What is the onset time of Endone (oxycodone) in a patient with normal renal and hepatic function?

Onset Time of Endone (Oxycodone)

Oral oxycodone (Endone) has an onset of action of approximately 10-30 minutes, with peak analgesic effect occurring at 1 hour after administration in patients with normal renal and hepatic function. 1, 2

Route-Specific Onset Times

Oral Administration (Standard Formulation)

• Immediate-release oral oxycodone begins producing clinical effects within 10-30 minutes of ingestion 1
• Peak plasma concentration and maximal analgesic effect occur at approximately 1 hour (60 minutes) after oral administration 2
• The duration of analgesic effect for immediate-release formulations is 3-6 hours 1

Controlled-Release Formulation

• Controlled-release oxycodone (OxyContin) has a slower onset, with effects commencing approximately 1 hour after administration 2
• Peak effect for controlled-release formulations occurs later but provides sustained analgesia for 10-12 hours 1, 2

Intravenous Administration

• When given intravenously, oxycodone demonstrates significantly faster onset, though this route is less commonly used in routine practice 3
• IV administration bypasses first-pass metabolism, resulting in more rapid onset compared to oral routes 3

Pharmacokinetic Considerations in Normal Function

• Oral bioavailability ranges from 60-87%, which is substantially higher than morphine 2
• Plasma half-life is 3-5 hours (approximately half that of morphine) 2
• Stable plasma levels are reached within 24 hours, much faster than morphine which requires 2-7 days 2
• Plasma protein binding is 45% 2

Clinical Comparison with Other Analgesics

• In comparative studies, oral oxycodone at 0.125 mg/kg provided similar pain relief to IV morphine 0.1 mg/kg at 30 minutes after administration, though IV morphine showed faster onset at 10 and 20 minutes 4
• The delayed onset of oral oxycodone compared to IV opioids is offset by easier administration and no requirement for IV access 4
• Oral oxycodone demonstrates onset of analgesia at 30 minutes that is comparable to naproxen in soft tissue injury pain control 5

Important Clinical Caveats

• The onset time represents when analgesic effects begin, not when peak analgesia is achieved - peak effect occurs at 1 hour 2
• Tablets must be swallowed whole and must not be broken, chewed, or crushed, as this can alter the pharmacokinetic profile and potentially cause rapid release of the entire dose 2
• There is no food interference with absorption 2
• Metabolism is more predictable than morphine, making titration easier and more reliable 2

Special Populations Requiring Dose Adjustment

Hepatic Impairment

• In patients with hepatic dysfunction, oxycodone demonstrates decreased intrinsic hepatic clearance due to reduced enzyme activity or intrahepatic shunting 1
• Oral oxycodone should be initiated at lower doses in patients with liver disease 1
• The bioavailability increases significantly in HCC patients (68%) compared to healthy individuals (17%) 1
• Recent guidelines suggest avoiding oxycodone in patients with end-stage liver disease 1

Renal Impairment

• Oxycodone is primarily eliminated in urine and should be carefully titrated with frequent monitoring in patients with renal impairment 1
• The half-life may be prolonged in renal insufficiency, though less dramatically than morphine 1

Elderly Patients

• No specific dose reduction is needed in the elderly for immediate-release formulations, though clinical monitoring remains essential 2
• However, elderly patients may experience prolonged duration of effect due to altered pharmacokinetics 1

Safety Monitoring During Onset Period

• Respiratory depression is the major adverse effect and can occur even at therapeutic doses, particularly when combined with benzodiazepines or other CNS depressants 1
• Common side effects during the onset period include nausea (most common), constipation, drowsiness, with less frequent vomiting, pruritus, and dizziness 2, 5
• Oxycodone causes somewhat less nausea, hallucinations, and pruritus compared to morphine 2
• The intensity of side effects tends to decrease over time with continued use 2