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Understanding Pharm: Opioid Classes

Please see our article on principles of pain management before continuing! Credit to WISE on call for their clear explanations of the opioid classes.

World Health Organization analgesic ladder

MildModerateSevere
Non-opioids
E.g. acetaminophen, NSAIDs		Weak opioids
E.g. codeine, dihydrocodeine		Strong opioids
E.g. morphine, hydromorphone, oxycodone, fentanyl

How to switch opioids?

Drug

  • Codeine
  • Morphine
  • Oxycodone
  • Hydromorphone

Oral

  • 100 mg
  • 10 mg
  • 5-7.5 mg
  • 2 mg

Parenteral (subQ/IV)

  • 50 mg
  • 5 mg
  • Not available
  • 1 mg

Mild pain

Acetaminophen (Tylenol)

  • Route of administration
    • Oral, rectal, IV
  • Starting dose
    • 650 mg
  • Onset of action
    • 60 minutes PO/PR
    • 10 minutes IV
  • Duration
    • 4-6 hours
  • Max daily dose
    • 3-4 grams/day
  • Contraindications
    • Safe to use in
      • Elderly
      • Renal failure
    • Avoid use in acute hepatic failure
    • Can be used with caution in someone with chronic hepatic failure
      • Maximum daily dose is 2 grams/day

NSAIDs

Ibuprofen (Advil, Motrin)

  • Drug of choice in inpatient setting due to shorter duration of action
  • Dosing
    • Oral
      • Starting dose – 400-600 mg
      • Onset of action – 30-60 min
      • Duration – 4-6 hours
      • Max daily dose – 2400 mg

Naproxen (Aleve, Naprosyn)

  • Most commonly used in outpatient setting due to long duration of action and ease of dosing
  • Dosing
    • Oral
      • Starting dose – 500 mg
      • Onset of action – 30-60 min
      • Duration – 8-12 hours
      • Max daily dose – 1000 mg

Ketorolac (Toradol)

  • Commonly given as a one-time IV/IM dose in the emergency room for acute inflammatory conditions like renal colic
  • Cannot be used for more than 5 days due to high risk of side effects
  • Dosing
    • Oral, IV, IM
    • Starting dose
      • 20 mg PO (if continuation of IM, otherwise 10)
      • 30 mg IV
      • 60 mg IM
    • Onset of action – 30 minutes
    • Duration – 4-6 hours
    • Max daily dose
      • 120 mg IV/IM
      • 40 mg PO

When to avoid NSAIDs?

  • Avoid in acute and chronic renal failure
  • Avoid in hepatic failure
  • Avoid in elderly
  • Avoid in bleeding disorders
  • Avoid in cardiac disorders
  • Avoid in patients with history of GI bleeding
  • Avoid in patients on anti-coagulants
  • Avoid in pregnant patients beyond 32 weeks
    • Due to concern of premature patent ductus arteriosus closure

Moderate pain

Tramadol

  • 1/6 as strong as morphine
  • Synthetic analogue of codeine
  • Less likely to lead to dependency
  • Dosing
    • Oral
    • Starting dose
      • 50 mg 
    • Onset of action – 60 minutes
    • Duration – 4-12 hours
    • Max daily dose
      • 400 mg
  • Contraindications
    • No contraindication to use in renal or hepatic failure
      • However, the half-life is prolonged in advanced renal failure or cirrhotic patients – requiring dose change
    • Elderly
      • High risk for delirium
      • Start at 25 mg
    • Risk for serotonin syndrome
      • Tramadol also acts as a serotonin and norepinephrine reuptake inhibitor
      • Avoid in patients who are also on
        • TCAs
        • MAOI
        • SSRIs, SNRIs
    • Decreases seizure threshold
      • Avoid in patients with seizures, anorexics, or patients on anti-epileptics

Codeine

  • Commonly used
    • As an anti-tussive
    • Pain relief usually formulated with acetaminophen
  • 1/6 as strong as morphine
  • Formulations
    • Tylenol #1 = 7.5 mg codeine/300 mg acetaminophen
    • Tylenol #2 = 15 mg codeine/300 mg acetaminophen
    • Tylenol #3 = 30 mg codeine/300 mg acetaminophen
    • Tylenol #4 = 60 mg codeine/300 mg acetaminophen
  • Dosing
    • Oral
    • Starting dose
      • 15 mg 
    • Onset of action – 30-60 minutes
    • Duration – 4-6 hours
    • Max daily dose
      • 360 mg
  • Contraindications
    • Avoid in renal disease
    • Avoid in hepatic disease
    • Elderly are more prone to sedative effects so use cautiously

Hydrocodone

  • Same potency as oral morphine
  • Consider hydrocodone as an alternative to IV pain medication in a patient who is tolerating oral medication
  • Formulations
    • Norco
      • 5/325
      • 7.5/325
      • 10/325
    • Vicodin
      • 5/300
      • 7.5/300
      • 10/300
  • Dosing
    • Oral
    • Starting dose – 5 mg 
    • Onset of action – 10-20 minutes
    • Duration – 4-8 hours
    • Max daily dose
      • 40 mg
  • Contraindications           
    • Avoid in renal failure
    • Avoid in hepatic failure (because of acetaminophen)
    • Elderly are vulnerable to sedative effects

