What are the differences between immediate‑release oxycodone and OxyContin (extended‑release oxycodone)?

Oxycodone vs OxyContin: Key Differences

Oxycodone and OxyContin are the same active drug (oxycodone hydrochloride), but differ fundamentally in their release mechanism: oxycodone refers to immediate-release formulations that work within 10–30 minutes and last 3–6 hours, while OxyContin is the brand name for extended-release oxycodone that takes approximately 1 hour to work and provides 10–12 hours of pain relief. 1

Release Mechanism and Pharmacokinetics

Immediate-Release (IR) Oxycodone:

• Onset of action occurs within 10–30 minutes after oral administration 1
• Duration of analgesia is 3–6 hours, requiring dosing every 4–6 hours 1, 2
• Plasma half-life is 3–5 hours 3
• Absorption follows a mono-exponential pattern with a lag time 4
• Brand names include Roxicodone (single-entity) and Percocet (combined with acetaminophen) 1

Extended-Release (ER) OxyContin:

• Onset of action is approximately 1 hour after administration 1
• Duration of analgesia is 10–12 hours, allowing twice-daily dosing 3, 4
• Absorption is bi-exponential: 38% absorbed rapidly (half-life 37 minutes) and 62% absorbed slowly (half-life 6.2 hours) 4
• Bioavailability is 102.7% relative to IR oxycodone solution, meaning they are essentially equivalent when total daily doses are matched 4
• Tablets must be swallowed whole and never broken, chewed, or crushed to maintain the controlled-release properties 2, 3

Clinical Indications: Critical Distinction

IR oxycodone is appropriate for:

• Acute pain management 5, 1
• Initial dose titration to determine analgesic requirements 5, 2
• Breakthrough pain in patients already on long-acting opioids 2
• Dosing is 5–15 mg every 4–6 hours as needed 5, 1

OxyContin (ER oxycodone) is appropriate for:

• Chronic pain requiring around-the-clock analgesia 5, 2
• Opioid-tolerant patients only 5
• Should NOT be used for acute pain according to emergency medicine guidelines 5, 1
• Should NOT be used as an "as-needed" analgesic 5

Prescribing Guidelines and Safety

The CDC recommends initiating opioid therapy with IR formulations rather than ER products for acute pain management. 1 This is a critical safety principle because:

• ER formulations like OxyContin are for opioid-tolerant patients only and carry higher overdose risk in opioid-naïve individuals 5
• Emergency medicine guidelines explicitly state that long-acting opioids should not be prescribed for new-onset acute pain 5
• Prescriptions must clearly state the release mechanism (IR vs. ER) and exact dose to prevent medication errors 1

Titration and Conversion

When converting from IR to ER oxycodone:

• Calculate the total daily dose of IR oxycodone the patient is taking 2
• Convert to an equivalent total daily dose of ER oxycodone divided into two doses (every 12 hours) 2, 3
• Close observation for excessive sedation and respiratory depression is mandatory during conversion 2
• The relative bioavailability between formulations requires careful monitoring despite theoretical equivalence 2

Titration principles:

• IR oxycodone allows faster titration because dose adjustments can be made every 4–6 hours 6
• Studies show no difference in the percentage of patients achieving stable pain control between IR and ER formulations (85–91% success rate), but IR may offer more flexibility during initial titration 6
• For chronic pain, around-the-clock dosing with ER formulations maintains therapeutic plasma levels and minimizes end-of-dose failures 5

Common Pitfalls to Avoid

• Never prescribe OxyContin for acute pain in opioid-naïve patients—this is a major safety error 5, 1
• Never crush, break, or chew ER tablets—this destroys the controlled-release mechanism and can cause fatal overdose 2, 3
• Do not assume IR and ER are interchangeable without dose adjustment—conversion requires calculation and monitoring 2
• Avoid confusing brand names: Roxicodone is IR, OxyContin is ER, and Percocet is IR oxycodone combined with acetaminophen 1
• When prescribing for discharge from the emergency department, use IR formulations for the lowest practical dose and limited duration (e.g., 1 week) 5

Both Formulations Share Common Features

• Both are Schedule II controlled substances under federal law 5, 1
• Oral bioavailability ranges from 60–87% for both formulations 3
• Plasma protein binding is 45% 3
• Hepatic metabolism via cytochrome P450 produces oxymorphone (potent analgesic) and noroxycodone (weak analgesic) 3, 7
• Side effects are identical: constipation (requiring prophylactic stool softeners), nausea, vomiting, drowsiness, dizziness, and pruritus 5, 3, 6
• Equianalgesic ratio to morphine is approximately 1:1.5–2 (oxycodone is more potent) 3