Opioid rotation from methadone to fentanyl in a patient with metastatic nasopharyngeal carcinoma: a case report

doi:10.15406/jcpcr.2025.16.00577

Journal of

eISSN: 2373-633X

Cancer Prevention & Current Research

Case Report Volume 16 Issue 2

Opioid rotation from methadone to fentanyl in a patient with metastatic nasopharyngeal carcinoma: a case report

Sami Ayed Alshammary,²

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Abdulaziz Samir Hazzazi,¹ Luma fraihat,³ Muner Alshehri⁴

¹Palliative care fellow, Palliative Care Department, King Abdullah Medical City, Saudi Arabia
²MD Palliative care unit in CCC, King Fahad Medical City, Saudi Arabia
³Department of Palliative Care, Comprehensive Cancer Center, King Fahad Medical City, Saudi Arabia
⁴MD Palliative medicine consultant, King Fahad Medical City, Saudi Arabia

Correspondence: Sami Ayed Alshammary, Department of Palliative Care, Comprehensive Cancer Center, King Fahad Medical City, Riyadh and Centre for Postgraduate Studies in Family Medicine, Ministry of Health, Riyadh, Saudi Arabia

Received: May 18, 2025 | Published: June 3, 2025

Citation: Hazzazi AS, Alshammary SA, fraihat L, et al. Opioid rotation from methadone to fentanyl in a patient with metastatic nasopharyngeal carcinoma: a case report. J Cancer Prev Curr Res. 2025;16(2):53‒54 DOI: 10.15406/jcpcr.2025.16.00577

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Abstract

Background: Methadone is a synthetic opioid that is useful in treating complex pain syndromes. However, its potential to prolong the QTc interval may lead to a serious cardiac risk, requiring careful monitoring and individualized care. Switching from methadone to another opioid has not been well studied and could prove difficult because it does not have a recognized dose conversion ratio.

Case: A 17-year-old male with metastatic nasopharyngeal carcinoma had worsening QTc prolongation while on methadone. So, a decision was made to stop methadone and rotate him to morphine. A conservative rotation ratio of 1:3 (methadone: morphine) was used, with a 20% further dose reduction to account for incomplete cross-tolerance. Upon follow-up, the dose of morphine was tapered up to 150 mg MEDD. He was then switched to fentanyl due to tolerance. His pain was eventually controlled on a fentanyl dose of 150 mcg /hr.

Conclusion: Opioid rotation from methadone can be performed safely with close monitoring. Further tapering up of the new opioid dose is expected to reach optimum pain control. Although we used a 1:3 (methadone: morphine) conversion ratio as a start, the dose that controlled the pain was almost 12 times more than the initially calculated dose.

Case presentation

A 17-year-old male with a history of metastatic nonkeratinizing squamous cell nasopharyngeal carcinoma to the liver, lungs, spine, and bones, post two lines of chemoimmunotherapy and radiotherapy, was admitted for evaluation and management of uncontrolled pain.

Before admission to our hospital, he was hospitalized in another hospital, where he was started on oral morphine and titrated up to 60 mg as a total daily dose. Despite this adjustment, his pain remained poorly controlled. Consequently, the patient was transitioned to oral methadone at a dose of 5 mg twice daily, increased later to 5 mg in the morning and 7.5 mg at night. The rationale behind the transition to methadone in particular was not mentioned. The latter dose resulted in notably improved analgesia. He was also on gabapentin 300 mg daily as an adjuvant.

Despite initial pain relief, the patient was admitted to our facility after one month, with worsening pain, he described his pain as a mixture of nociceptive somatic type mainly in the back at the site of metastatic disease, in addition to neuropathic type in lower limbs, aggravated by movement, wasn’t relieved by the medications it was severe in intensity rated 8/10 on numerical pain scale.

Whole spine MRI showed: C5, L3, and right sacral bone lesions without spinal canal stenosis or compression.ECG showed a prolonged QTc interval of 483 ms. In light of this finding, we planned to taper methadone and introduce morphine gradually. Unfortunately, his QTc increased the following day to 490 ms. Given the increasing cardiac risk, we discontinued methadone abruptly and initiated opioid rotation to morphine.

We calculated the morphine dose using the conversion ratio of methadone-to-morphine 1:3, followed by a 20% dose reduction to account for incomplete cross-tolerance. So, we initiated morphine syrup 5mg every four hours regularly and 3mg every hour as needed.

Morphine was tapered up further in the following days until a dose of 144 mg as a total daily dose was reached, without adequate control.

The patient was then rotated to fentanyl infusion at a rate of 60 mcg/hr and doluxetine was started in addition to gabapentin he was on, both used as an adjuvant, fentanyl dose was not enough to control his severe pain, and it was increased until a dose of 150 mcg/hr infusion, he felt better and the pain score declined with a maximum severity of 5/10 and a minimum of 2/10. Breakthrough fentanyl was required 3- 4 times daily on average. No adverse effects were reported aside from mild, tolerable dizziness. He expressed satisfaction with his pain management after the transition.

Discussion

Methadone continues to serve as a valuable option for relieving refractory cancer-related pain,¹ particularly in the presence of neuropathic pain. However, its use is associated with a risk of QTc interval prolongation and unpredictable pharmacokinetics.²

In our reported case, the patient had advanced disease, and he was still receiving palliative chemotherapy, so his ECG was monitored, and QTc prolongation was observed, which prompted a switch to other opioids to prevent potential cardiac complications. We used a 1:3 methadone to morphine conversion ratio, which is slightly more conservative than the 1:4.7 ratio described by Walker et al.³ in addition to a 20% dose reduction to account for incomplete cross-tolerance and avoid opioid toxicity.

The patient wasn’t controlled on our starting conversion ratio, and we needed to increase the opioids up to 12 times the initial calculated morphine dose, which was given as fentanyl at the end, to achieve fair control of the pain.

Literature on rotation from methadone is limited, with some of it highlighting potential risks. For instance, Moryl et al.⁴ in a prospective study, found that the majority of patients (12 out of 13) who switched from methadone to other opioids had worse pain control despite dose escalation, often requiring them to switch back to methadone with only one patient remained successfully on the new opioid. Another case study concluded that switching from methadone to non-NMDA-active opioids can worsen pain and increase opioid requirements. In this case, the patient was switched from methadone to morphine because of somnolence and dysphoria, which resulted in worse pain and increased opioid requirements. Eventually, the patient was switched back to methadone.⁵

We initially thought that our patient wasn't responding well to the switch we did, but he improved after increasing fentanyl infusion to the doses mentioned above. This emphasizes the challenge of achieving comparable analgesia, as well as methadone’s unique efficacy in specific clinical scenarios.

On the other hand, Bhimji⁶ described a successful transition using a 1:5 ratio and a 75% dose reduction due to renal failure and high dose dependency, illuminating yet more why patient-specific planning is essential, particularly when renal impairment or high opioid tolerance is involved.

Taken together, these studies highlight the need for a tailored risk-reduction plan when switching from methadone to another opioid. In our case, conservative dosing conversion, accompanied by close inpatient monitoring and timely dose increases, allowed for a smooth transition without significant complications, demonstrating that this strategy is an effective method for discontinuing methadone safely when QTc prolongation is evident.

Conclusion

This case points out a safe and effective opioid rotation method from methadone to other opioids in a scenario of worsening QTc prolongation while using methadone. Conservative conversion and cross-tolerance reduction enabled safe and efficient pain control. Increasing the dose of opioids with time is expected. Further studies are required to guide clinical judgment regarding opioid rotation from methadone to other opioids, particularly in the context of conversion ratio variability (Appendix A).