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.

Anticholinergics: Generic and Brand Names

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

• Anticholinergics
  • atropine sulfate
  • 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

• More sensitive to the adverse effects of the drug (e.g. constipation, urinary retention, heat intolerance, confusion).
• Dicyclomine is not recommended for use in 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

Half-life (T1/2)	Metabolism	Excretion
2.5 h	liver	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:

• Acute pain related to GI, CNS, GU, and CV effects
• Decreased cardiac output related to CV effects
• Impaired urinary elimination related to effects on the bladder
• Constipation related to GI effects

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.

Recommended Resources

Our recommended nursing pharmacology resources and books:

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See Also

Here are other nursing pharmacology study guides:

• Nursing Pharmacology – Study Guide for Nurses
  Our collection of topics related to nursing pharmacology
• Pharmacology Nursing Mnemonics & Tips
  These nursing mnemonics aim to simplify the concepts of pharmacology through the use of a simple, concise guide.
• Generic Drug Name Stems Cheat Sheet
  Learn about these generic drug name stems to help you make sense of drugs easier!
• Common Drugs and Their Antidotes
  A guide to drug antidotes that nurses should be familiar about.
• IV Fluids and Solutions Guide & Cheat Sheet
  Get to know the different types of intravenous solutions or IV fluids in this guide and cheat sheet.
• Drug Dosage Calculations NCLEX Practice Questions (100+ Items)
  Care to take the challenge? This quiz aims to help students and registered nurses alike grasp and master the concepts of medication calculation.

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• Lisinopril
• Metoprolol
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References and Sources

References and sources for this pharmacology guide for Anticholinergics:

• Karch, A. M., & Karch. (2011). Focus on nursing pharmacology. Wolters Kluwer Health/Lippincott Williams & Wilkins. [Link]
• Katzung, B. G. (2017). Basic and clinical pharmacology. McGraw-Hill Education.
• Lehne, R. A., Moore, L. A., Crosby, L. J., & Hamilton, D. B. (2004). Pharmacology for nursing care.
• Smeltzer, S. C., & Bare, B. G. (1992). Brunner & Suddarth’s textbook of medical-surgical nursing. Philadelphia: JB Lippincott.