Inconsistencies in opioid equianalgesic ratios: clinical and research implications

Conversion ratios: Why is it so challenging to construct opioid conversion tables?

Standardizing opioid management is challenging due to the absence of a ceiling dose, the unknown ideal therapeutic plasma level, and the lack of an clear relationship between dose and therapeutic response. Opioid rotation or conversion, which is switching from one opioid, route of administration, or both, to another, to improve therapeutic response and reduce toxicities, occurs in 20-40 percent of patients treated with opioids. Opioid conversion is often needed when there are adverse effects, toxicities, or inability to tolerate a certain opioid formulation. A majority of patients benefit from opioid conversion, leading to improved analgesia and less adverse effects. There are different published ways of converting opioids in the literature. This review of 20 years of literature is centered on opioid conversions and aims to discuss the complexity of converting opioids. We discuss study designs, outcomes and measures, pain phenotypes, patient characteristics, comparisons of equivalent doses between opioids, reconciling conversion ratios between opioids, routes, directional differences, half-lives and metabolites, interindividual variability, and comparison to package insert information. Palliative care specialists have not yet come to a consensus on the ideal opioid equianalgesic table; however, we discuss a recently updated table, based on retrospective evidence, that may serve as a gold standard for practical use in the palliative care population. More robust, well-designed studies are needed to validate and guide future opioid conversion data.

The Effect of Intraoperative Fentanyl Consumption on Prognosis of Colorectal Liver Metastasis treated by Simultaneous Resection: A Propensity Score Matching Analysis

Background: No previous studies have reported the effect of intraoperative opioid consumption in colorectal liver metastasis (CRLM).

Methods: Medical records of patients who received simultaneous resection of CRLM were retrospectively reviewed. Patients with epidural anesthesia, intraoperative morphine, or intraoperative oxycodone were excluded. Patients were separated into high- and low-dose groups by median intraoperative equianalgesic fentanyl dose. Short-term outcomes, progression-free surcical (PFS) and overall survival (OS) were compared between groups before and after 1:1 propensity score matching (PSM). Univariable and multivariable Cox regression analysis were performed to identify independent predictors of survival.

Results: The final study population included 343 patients. Patients were separated into the low dose group (n=172) and the high dose group (n=171) by median intraoperative equianalgesic fentanyl dose (8.33 μg/kg). After PSM, 55 patients in the low dose group were matched to 55 patients in the high dose group and the baseline characteristics of the two groups were balanced. The two groups had no statistically significance difference in severity and categories of postoperative complications before and after PSM. Before PSM, the two groups had similar PFS (median 10.2 vs. 12.4 months, P=0.54) and OS (median 59.0 vs. 58.3 months, P=0.76). Univariate and multivariate Cox regression analyses revealed no statistically significant association between intraoperative equianalgesic fentanyl and PFS (multivariate HR=0.852, 95% CI 0.655-1.11, P=0.235) and OS (multivariate HR=1, 95% CI 0.68-1.49, P = 0.981). After PSM, the two groups also had similar PFS (median 9.2 vs. 10.7 months, P=0.98) and OS (median 51.0 vs. 46.0 months, P=0.39). Univariate and multivariate Cox regression analyses revealed no statistically significant association between intraoperative equianalgesic fentanyl and PFS (multivariate HR=1.05, 95% CI 0.632-1.73, P=0.861) and OS (multivariate HR=1.74, 95% CI 0.892-3.38, P = 0.105).

Conclusion: Intraoperative opioids consumption was not correlated with outcomes of CRLM patients treated with simultaneous resection.

High-dose opioid utilization and mortality among individuals initiating hemodialysis

BACKGROUND

Individuals undergoing hemodialysis in the United States frequently report pain and receive three-fold more opioid prescriptions than the general population. While opioid use is appropriate for select patients, high-dose utilization may contribute to an increased risk of death due to possible accumulation of opioid metabolites.

METHODS

We studied high-dose opioid utilization (≥120 morphine milligram equivalents [MME] per day) among adults initiating hemodialysis in the United States between 2007 and 2014 using national registry data. We calculated the cumulative incidence (%) of high-dose utilization and depicted trends in the average percentage of days individuals were exposed to opioids. We used adjusted Cox proportional hazards models to identify which opioid doses were associated with mortality.

