From the Guidelines
A 15 mg oxycodone tablet is approximately equivalent to 22.5-30 mg of oral morphine, considering the relative effectiveness of oxycodone compared to oral morphine is between 1.5-2. This is based on the standard opioid conversion ratio provided in the study by 1, which compares the relative effectiveness of selected opioids for moderate to severe pain. According to the study, oxycodone has a relative effectiveness of 1.5-2 compared to oral morphine.
When considering opioid conversions, it's essential to keep in mind that individual responses to these medications can vary significantly, and conversions are not exact. Patients may experience different levels of pain relief or side effects when switching between opioids, even at equivalent doses. Any conversion between opioid medications should only be done under medical supervision, as improper conversion can lead to either inadequate pain control or dangerous overdose.
Key points to consider when converting between opioids include:
- The relative effectiveness of the opioids being compared
- The route of administration (e.g., oral, intravenous)
- The individual patient's response to the medication
- The potential for tolerance and dose escalation
- The need for medical supervision to ensure safe and effective conversion.
As noted in the study by 1, switching to another opioid should be done cautiously with a dose reduction of the newly prescribed opioid, due to the variability in relative effectiveness among individual patients.
From the Research
Morphine Equivalent of Oxycodone
To determine the morphine equivalent of 15 mg of oxycodone, we need to consider the conversion ratio between oxycodone and morphine.
- According to the study 2, the equivalence with regard to morphine is 1:2 for oxycodone in terms of analgesic effect, but the ratio of 1/1.5-2 is mentioned for the treatment of cancer pain.
- However, the study 3 provides a conversion factor of 1.2 to convert IV PCA morphine to CR oxycodone.
Calculation of Morphine Equivalent
Using the conversion ratio of 1:2 for oxycodone to morphine from study 2, we can calculate the morphine equivalent as follows:
- 15 mg of oxycodone is equivalent to 15 x 2 = 30 mg of morphine. Alternatively, using the conversion factor of 1.2 from study 3, the calculation would be:
- 15 mg of oxycodone is equivalent to 15 x (1/1.2) = 12.5 mg of morphine, but this conversion factor is for IV PCA morphine to CR oxycodone, which may not be directly applicable to oral oxycodone.
Variability in Conversion Ratios
It's essential to note that the conversion ratios between oxycodone and morphine can vary depending on the specific context, such as the type of pain being treated and the individual patient's response to the medication, as mentioned in study 4.
- The relative potency of oxycodone can be variably higher, which increases the risk of over- and underdosing.
- The time to onset of analgesia following intravenous or oral administration of oxycodone is shorter than that of morphine, which may lead to a higher risk of addictive behavior.
Clinical Implications
When converting between oxycodone and morphine, it's crucial to consider the individual patient's needs and response to the medication, as well as the potential risks and side effects associated with each medication, as discussed in study 5.
- Renal impairment and the risk of toxicity caused by accumulation of opioids and/or active metabolites should be taken into account when treating patients with cancer pain.