Clinical analgesic equivalence for morphine and hydromorphone with prolonged PCA

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.

Ultrasound-guided erector spinae plane block for postoperative analgesia in laparoscopic liver resection: A prospective, randomised controlled, patient and observer-blinded study

BACKGROUND

Erector spinae plane block (ESPB) has been reported to manage postoperative pain effectively after various types of surgery. However, there has been a lack of study on the effect of ESPB after liver resection.

OBJECTIVES

To investigate the analgesic effects of ESPB on pain control after laparoscopic liver resection compared with conventional pain management.

DESIGN

Prospective, randomised controlled study.

SETTING

A single tertiary care centre from February 2019 to February 2020.

PATIENTS

A total of 70 patients scheduled to undergo laparoscopic liver resection.

INTERVENTIONS

In the control group (n = 35), no procedure was performed. In the ESPB group (n = 35), ESPB was performed after induction of general anaesthesia. A total of 40 ml of ropivacaine 0.5% was injected at the T9 level bilaterally. After surgery, intravenous fentanyl patient-controlled analgesia was initiated. Fentanyl and hydromorphone were administered as rescue analgesics.

MAIN OUTCOME MEASURES

The primary outcome was the cumulative postoperative opioid consumption at 24 h (morphine equivalent). The secondary outcomes were rescue opioid (fentanyl) dose in the postanaesthesia care unit (PACU) and pain severity at 1, 6, 12, 24, 48 and 72 h, assessed using a numerical rating scale (NRS) score.

RESULTS

The median [IQR] postoperative opioid consumption during 24 hours following surgery was 48.2 [17.1] mg in the control group and 45.5 [35.8] mg in the ESPB group (median difference, 4.2 mg; 95% CI, -4.2 to 13.3 mg; P = 0.259). Conversely, rescue opioid in PACU was 5.3 [5.0] mg in the control group and 3.0 [1.5] mg in the ESPB group (median difference, 2.5 mg; 95% CI, 1.0 to 5.0 mg; P < 0.001). There was no significant difference in NRS scores point between the groups at any time.

CONCLUSION

ESPB does not provide analgesic effect within 24 h after laparoscopic liver resection.

TRIAL REGISTRATION

Clinical Trial Registry of Korea (https://cris.nih.go.kr.), identifier: KCT0003549).

Relevance of Mu-Opioid Receptor Splice Variants and Plasticity of Their Signaling Sequelae to Opioid Analgesic Tolerance

Opioid dose escalation to effectively control pain is often linked to the current prescription opioid abuse epidemic. This creates social as well as medical imperatives to better understand the mechanistic underpinnings of opioid tolerance to develop interventions that minimize it, thereby maximizing the analgesic effectiveness of opioids. Profound opioid analgesic tolerance can be observed in the absence of mu-opioid receptor (MOR) downregulation, aggregate MOR G protein uncoupling, and MOR desensitization, in the absence of impaired G protein coupled receptor kinase phosphorylation, arrestin binding, or endocytosis. Thus, we have explored alternative biochemical sequelae that might better account for opioid analgesic tolerance. Our findings indicate that substantial plasticity among upstream and downstream components of opioid receptor signaling and the emergence of alternative signaling pathways are major contributors to opioid analgesic tolerance. An exemplar of this plasticity is our findings that chronic morphine upregulates the MOR variants MOR-1B2 and MOR-1C1 and phosphorylation of their C-terminal sites not present in MOR-1, events causally associated with the chronic morphine-induced shift in MOR G protein coupling from predominantly Gi/Go inhibitory to Gs-stimulatory adenylyl cyclase signaling. The unique feature(s) of these variants that underlies their susceptibility to adapting to chronic morphine by altering the nature of their G protein coupling reveals the richness and pliability of MOR signaling that is enabled by generating a wide diversity of MOR variants. Furthermore, given differential anatomical expression patterns of MOR variants, MOR splice variant-dependent adaptations to chronic morphine could enable mechanistic underpinnings of tolerance and dependence that are CNS region- and cell-specific.

Practical management of opioid rotation and equianalgesia

Purpose

To review the recent literature on opioid rotation (ie, switching from one opioid drug to another or changing an opioid’s administration route) in cancer patients experiencing severe pain and to develop a novel equianalgesia table for use in routine clinical practice.

Methods

The MEDLINE database was searched with terms “cancer pain,” “opioid rotation,” “opioid switching,” “opioid ratio,” “opioid conversion ratio,” and “opioid equianalgesia” for the major opioids (morphine, oxycodone, fentanyl, and hydromorphone) and the intravenous, subcutaneous, oral, and transdermal administration routes. Selected articles were assessed for the calculated or cited opioid dose ratio, bidirectionality, and use of the oral morphine equivalent daily dose or a direct drug-to-drug ratio.

