Drugs Affecting Autonomic Nervous System 2 Drugs Affecting

Drugs Affecting Autonomic Nervous System 2

Drugs Affecting the Autonomic Nervous System • Cholinergic Agents • Cholinergic Blocking Agents

Cholinergic Agents • Drugs that stimulate the parasympathetic nervous system (PSNS) • The PSNS is the opposing system to the SNS Also known as cholinergic agonists or parasympathomimetics • Mimic the effects of the PSNS neurotransmitter Acetylcholine (ACh)

Cholinergic Agents • Drugs that stimulate the parasympathetic nervous system (PSNS) • The PSNS is the opposing system to the SNS • Also known as cholinergic agonists or parasympathomimetics • Mimic the effects of the PSNS neurotransmitter • Acetylcholine (ACh)

Cholinergic Receptors Two types, determined by: • Location • Action once stimulated Nicotinic receptors and Muscarinic receptors

Drug Effects of Cholinergic Agents “SLUDGE” • • • Salivation Lacrimation Urinary incontinence Diarrhea Gastrointestinal cramps Emesis

Drug Effects of Cholinergic Agents • Stimulate intestine and bladder – Increased gastric secretions – Increased gastrointestinal motility – Increased urinary frequency • Stimulate pupil – Constriction (miosis) – Reduced intraocular pressure • Increased salivation and sweating

Drug Effects of Cholinergic Agents • Cardiovascular effects – Decreased heart rate – Vasodilation • Respiratory effects – Bronchial constriction, narrowed airways

Cholinergic Agents: Therapeutic Uses Direct-Acting Agents • Reduce intraocular pressure • Useful for glaucoma and intraocular surgery Examples: acetylcholine, carbachol, pilocarpine Topical application due to poor oral absorption

Cholinergic Agents: Therapeutic Uses Direct-Acting Agent—bethanechol • Increases tone and motility of bladder and GI tract • Relaxes sphincters in bladder and GI tract, allowing them to empty • Helpful for postsurgical atony of the bladder and GI tract • Oral dose or SC injection

Cholinergic Agents: Therapeutic Uses Indirect-Acting Agents • Cause skeletal muscle contractions • Used for diagnosis and treatment of myasthenia gravis • Used to reverse neuromuscular blocking agents • Used to reverse anticholinergic poisoning (antidote) Examples: physostigmine, pyridostigmine

Cholinergic Agents: Side Effects Side effects are a result of overstimulation of the PSNS. • Cardiovascular: – Bradycardia, hypotension, conduction abnormalities (AV block and cardiac arrest) • CNS: – Headache, dizziness, convulsions • Gastrointestinal: – Abdominal cramps, increased secretions, nausea, vomiting

Cholinergic Agents: Side Effects Side effects are a result of overstimulation of the PSNS. • Respiratory: – Increased bronchial secretions, bronchospasms • Other: – Lacrimation, sweating, salivation, loss of binocular accommodation, miosis

Cholinergic Agents: Interactions • Anticholinergics, antihistamines, sympathomimetics • Antagonize cholinergic agents, resulting in decreased responses

Cholinergic Agents: Nursing Implications • Keep in mind that these agents will stimulate the PSNS and mimic the action of ACh. • Assess for allergies, presence of GI or GU obstructions, asthma, peptic ulcer disease, or coronary artery disease. • Perform baseline assessment of VS and systems overview.

Cholinergic Agents: Nursing Implications • Medications should be taken as ordered and not abruptly stopped. • The doses should be spread evenly apart to optimize the effects of the medication. • Overdosing can cause life-threatening problems. Patients should not adjust the dosages unless directed by the physician.

Cholinergic Agents: Nursing Implications • Atropine is the antidote for cholinergics. It should be available in the patient’s room for immediate use if needed. • Patients should notify their physician if they experience muscle weakness, abdominal cramps, diarrhea, or difficulty breathing.

Cholinergic Agents: Nursing Implications Monitor for side effects, including: Increased respiratory secretions Abdominal cramping Bronchospasms Dysrhythmias Difficulty breathing Hypotension Nausea and vomiting Bradycardia Diarrhea Increased sweating Increase in frequency and urgency of voiding patterns

Cholinergic Agents: Nursing Implications Monitor for therapeutic effects: • Alleviated signs and symptoms of myasthenia gravis • In postoperative patients with decreased GI peristalsis, look for: – Increased bowel sounds – Passage of flatus – Occurrence of bowel movements • In patients with urinary retention/hypotonic bladder, urination should occur within 60 minutes of bethanecol administration

Cholinergic Blocking Agents • Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)

Cholinergic Blocking Agents: Mechanism of Action • Competitive antagonists • Compete with ACh • Block ACh at the muscarinic receptors in the PSNS – As a result, ACh is unable to bind to the receptor site and cause a cholinergic effect.

