What is the oral (PO) morphine equivalent for a patient requiring intravenous (IV) morphine 6 milligrams every 4 hours and oral oxycodone (oxycodone) immediate release (IR) 15 milligrams?

From the Guidelines

To convert the patient's morphine regimen to oral (PO) form, I recommend changing the morphine 6 mg IV/SC q4h to oral morphine 18-20 mg q4h, considering the standard 1:3 to 1:3.3 parenteral-to-oral morphine ratio. This conversion uses the standard parenteral-to-oral morphine ratio, as oral morphine has approximately 30-33% bioavailability compared to parenteral routes 1. The patient should continue taking the oxycodone IR 15 mg as prescribed since it's already in oral form.

When making this conversion, it's essential to monitor the patient closely for adequate pain control and side effects for 24-48 hours after the switch. Dose adjustments may be necessary based on the patient's response. The conversion maintains analgesic equivalence while transitioning to the oral route, which is generally preferred for long-term pain management due to convenience, cost-effectiveness, and patient comfort. Some key points to consider when converting opioids include:

• Using the morphine milligram equivalent (MME) doses for commonly prescribed opioids, as outlined in the CDC clinical practice guideline for prescribing opioids for pain - United States, 2022 1
• Being cautious with methadone dose conversions due to its long and variable half-life
• Avoiding the use of calculated MME doses to determine new opioid doses when converting, as this can lead to overdose due to incomplete cross-tolerance and individual variability in opioid pharmacokinetics
• Considering the patient's individual needs and response to the medication when making dose adjustments.

If the patient experiences breakthrough pain, the oxycodone IR can be used as needed, or the oral morphine dose may need adjustment. It's crucial to prioritize the patient's safety and adjust the medication regimen accordingly to minimize the risk of overdose or other adverse effects.

From the FDA Drug Label

For conversion from parenteral morphine to morphine sulfate tablets, anywhere from 3 to 6 mg of oral morphine sulfate may be required to provide pain relief equivalent to 1 mg of parenteral morphine The patient is currently requiring morphine 6 mg q4h, which is a parenteral dose. To convert this to an oral dose, we can use the conversion ratio provided in the drug label.

• Since 1 mg of parenteral morphine is equivalent to 3-6 mg of oral morphine,
• 6 mg of parenteral morphine would be equivalent to 18-36 mg of oral morphine. Given that the patient is also taking oxycodone IR 15 mg, we need to consider the total opioid dose when converting to oral morphine. However, the label does not provide a direct conversion from oxycodone to morphine, so we cannot determine the exact oral morphine dose that is equivalent to the patient's current regimen. 2

From the Research

Morphine to Oral Medication Conversion

To convert a patient's morphine medication to an oral form, we need to consider the patient's current dosage and the equivalent oral dosage. The patient is currently taking morphine 6 mg q4h and oxycodone IR 15 mg.

Current Dosage and Equivalent Oral Dosage

• The patient's current morphine dosage is 6 mg q4h, which is equivalent to 36 mg per day (6 mg x 6 doses per day).
• According to the studies, the analgesic effect of morphine and oxycodone is estimated to be equal 3.
• However, the relative potency of oxycodone is variably higher, which increases the risk of over- and underdosing 3.

Conversion to Oral Morphine

• A study comparing the efficacy of morphine sulfate immediate release vs. oxycodone/acetaminophen for acute pain in the emergency department found that morphine sulfate immediate release provides similar analgesic efficacy to oxycodone 4.
• Another study found that 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 3.
• Based on these studies, we can estimate the equivalent oral dosage of morphine. However, the exact conversion ratio is not provided in the studies.

Limitations

• There is no direct evidence in the provided studies to support a specific conversion ratio from IV morphine to oral morphine or oxycodone.
• The studies provided are focused on comparing the efficacy of different opioids, rather than providing conversion ratios.
• Therefore, the conversion of the patient's morphine medication to an oral form should be done with caution and under the guidance of a healthcare professional.