Results

Twenty publications met our selection criteria and were analyzed in detail. We did not find any large-scale, prospective, double-blind randomized controlled trial with robust design, and most of the studies assessed relatively small numbers of patients. Bidirectionality was investigated in seven studies only.

Conclusion

The updated equianalgesic table presented here incorporates the latest data and provides information on bidirectionality. Despite the daily use of equianalgesic tables, they are not based on high-level scientific evidence. More clinical research is needed on this topic.

Doctor Shopping Behavior and the Diversion of Prescription Opioids

OBJECTIVES

"Doctor shopping" as a means of prescription opioid diversion is examined. The number and percentage of prescriptions and morphine-equivalent milligrams diverted in this manner are estimated by state and molecule for the period 2008-2012.

METHODS

Eleven billion prescriptions with unique patient, doctor, and pharmacy identifiers were used to construct diversion "events" that involved between 1 and 6 unique doctors and between 1 and 6 unique pharmacies. Diversion thresholds were established based on the probability of each contingency.

RESULTS

A geographically widespread decline occurred between 2008 and 2012. The number of prescriptions diverted fell from approximately 4.30 million (1.75% of all prescriptions) in 2008 to approximately 3.37 million (1.27% of all prescriptions) in 2012, and the number of morphine-equivalent milligrams fell from approximately 6.55 metric tons (2.95% of total metric tons) in 2008 to approximately 4.87 metric tons (2.19% of total metric tons) in 2012.

CONCLUSIONS

Diversion control efforts have likely been effective. But given increases in opioid-related deaths, opioid-related drug treatment admissions, and the more specific resurgence of heroin-related events, it is clear that additional public health measures are required.

Opioid Conversions in Acute Care

Objective:

To discuss the historical basis and limitations of opioid conversion tables, review the relevant literature, and establish an evidence-based equianalgesic dose ratio (EDR) table for performing conversions in the acute care setting.

Data Sources:

Articles were identified through searches of MEDLINE (1966–January 2007) using the key words opioid, tolerance, conversion, dose, equianalgesic, equipotent, acute care, morphine, hydromorphone, fentanyl, methadone, and oxycodone. Additional references were located through a review of the bibliographies of articles cited and references cited in conversion tables.

Study Selection and Data Extraction:

All data sources identified were evaluated, and all information deemed relevant was included, with the exception of case series and case reports when higher level evidence was available.

Data Synthesis:

Opioid conversion tables are published in major textbooks, medical references, national guidelines, and review articles. Some conversion tables do not accurately reflect the dose ratios for which evidence is available. There is marginal evidence-based clinical data to support the dose ratios cited in these tables, particularly in the acute care setting where the clinical status of patients often changes rapidly. The barriers when performing route and opioid-to-opioid conversions in the acute care setting are formidable, but EDRs are provided, based on the best available evidence.

Conclusions:

In the acute care setting, calculation of dose ratios for opioids, based solely on opioid conversion tables, is an oversimplification of pain management, with a potential for adverse consequences. The calculation of EDRs is one step in an interdisciplinary process that must take into account patient- and institution-specific factors.

Multimodal pain management in total knee arthroplasty: a prospective randomized controlled trial

We analyze the effects of a multimodal analgesic regimen on postoperative pain, function, adverse effects and satisfaction compared to patient-controlled analgesia (PCA). Thirty-six patients undergoing TKA were randomized to receive either (1) periarticular injection before wound closure (30cc 0.5% bupivacaine, 10mg MSO4, 15 mg ketorolac) and multimodal analgesics (oxycodone, tramadol, ketorolac; narcotics as needed) or (2) hydromorphone PCA. Preoperative and postoperative data were collected for VAS pain scores, time to physical therapy milestones, hospital stay length, patient satisfaction, narcotic consumption and medication-related adverse effects. The multimodal group had lower VAS scores, fewer adverse effects, lower narcotic usage, higher satisfaction scores and earlier times to physical therapy milestones. Multimodal pain management protocol decreases narcotic usage, improves pain scores, increases satisfaction and enhances early recovery.

WITHDRAWN: Hydromorphone for acute and chronic pain

The original author team were unavailable to complete the update. At September 2013, a new author team is preparing a new protocol for publication in early 2014, with the revised title 'Hydromorphone for cancer pain'.

The editorial group responsible for this previously published document have withdrawn it from publication.

Versatility of different pharmaceutical formulations of hydromorphone in the management of severe cancer pain and pain in palliative care

SUMMARY The management of severe pain situations requires therapeutic expertise in dealing with changes in pain intensity, analgesic limitations and individual patient needs. Opioids are the treatment of choice in severe pain. The availability of a broad range of opioids and formulations refined the options for improved pain treatment with a specific substance. These may include oral formulations, injectables and other applications suitable for different patient needs. Moreover, variable drug concentrations are most useful in clinical practice. This article briefly reviews the versatility of different hydromorphone formulations in the management of severe pain in palliative care and cancer. Limiting strong opioid treatment with one opioid substance in different formulations (adjuvants if necessary), according to varying requirements of patients, would be eligible for achieving a well-tolerated and effective pain therapy. Its versatility renders hydromorphone suitable for consistent opioid administration with predictable substance release, and may thus contribute to reducing the need for opioid change.

