What are the guidelines for prescribing opioid drugs, such as morphine (opioid analgesic), oxycodone (opioid analgesic), or hydrocodone (opioid analgesic), for pain management?

Opioid Prescribing Guidelines for Pain Management

First-Line Approach: Prioritize Non-Opioid Therapies

For acute pain conditions (low back pain, neck pain, musculoskeletal injuries, dental pain, kidney stones, headaches), nonopioid therapies are at least as effective as opioids and should be maximized first 1. Only consider opioids when benefits clearly outweigh risks, contraindications exist to non-opioid options, or other therapies have failed 1.

When Opioids Are Indicated

Opioids have an important role for:

• Severe traumatic injuries (crush injuries, burns) 1
• Invasive surgeries with expected moderate to severe postoperative pain 1
• Moderate to severe cancer pain 1, 2
• Other severe acute pain when NSAIDs are contraindicated or ineffective 1

Selecting the Right Opioid

First-Choice Opioid: Morphine

Oral morphine is the opioid of first choice for moderate to severe pain due to its effectiveness, tolerability, and low cost 1, 2. This applies particularly to cancer pain and established moderate-severe pain requiring opioid therapy 1.

Initial Dosing for Opioid-Naive Patients

Start with 5-15 mg oral morphine every 4-6 hours as needed, or 2-5 mg IV for opioid-naive patients 3, 4. For elderly patients (>70 years), reduce to approximately 10 mg/day divided into multiple doses (roughly 2 mg per dose) 3.

Critical pitfall: An initial dose of 20 mg oral morphine or equivalent of 60 mg/day presents high risk of excessive adverse effects (constipation, nausea, respiratory depression) in opioid-naive patients 3.

Alternative Opioids

Oxycodone: Appropriate alternative to morphine, particularly for visceral pain where it may have superior efficacy 5. Initial dosing: 5-15 mg every 4-6 hours for opioid-naive patients 4. Oxycodone is 1.5 times more potent than morphine (5 mg oxycodone = 7.5 mg morphine) 6.

Hydrocodone: Commonly prescribed but associated with substantially higher rates of long-term use compared to oxycodone (12% vs 2% transition to long-term use) 7. Use with caution given this increased risk profile 7.

Fentanyl (transdermal): Reserved for patients with stable opioid requirements already controlled on other opioids—NOT for initial therapy or unstable pain 1, 2. Conversion from IV to transdermal fentanyl uses 1:1 ratio 2.

Methadone: Only for use after failure of other opioid therapy and only by clinicians with specific training due to marked inter-individual variability in half-life 2, 8.

Formulation Selection

Always prescribe immediate-release (short-acting) opioids for initial therapy and acute pain 1, 8. Extended-release formulations should be avoided for opioid initiation and are associated with increased adverse consequences 8.

Dosing Strategy

• Prescribe "as needed" rather than scheduled dosing (e.g., "hydrocodone 5 mg/acetaminophen 325 mg, one tablet every 4 hours AS NEEDED for moderate to severe pain") 1
• For acute pain, provide ≤5 days supply unless trauma/surgery with expected longer pain duration 9
• For chronic cancer pain, administer on around-the-clock basis once dose is established 4

Route of Administration

Oral route is first choice 1. The oral-to-parenteral potency ratio for morphine is 1:3 (30 mg oral = 10 mg IV/IM) 3, 6. Use parenteral route for severe pain requiring urgent relief 3.

Subcutaneous infusions are preferred over IV when continuous infusion is needed, as they don't require venous access and have lower infection risk 1.

Opioid Conversion and Rotation

When switching between opioids:

1. Calculate the equianalgesic dose using standard conversion tables 1, 6
2. Reduce the calculated dose by 25-50% to account for incomplete cross-tolerance 1, 8
3. Exception: If previous opioid was ineffective, may use 100% of equianalgesic dose or increase by 25% 1

Key conversion factors:

• Oral morphine to IV morphine: 1:3 ratio 1, 3
• Oxycodone to morphine: multiply oxycodone dose by 1.5 6
• See detailed conversion tables for transdermal fentanyl 1

Dosing Thresholds and Safety

Consider up to 40 morphine milligram equivalents (MME) as low dose, 41-90 MME as moderate dose, and >91 MME as high dose 8. Recommend long-acting or high-dose opioids only in specific circumstances with severe intractable pain 8.

Special Populations

Renal Impairment

Use all opioids with caution at reduced doses and frequency in renal impairment 1. Fentanyl and buprenorphine (transdermal or IV) are safest choices in chronic kidney disease stages 4-5 (eGFR <30 ml/min) 1.

Pediatric Patients

Never prescribe codeine or tramadol for patients <12 years, adolescents 12-18 years with obesity/sleep apnea/severe lung disease, post-tonsillectomy/adenoidectomy patients <18 years, or breastfeeding patients 9.

Mandatory Adjunctive Measures

• Laxatives must be routinely prescribed for prophylaxis and management of opioid-induced constipation 1
• Provide naloxone and education on its use 1
• Prescribe antiemetics (metoclopramide, antidopaminergics) for opioid-related nausea/vomiting 1
• Monitor with prescription drug monitoring programs (PDMPs) and urine drug testing 8
• Provide breakthrough medication: immediate-release morphine 10-15 mg every 4 hours as needed when using extended-release formulations 6

Monitoring and Reassessment

• Assess efficacy and adverse effects every 60 minutes for oral administration, every 15 minutes for IV 3
• If pain persists, increase dose by 50-100% of previous dose 3
• Periodically assess for ≥30% improvement in pain relief and/or functional status without adverse consequences 8
• Discontinue for lack of response, adverse consequences, or abuse 8

Critical Contraindications

• Avoid transdermal fentanyl with fever or topical heat sources (accelerates absorption) 1
• Do not use fentanyl patches for unstable pain requiring frequent dose changes 1
• Pain should be relatively well controlled on short-acting opioid before initiating fentanyl patch 1