RESULTS

Among 327,344 adults undergoing hemodialysis, the cumulative incidence of high-dose utilization was 14.9% at 2 years after initiating hemodialysis. Among patients with ≥1 opioid prescription during follow-up, the average percentage of days exposed to high-dose utilization increased from 13.9% in 2007 to 26.1% in 2014. Compared to 0MME per day, doses < 60MME were not associated with an increased risk of mortality, but high-dose utilization was associated with a 1.63-fold (95% CI, 1.57, 1.69) increased risk of mortality. The risk of mortality associated with opioid dose was highest in the first year after hemodialysis initiation.

CONCLUSIONS

The risk of mortality associated with opioid utilization among individuals on hemodialysis increases as doses exceed 60MME per day and is greatest during periods of high-dose utilization. Patients and clinicians should carefully weigh the risks and benefits of opioid doses exceeding 60MME per day.

Opioid rotation from transdermal fentanyl to continuous subcutaneous hydromorphone in a cachectic patient: A case report and review of the literature

Opioid rotation from transdermal fentanyl to an alternate opioid is often necessitated in advanced disease, but is fraught with uncertainty due to variable absorption from the patch in end-stage illness and the lack of a clearly established opioid rotation ratio. The manufacturer of transdermal fentanyl provides opioid rotation recommendations only for rotation from the oral morphine equivalent daily dose (MEDD) of opioid to the patch, not in the opposite direction. This is a case report of a single patient with cancer and cachexia admitted to the palliative care unit of a large academic medical centre in Canada. The patient is a 50-year-old female with widely metastatic breast cancer who developed opioid toxicity when maintenance transdermal fentanyl patch therapy (100 μg patch applied every 72 h) was rotated to subcutaneous hydromorphone infusion to improve pain control. Hydromorphone was initiated at a rate of 1 mg/h by continuous infusion based on an opioid rotation ratio for transdermal fentanyl (μg/h):MEDD (mg/day) of 1:2.4. Opioid toxicity eventually resolved with downward titration of hydromorphone to only 30% of the initially estimated equianalgesic dose. This case highlights the need for close follow-up of all patients undergoing opioid rotation from transdermal fentanyl and reinforces the need to reduce the initial dose of the new opioid by 30%-50% of the calculated MEDD, especially when rotating from a high dose of transdermal fentanyl, or if there are factors potentially impairing absorption from the patch such as age, cachexia and weight loss, or if rotation is performed for reasons other than uncontrolled pain.

Association of Opioid Use in the Week Before Death Among Patients With Advanced Lung Cancer Having Sepsis

Opioid use can induce immunosuppression; however, it is unclear whether opioid use increases infections in patients with advanced cancers. This study assessed the association between opioid use in the week before death and mortality among patients with advanced lung cancer having sepsis. Data on opioid usage in the week before death, general information, and clinical information of the patients were collected retrospectively. The primary outcome was the association between opioid use in the week before death and mortality after sepsis. The study included 980 patients who died of advanced lung cancer between January 2003 and June 2017 (sepsis related: 413, unrelated to sepsis: 567). The average morphine equivalent daily dose in the final week was higher in the sepsis group (313.5 ± 510.5 mg) than in the nonsepsis group (125.2 ± 246.9 mg, P < .001). A significant association was found between the average morphine equivalent daily dose in the final week and mortality due to sepsis (odds ratio: 1.02, 95% confidence interval: 1.01-1.02, P < .001). This was especially evident when the dose was increased by 10 mg in the final week. Furthermore, older age, male sex, and a lower body mass index were associated with an increased risk of mortality after developing sepsis. Opioid use in the week before death may be associated with mortality for patients with advanced lung cancer having sepsis.

Association between perioperative statin use and postoperative pain after total knee arthroplasty

BACKGROUND AND OBJECTIVES

Data is insufficient to determine whether perioperative statin use increases or decreases postoperative pain. This study aimed to investigate the association between perioperative statin use and pain outcomes after total knee arthroplasty performed under spinal anesthesia.

METHODS

This is a retrospective, observational study based on medical records from a tertiary hospital between January 2005 and October 2017. Medical records of patients who underwent elective total knee arthroplasty under spinal anesthesia as inpatients were analyzed. Pain outcomes were compared through postoperative day (POD) 3 in patients who were taking statins perioperatively versus patients who were not taking statins.

