Cholinergic Drugs Study Guide

Cholinergic Drugs are agents that influence the activity of cholinergic receptors, which are divided into several categories, primarily muscarinic and nicotinic types. These drugs play a crucial role in pharmacology, specifically in managing various diseases and regulating physiological functions.

1. Anatomy & Physiology (A&P) of the Nervous System: Describe the structures and functions connected to the parasympathetic and sympathetic nervous systems.
2. Homeostasis & Cholinergic Activity: Identify mechanisms regulating homeostasis related to cholinergic receptor activity.
3. Pharmacological Management: Discuss the use of cholinergic and anticholinergic medications in treatment and expected physiological benefits.
4. Therapeutic Effects & Nursing Considerations: Examine the therapeutic indications, mechanisms of action (MOA), nursing implications, and common side effects of cholinergic and anticholinergic medications.

Types of Receptors:
- Nicotinic N: Not discussed in detail.
- Nicotinic M: Not discussed in detail.
- Muscarinic Receptors: Focus on muscarinic receptors.
- Effects of Activation:
  - Contraction of ciliary eye muscles.
  - Decreased heart rate.
  - Constriction of bronchi.
  - Voiding of bladder.
  - Increased gastrointestinal tone and motility.
  - Sweating and vasodilation.

Key Points:
- Understand the specific receptors affected by drugs.
- Know the normal physiological responses associated with receptor activation.
- Determine whether drugs enhance or suppress receptor activity.

Definition: Agents that produce effects through direct interaction with muscarinic receptors.
Physiological Effects:
- Heart: Causes bradycardia (slowed heart rate).
- Exocrine Glands: Increases secretions such as sweating, salivation, bronchial secretions, and gastric acid secretion.
- Smooth Muscle Effects:
- Lung: Bronchoconstriction.
- Gastrointestinal Tract: Increased tone and motility.
- Bladder: Detrusor muscle contraction.
- Vascular: Causes relaxation leading to vasodilation and hypotension.
- Eye: Leads to pupil constriction and ciliary contraction.
Example Drug - Bethanechol [Urecholine, Duvoid]:
- Type: Parasympathomimetic agent (promotes rest and digest).
- Mechanism of Action: Selectively agonizes muscarinic cholinergic receptors.
- Physiological Effects of Bethanechol:
- Lung: Bronchoconstriction.
- Gastrointestinal: Increases tone and motility.
- Bladder: Detrusor muscle contraction, relaxation of trigone and sphincter.
Therapeutic Uses: Primarily for urinary retention.
Adverse Effects:
- Cardiovascular: Hypotension.
- Gastrointestinal: Increased tone and motility, potential for exacerbating asthma, dysrhythmias in hyperthyroid patients.
Nursing Considerations for Bethanechol:
- Administer on an empty stomach (1 hour before or 2 hours after meals) to avoid nausea/vomiting caused by food interactions.
- Typical dosing schedule: 3-4 times daily.
- Treatment for overdose: Atropine.

Causes: Ingestion of certain mushrooms or overdose of direct-acting muscarinic agonists/cholinesterase inhibitors (e.g., Aricept).
Symptoms of Toxicity:
- Profuse salivation.
- Lacrimation (tearing).
- Visual disturbances.
- Bronchospasm.
- Diarrhea.
- Bradycardia and potential cardiovascular collapse.
Treatment: Administer atropine and provide supportive therapy.

Definition: Drugs that inhibit cholinergic activity by blocking muscarinic receptors.
Mechanism of Action: Anticholinergics predominantly block muscarinic receptor activity.
Therapeutic Uses:
- Treatment for bradycardia, pre-anesthetic medication, and eye surgeries.
Common Examples: Atropine, scopolamine, diphenhydramine.
Adverse Effects:
- Xerostomia (dry mouth).
- Blurred vision and photophobia.
- Elevated intraocular pressure.
- Urinary retention.
- Constipation.
- Anhidrosis (lack of sweat).
- Tachycardia.

Characteristics: Best-known muscarinic antagonist.
Mechanism of Action: Blocks acetylcholine receptors.
Pharmacologic Effects of Atropine:
- Heart: Increases heart rate.
- Exocrine Glands: Decreases secretions.
- Smooth Muscle: Relaxes bronchi, reduces urinary bladder tone, decreases gastrointestinal motility.
- Eyes: Causes mydriasis (dilation) and cycloplegia (fixed dilation).

Drug introductions: Specific anticholinergic drugs for managing OAB include oxybutynin [Ditropan XL, Oxytrol, Gelnique] in various forms (syrup, tablets, patches).
Considerations: Patients allergic to topical medications should not attempt alternative routes of the same medication.

Ipratropium Bromide:
- Used for asthma and COPD; administered via inhalation or nasal spray; generally not associated with common antimuscarinic side effects.
Diphenhydramine: Antihistamine with significant anticholinergic effects.
Scopolamine: Similar actions to atropine, effective for motion sickness, and used for cycloplegia, mydriasis, pre-anesthetic sedation, and obstetric amnesia.

Definition: Medications that prevent acetylcholine from activating nicotinic M receptors, causing muscle relaxation and paralysis. Used for surgeries, intubation, and mechanical ventilation.
Notable Characteristics:
- No oral forms available.
- No effects on the central nervous system; solely induce paralysis without sedation.
Examples of Neuromuscular Blockers:
- Pancuronium.
- Vecuronium.
- Rocuronium.
- Succinylcholine: Quick onset and short duration (5-10 minutes).

Onset: Rapid paralysis; the effect declines quickly.
Adverse Effects:
- Respiratory arrest.
- Cardiac effects.
- Risk of malignant hyperthermia (abnormal temperature and muscle spasms, which can be life-threatening).
Important Note: Do not provide analgesic or sedative effects; patients remain aware during procedures.

Scenario: A patient using oxybutynin [Ditropan] for overactive bladder also takes diphenhydramine for hay fever. Possible toxic symptoms to monitor:
- Dry mouth, increased temperature, and blurred vision (Option B).