Analgesics: Nursing Pharmacology

Overview

• Analgesics are medications used to relieve pain.
• Categories:
  • Non-opioid analgesics
  • Opioid analgesics
• Other medications sometimes used as analgesics:
  • Antidepressants (e.g., amitriptyline)
  • Anticonvulsants (e.g., gabapentin)
  • Corticosteroids (e.g., dexamethasone)
  • Local anesthetics (e.g., lidocaine)

Non-Opioid Analgesics

Types

• NSAIDs (Non-steroidal anti-inflammatory drugs)
• Acetaminophen

Mechanism of Action

• NSAIDs inhibit cyclooxygenase (COX) enzymes:
  • COX-1: Platelet aggregation, protective mucus production, renal vasodilation.
  • COX-2: Inflammation, prostaglandin production.
• Acetaminophen inhibits COX enzymes in the central nervous system.

Common NSAIDs and Their Characteristics

• Aspirin (oral): Widely used NSAID.
• Non-selective COX inhibitors: Ibuprofen, naproxen, ketorolac.
• Selective COX-2 inhibitors: Celecoxib.

Administration Routes

• NSAIDs: Oral, intramuscular, intravenous, topical, rectal.

Side Effects

• Gastrointestinal issues: Gastritis, gastric ulcers, bleeding.
• Renal impairment: Hyperkalemia, nephropathy, renal failure.
• Others: Headache, drowsiness, dizziness, hypersensitivity reactions.
• Less frequent with selective COX-2 inhibitors.

Contraindications and Cautions

• Avoid during third trimester of pregnancy.
• Avoid in renal or hepatic impairment.
• Avoid if allergic to any NSAIDs.
• Aspirin contraindicated in children with viral infections, except Kawasaki disease.
• Ketorolac: Short-term use, contraindicated in children, during labor, renal disease.

Acetaminophen

Uses

• Preferred for clients with bleeding disorders, peptic ulcers, aspirin allergies.
• First-line for children with fever or pain, especially viral infections.

Administration

• Routes: Oral, rectal, intravenous.

Side Effects and Warnings

• Metabolized in liver: Risk of acute liver failure.
• Limit dosage to 4 grams/day.
• Early overdose symptoms: Nausea, vomiting, abdominal pain.
• Late symptoms: Jaundice, coagulopathy, hepatic encephalopathy, renal failure.

Opioid Analgesics

Mechanism of Action

• Activate opioid receptors (mu, delta, kappa) in the brain.

Categories

• Full agonists: Morphine, methadone, meperidine, codeine, oxycodone, fentanyl.
• Partial agonists: Tramadol.
• Mixed agonist-antagonists: Buprenorphine.

Routes of Administration

• Oral, intravenous, intramuscular, subcutaneous, transdermal, epidural, intrathecal, topical.

Side Effects

• Sedation, nausea, vomiting, constipation, urinary retention.
• Decreased blood pressure, orthostatic hypotension.

Boxed Warnings

• Respiratory depression, sedation, coma, death.
• Risk of neonatal opioid withdrawal syndrome.
• Dependence and addiction risk.

Contraindications

• Respiratory depression, head trauma, increased intracranial pressure, coma.
• Avoid with CNS depressants (alcohol, barbiturates, benzodiazepines).

Nursing Considerations

Assessment and Monitoring

• All analgesics:

  • Vital signs, pain assessment, goal setting.
  • Monitor for side effects, reassess therapeutic effect.

• NSAIDs: Baseline labs (CBC, BUN, creatinine), monitor renal function.

• Acetaminophen: Baseline liver function tests.

• Opioid analgesics: Monitor consciousness, hold if respiratory rate <12/min, fall precautions, have naloxone available.

Client Education

• Non-pharmacological pain management methods.
• Management of side effects.
• NSAIDs: Take with meals/milk, avoid alcohol.
• Acetaminophen: Limit to 4 grams/day, avoid alcohol.
• Opioid analgesics: Follow prescription, avoid alcohol, manage sedation and constipation, urinary retention precautions.