RESULTS

A total of 1088 propensity-matched participants were included in the final analysis (544 patients in the statin group and 544 patients in the non-statin group). The total morphine equivalent consumption through POD 3 was higher in the statin group than in the non-statin group (mean (SD), statin group: 525.4 (119.7) vs non-statin group: 495.3 (115.3), 95% CI of the difference: 15.9 to 44.4, p<0.001). In the linear regression analysis, the total morphine equivalent consumption through POD 3 was 30.14 mg higher in the statin group compared with the non-statin group (95% CI 15.93 to 44.35; p<0.001).

CONCLUSIONS

Perioperative statin use is associated with a significant increase in postoperative opioid consumption after total knee arthroplasty performed under spinal anesthesia; however, this increase was so marginal that its clinical importance remains controversial.

Association Between Opioid Use and Survival Time in Patients With Unresectable Pancreatic Cancer: 10 Years of Clinical Experience

OBJECTIVES

Patients with pancreatic cancer generally experience increasing pain as their disease progresses, making the titration of opioids difficult. This study aimed to determine a correlation between prescribed opioid doses and survival time in patients with unresectable pancreatic cancer.

METHODS

This retrospective observational cohort study in a tertiary care institution reviewed the medical records of patients diagnosed with unresectable pancreatic cancer and treated over a 10-year period.

RESULTS

We screened 1152 patients with unresectable pancreatic cancer, and 566 were eligible for inclusion in this study. There was a statistically significant negative correlation between initial opioid dose and survival time from initial opioid dose (correlation coefficient, -0.184; P < 0.01) and survival time from initial pancreatic cancer diagnosis (correlation coefficient, -0.177; P < 0.01). In addition, there were 0.8% and 0.6% increases in initial opioid dosage (morphine equivalent daily dose) and rate of increasing opioid dose (morphine equivalent daily dose per month), respectively, associated with the risk of early death (≤180 days, P < 0.05).

CONCLUSIONS

Correlations between patient survival, initial opioid dose, final opioid dose, and the rate of increase of opioid dosage could provide useful information for clinicians treating unresectable pancreatic cancer patients.

Relationship between pain outcomes and smoking history following video-assisted thoracic surgery for lobectomy: a retrospective study

Purpose

The relationship between chronic smoking history and postoperative pain remains controversial. This study aimed to elucidate this relationship in non-small cell lung cancer (NSCLC) patients who underwent video-assisted thoracic surgery (VATS) lobectomy.

Patients and methods

This retrospective observational study included NSCLC patients treated with VATS lobectomy between January 2011 and July 2017. Demographic and clinical information, including preoperative smoking history, was collected. The primary goal was to investigate the relationship between smoking history and postoperative pain outcomes (oral morphine equivalent [OME] consumption and pain score). Multivariate linear regression analysis was performed, and P<0.05 was considered as statistically significant.

Results

A total of 1,785 patients were included in the final analysis. Multivariate linear regression analysis revealed that total smoking amount (in packs), status as current smoker, and cessation time did not have an association with OME consumption (mg) or pain scores on postoperative days 0–2 (P>0.05). However, patients who had never smoked consumed less morphine equivalent analgesics (mg) on postoperative days 0–2 (coefficient: −17.48, 95% CI [−33.83, −1.13], P=0.036) compared to patients who had a history of smoking.

Conclusion

Patients who had never smoked had lower opioid analgesics consumption on the days immediately following surgery, while being a current smoker or the total amount of smoking in packs did not affect postoperative pain outcomes after VATS lung lobectomy.

Long-Term Oncologic Outcomes, Opioid Use, and Complications after Esophageal Cancer Surgery

Effective and adequate opioid use and prevention of postoperative complications are important for enhanced recovery after surgery. We examined the effects of postoperative opioid use and postoperative complications on overall survival and recurrence-free survival after esophageal cancer surgery. This retrospective cohort study analyzed the records of patients diagnosed with esophageal cancer who underwent the Ivor Lewis operation between January 2005 and December 2011. We collected data on total opioid use for 8 days postoperatively, as well as information on postoperative complications (Clavien-Dindo classification). One hundred and twenty-one patients were included in the final analysis. Total opioid use was not significantly associated with overall survival (p = 0.520) and recurrence-free survival (p = 0.818). In contrast, the hazard ratio of postoperative overall survival was significantly higher with respect to Clavien-Dindo classification 1-2 (hazard ratio: 2.009, p = 0.046), 3a-3b (hazard ratio: 5.759, p < 0.001), and 4a-5 (hazard ratio: 3.982, p = 0.020) complications compared to no complications. Additionally, the hazard ratio of the recurrence-free survival was significantly higher in class 1-2 complications (hazard ratio: 2.336, p = 0.028) compared to none. Our study demonstrates that postoperative opioid use is not associated with survival and recurrence-free survival after esophageal cancer surgery, while postoperative complications may increase the hazard ratio for survival and recurrence-free survival.

