Autonomic Nervous System and Gastrointestinal Pharmacology

Posted on Mar 13, 2026 in Airports

Autonomic Nervous System Responses

Sympathetic vs. Parasympathetic Drug Classifications

• Sympathetic (Fight or Flight): Adrenergic
• Parasympathetic (Rest and Digest): Cholinergic

Drug Categories

• Sympathetic: Adrenergic agonists, Adrenergic-blocking drugs, Sympathomimetic drugs, Sympatholytics
• Parasympathetic: Cholinergic agonist drugs, Cholinergic-blocking drugs, Anticholinergic drugs, Parasympatholytics (r/t acetylcholine)

Nervous System Receptors

Sympathetic (r/t Adrenaline)

• α Receptor:
  • α1: All sympathetic organs excluding the heart (Vasoconstriction, ↑ blood glucose)
  • α2: CNS receptors only (↓ epinephrine and norepinephrine levels)
• β Receptor:
  • β1: Heart and kidneys (↑ HR, ↑ contraction force, ↑ kidney blood flow)
  • β2: All sympathetic organs excluding the heart (bronchial/uterine dilation)
  • β3: Bladder

Parasympathetic (r/t Acetylcholine)

• Muscarinic Receptors: Heart and targeted parasympathetic organs (↓ HR, ↑ bile secretion, ↑ GI activity)
• Nicotinic Receptors: Smooth muscles of postganglionic neurons (Involved in neuromuscular transmission)

ANS Drug Terminology

• Agonist (-mimetic): Produce response/action. Mechanism: “Mimic” = copy natural actions. Use: Stimulate underactive systems (asthma, hypotension).
• Antagonist (anti-/-blocker/-lytic): Block response/action. Mechanism: “Anti” = against natural body actions. Use: Calm overactive systems (HTN, tachycardia).

Common Urinary Problems

1. Overactive Bladder (OAB): Incontinence and urgency; involuntary bladder contractions.
2. Neurogenic Bladder: Inability to perceive bladder fullness or control sphincters.
3. Benign Prostatic Hyperplasia (BPH): Bladder neck block prevents complete urination.
4. Urinary Retention: Impaired emptying; bladder distention.
5. Urinary Frequency: Voiding > 4-6 times daily in small amounts.
6. Urinary Urgency: Sudden, strong desire to void.

Post-Operative Urinary Retention (POUR) Interventions

• Catheterization, ambulation, running water, warm compress.
• Assess bladder volume via ultrasound before catheterization.
• Nonpharmacological measures stimulate the parasympathetic NS.

Urinary Medications

• Anticholinergics (OAB): tolterodine (Detrol), oxybutynin (Ditropan).
• Alpha Blockers (BPH): tamsulosin (Flomax), doxazosin (Cardura).
• Cholinergic Agonist (Retention): bethanechol (Urecholine).
• 5-Alpha-reductase Inhibitor (BPH): finasteride (Proscar).

UTI Management

• Signs/Symptoms: Dysuria, frequency, hematuria, fever, ↑ WBCs, cloudy/odorous urine, confusion (elderly).
• Patient Education: Wipe front to back, increase water (2-3L), wear cotton underwear, empty bladder before/after intercourse.
• Antibiotics: trimethoprim/sulfamethoxazole (Bactrim), ciprofloxacin (Cipro), cefepime (Maxipime), nitrofurantoin (Macrodantin).
• Analgesic: phenazopyridine (Pyridium) for dysuria relief.

Antiemetic Drug Comparison

• Anticholinergic: scopolamine (motion sickness).
• Antihistamines: Diphenhydramine, dimenhydrinate, meclizine (motion sickness/vertigo).
• Antidopaminergics: Prochlorperazine, promethazine (chemo/post-op nausea).
• Prokinetic: Metoclopramide (gastroparesis).
• Serotonin Blockers: Ondansetron (chemo/post-op nausea).

Laxative and Antiulcer Medications

• Laxatives: Osmotic (Miralax), Stimulant (Senna), Bulk-forming (Psyllium), Emollient (Docusate).
• Antiulcer: Antacids (Tums), H2 Antagonists (famotidine), Proton Pump Inhibitors (omeprazole), Mucosal Protectants (sucralfate).