Centeno, C., & Vara, F. (2005). Intermittent subcutaneous methadone administration in the management of cancer pain. Journal of Pain and Palliative Care Pharmacotherapy, 19(2), 7–12.

To study the dose, level of pain, and toxicity symptoms associated with intermittent subcutaneous methadone injections used to treat cancer pain

Over seven days, patients whose pain was well controlled with oral methadone received subcutaneous methadone via a butterfly needle that was used exclusively for methadone. The conversion ratio, oral methadone to subcutaneous methadone, was 1:1.

• The sample was composed of 10 patients.
• The age range of patients was 46–81 years.
• The sample consisted of two females and eight males.
• All patients had advanced cancer (the study comprised multiple diagnoses), were hospitalized in a palliative care unit, and had achieved pain control (a pain rating of less than 5 on a 0–10 scale) on stable methadone doses.

• Single site
• Inpatient
• Palliative care unit, Spain

• Numeric Rating Scale (NRS), 0–10, to measure the local discomfort of each injection
• Methadone dose used
• Toxicity symptoms

Two of 10 patients withdrew because of nonpainful irritation at the injection site. Compared to the methadone doses other patients were taking, these two patients took significantly higher doses: 40–45 mg, either every 8 hours or every 12 hours. All other patients’ doses were 5–25 mg, either every 8 hours or every 12 hours. Eight patients completed the study over seven days. Pain levels went from 3.3 to 3.5 on a  0–10 scale.

Intermittent subcutaneous methadone administration seems to be a useful alternative when oral administration is not feasible.

The study had a small sample size.

The conversion ratio, oral to subcutaneous methadone, was 1:1. This is not the currently recommended conversion ratio, though patients in the study experienced no increase in toxicity as the result of the 1:1 conversion. However, the duration of the study was only seven days; a longer duration may have resulted in toxicity effects. Higher doses caused local irritation. At even higher doses, clinicians may have to consider other strategies, such as adding dexamethasone to the infusion. If a patient is unable to take oral methadone, alternatives other than subcutaneous methadone—transdermal or buccal administration—are available.