Pain Management

Cancer Pain Management

A Strategy for Conversion From Subcutaneous to Oral Ketamine in Cancer Pain Patients: Effect of a 1:1 Ratio

Benítez-Rosario MA, Salinas-Martín A, González-Guillermo T, et al (Univ Hosp La Candelaria, Tenerife, Spain; et al) J Pain Symptom Manage 41:1098-1105, 2011^§

Abstract

Context

No consensus exists about the most appropriate dose ratio for conversion from parenteral to oral ketamine.

Objectives

To confirm that a 1:1 dose ratio is suitable for converting subcutaneous (s.c.) to oral ketamine in cancer patients.

Methods

Patients with opioid poorly responsive cancer pain, who responded to 0.4, 0.6, or 0.8 mg s.c. ketamine bolus, were treated with 0.1, 0.15, or 0.2 mg/kg/h ketamine infusion, respectively. Switching to the oral route, by applying a 1:1 dose ratio, was carried out in patients who experienced adequate pain relief and continued to need ketamine as a coanalgesic. Pain, somnolence, feelings of insobriety, confusion, and cardiovascular parameters were assessed throughout the process.

Results

Twenty-nine patients were enrolled in the study. Ketamine infusion decreased pain intensity from severe to no pain or slight pain in 23 of 29 and six of 29 patients, respectively. The median of s.c. ketamine doses was 0.2 mg/kg/h (range 0.1–0.5). After oral switching, 27 of 29 patients remained as successfully controlled as when receiving s.c. ketamine. The other two patients needed a slight dose ratio readjustment, to 1:1.3 and 1:1.5, to maintain pain control. The median of oral ketamine doses was 300 mg/day (interquartile range 240–382.5). Seven of 29 patients receiving s.c. ketamine developed moderate and transitory side effects, such as feelings of insobriety and somnolence. No side effects were present while receiving oral ketamine. No significant changes were observed in cardiovascular parameters.

Conclusion

A 1:1 dose ratio for conversion from s.c. to oral ketamine is safe and effective in cancer pain patients (Fig 1, Tables 2 and 4).

Figure 1 Pain intensity during the conversion from parenteral to oral ketamine. Slight: 1–3/10; moderate: 4–6/10; severe: ≥7/10. The medians and ranges of pain intensity (expressed on a numerical rating scale) and significance levels are in the bottom box. Statistical difference vs. a) “before starting ketamine” and b) “the end of s.c. ketamine” (Friedman-Dunn multiple comparisons test) (n = 29 patients). (Reprinted from Benítez-Rosario MA, Salinas-Martín A, González-Guillermo T, et al. A strategy for conversion from subcutaneous to oral ketamine in cancer pain patients: effect of a 1:1 ratio. J Pain Symptom Manage. 2011;41:1098-1105, Copyright 2011, with permission from U.S. Cancer Pain Relief Committee.)

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