Morphine

  • Dosing
    • Oral, IV, subcutaneous (not recommended as it can cause local tissue damage and pain)
    • Starting dose
      • 7.5-15 mg PO
      • 2-5 mg IV
    • Onset of action
      • 30-60 min PO
      • 5-10 min IV
      • 15-30 min subcutaneous
    • Duration
      • 3-5 hours
    • Max daily dose
      • None
      • Dose should be adjusted based on adverse effects such as respiratory depression and sedation
  • Contraindications
    • Can be given in hepatic failure but half life is increased
    • Avoid in renal failure
    • Elderly are vulnerable to sedative effects

Oxycodone

  • 1.5x potency of oral morphine
  • Overall safe medication to be used in the acute hospital setting
    • Limit to less than a week as it is highly addicting
  • Formulations
    • Roxicodone, OxyIR (oxycodone)
      • 5
      • 7.5
      • 10
    • Percocet (oxycodone/acetaminophen)
      • 5/325
      • 7.5/325
      • 10/325
  • Dosing
    • Oral
    • Starting dose
      • 5 mg
    • Onset of action
      • 10-15 mins
    • Duration
      • 4-6 hours
    • Max daily dose
      • None
      • Dose should be adjusted based on adverse effects such as respiratory depression and sedation
  • Contraindications
    • Safe to use in renal and hepatic failure

Safest drugs to use with respect to renal and hepatic failure are from weakest to strongest tramadol, oxycodone, hydromorphone, fentanyl (although dose adjustments may be required). From the moderate opioids oxycodone still does have a high potential for addiction – should be used in the short term.

Severe pain

Hydromorphone

  • 5x as potent as oral morphine
  • Formulations
    • Dilaudid
  • Dosing
    • Oral, IV, subcutaneous
    • Starting dose
      • 1-5 mg PO
      • 0.2 – 1 mg IV
    • Onset of action
      • 15-30 mins PO
      • 5-15 mins IV
    • Duration of action
      • 4-6 hours
    • Max daily dose
      • None
      • Dose should be adjusted based on adverse effects such as respiratory depression and sedation
  • Contraindications 
    • Avoid use in opioid naïve patient
    • Safe to use in renal and hepatic failure Use cautiously in those who are at risk for respiratory depression

Fentanyl

  • Severe acute pain in hospitalized patients
  • Should only be used if other agents have failed
  • 10x stronger than IV morphine
  • Formulations
    • Duragesic
    • Actiq
    • Fentora
  • Dosing
    • IV, IM, transdermal
    • Starting dose
      • 12.5-25 mcg IV
      • 25-50 mcg IM
    • Onset of action
      • Immediate iV
      • 15 mins IM
    • Duration of action
      • 30 mins – 2 hours
    • Max daily dose
      • None
      • Dose should be adjusted based on adverse effects such as respiratory depression and sedation
  • Contraindications 
    • DO NOT use in opioid naïve patient
    • Safe to use in renal and hepatic failure
    • Use cautiously in those who are at risk for respiratory depression

Monitoring pain after medication is provided

  • Re-evaluate patient after one-time dose, after you expect medication to have taken effect
    • Ask patient to rate pain
    • Ask patient and nurse if there were any side effects
  • If pain has not relieved, evaluate patient for any evolving medical condition
    • If no evolving disease then increase dose of pain medication, or higher potency pain medication

Starting opioids on the ward

Start the patient on short acting opioids initially. Then after 24 hours add up all of the prns they used to get the total mg of opioids they used in 24 hours. You can use this as your basal opioid dose for long acting opioids.

E.g. Patient used 4 of his morphine IR 15 mg breakthrough in 24 hours, a total of 60 mg of morphine in 24 hours. The patient should therefore be started on 30 mg of morphine contin, BID, with 10 mg of morphine IR q4h PRN.

Patients who are on opioids should also be placed on bowel protocol which would typically involve PEG 17 g PO once daily and senna 2 tabs PO qhs (although this would be through the bowel care order set).

Breakthrough dosing on the ward

Add up all the mg of opioids patient has received in the last 24 hours.

  • E.g. patient is receiving 30 mg of morphine contin BID, and is on morphine 10 mg IR q4h PRN. The patient has used 4 breakthrough doses. The patient has used a total of 100 mg of morphine in 24 hours.

Increase the dose of opioids by 30 – 50 %, and then divide it in 2 if the patient is on BID dosing.

  • E.g. 100 mg x 50 % = 150 mg
  • 150 mg / 2 = 75 mg

Breakthrough is typically 1/6 of the dose of basal opioids.

150/6 = 25 mg

Therefore, this patient’s new morphine dosing regimen would be 75 mg BID or morphine contin, with 25 mg morphine IR q4h.