From the Guidelines
Morphine does not typically prolong the QT interval on an electrocardiogram (ECG) at standard therapeutic doses. Unlike some other opioids such as methadone which are known to cause QT prolongation, morphine is generally considered safe in this regard and is not associated with significant QT interval changes at standard therapeutic doses 1. This makes morphine a preferred opioid option for patients who have risk factors for QT prolongation or who have a history of cardiac arrhythmias. The lack of QT prolongation with morphine is related to its pharmacological properties and how it interacts with cardiac ion channels.
Some key points to consider when using morphine include:
- Morphine is available in a wide range of formulations and routes, including oral, parenteral, and rectal delivery 1.
- Morphine-6-glucoronide, an active metabolite of morphine, contributes to analgesia and may worsen adverse effects as it accumulates in patients with renal insufficiency 1.
- While all medications should be used cautiously in patients with cardiac conditions, morphine does not require specific ECG monitoring for QT changes when used at standard doses.
- However, in cases of significant overdose or when used in combination with other QT-prolonging medications, monitoring may still be warranted as part of overall patient care.
It's worth noting that other opioids, such as methadone, have been associated with QT prolongation, particularly at high doses 1. Therefore, morphine may be a safer option for patients who are at risk of QT prolongation or who have a history of cardiac arrhythmias. Overall, morphine is a safe and effective option for managing pain in patients with cancer, and its lack of association with QT prolongation makes it a preferred choice for patients with cardiac risk factors.
From the Research
Morphine and QT Interval Prolongation
- Morphine is not associated with QT interval prolongation, as shown in a study published in the British Journal of Clinical Pharmacology in 2009 2.
- This study found that neither morphine nor tramadol doses were associated with the QT interval length.
- Another study published in Pain in 2003 compared the effects of intravenous methadone and morphine on QTc intervals, and found that morphine did not significantly affect QTc intervals, with a mean difference of 9.0 (+/- 6.1)ms, p=0.15 3.
- A case report published in the Journal of Addiction Medicine in 2020 mentioned a patient who was switched from methadone to oral hydromorphone after developing a prolonged QTc interval, and also attempted a trial of slow-release oral morphine, but this was discontinued due to myoclonus, not QT interval prolongation 4.
- There is no evidence to suggest that morphine prolongs the QT interval, and it may be considered a safer alternative to other opioids in terms of QT interval prolongation.
Comparison to Other Opioids
- Methadone has been consistently shown to be associated with QT interval prolongation, with a significant increase in QTc intervals observed in patients taking methadone 5, 3.
- Oxycodone has also been shown to be associated with QT interval prolongation, with a dose-dependent increase in QTc intervals observed in patients taking oxycodone 2.
- Buprenorphine has not been shown to prolong the QT interval, with no significant difference in QTc intervals observed in patients taking buprenorphine compared to controls 5.