Efficacy, Safety, and Feasibility of the Morphine Microdose Method in Community-Based Clinics

Abstract

Objectives: The goal of this study was to assess the success of the morphine microdose method in a community pain clinic setting by monitoring follow-up frequency, dose escalation, and monotherapy/polytherapy ratio. The morphine microdose method involves a pretrial reduction or elimination of systemic opioids followed by a period of abstinence. Intrathecal (IT) morphine is then started at doses of less than 0.2 mg per day. Systemic opioid abstinence is then continued after pump implant and IT morphine monotherapy.

Design: Retrospective review of medical records.

Setting: Private and academic pain clinic practices.

Subjects: Chronic noncancer pain patients.

Methods: We reviewed the charts of 60 patients who had completed a microdose regimen and had an IT pump implanted between June 11, 2008, and October 11, 2014. During IT therapy, dose change over time, pain scores, side effects, max dose, and duration were recorded.

Results: The majority of patients (35/60, 58%) were successfully managed solely on morphine microdose monotherapy. These patients did not require additional oral therapy. There was a significant reduction in mean pain scores, from 7.4 ± 0.32 before microdose therapy to 4.8 ± 0.3 after microdose therapy.

Conclusions: Microdose therapy achieved analgesia, improved safety, and avoided systemic side effects. The safety of IT therapy was increased by using a lower concentration (2 mg/mL) and lower daily doses (<3 mg/d) of morphine. Furthermore, microdose therapy was feasible, safe, and cost-effective in the outpatient setting.

Figures

Figure 1

Microdose patient groups. Among the 60 patients who completed the microdose studies, 35 patients completed morphine monotherapy. Polytherapy is defined as morphine plus another drug and was completed by 13 patients. Hydromorphine monotherapy is hydromorphone only and was completed by seven patients. Surgical complications that required removal of the pump occurred in two patients. Three patients were excluded due to a diagnosis of cancer or degenerative neurological disease after the implant.

Figure 2

Time course of morphine dose. Morphine doses at years 1, 2, 3, and 4 are shown. The year 0 doses were the initial infusion doses of morphine microdose therapy. The interquartile range box contained 50% of patients. The line transecting the box represents the median. The whiskers extending from the box represent the minimum and maximum values within 1.5 times the interquartile distance. The open circles represent outliers, which are outside the 1.5 quartile distance. The morphine doses at years 2, 3, and 4 were significantly higher than at year 0.

Figure 3

Pain scores. Box plot of pain scores show the scores at years 1, 2, 3, and 4. The pain score at year 0 was the average score before the microdose therapy was initiated. Pain scores at years 1, 2, 3, and 4 were significantly lower than the pain score at year 0.

Figure 4

Dose escalation. Dose escalation of three groups: non–statistically different from average (Average), statistically higher than average (High), and statistically lower than average (Low). The gray line represents the average group, the broken line represents the low group, and the solid line represents the high group.