Nervous System & Pain Drugs

CNS vs. PNS

• CNS = Brain + Spinal Cord

• PNS = Nerves connecting CNS to body

Sympathetic vs. Parasympathetic Nervous System

• Sympathetic = Fight/Flight

• Parasympathetic = Rest/Digest

are branches of autonomic nervous system

Key Neurotransmitters

• ACh = Rest & contraction

• Norepinephrine = Excite

• Epinephrine = Emergency hormone

Acute vs. Chronic Pain

• Acute Pain = sudden, short-term, protective

• Chronic Pain = >3–6 months, affects life

Nociceptive vs. Neuropathic Pain

• Nociceptive: tissue damage (aching, throbbing)

• Neuropathic: nerve damage (burning, shooting)

Ways to Assess Pain

• 0–10 scale

• FACES

• FLACC

Non-opioid Analgesics - Types, MoA, Nursing Considerations

Treat pain without activating opioid receptors

• They inhibit cyclooxygenase (COX), reducing inflammation, redness, and pain transmission

• Acetaminophen:

  • Safe, but has a liver risk

• NSAIDs:

  • Reduce inflammation, but has GI/CV risks

• Nursing tip: Take with food, monitor dose, assess pain

Types of COX Enzymes

• COX-1: Maintains homeostasis, supports platelets, renal function, and gastric mucosal barrier.

• COX-2: Drives inflammation and pain after injury.

Acetaminophen

Nonopioid Analgesic

• MoA: may inhibit COX in the CNS, but not peripherally (MoA is unkown)

• Indication: mild to moderate pain

• Contraindication: Liver impairment

• Adverse Effects:

  • very few adverse effects, but if overdosed, hepatotoxicity may occur:

    • Hepatotoxicity from acetaminophen can present as nausea, fatigue, and jaundice

• Max dose is 4000mg in 24 hours

NSAIDs

Nonopioid Analgesics - includes aspirin, Ibuprofen, naproxen sodium, tramadol

• MoA: Inhibits the COX to decrease the production of inflammatory cytokines, reducing inflammation and pain

• Indication: Temporarily relieves minor aches and pains, Temporarily reduces fever

• Contraindication: Allergic reaction to aspirin, caution in asthma and liver/renal impairment

• Interactions: ACE Inhibitors, Lithium, Warfarin

• GI/CV risks

Adverse Effects of NSAIDS (Ibuprofen)

• Decreased hemoglobin

• Edema

• Skin rash

• GI upset

• Heartburn

• Risk of GI ulcers

• Dizziness

• Aspirin may cause Reye’s Syndrome

Nursing Considerations for Nonopioid Analgesics

• Assess pain before and after administration.

• Monitor for signs of overdose, bleeding, liver damage, or allergic reactions.

• Avoid alcohol with acetaminophen

• Take NSAIDs with food to minimize GI upset

• Do not exceed recommended dosages

Opioid Analgesics

For moderate–severe pain

• Contraindications: respiratory issues and gastrointestinal obstruction

• Risks: Respiratory depression, constipation, sedation

  • Most serious effect – respiratory depression​

  • Most common effect – constipation

• Nursing tip: Monitor breathing, bowel regimen

• Naloxone (narcan) = antidote

• Store safely, never do double doses

• Drugs: Codeine, Morphine, Fentanyl, Oxycodone, Methadone

Codeine

• Derived from the opium poppy

• Used for mild to moderate pain.

• Converted to morphine in the liver so effects may vary based on metabolism

Morphine

Opioid used to treat both acute and chronic types of pain

• Same adverse effects as any opioid, plus flushing, pruritis, hypotension, and urinary retention

Fentanyl

Synthetic opioid

• Used for severe pain and is very potent.

• Given intravenously and via patch.

• Contributes to opioid-related deaths due to misuse.

Oxycodone

Semisynthetic opioid

• Used for moderate to severe pain.

• Frequently used because of its favorable side effect profile compared with other agents

• Can have acetaminophen in them already, varying by drug​

Methadone

Synthetic opioid

• Used for opioid use disorders and chronic pain.

• Long half-life helps in withdrawal management.