A prospective review of hip fracture subtypes, surgical procedure, cognitive status, and analgesia use across 4 Australian hospitals

OBJECTIVES

To correlate analgesia use among patients with hip fracture requiring surgery with hip fracture subtype, cognitive status, and type of surgery in the postacute period.

DESIGN AND PARTICIPANTS

Prospective review of patients with hip fractures requiring surgical intervention. A total of 415 patients (mean age: 81.2 ± 9.1 years, 74.3% women) presented with 195 subcapital fractures (39 undisplaced, 156 displaced) and 220 trochanteric fractures (136 stable, 84 unstable) requiring surgery.

SETTING

Inpatient orthopedic units in 4 Australian hospitals.

MEASUREMENTS

The primary outcome measures were mean analgesia usage (oral morphine equivalent) for 4 defined time intervals and total amount 36 hours following surgery.

RESULTS

Patients with subtrochanteric fractures required more analgesia compared with displaced-subcapital, undisplaced-subcapital, basicervical, stable-pertrochanteric, and unstable-pertrochanteric fractures in the 24 to 36 hours following operation (24.7 vs 11.3 vs 8.8 vs 12.1 vs 7.6 vs 9.7, P = .001). Total analgesia requirements were higher in patients treated with an intramedullary nail, increasing by 1.3- to 3.3-fold in the 36 hours postsurgery. Patients with cognitive impairment utilized markedly less analgesia at all time periods measured. At 24 to 36 hours, higher levels of analgesia were noted in patients with higher premorbid level of mobility (P = .015) and activities of daily living function (P = .007).

CONCLUSION

Important differences in utilization of analgesia following hip fracture across readily defined clinical groups exist. Proactive pain management for those with cognitive impairment, certain hip fracture subtypes, and surgical procedures may enable early functional mobility and other activities.

Study on the activation of the opioid receptors by a set of morphine derivatives in a well-defined assay system

As a first step in our search for new opiates, we have established cellular assays to monitor opioid receptor activation and study the activities of a set of morphine derivatives. Intracellular calcium changes were monitored in human embryonic kidney-293 T cells expressing individual opioid receptors upon cotransfection with a chimeric G protein. This assay was validated by comparing the potencies of the endogenous peptides to reported values. All of the opiates were found to interact with the three opioid receptor subtypes but with a range of differences in efficacies and potencies. Most of the opiates preferentially acted at the μ receptor. None of the opiates showed a preference for the δ receptor. Only oripavine and its precursor thebaine showed a preference for the κ over the μ receptor. The results indicate that the opiates with a C-3 hydroxyl group or C-6 ketone group but in the presence of a 7, 8-single bond exhibit higher activity. It is noteworthy that the 6-O-methyl group seems to improve the selectivity for κ receptor. This is the first comparative and comprehensive report on the activation of the three different opioid receptors by a set of morphine derivatives in a well-defined assay system. These data can serve as a basis for the characterization of novel opiates.

Opioid rotation: the science and the limitations of the equianalgesic dose table

Opioid rotation refers to a switch from one opioid to another in an effort to improve the response to analgesic therapy or reduce adverse effects. It is a common method to address the problem of poor opioid responsiveness despite optimal dose titration. Guidelines for opioid rotation are empirical and begin with the selection of a safe and reasonably effective starting dose for the new opioid, followed by dose adjustment to optimize the balance between analgesia and side effects. The selection of a starting dose must be based on an estimate of the relative potency between the existing opioid and the new one. Potency, which is defined as the dose required to produce a given effect, differs widely among opioids, and among individuals under varying conditions. To effectively rotate from one opioid to another, the new opioid must be started at a dose that will cause neither toxicity nor abstinence, and will be sufficiently efficacious in that pain is no worse than before the change. The estimate of relative potency used in calculating this starting dose has been codified on "equianalgesic dose tables," which historically have been based on the best science available and have been used with little modification for more than 40 years. These tables, and the clinical protocols used to apply them to opioid rotation, may need revision, however, as the science underlying relative potency evolves. Review of these issues informs the use of opioid rotation in the clinical setting and defines key areas for future research.