Association of high-dose postoperative opioids with recurrence risk in esophageal squamous cell carcinoma: reinterpreting ERAS protocols for long-term oncologic surgery outcomes

Esophageal squamous cell carcinoma (ESCC) is associated with a poor prognosis and high postoperative recurrence rate. Although postoperative opioid use has been associated with cancer recurrence, its relevance in ESCC has not been determined. Therefore, this study investigated whether high-dose postoperative opioid use was associated with recurrence risk in patients with ESCC. For this retrospective analysis, the medical records of patients who were diagnosed with ESCC and who underwent surgery between January 2006 and December 2010 in the National Cancer Center, Korea were evaluated. Total opioid administration over a 10-day period, from during surgery to postoperative day 9, was calculated. A cutoff value was determined using receiver operating characteristic curve analysis, and patients were classified into the high-use and low-use groups. The primary and secondary outcomes of the study were freedom from recurrence and overall survival, respectively. After propensity score matching, the effect of opioid use on freedom from recurrence and overall survival was evaluated using the Kaplan-Meier method. The final analysis set included 258 patients. The cumulative opioid dose cutoff point was 1783.5 mg of oral morphine. High-dose postoperative opioid use was a significant factor affecting recurrence (Hazard ratio [HR], 2.162; 95% confidence interval [CI], 1.583-2.954; P < 0.0001). In contrast, postoperative opioid use was not associated with death (HR, 1.274; 95% CI, 0.922-1.761; P = 0.1422). In patients with ESCC, compared with low-dose opioid use, high-dose intraoperative and postoperative opioid use was significantly associated with an increased risk of recurrence. However, opioid dosage did not affect overall survival.

Investigation of opioid use and long-term oncologic outcomes for non-small cell lung cancer patients treated with surgery

Opioids are commonly used for postoperative pain control in cancer patients. In addition to pain control, an association between opioid use and long-term oncologic outcomes, such as recurrence or overall survival, has been postulated. The aim of this study was to determine whether postoperative opioid use in patients with non-small cell lung cancer is associated with long-term oncologic outcomes, including recurrence and death. Data obtained from 1009 medical records of patients who underwent curative resection at the National Cancer Center, Korea between January 2006 and December 2010 were retrospectively analyzed. Seven-day opioid use was divided into four quartiles to analyze probability of recurrence and death. Multivariate regression analyses of recurrence and death was conducted, including the calculation of odds ratios. A total of 871 patients were analyzed. When opioid dosage was examined by quartiles, the probability of death and recurrence increased gradually with increasing opioid use. However, in the multivariate regression analysis, the amount of opioid usage did not affect the risk of recurrence or death of lung cancer (P = 0.520 for recurrence; P = 0.659 for death). Opioid use was correlated with outcome when stratified by lung cancer stage (P = 0.004 for recurrence; P = 0.049 for death); however, the odds ratios only slightly increased (1.001 for stage IA–IIIA) for both outcomes. In non-small cell lung cancer patients, the amount of opioid usage does not affect the risk of recurrence and death of lung cancer. There was an association with stage (IA–IIIA), but the effect was negligible. A well-designed prospective study is needed.

Benzodiazepines May be Worse Than Opioids: Negative Medication Effects in Severe Chronic Pain

OBJECTIVES

Opioid prescription for noncancer pain is increasing in Europe and the United States. Research and guidance have focused on the potential for dependency and medical side effects with high doses. In contrast, benzodiazepines have received little attention in the chronic pain literature, despite evidence for dependency and cognitive impairment in long-term use. We aimed to examine the relationship between these classes of medication use, mood, and functioning.

METHODS

This cross-sectional study included patients (N=229) with disabling chronic pain who were about to start intensive pain rehabilitation. They completed self-report measures of mood, functioning, and responses to pain. We examined each patient's medication use and calculated a single morphine equivalent (ME) dose per person, and a similar diazepam equivalent (DE) dose. We examined the relationship between drug dose, mood, and functioning.

RESULTS

Higher DE doses were associated with worse outcomes in most domains. Higher ME doses were more narrowly associated with worse functioning. There was no evidence for any benefit of these drugs; higher doses were not associated with less pain, fear, or disability. Higher ME doses were not more problematic, contrary to our predictions. The combination of opioids and benzodiazepines was associated with particularly poor outcomes for mood.

