What is the rationale for administering an opioid when a patient’s pain is assessed as moderate to severe?

Rationale for Administering Opioids in Moderate to Severe Pain

Opioids are indicated for moderate to severe pain because they are the most effective pharmacologic agents for achieving adequate analgesia when pain intensity reaches levels (4-10 on a 0-10 scale) where nonopioid analgesics alone are insufficient to provide relief and restore function. 1

Pain Intensity-Based Treatment Algorithm

Severe Pain (7-10/10)

• Opioid-naïve patients with severe pain require rapid titration of short-acting opioids because these formulations provide rapid onset of analgesic effect necessary for urgent relief 1
• Oral morphine 20-40 mg or IV/SC morphine 5-10 mg should be initiated immediately, as strong opioids are the mainstay of therapy for moderate-severe cancer-related pain 1, 2
• The route selection (oral vs parenteral) depends on urgency of relief needed—parenteral routes are reserved for patients requiring urgent relief or unable to tolerate oral administration 1, 2

Moderate Pain (4-6/10)

• Treatment pathways for moderate pain mirror those for severe pain, with the primary difference being slower titration of short-acting opioids rather than rapid escalation 1
• This approach recognizes that moderate pain still requires opioid analgesia but allows for more gradual dose adjustment to minimize adverse effects 1

Mild Pain (1-3/10)

• Nonopioid analgesics (NSAIDs, acetaminophen) are first-line, with consideration of slower opioid titration only if nonopioids are contraindicated or ineffective 1

Pharmacologic Rationale

Superior Efficacy for Moderate-Severe Pain

• Strong opioids provide effective pain relief that nonopioid analgesics cannot achieve at moderate to severe intensities 1
• Morphine has been the standard since 1977 in palliative care for moderate-severe chronic cancer pain because it is effective, widely tolerated, simple to administer, and inexpensive 1
• Oral morphine is the only opioid on the WHO essential drug list for adults and children with pain 1

Multimodal Enhancement

• Opioids should be combined with nonopioid analgesics (acetaminophen 1000 mg every 4-6 hours, ibuprofen 400 mg every 4-6 hours if no contraindications) to enhance analgesic effect 2
• Adjuvant analgesics (antidepressants, anticonvulsants, corticosteroids) should be added for specific pain syndromes to enhance opioid effects 1

Clinical Management Principles

Dosing Strategy

• Analgesics must be administered on a regular schedule, not "as needed," for baseline pain control once moderate-severe pain is established 2
• Rescue doses (10-20% of total daily opioid dose as immediate-release formulation) should be prescribed for breakthrough pain episodes 1, 2
• Assessment intervals are critical: every 60 minutes for oral opioids, every 15 minutes for IV opioids to determine subsequent dosing 1

Titration Approach

• If pain score remains unchanged or increases after initial dose, administer 50-100% of the previous rescue dose 1
• If pain decreases to 4-6, repeat the same dose and reassess at appropriate intervals 1
• After 2-3 cycles without improvement in moderate-severe pain, consider changing route from oral to IV or implementing alternate strategies 1

Essential Prophylaxis

Mandatory Co-Prescribing

• Stimulant laxatives must be prescribed prophylactically for all patients on opioids to prevent opioid-induced bowel dysfunction 1
• Antiemetics (metoclopramide or antidopaminergics) should be provided for opioid-induced nausea/vomiting 2, 3

Monitoring Requirements

• Close monitoring for respiratory depression is required, especially within the first 24-72 hours of initiation and following dose increases 3
• Naloxone should be available and diluted in normal saline, administered every 30-60 seconds until improvement if respiratory depression occurs 3

Common Pitfalls to Avoid

Inappropriate Delays

• Do not delay strong opioids for severe pain—the WHO ladder allows starting at step 3 for very severe pain, bypassing weak opioids entirely 2
• Weak opioids (codeine, tramadol) are inadequate for severe pain and should not be used when pain intensity is 7-10/10 2

Formulation Errors

• Never prescribe two sustained-release opioids together 2
• Do not use transdermal fentanyl for rapid titration—it is only appropriate once pain is controlled with other opioids 2, 4
• Avoid extended-release formulations for initial titration; use immediate-release opioids first 1

Special Population Considerations

• In renal impairment (eGFR <30 mL/min), start with one-fourth to one-half the usual dose, with fentanyl and buprenorphine as preferred alternatives 2, 3
• In hepatic impairment, start with one-fourth to one-half the usual dose, reducing dose rather than extending intervals 3