Conversion calculations between opioids - oxycodone

Overview

Oxycodone - a semisynthetic strong opioid, commonly used as a first-line or alternative strong opioid to morphine, with a similar overall profile but some practical dosing and tolerability differences
Widely prescribed, often preferred over morphine in some settings for its slightly more favourable side-effect profile (less nausea/hallucination in some patients) and availability in combination and various formulation options

Hepatically metabolised (partly via CYP2D6/CYP3A4) to noroxycodone and oxymorphone (a minor but active metabolite) - genetic variation in CYP2D6 metaboliser status can affect individual response, though this is rarely tested for clinically in routine practice

Available in immediate-release and modified-release oral formulations, and parenteral (SC/IV) forms; combination products (e.g. with naloxone, to reduce constipation) are also available in some formulations

Oral morphine to oral oxycodone: approximately 1.5-2:1 (oxycodone is roughly 1.5-2x more potent than morphine on a mg-for-mg oral basis) - conversion ratios vary slightly between reference sources and should be checked against the specific local guideline/tool used
As with all opioid conversions, reduce the calculated equivalent dose by ~25-50% when switching between opioids (incomplete cross-tolerance) and titrate to effect, rather than converting at the full calculated equivalent dose

Renal impairment (some dose caution needed, though generally better tolerated than morphine in mild-moderate impairment), opioid-induced constipation, combination products with naloxone (reduces constipation via local gut action without reversing systemic analgesia at standard doses)

Oxycodone potency relative to morphine is a frequently tested numeric fact given its clinical importance for safe conversion - always cross-check the specific ratio against the current local reference (e.g. Therapeutic Guidelines: Palliative Care) rather than relying on memory alone for an actual clinical conversion

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