A new extended release formulation (OROS) of hydromorphone in the management of pain

Opioid analgesics are essential in the treatment of moderate to severe cancer-related pain. Opioids are also recognized as important in the management of other severe, persistent refractory painful conditions, such as sickle cell disease and arthritis. In the clinical practice of pain management, stable opioid dosing generally depends on achieving maximal analgesia with tolerable side effects typical of opioid analgesics. There is a wide interindividual variability of responsiveness to exogenous opioids both in terms of analgesic efficacy and side effects. Optimizing pain management for the individual patient may require sequential trials of opioid medications until the regimen with the most favorable therapeutic ratio of efficacy to side effects is determined.

Pharmacokinetics of a controlled-release liposome-encapsulated hydromorphone administered to healthy dogs

The purpose of the study was to assess the pharmacokinetics of liposome-encapsulated (DPPC-C) hydromorphone administered intravenously (IV) or subcutaneously (SC) to dogs. A total of eight healthy Beagles aged 12.13 +/- 1.2 months and weighing 11.72 +/- 1.10 kg were used. Dogs randomly received liposome encapsulated hydromorphone, 0.5 mg/kg IV (n = 6), 1.0 mg/kg (n = 6), 2.0 mg/kg (n = 6), or 3.0 mg/kg (n = 7) SC with a 14-28 day washout between trials. Blood was sampled at serial intervals after drug administration. Serum hydromorphone concentrations were measured using liquid chromatography with mass spectrometry. Serum concentrations of hydromorphone decreased rapidly after IV administration of the DPPC-C formulation (half-life = 0.52 h, volume of distribution = 12.47 L/kg, serum clearance = 128.97 mL/min/kg). The half-life of hydromorphone after SC administration of DPPC-C formulation at 1.0, 2.0, and 3.0 mg/kg was 5.22, 31.48, and 24.05 h, respectively. The maximum serum concentration normalized for dose (C(MAX)/D) ranged between 19.41-24.96 ng/mL occurring at 0.18-0.27 h. Serum hydromorphone concentrations fluctuated around 4.0 ng/mL from 6-72 h after 2.0 mg/kg and mean concentrations remained above 4 ng/mL for 96 h after 3.0 mg/kg DPPC-C hydromorphone. Liposome-encapsulated hydromorphone (DPPC-C) administered SC to healthy dogs provided a sustained duration of serum hydromorphone concentrations.

The relative abuse liability of oral oxycodone, hydrocodone and hydromorphone assessed in prescription opioid abusers

Abuse of prescription opioids has risen precipitously in the United States. Few controlled comparisons of the abuse liability of the most commonly abused opioids have been conducted. This outpatient study employed a double-blind, randomized, within-subject, placebo-controlled design to examine the relative abuse potential and potency of oral oxycodone (10, 20 and 40 mg), hydrocodone (15, 30 and 45 mg), hydromorphone (10, 17.5 and 25mg) and placebo. Healthy adult volunteers (n=9) with sporadic prescription opioid abuse participated in 11 experimental sessions (6.5h in duration) conducted in a hospital setting. All three opioids produced a typical mu opioid agonist profile of subjective (increased ratings of liking, good effects, high and opiate symptoms), observer-rated, and physiological effects (miosis, modest respiratory depression, exophoria and decrements in visual threshold discrimination) that were generally dose-related. Valid relative potency assays revealed that oxycodone was roughly equipotent to or slightly more potent than hydrocodone. Hydromorphone was only modestly more potent (less than two-fold) than either hydrocodone or oxycodone, which is inconsistent with prior estimates arising from analgesic studies. These data suggest that the abuse liability profile and relative potency of these three commonly used opioids do not differ substantially from one another and suggest that analgesic potencies may not accurately reflect relative differences in abuse liability of prescription opioids.

Dose-related thermal antinociceptive effects of intravenous hydromorphone in cats

OBJECTIVE

To describe the dose-related thermal antinociceptive effects of intravenous (i.v.) hydromorphone in cats.

STUDY DESIGN

Randomized, blinded, crossover design.

ANIMALS

Seven adult cats (3.5-7.4 kg), two spayed females, and five neutered males.

METHODS

Hydromorphone (0.025, 0.05, or 0.1 mg kg(-1)) was administered i.v.. Skin temperature and thermal threshold were measured before and at selected time points to 720 minutes post-administration. Statistical analysis of mean thermal threshold and skin temperatures over time for each dose and between doses was by way of a split-plot model and post hoc Bonferroni t-tests. p < 0.05 was considered significant.

RESULTS

A significant difference from baseline for mean thermal threshold was identified for the 0.05 mg kg(-1) dose (5-80 minutes, peak thermal threshold 46.9 +/- 6.2 degrees C) and 0.1 mg kg(-1) dose (5-200 minutes, peak thermal threshold 54.9 +/-0.2 degrees C). The thermal threshold was significantly greater after the 0.1 mg kg(-1) dose from 5 to 200 minutes compared to the 0.025 mg kg(-1) and 0.5 mg kg(-1) doses. The thermal threshold was significantly greater from 35 to 80 minutes for the 0.05 mg kg(-1) dose when compared with the 0.025 mg kg(-1) dose. Skin temperature was significantly increased from 35 to 140 minutes following the 0.1 mg kg(-1) dose.

