What is the difference between Roxanol (Morphine) and OxyCodone (Oxycodone) for pain management?

Roxanol (Morphine) vs. OxyCodone for Pain Management

For moderate to severe pain management, oral morphine remains the gold standard first-choice opioid, but oxycodone is an equally effective alternative with approximately 1.5-2 times greater potency than morphine and may offer advantages in specific pain types, particularly visceral pain. 1, 2, 3

Relative Potency and Dosing Equivalence

• The oral morphine to oral oxycodone potency ratio is approximately 1.5-2:1, meaning 10 mg of oxycodone is roughly equivalent to 15-20 mg of morphine 2, 4, 5
• When converting from oral to parenteral morphine (Roxanol can be given IV/SC), divide the oral dose by 2-3 to achieve equianalgesic effect 1
• For opioid-naïve patients starting oxycodone, begin with 5 mg combined with acetaminophen for moderate pain 2, 6
• For morphine, the recommended starting dose is 0.1 mg/kg IV, then 0.05 mg/kg at 30 minutes, with maximum suggested dose of 10 mg 1

Comparative Efficacy

• Both agents demonstrate similar clinical efficacy for cancer pain and general pain management 1, 4, 7
• A recent 2021 randomized controlled trial showed that 15 mg morphine immediate release with acetaminophen provided equivalent pain reduction to 10 mg oxycodone with acetaminophen at 60 minutes (NRS reduction of 4.2 vs 3.61, not statistically different) 7
• Oxycodone may have superior efficacy for visceral pain due to its activity at kappa-opioid receptors in addition to mu-receptors, whereas morphine acts primarily at mu-receptors 5, 8
• In experimental pain models, oxycodone demonstrated superior analgesic effect compared to morphine for mechanical and thermal stimulation of the esophagus (P<0.001) 8

Side Effect Profile Differences

• Oxycodone causes somewhat less nausea, hallucinations, and pruritus compared to morphine 4
• Morphine carries higher risk of toxicity in renal failure due to accumulation of active metabolites and has longer time to reach stable plasma levels (2-7 days vs 24 hours for oxycodone) 4
• Oxycodone metabolism is more predictable than morphine, making titration easier 4
• Both agents showed similar rates of nausea/vomiting in head-to-head comparison 7
• Oxycodone demonstrated lower rates of drug likeability compared to oxycodone/acetaminophen combinations, which may reduce abuse potential 7

Pharmacokinetic Advantages

• Oxycodone has faster time to stable plasma levels (24 hours) compared to morphine (2-7 days), allowing for more rapid titration 4
• Oxycodone oral bioavailability is 60-87% with 45% plasma protein binding 4
• Plasma half-life of oxycodone is 3-5 hours (half that of morphine), reducing risk of dose stacking 4
• Morphine has longer onset of action and greater risk for dose stacking, placing patients at higher risk for toxicity and hypoventilation 1

Clinical Decision Algorithm

Choose Morphine (Roxanol) when:

• Cost is a primary concern (morphine is less expensive and on WHO essential drug list) 1
• Treating acute severe pain in emergency settings where IV/SC route is needed for rapid titration 1
• Patient has stable pain and you have experience with morphine dosing 1

Choose Oxycodone when:

• Treating visceral pain syndromes (abdominal, pelvic pain) 5, 8
• Patient has renal impairment (oxycodone has more predictable metabolism) 4
• Patient experienced intolerable side effects with morphine (nausea, hallucinations, pruritus) 4
• Faster titration is needed (reaches steady state in 24 hours vs 2-7 days) 4
• Patient requires oral route with controlled-release formulation for stable pain 1, 4

Critical Safety Considerations

• Both agents require routine prophylactic laxative prescription for opioid-induced constipation 2, 3
• Prescribe breakthrough doses at 10-15% of total daily dose; if more than 4 breakthrough doses needed daily, increase baseline regimen 2
• Start opioid-naïve patients at lowest effective dose (equivalent to 20-30 MME/day) and exercise caution before escalating to ≥50 MME/day 9
• Assess risks of dependence, addiction, and abuse before initiating therapy, and avoid coprescribing benzodiazepines 9, 3
• Use metoclopramide or antidopaminergic drugs for opioid-related nausea/vomiting 2