Analgesics: Acetaminophen, Ibuprofen, Aspirin

Analgesics - Study Notes

• Acetaminophen:
  • Use: Mild to moderate pain and fever, first-line analgesic
  • MOA: Centrally acting weak COX-1 and COX-2 inhibitor, may activate serotonergic pathways
  • PK: Absorbed GI tract, metabolized liver, excreted in urine. Half-life ~2-3 hours.
  • Max Dose: 4 grams/day
  • Side effects: Risk of liver damage with overdose
  • Use in Pregnancy: Suitable if non-pharmacologic therapy fails
• Ibuprofen:
  • Use: NSAID for pain, inflammation, and fever
  • MOA: Inhibits COX-1 and COX-2, reducing prostaglandin synthesis.
  • PK: Well absorbed orally, metabolized liver, excreted in urine. Half-life ~2 hours.
  • Side effects: Contraindicated in late pregnancy; associated GI side effects.
• Aspirin:
  • Use: NSAID for pain, fever, inflammation, and antiplatelet agent
  • MOA: Irreversibly inhibits COX-1 and COX-2, decreasing prostaglandin and thromboxane synthesis
  • PK: Rapidly absorbed stomach/small intestine, metabolized to salicylic acid, excreted in urine
  • Side effects: Avoid in children under 12 (Reye's syndrome risk)
  • Forms: Oral and rectal
• Morphine:
  • Use: Opioid analgesic for moderate to severe pain
  • MOA: µ-opioid receptor agonist, altering pain perception in the CNS
  • PK: Onset ~30 minutes (oral), ~5 minutes (IV). Metabolized liver, excreted in urine. Half-life 2-4 hours.
  • Side effects: Respiratory depression, sedation; use cautiously in renal impairment
• Gabapentin:
  • Use: Antiepileptic used as adjuvant for neuropathic pain
  • MOA: Modulates calcium channels, reduces excitatory neurotransmitter release
  • PK: Absorbed small intestine; not metabolized, excreted unchanged in urine. Half-life ~5-7 hours.
  • Side effects: Dizziness, fatigue, dose adjustment required in renal impairment
• Tramadol:
  • Use: Centrally acting synthetic opioid for moderate to severe pain
  • MOA: µ-opioid receptor agonist, inhibits serotonin and norepinephrine reuptake
  • PK: Metabolized liver (CYP2D6 and CYP3A4), excreted in urine. Half-life ~6 hours
  • Side effects: Risk of serotonin syndrome with SSRIs; abuse potential exists
• Ketorolac:
  • Use: NSAID for short-term management of moderate to severe pain
  • MOA: Inhibits COX-1 and COX-2, reducing prostaglandin synthesis
  • PK: Rapidly absorbed, metabolized in the liver, excreted in urine. Half-life ~4-6 hours.
  • Side effects: Limit use to 5 days; risk of GI bleeding, renal impairment
• Oxycodone:
  • Use: Opioid analgesic for moderate to severe pain
  • MOA: µ-opioid receptor agonist, altering CNS pain perception
  • PK: Absorbed GI tract, metabolized in the liver (CYP3A4 and CYP2D6), excreted in urine. Half-life ~3–6 hours
  • Forms: Immediate and extended-release
  • Side effects: Monitor for respiratory depression
• Fentanyl:
  • Use: Potent opioid analgesic for chronic and severe pain
  • MOA: µ-opioid receptor agonist, rapid CNS penetration
  • PK: Onset immediate (IV), transdermal onset 6-12 hours, metabolized in the liver (CYP3A4); excreted in urine
  • Side Effects: Not for opioid-naive patients, risk of overdose (improper patch use)
• Pregabalin:
  • Use: Anticonvulsant for neuropathic pain and fibromyalgia.
  • MOA: Binds to calcium channels, inhibiting excitatory neurotransmitter release
  • PK: Absorbed orally, not metabolized, excreted unchanged in urine. Half-life ~6 hours.
  • Side effects: Dizziness, weight gain, peripheral edema; dose adjustment needed in renal impairment.

Study notes covering common analgesics. Includes acetaminophen, ibuprofen and aspirin. Focuses on uses, mechanisms of action (MOA), pharmacokinetics (PK), and side effects.