CONCLUSIONS

A dose-related antinociceptive effect was demonstrated for i.v. hydromorphone in cats.

CLINICAL RELEVANCE

Hydromorphone at doses less than 0.1 mg kg(-1) has a modest antinociceptive effect and a short duration of action. At a dose of 0.1 mg kg(-1) i.v., onset of analgesia is rapid with a clinically useful duration of effect, but is associated with a rise in skin temperature.

Chronic pain in end-stage renal disease

A growing body of literature has shown that chronic pain is common for patients with end-stage renal disease (ESRD), is typically moderate or severe, and impacts virtually every aspect of health-related quality of life. Unfortunately, there is a lack of clinical and research focus in this area in nephrology, and pain in ESRD is undertreated. This article will review the epidemiology of chronic pain in ESRD, discuss basic principles of pain assessment and management, and highlight some of the challenges in pain management in ESRD with the hope of guiding health professionals in the effective management of pain in patients with ESRD.

Hydromorphone

Hydromorphone is a semi-synthetic opioid that has been used widely for acute pain, chronic cancer pain and to a lesser extent, in chronic nonmalignant pain. Its pharmacokinetics and pharmacodynamics have been well studied, including immediate release oral preparations, a variety of slow release oral preparations, as well as administration through intravenous, subcutaneous, epidural, intrathecal and other routes. It is known to be metabolized to analgesically inactive metabolites that have been associated with neuroexcitatory states and other toxicity. There is no evidence that hydromorphone has any greater abuse liability than other opioids. Further research is needed to address remaining areas of uncertainty: equianalgesic ratios; relative risk of toxicity compared with other opioids, its use in nonmalignant pain, and the role of specific hydromorophone metabolites in the development of toxicity, particularly in association with organ failure.

Identification and synthesis of norhydromorphone, and determination of antinociceptive activities in the rat formalin test

The main objective of this paper is to report the identification and synthesis of norhydromorphone, a novel metabolite of hydromorphone, and its antinociceptive activities when tested in the formalin test as compared to other known analgesics. In addition, we are reporting for the first time the lack of antinociceptive activities of hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide in the rat formalin test. Norhydromorphone was isolated and identified as a metabolite of hydromorphone in a cancer patient's urine. An authentic standard of norhydromorphone was synthesized. The identity of norhydromorphone in the urine sample was confirmed by comparing the LC retention time and MS ion fragmentation with the synthetic standard using a liquid chromatographic-mass spectrometric-mass spectrometric (LC-MS-MS) assay. Norhydromorphone was found to be a minor metabolite of hydromorphone in the urine. Additionally, the antinociceptive activities of norhydromorphone, hydromorphone, morphine, dihydromorphine, dihydroisomorphine, hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide were determined in the rat formalin test following intraperitoneal (i.p.) administration. Only limited antinociception was observed and no significant increase in antinociception was detected at the three doses tested. The increased polarity of norhydromorphone as compared to hydromorphone due to the primary piperidine nitrogen may make it less favorable to cross the blood-brain-barrier (BBB), which may be partly responsible. In addition, lower intrinsic antinociceptive activity, which remains to be determined, could also contribute to the low antinociception. Our results also show that hydromorphone was five times as potent as morphine in the formalin test, while dihydromorphine and dihydroisomorphine were equipotent to and 36% as potent as morphine, respectively. Hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide did not exhibit any antinociceptive effect at the doses tested. The results further underscore the importance of a free C3-OH to the analgesic effect of morphine alkaloids.

Pharmacokinetic and pharmacodynamic evaluation of intravenous hydromorphone in cats1

This study describes the pharmacokinetics of intravenous hydromorphone in cats and the simultaneous measurement of antinociceptive pharmacodynamic effects using a thermal threshold testing system. Following establishment of a baseline thermal threshold, six adult cats were administered 0.1 mg/kg of hydromorphone intravenously. Thermal threshold testing and blood collection were conducted simultaneously at predetermined time points. Plasma hydromorphone concentrations were determined by a liquid chromatographic-mass spectral method and pharmacokinetic analysis was performed by nonlinear least squares regression analysis. Plasma hydromorphone concentrations declined rapidly over time, and were below the limit of quantification of the assay (LOQ = 1.0 ng/mL) by 360 min. In contrast, thermal thresholds rose from a pretreatment value of 40.9 +/- 0.65 degrees C (mean +/- SEM) to instrument cut-out (55 degrees C) within 15 min and remained significantly elevated from 15-450 min after treatment. Inspection of the data revealed no direct correlation between plasma hydromorphone concentrations and the antinociceptive effect of this drug in cats. These findings support the importance of conducting pharmacokinetic studies in parallel with objective measurements of drug effect.

