Pharmacology & Anesthesia: Narcotic Analgesia

Narcotics/Opioids

Effects

  • Mechanism of Action: CNS Mu-Opioid Receptor Agonist
  • Effects: Analgesia
  • Metabolism in Liver & Excreted in Kidney

Morphine Equivalent Dose (MED)

  • *Compared to Oral Morphine Effects
  • Oral:
    • Tramadol: 0.1
    • Codeine: 0.15
    • Morphine: 1.0
    • Hydrocodone: 1.0
    • Oxycodone: 1.5
    • Hydromorphone (Dilaudid): 4.0
    • Meperidine (Demerol): 7.5
      • Not Recommended for Analgesia
    • Methadone: 4-14 Depending on Dose (Higher Conversion at Higher Doses)
  • Parenteral (IV):
    • Morphine: 3.0
    • Hydromorphone (Dilaudid): 15-20
    • Fentanyl: 300
    • Sufentanil: 3,000

Incomplete Cross-Tolerance

  • Opioids May Have Greater-Than-Anticipated Effect at the Same Equianalgesic Dose of Another Opioid
  • Overall Dose Should Be Decreased 25% When Converting from One Opioid to Another

General Complications

  • Respiratory Depression (Blunted CO2 Drive)
  • Histamine Release (Hypotension)
  • No Cardiac Effects
  • Nausea & Vomiting
  • Constipation

Opioid Overdose

  • Presentation:
    • Altered Mental Status
    • Decreased Respiratory Rate < 12 – Strongest Predictor of Overdose
    • Decreased Tidal Volume
    • Constricted Pupils
  • Treatment: Naloxone (Narcan)
    • Mechanism: Opioid Receptor Antagonist
    • Dosing: 0.4-2.0 mg
      • Repeat Every 2-3 Minutes as Needed
    • Goal: Adequate Ventilation (Not Normal Level of Consciousness)
    • Half-Life is Shorter than Opioids – May Need to Further Repeat Dosing Even After Reversal Has Been Seen

Postoperative Opioid Prescription & Abuse

Postoperative Prescription

  • Most Patients Require Less than 15 Tablets
  • In General 0-10x 5 mg Tablets of Narcotic Analgesia Should Be Prescribed
    • Includes: Oxycodone, Hydrocodone, etc.
  • Regardless of Initial Quantity, 9% Require an Opioid Prescription Refill
  • 72% of Prescribed Opioids to Surgical Patients are Not Used from Postoperative Period
    • Excess Should Be Returned to Local DEA Authorized Location

Opioid Abuse

  • Most Likely Source of Misused Opioids (> 50%) is Leftover Pills of a Friend or Relative
  • Surgeons Provide 10% of All Opioid Prescriptions
  • Among Opioid-Naive Patients 6-10% Continue Filling Opioid Prescriptions 3-6 Months After Common Surgical Procedures
  • Postoperative Risk Factors for Developing Chronic Opioid Use:
    • Younger Age
    • Tobacco or Substance Use Disorders
    • Depression/Anxiety
    • Chronic Pain Syndrome

Oral (PO) Agents

Morphine

  • The Prototype Opioid
  • Routes: PO or IV
  • Onset:
    • PO: 30 Minutes
    • IV: 5-10 Minutes
  • Duration of Effect: 3-5 Hours
  • Dose:
    • PO: 10-30 mg Every 3-4 Hours as Needed
    • IV: 1-4 mg Every 3-4 Hours as Needed
  • Multiple Active Metabolites
    • One is More Potent
    • Avoid in Renal Failure – Unable to Excrete & Higher Risk of Overdose

Tramadol (Ultram)

  • Onset: 30-60 Minutes
  • Duration of Effect: 3-4 Hours
  • Dose: 25-100 mg Every 4-6 Hours as Needed

Oxycodone (OxyCONTIN/Roxicodone)

  • Onset: 10-15 Minutes
  • Duration of Effect: 3-6 Hours
  • Dose: 5-15 mg Every 4-6 Hours as Needed
  • Percocet – Also Contains 325 mg Acetaminophen
    • 5/325 or 10/325 mg

Hydrocodone

  • Most Commonly Given as Tylenol Combination
  • Norco, Vicodin or Lorcet – Also Contains 325 mg Acetaminophen
    • 5/325 or 10/325 mg

Parenteral (IV) Agents

Morphine

  • *See Above

Hydromorphone (Dilaudid)

  • Can Also Be Given PO
  • Onset:
    • PO: 15-30 Minutes
    • IV: 5-10 Minutes
  • Duration of Effect: 3-4 Hours
  • Dose:
    • PO: 1-2 mg Every 4-6 Hours as Needed
    • IV: 0.2-1.0 mg Every 2-4 Hours as Needed
  • PCA Dosing:
    • Demand Dose: 0.1-0.4 mg
    • Lockout Interval: 8-15 Minutes
    • Basal Dose: Generally Not Recommended in Opioid-Naïve Patients
    • Maximum Cumulative Dose: 1.5 mg Per Hour or 4-6 mg Every 4 Hours

Fentanyl

  • Can Also Be Given IM or by Transdermal Patch
  • Onset: 1-2 Minutes
  • Duration of Effect: 30-60 Minutes
    • Short Acting
  • Dose: 25-100 mcg IV Every Hour as Needed
    • Continuous Sedation in ICU: 1-2 mcg/kg/Hour
  • PCA Dosing:
    • Demand Dose: 5-20 mcg
    • Lockout Interval: 5-15 Minutes
    • Basal Dose: Generally Not Recommended in Opioid-Naïve Patients
    • Maximum Cumulative Dose: 75-100 mcg Per Hour or 300-400 mcg Every 4 Hours
  • No Histamine Release
  • No Active Metabolites (Safer in Dialysis)

Remifentanil (Ultiva)

  • Highly Potent
  • Fastest & Shortest Acting – Used for Periprocedural Anesthesia
    • Not Used for Routine Pain Control
  • Onset: 1-3 Minutes
  • Duration of Effect: 5-10 Minutes
  • Dose: 0.5-15 mcg/kg/Hour Infusion

Sufentanil

  • Most Potent
  • Fast & Short Acting – Used for Periprocedural Anesthesia
    • Not Used for Routine Pain Control
  • Dose: 0.5-10 mcg/kg/Hour Infusion

Meperidine (Demerol)

  • Also Given IM
  • Generally Not Used for Pain Control Due to Side Effects
  • Risk for Neurotoxicity (Tremors & Seizure) Mn
    • Toxic Metabolite (Normeperidine) – Longer Half-Life but No Analgesic Effect
    • Avoid in Renal or Hepatic Failure
  • No Histamine Release

Mnemonics

Side Effects of Meperidine (Demerol)

  • Demerol Causes Tremors: “Tremor-ol”