Understanding Palliative Care: Pain Management

World Health Organization analgesic ladder

“By the” principles of pain management

• By mouth – oral whenever possible
• By the clock – given at regular intervals instead of as added if possible
  • Usually dose opioids every 4 hours
• By the ladder – given according to WHO ladder
• Start low, go slow
• Use adjuvant analgesics at any point in the ladder – adjuvant analgesic is a medication for which its primary use is not pain but it may still have an analgesic effect
  • Examples include
    • NSAIDs like diclofenac for bone mets, liver capsule pain and tissue infiltration
    • Antidepressants such as those that end in -triptyline (amitrptyline, nortriptyline) for nerve pain
    • Anticonvulsants such as gabapentin or pregabalin for nerve pain
    • Corticosteroids like dexamethasone for increased ICP, soft tissue infiltration, liver capsule pain and nerve compression
    • Bisphosphonates for malignant bone pain

How to manage dosing for breakthrough pain?

• When pain is greater than baseline an as needed dose of opioids may be needed for breakthrough pain
• 2 methods to dose breakthrough pain
  • Breakthrough dose = Provide 10% of their 24 hour dose of opioids every 2 hours as needed
    • Patient on morphine 5 mg PO every 4 hours
    • How to calculate breakthrough?
      • 24 hour dose = 5 x 6 = 30 mg / 24 hours
      • 0.10 x 30 = 3
      • Breakthrough dose = 3 mg every 2 hours as needed
  • Breakthrough dose = Provide half of the regularly scheduled dose, in half the time as needed
    • Patient on morphine 5 mg PO every 4 hours
    • How to calculate breakthrough?
      • Regularly scheduled dose is 5 mg, and schedule is every 4 hours
      • Half of the scheduled dose is 2.5, and half of the schedule is 2 hours
      • Breakthrough dose = 2.5 mg every 2 hours

How to increase opioid doses?

• Titrate up doses 30-50 %
• When escalating opioid dosage you must take into account both the regularly scheduled doses as well as the prn breakthrough doses
• Example: John is prescribed 30 mg, 2 times per day of morphine, with 10 mg of prn morphine
  • Calculating total daily morphine including breakthrough dose
    • On each of the past 3 days he has taken four 10 mg breakthrough doses
    • Total daily morphine = daily scheduled morphine + daily prn morphine
    • Total daily morphine = (30 x 2) + (10 x 4)
    • Total daily morphine = 60 + 40 = 100 mg
  • Calculating the increase in total daily and regularly scheduled morphine
    • We can increase the total daily morphine by 30 to 50 %
    • Let’s say we decide to increase the total daily morphine by 50 %, so the new total daily morphine is 150 mg
    • Regularly scheduled morphine dose = 150 / 4 = 37.5 mg
  • Calculating breakthrough
    • Breakthrough dose = 10 % of 24 hour dose
    • Breakthrough dose = 0.10 x 150 mg = 15 mg
    • Breakthrough dose is 15 mg morphine provided every 2 hours

How to switch opioids?

When converting from one opioid to another we convert to morphine first and then to another opioid – this is referred to as morphine equivalent dosing

1. Calculate total daily opioid dose
   • e.g. patient is taking hydromorphone 2 mg PO Q4H. Please convert to PO morphine
   • Total 24 hour dose of hydromorphone is 2 x 6 = 12 mg oral hydromorphine / day
2. Convert current opioid dose to morphine by using the morphine dose conversion table
   • 2 mg oral hydromorphone is equivalent to 10 mg oral morphine
   • 12 x 5 = 60 mg oral morphine / day
   • At this point if you wanted to convert to another opioid besides morphine you would use the morphine conversion table to convert it to the opioid of choice e.g. to convert to codeine we would do 60 x 10 = 600 mg codeine / day
3. Make sure to account for incomplete cross-tolerance by decreasing dose by 30 %
   • 60 – (60 x 0.30) = 42 mg hydromorphone / day
4. Divide total new daily dose by 6 in order to determine the dose of morphine taken at regularly scheduled intervals
   • 42 / 6 = 7
   • 7 mg PO Q4H
5. Determine the breakthrough dose as 10 % of total daily dose
   • 10 % of 42 = 4 mg Q2H PRN

How to change dosage when switching the route of administration?

• Similar principle applies when switching between different routes of administration (except you do not need to account for incomplete cross-tolerance)
• Different routes of administration
  • Oral (preferred method)
    • Oral is half as potent as parenteral (subcutaneous, IM)
  • Intramuscular – rarely used this route in palliative care due to the prevalence of cachexia
  • IV/subcutaneous
    • Intermittent injection
    • Continuous infusion using a patient controlled analgesia pump (PCA)
  • Transdermal/topical
    • Fentanyl patch
      • NEVER prescribe fentanyl patch to an opioid naive patient

What are the short and long term side effects of opioids?

• Short term side effects (5-10 days)
  • Nausea and vomiting
    • Antiemetic may be required during this time
  • Drowsiness
• Long term side effects
• Constipation
  • Requires prophylactic treatment
  • Prophylaxis typically involves combination of stimulant and osmotic laxative
    • Senna or bisacodyl + lactulose or PEG

What happens when patient’s pain is well controlled?

• Patients may be switched from short acting (q4h) to long-acting (q12h) opioids (long acting version of opioid as contin after name) after stable dose has been achieved using the short acting opioids
• Long acting opioids are also known as sustained or controlled release preparations
• Long acting opioids are rarely started in opioid naive patients
• Long acting opioids are given every 12 hours
  • In order to convert someone from short to long acting opioids, take the total daily dose of opioids and divide it by 2 to give the equivalent 12 hour dose
  • Make sure to still provide breakthrough opioids as well