DISCUSSION

This study is the first to examine both opioid and benzodiazepine use together in chronic pain. We found the anticipated negative effects of opioid medication, and particularly consistent associations between benzodiazepine use and poor well-being. Future guidance on chronic pain prescription should focus on restricting benzodiazepine use.

Risk factors for opioid overdose and awareness of overdose risk among veterans prescribed chronic opioids for addiction or pain

Rising overdose fatalities among U.S. veterans suggest veterans taking prescription opioids may be at risk for overdose. However, it is unclear whether veterans prescribed chronic opioids are aware of this risk. The objective of this study was to identify risk factors and determine awareness of risk for opioid overdose in veterans treated with opioids for chronic pain, using veterans treated with methadone or buprenorphine for opioid use disorder as a high-risk comparator group. In the current study, 90 veterans on chronic opioid medication, for either opioid use disorder or pain management, completed a questionnaire assessing risk factors, knowledge, and self-estimate of risk for overdose. Nearly all veterans in both groups had multiple overdose risk factors, although individuals in the pain management group had on average a significantly lower total number of risk factors than did individuals in the opioid use disorder group (5.9 versus 8.5, p < .0001). On average, participants treated for pain management scored slightly but significantly lower on knowledge of opioid overdose risk factors (12.1 versus 13.5, p < .01). About 70% of participants, regardless of group, believed their overdose risk was below that of the average American adult. There was no significant relationship between self-estimate of overdose risk and either number or knowledge of opioid overdose risk factors. Our results suggest that veterans in both groups underestimated their risk for opioid overdose. Expansion of overdose education to include individuals on chronic opioids for pain management and a shift in educational approaches to overdose prevention may be indicated.

Association of increased postoperative opioid administration with non-small-cell lung cancer recurrence: a retrospective analysis

BACKGROUND

Evidence suggests that opioid-sparing anaesthetic techniques might be associated with increased cancer-free postoperative survival. This could be related to suppression of natural killer cells by opioid analgesics in the perioperative period. This retrospective analysis tested the hypothesis that greater opioid use in the postoperative period is associated with a higher incidence of recurrences after surgery for lung cancer.

METHODS

The medical records of 99 consecutive patients who underwent video-assisted thoracoscopic surgery with lobectomy for Stage I or IIa biopsy-proven non-small-cell lung cancer (NSCLC) were reviewed. Perioperative information including patient characteristics, laboratory data, and surgical, anaesthetic, nursing, and pharmacy reports were collected. Doses of opioids administered intra-operatively and for the first 96 h after operation were converted into equianalgesic doses of oral morphine using a standard conversion table. Data were then compared with the National Cancer Registry's incidence of disease-free survival for 5 yr.

RESULTS

A total of 99 patients with similar characteristics were included in the final analysis, 73 of whom were NSCLC recurrence-free at 5 yr and 26 had NSCLC recurrence within 5 yr. Total opioid dose during the 96 h postoperative period was 124 (101) mg of morphine equivalents in the cancer-free group and 232 mg (355) mg in the recurrence group (P=0.02).

CONCLUSIONS

This retrospective analysis suggests an association between increased doses of opioids during the initial 96 h postoperative period with a higher recurrence rate of NSCLC within 5 yr.

Quality assessment of the methods used in published opioid conversion reviews

The study objective was to assess methodological quality of opioid conversion systematic reviews. The electronic databases PubMed, EMBASE, and Scopus were used to identify the systematic reviews from the earliest available date until April 2012. Studies were not restricted based on type of opioid, country, or languages. Methodological quality was evaluated using the "Assessment of Multiple Systematic Reviews (AMSTAR)." A total of 2772 articles were found from which five met inclusions criteria. No review mentioned about the duplicate study selection and data extraction. Two reviews included a list of studies that were excluded studies. One study did not provided information on the characteristics of primary studies that were included. Of the three reviews that evaluated the quality of primary studies, two used the quality of included studies in formulating conclusions. Only two reviews provided information about conflicts of interest. Of the five included systematic reviews, three reached a moderate score; two had poor quality. Specific recommendations to improve methodological quality would include performing the data selection and extraction in duplicate, listing or showing the flowchart of studies that were included and excluded along with the reasons, including the main studies data illustrating tables, and including an assessment of the quality of the primary included studies.