Managing pain in mucositis

OBJECTIVE

To discuss pharmacologic and nonpharmacologic approaches available to manage pain.

DATA SOURCE

Published journal articles, book chapters, clinical experience.

CONCLUSION

Pain management requires treatment directed at the various factors involved in the pain experience.

IMPLICATIONS FOR NURSING PRACTICE

Nurses need to assess pain daily and follow patients closely until mucositis resolves. Management targeted to specific dimensions of pain can improve the effectiveness of pain control.

Clinical application of opioid equianalgesic data

Physicians and other healthcare professionals may often be faced with the need to change opioids during the course of a patient's opioid analgesic care due to a number of clinical reasons. The act of converting opioid analgesics, for many physicians, nurses, and pharmacists, who do not receive adequate training, remains a challenging and often uncomfortable aspect of pain treatment. Part of the challenge clinicians face is secondary to the relatively weak literature evidence base that exists to support the equianalgesic ratios provided in textbooks, journals, and other medical resources. Another aspect involves the lack of a widely recognized treatment algorithm or guideline to assist clinicians with opioid conversion. The final decision on which opioid dose to prescribe must involve a thorough clinical assessment to minimize the risk of prescribing inappropriate opioid doses over or under the patient's actual need. The purpose of this paper is to provide the clinician with an approach for dealing with the conversion between opioid analgesics that is standardized, yet allows for individualized results to meet unique patient needs. We present a 5-step process as a guide for clinicians faced with the need to change a patient's opioid regimen. This approach may help to build a comfort level when dealing with the clinical challenges of converting from one opioid to another.

Pharmacokinetics and bioavailability of single-dose intranasal hydromorphone hydrochloride in healthy volunteers

We evaluated pharmacokinetics and absolute bioavailability of single doses of hydromorphone hydrochloride after administration of 1.0 and 2.0 mg of intranasal (IN) and 2.0 mg of IV hydromorphone hydrochloride. An open-label, randomized, three-way crossover study was conducted in 24 healthy volunteers (13 men and 11 women). IN doses were delivered as 0.1-mL metered-dose sprays into one or both nostrils for 1.0- and 2.0-mg doses, respectively. Blood samples were taken serially from 0 to 16 h after each dose. Plasma hydromorphone concentrations were determined by liquid chromatography-mass spectrometry-mass spectrometry. Noncompartmental analysis was used to estimate pharmacokinetic variables. Mean hydromorphone bioavailabilities and percent coefficient of variation of 52.4% (22.7) and 57.5% (18.6) were seen after the 1.0- and 2.0-mg IN doses, respectively. Median times to maximum concentration were 20 and 25 min for IN doses. Adverse events included somnolence and dizziness with all routes of administration and a bad taste after IN doses. Dose proportionality for the 1.0- and 2.0-mg IN doses was observed. IN hydromorphone hydrochloride met the minimum requirements for safety and demonstrated rapid nasal drug absorption and clinically relevant bioavailability. Results support further development of this novel hydromorphone hydrochloride nasal spray.

IMPLICATIONS

Pharmacokinetics and bioavailability were determined for two doses of intranasal hydromorphone in healthy volunteers. Rapid, reliable absorption, and predictable pharmacokinetics support the investigation of hydromorphone hydrochloride nasal spray as a therapeutic alternative to oral and IM administration.

Pharmacokinetic drug interactions of morphine, codeine, and their derivatives: theory and clinical reality, part I

Pharmacokinetic drug-drug interactions with morphine, hydromorphone, and oxymorphone are reviewed in this column. Morphine is a naturally occurring opiate that is metabolized chiefly through glucuronidation by uridine diphosphate glucuronosyl transferase (UGT) enzymes in the liver. These enzymes produce an active analgesic metabolite and a potentially toxic metabolite. In vivo drug-drug interaction studies with morphine are few, but they do suggest that inhibition or induction of UGT enzymes could alter morphine and its metabolite levels. These interactions could change analgesic efficacy. Hydromorphone and oxymorphone, close synthetic derivatives of morphine, are also metabolized primarily by UGT enzymes. Hydromorphone may have a toxic metabolite similar to morphine. In vivo drug-drug interaction studies with hydromorphone and oxymorphone have not been done, so it is difficult to make conclusions with these drugs.

Advances in cancer pain management

Although most patients with cancer pain can attain a favorable balance between analgesia and side effects with a conventional approach to opioid therapy, a substantial minority cannot. For these patients, an important subgroup of whom have neuropathic pain, alternative therapeutic strategies are needed. With a detailed assessment, clinicians should be able to choose among the large and diverse group of options available and implement an approach, or combination of approaches, that have a high probability of improving analgesic outcomes.