Cholinergic Blocking Agents: Mechanism of Action • Once these drugs bind to receptors, they inhibit nerve transmission at these receptors.

Drug Effects of Cholinergic Blocking Agents • Cardiovascular – Small doses: decrease heart rate – Large doses: increase heart rate • CNS – Small doses: decrease muscle rigidity and tremors – Large doses: drowsiness, disorientation, hallucinations

Drug Effects of Cholinergic Blocking Agents • Eye – Dilated pupils (mydriasis) – Decreased accommodation due to paralysis of ciliary muscles (cycloplegia) • Gastrointestinal – Relax smooth muscle tone of GI tract – Decrease intestinal and gastric secretions – Decrease motility and peristalsis

Drug Effects of Cholinergic Blocking Agents • Genitourinary – Relaxed detrusor muscle – Increased constriction of internal sphincter – Result: urinary retention • Glandular – Decreased bronchial secretions, salivation, sweating • Respiratory – Decreased bronchial secretions – Dilated bronchial airways

Cholinergic Blocking Agents: Therapeutic Uses CNS Decreased muscle rigidity and muscle tremors • Parkinson’s disease • Drug-induced extrapyramidal reactions

Cholinergic Blocking Agents: Therapeutic Uses Cardiovascular Affect the heart’s conduction system • Low doses: slow the heart rate • High doses: block inhibitory vagal effects on the SA and AV node pacemaker cells – Result: increased heart rate

Cholinergic Blocking Agents: Therapeutic Uses Atropine Used primarily for cardiovascular disorders • Sinus node dysfunction • Symptomatic second-degree heart block • Sinus bradycardia with hemodynamic compromise (advanced life support)

Cholinergic Blocking Agents: Therapeutic Uses Respiratory Blocking the cholinergic stimulation of the PSNS allows unopposed action of the SNS. • Results: – Decreased secretions from nose, mouth, pharynx, bronchi – Relaxed smooth muscles in bronchi and bronchioles – Decreased airway resistance – Bronchodilation

Cholinergic Blocking Agents: Therapeutic Uses Respiratory agents are used to treat: • • Exercise-induced bronchospasms Chronic bronchitis Asthma Chronic obstructive pulmonary disease

Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal PSNS controls gastric secretions and smooth muscles that produce gastric motility. • Blockade of PSNS results in: – Decreased secretions – Relaxation of smooth muscle – Decreased GI motility and peristalsis

Cholinergic Blocking Agents: Therapeutic Uses Gastrointestinal agents are used to treat: • Peptic ulcer disease • Irritable bowel disease • GI hypersecretory states

Cholinergic Blocking Agents: Therapeutic Uses Genitourinary • Relaxed detrusor muscles of the bladder • Increased constriction of the internal sphincter • Reflex neurogenic bladder • Incontinence

Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Cardiovascular Increased heart rate, dysrhythmias CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium

Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Eye Dilated pupils, decreased visual increased intraocular pressure accommodation, Gastrointestinal Decreased salivation, decreased gastric secretions, decreased motility

Cholinergic Blocking Agents: Side Effects Body System Side/Adverse Effects Genitourinary Urinary retention Glandular Decreased sweating Respiratory Decreased bronchial secretions

Cholinergic Blocking Agents: Interactions • Antihistamines. • When given with cholinergic blocking agents, cause ADDITIVE cholinergic effects, resulting in increased effects

Cholinergic Blocking Agents: Nursing Implications • Keep in mind that these agents will block the action of ACh in the PSNS. • Assess for allergies, presence of BPH, glaucoma, tachycardia, MI, CHF, hiatal hernia, and GI or GU obstruction. • Perform baseline assessment of VS and systems overview.

Cholinergic Blocking Agents: Nursing Implications • Medications should be taken exactly as prescribed to have the maximum therapeutic effect. • Overdosing can cause life-threatening problems. • Blurred vision may cause problems with driving or operating machinery. • Patients may experience sensitivity to light and may want to wear dark glasses or sunglasses.

Cholinergic Blocking Agents: Nursing Implications • When giving ophthalmic solutions, apply pressure to the inner canthus to prevent systemic absorption. • Dry mouth may occur; can be handled by chewing gum, frequent mouth care, and hard candy. • Check with physician before taking any other medication, including OTC medications. • ANTIDOTE for atropine is physostigmine salicylate (Antilirium).

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