
  • Treatment of irritable or hyperactive bowel in adults.

Here are some important aspects to remember for indication of anticholinergics in different age groups:

Children

Adults

  • Adults should be cautioned of these drugs’ adverse effects.
  • Use of these drugs among pregnant women is not allowed because they can cross placenta and cause adverse effects to the fetus.

Older adults

  • Dose adjustment is needed as this age group is also more susceptible to drug side effects.
  • They are more likely to have toxic levels of the drug because of renal or hepatic impairments.

Pharmacokinetics


Here are the characteristic interactions of anticholinergics and the body in terms of absorption, distribution, metabolism, and excretion:

Route Onset Peak Duration
IM 10-15 min 30 min 4 h
IV Immediate 2-4 min 4 h
Subcutaneous Varies 1-2 h 4 h
Topical 5-10 min 30-40 min 7-14 d
T1/2: 2.5 h
Metabolism: liver
Excretion: urine

Contraindications and Cautions


The following are contraindications and cautions for the use of anticholinergics:

  • Allergy to any component of the drug. To prevent hypersensitivity reaction
  • Glaucoma. Can be exacerbated by blockade of PNS.
  • Intestinal atony, paralytic ileus, GI obstruction. Can be exacerbated with further slowing of GI activity.
  • Pregnancy. Potential adverse effects on the fetus.

Adverse Effects


Use of anticholinergic agents may result to these adverse effects:

  • CNS: blurred vision, pupil dilation, photophobia, cycloplegia, increased intraocular pressure, weakness, dizziness, insomnia
  • CV: tachycardia, palpitation
  • GI: dry mouth, altered taste perception, nausea, heartburn, constipation
  • GU: urinary hesitancy and retention, heat prostration

Interactions


The following are interactions involved in the use of anticholinergics:

  • Antihistamines, antiparkinsonisms, MAOIs, TCAs. These drugs also have anticholinergic effects so incidence of anticholinergic effects increases.
  • Phenothiazines. Decreased effectiveness of this drug.
  • Burdock, rosemary, turmeric. Risk for exacerbated anticholinergic agents

Nursing Considerations


Here are important nursing considerations when administering anticholinergics:

Nursing Assessment

These are the important things the nurse should include in conducting assessment, history taking, and examination:

  • Assess for contraindications or cautions (e.g., history of allergy to drug, GI obstruction, hepatorenal dysfunction, etc.) to avoid adverse effects.
  • Establish baseline physical assessment to monitor for any potential adverse effects.
  • Assess neurological status (e.g., orientation, affect, reflexes) to evaluate any CNS effects.
  • Assess abdomen (e.g., bowel sounds, bowel and bladder patterns, urinary output) to evaluate for GI and GU adverse effects.
  • Monitor laboratory test results to determine need for possible dose adjustments and to identify potential toxicity.

Nursing Diagnoses and Care Planning

Here are some of the nursing diagnoses that can be formulated in the use of this drug for therapy:

Implementation with Rationale

These are vital nursing interventions done in patients who are taking anticholinergics:

  • Ensure proper administration of the drug to ensure effective use and decrease the risk of adverse effects.
  • Monitor patient response (e.g., blood pressure, ECG, urine output) for changes that may indicate need to adjust dose.
  • Provide comfort measures (e.g., sugarless lozenges, lighting control, small and frequent meals) to help patient cope with drug effects.
  • Provide patient education about drug effects and warning signs to report to enhance knowledge about drug therapy and promote compliance.

Evaluation

Here are aspects of care that should be evaluated to determine effectiveness of drug therapy:

  • Monitor patient response to therapy (improvement in condition being treated).
  • Monitor for adverse effects (e.g., photophobia, heat intolerance, urinary retention).
  • Evaluate patient understanding on drug therapy by asking patient to name the drug, its indication, and adverse effects to watch for.
  • Monitor patient compliance to drug therapy.

Practice Quiz: Anticholinergics


Here are some practice questions for this study guide:

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1. Anticholinergic drugs are used

A. To allow the sympathetic system to dominate
B. To block the parasympathetic system, which is commonly hyperactive
C. As the drugs of choice for treating ulcers
D. To stimulate GI activity

1. Answer: A. To allow the sympathetic system to dominate

It decreases GI activity and secretions in the treatment of ulcers and to decrease other parasympathetic activities to allow the sympathetic system to dominate. More specific and less systemically toxic drugs are available for treatment of ulcers.

2. Atropine and scopolamine work by blocking what receptor(s) in the parasympathetic nervous system?

A. Nicotinic receptors only
B. Muscarinic and nicotinic receptors
C. Muscarinic receptors only
D. Adrenergic receptors to allow cholinergic receptors to dominate

2. Answer: C. Muscarinic receptors only

Atropine and scopolamine work by blocking only the muscarinic effectors in the parasympathetic nervous system and the few cholinergic receptors in the SNS.

3. Which of the following suggestions would the nurse make to help a patient who is receiving an anticholinergic agent reduce the risks associated with decreased sweating?

A. Covering the head and using sunscreen
B. Ensuring hydration and temperature control
C. Changing position slowly and protecting from the sun
D. Monitoring for difficulty swallowing and breathing

3. Answer: B. Ensuring hydration and temperature control

This drug blocks sweating, which is the body’s way of cooling off. This places the patient at an increased risk for heat stroke. Extremes of temperature should be avoided.

4. Which of the following would the nurse be least likely to include when developing a teaching plan for a patient who is receiving an anticholinergic agent?

A. Encouraging the patient to void before dosing
B. Setting up a bowel program to deal with constipation
C. Encouraging the patient to use sugarless lozenges to combat dry mouth
D. Performing exercises to increase the heart rate

4. Answer: D. Performing exercises to increase the heart rate

Exercises should be avoided because this drug blocks sweating. This placed the patient at increased risk for heat stroke.

5. Remembering that anticholinergics block the effects of PNS, the nurse would question an order for an anticholinergic drug for patients with which of the following conditions?

A. Biliary spasms
B. Bradycardia
C. Glaucoma
D. Asthma

5. Answer: C. Glaucoma

All other options are indications for atropine.

See Also


Related posts:

Further Reading and Resources


Recommended resources and books:
  1. Focus on Nursing Pharmacology - Easy to follow guide for Pharmacology
  2. NCLEX-RN Drug Guide: 300 Medications You Need to Know for the Exam - Great if you're reviewing for the NCLEX
  3. Nursing 2017 Drug Handbook (Nursing Drug Handbook) - Reliable nursing drug handbook!
  4. Lehne's Pharmacology for Nursing Care - Provides key information on commonly used drugs in nursing
  5. Pharmacology and the Nursing Process - Learn how to administer drugs correctly and safely!
  6. Pharm Phlash Cards!: Pharmacology Flash Cards - Flash Cards for Nursing Pharmacology
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