Sex hormone suppression by intrathecal opioids: a prospective study

OBJECTIVE

Sexual dysfunction and low testosterone levels have been observed previously in males with chronic noncancer pain treated with intrathecal opioids. To investigate the hypothesis that intrathecal opioids suppress the hypothalamic-pituitary-gonadal axis, a prospective nonrandomized investigation of the function of this axis was undertaken.

DESIGN

Ten males with chronic noncancer pain were evaluated for clinical and biochemical evidence of hypogonadism at baseline and during the first twelve weeks of intrathecal opioid therapy.

RESULTS

Intrathecal opioid administration resulted in a significant (p <0.0001) reduction in serum testosterone, from 7.7 +/- 1.1 (mean +/- SEM) nmol/L at baseline to 2.0 +/- 0.7, 2.8 +/- 0.5, and 4.0 +/- 0.9 nmol/L at 1, 4, and 12 weeks, respectively. This was associated with a reduction in libido and potency. Luteinizing hormone and follicle-stimulating hormone levels remained within reference ranges, indicating central rather than peripheral suppression.

CONCLUSIONS

Administration of intrathecal opioids may result in hypogonadotrophic hypogonadism. As part of the consent for therapy process, patients should be informed about this effect and its management. With long-term intrathecal opioid administration, the hypothalamic-pituitary-gonadal axis should be monitored. Where indicated, testosterone replacement should be undertaken to improve sexual function and prevent the potential metabolic effects of hypogonadism, in particular, osteoporosis.

Hydromorphone for acute and chronic pain

BACKGROUND

While morphine is the gold standard for the management of severe cancer pain, some patients either do not achieve adequate analgesia, or suffer intolerable morphine-related toxicity. For these patients alternatives such as hydromorphone are recommended. However, there appear to be gaps in our understanding of the efficacy and potency of hydromorphone.

OBJECTIVES

This review explores and assesses the evidence for the efficacy of hydromorphone in the management of pain.

SEARCH STRATEGY

Randomised trials which included hydromorphone were sought using electronic databases and by handsearching relevant journals. Date of the most recent search: February 2000.

SELECTION CRITERIA

RCTs which involved the administration of hydromorphone, for both acute and chronic pain conditions, in adults and children, were included.

DATA COLLECTION AND ANALYSIS

A data extraction form was designed for the purpose of the review. The validity of each trial for inclusion was assessed using criteria described in the Cochrane Handbook. A grade was allocated to each study on the basis of allocation concealment. A checklist was used to assess blinding.

MAIN RESULTS

Forty three studies (2725 subjects) were included in the review. Approximately half of these studies received a low quality score. In addition, the heterogeneity of the studies precluded combination of data and results. A meta-analysis was therefore not possible. Of the 43 included studies, 11 (645 subjects) involved chronic pain conditions (all cancer) and 32 (2080 subjects) acute pain. Three studies were placebo-controlled. Of the remainder, hydromorphone was compared with other opioids (morphine, fentanyl, sufentanyl, meperidine, oxycodone, diamorphine), bupivicaine and with itself, using different formulations. The routes of administration included intravenous, oral, spinal, intramuscular and subcutaneous. Overall, hydromorphone appears to be a potent analgesic. The limited number of studies available suggest that there is little difference between morphine and hydromorphone in terms of analgesic efficacy, adverse effect profile and patient preference. However, as most studies involved small numbers of patients, it is difficult to determine real differences between both drugs. In the context of both acute and chronic pain, the issue of equi-analgesic ratios between morphine and hydromorphone was not resolved.

REVIEWER'S CONCLUSIONS

The studies included in this review were varied in terms of quality and methodology. However, the majority demonstrated that hydromorphone is a potent analgesic, that the clinical effects of hydromorphone appear to be dose-related, and that the adverse effect profile of hydromorphone is similar to that of other mu opioid receptor agonists.

Patient-controlled analgesia: an appropriate method of pain control in children

Patient-controlled analgesia (PCA) is an analgesic technique originally used in adults but now with an established role in paediatric practice. It is well tolerated in children as young as 5 years and has uses in postoperative pain as well as burns, oncology and palliative care. The use of background infusions is more frequent in children and improves efficacy; however, it may increase the occurrence of adverse effects such as nausea and respiratory depression. Monitoring involves measurement of respiratory rate, level of sedation and oxygen saturation. Efficacy is assessed by self-reporting, visual analogue scales, faces pain scales and usage patterns. This is optimally performed both at rest and on movement. The selection of opioid used in PCA is perhaps less critical than the appropriate selection of parameters such as bolus dose, lockout and background infusion rate. Moreover, opioid choice may be based on adverse effect profile rather than efficacy. The concept of PCA continues to be developed in children, with patient-controlled epidural analgesia, subcutaneous PCA and intranasal PCA being recent extensions of the method. There may also be a role for patient-controlled sedation. PCA, when used with adequate monitoring, is a well tolerated technique with high patient and staff acceptance. It can now be regarded as a standard for the delivery of postoperative analgesia in children aged >5 years.

Equianalgesic dose ratios for opioids. a critical review and proposals for long-term dosing

Clinicians involved in the opioid pharmacotherapy of cancer-related pain should be acquainted with a variety of opioids and be skilled in the selection of doses when the type of opioid or route of administration needs changing. The optimal dose should avoid under-dosing or overdosing, both associated with negative outcomes for the patient. Although equianalgesic dose tables are generally used to determine the new doses in these circumstances, the evidence to support the ratios indicated in these tables largely refers to the context of single dose administration. The applicability of these ratios to the setting of chronic opioid administration has been questioned. A systematic search of published literature from 1966 to September 1999 was conducted to critically appraise the emerging evidence on equianalgesic dose ratios derived from studies of chronic opioid administration. There were six major findings: 1) there exists a general paucity of data related to long-term dosing and studies are heterogeneous in nature; 2) the ratios exhibit extremely wide ranges; 3) methadone is more potent than previously appreciated; 4) the ratios related to methadone are highly correlated with the dose of the previous opioid; 5) the ratio may change according to the direction the opioid switch; and 6) discrepancies exist with respect to both oxycodone and fentanyl. Overall, these findings have important clinical implications for clinicians and warrant consideration in the potential revision of current tables. The complexity of the clinical context in which many switches occur must be recognized and also appreciated in the design of future studies.

Accuracy in equianalgesic dosing. conversion dilemmas

The clinical benefit and increased application of opioid rotation has focused attention on efficacy differences between opioids and their respective equianalgesic dose ratios. Understanding the differences between the opioids is critical to understanding their equianalgesic dose ratios and for adjusting therapy following rotation to a new analgesic. The purpose of this article is to describe controversies regarding the relative potencies of these agents as presented in current equianalgesic charts and to provide pharmacologic information to assist the clinician with opioid rotation.

Strategies to manage the adverse effects of oral morphine: an evidence-based report

Successful pain management with opioids requires that adequate analgesia be achieved without excessive adverse effects. By these criteria, a substantial minority of patients treated with oral morphine (10% to 30%) do not have a successful outcome because of (1) excessive adverse effects, (2) inadequate analgesia, or (3) a combination of both excessive adverse effects along with inadequate analgesia. The management of excessive adverse effects remains a major clinical challenge. Multiple approaches have been described to address this problem. The clinical challenge of selecting the best option is enhanced by the lack of definitive, evidence-based comparative data. Indeed, this aspect of opioid therapeutics has become a focus of substantial controversy. This study presents evidence-based recommendations for clinical-practice formulated by an Expert Working Group of the European Association of Palliative Care (EAPC) Research NETWORK: These recommendations highlight the need for careful evaluation to distinguish between morphine adverse effects from comorbidity, dehydration, or drug interactions, and initial consideration of dose reduction (possibly by the addition of a co analgesic). If side effects persist, the clinician should consider options of symptomatic management of the adverse effect, opioid rotation, or switching route of systemic administration. The approaches are described and guidelines are provided to aid in selecting between therapeutic options.

The pharmacological basis of contemporary pain management

Pain management has become an increasingly well researched area in medicine over recent years, and there have been advances in a number of areas. While opioids remain an integral part of pain-management strategies, there is now an emphasis on the use of adjuvant drugs, such as paracetamol and anti-inflammatory agents, which through physiological or pharmacological synergism, both enhance pain control and reduce opioid use. The management of neuropathic pain continues to be a challenge. Anti-epileptics and antidepressants, together with clonidine and ketamine, provide the foundations for treatment. Another area of interest has been the widespread use of patient-controlled analgesia and the administration of some drugs, especially opioids, by means other than traditional oral and parenteral routes. The number of new drugs that have reached the stage of clinical trials has been small, yet they offer exciting possibilities. The epibatidine analogue ABT-594 and zinconitide both offer novel approaches to the management of neuropathic pain states, while selective cyclo-oxygenase-2 inhibitors and nitroaspirins may see advances in the management of nociceptive pain states.

Opioid Equianalgesic Calculations

Among the knowledge required by healthcare professionals to manage pain is an understanding of the differences between opioid agents and formulations. As the list of new opioid formulations continues to grow, it is increasingly important that clinicians understand the basic pharmacology of these analgesics and how to calculate equianalgesic doses. Administering an equianalgesic dose increases the likelihood that the transition to another opioid or route will be tolerated without loss of pain control or excessive side effects. Although calculation of equianalgesic doses requires relatively simple mathematical skills, few clinicians are prepared to compute them. The purpose of this article is to provide a basic review of the pharmacology of opioids, explain how to calculate an equianalgesic dose, and briefly describe some of the current controversies of the relative potencies of opioids listed in equianalgesic tables.