[Treatment of nociceptive pain in primary care setting]

The pharmacological treatment of chronic pains induced by an excess of nociception is mainly based on analgesics which are classified according to their pharmacological nature (not opioid/opioid) and to their power according to the three World Health Organization steps. Their use is founded on a strategy which differs from the nature of pain (cancer pain vs no cancer pain), in particular with regard to the use of the strong opioids.

New insights into the neuroanatomical distribution and phylogeny of opioids and POMC-derived peptides in fish

This review re-evaluates the use of immunological probes to map enkephalinergic, dynorphinergic, and endorphinergic circuits in the CNS of lobe-finned fishes, ray-finned fishes, and cartilaginous fishes in light of the characterization of proenkephalin, prodynorphin, and POMC sequences from representatives of these groups of fish over the past 20 years. The use of α-MSH specific antisera is a reliable method for detecting POMC immunopositive cell bodies and fibers. Since α-MSH and β-endorphin are co-localized in the same neurons, these studies also reveal the distribution of endorphinergic networks. Met-enkephalin specific antisera can be used to detect enkephalinergic circuits in the CNS of gnathostomes because of the ubiquitous presence of this pentapeptide in the proenkephalin sequences of gnathostomes. However, the use of leu-enkephalin specific antisera to detect enkephalinergic networks is more problematic. While this immunological probe is appropriate for analyzing enkephalinergic networks in mammals and perhaps teleosts, for the lungfishes and cartilaginous fishes this probe is more likely able to detect dynorphinergic circuits. In this regard, there is a need to re-examine dynorphinergic networks in non-mammalian gnathostomes by using species specific antisera directed against dynorphin end-products.

REGIONAL ANALGESIA FOR POST-OPERATIVE PAIN MANAGEMENT--INITIAL EXPERIENCE IN A LOW RESOURCE SETTING

OBJECTIVE

The aim of this study is to demonstrate the use of some regional anaesthetic techniques in effective postoperative pain control in a low resource setting. We also wanted to find out the potential benefits and prospects of regional techniques to achieve effective postoperative analgesia.

DESIGN

This study was a prospective observational study in which 25 patients presenting for various orthopaedic and general surgical procedures were recruited randomly.

SETTING

Ahmadu Bello University Teaching Hospital (ABUTH), Zaria, Nigeria from December, 2008 to May, 2009.

SUBJECTS

Eligible patients were males and females aged 21-55 years. These included emergency and elective cases.

RESULTS

The age range was 21-55 years with a mean age of 34 years. Of the 25 patient studied, 14 of them were men and 11 women constituting 56% and 44% respectively. Our study shows that Hausa/Fulani ethnic group made up 75% of the study population. Intraoperatively, the anaesthetic techniques used were general anaesthesia (only) in 13 patients (52%), Regional techniques consisting of spinals, epidurals, combined spinals and epidurals and brachial plexus blocks in nine patients (36%) and three (12%) of the patients had a combination of general anaesthesia (GA) and regional anaesthesia (RA). For post-operative pain management, nine patients (36%) had continuous brachial plexus block using intermittent injections, 13 (52%) patients had epidural catheters with intermittent top-up injections and three (12%) patients received combined spinal and epidural with an epidural catheter left in-situ for intermittent top-ups. The drugs used for top-ups included 0.125% plain bupivacaine (15 patients), 0.125% plain bupivacaine + 2.5 mcgs/ml Fentanyl (10 patients) in 10 ml aliquots. The outcome was good in most patients with 19 patients (82.4%) experiencing only mild pain (numeric pain score 0-3). Onset of post-operative pain was 13-18 hours in most (52%) of patients with majority of patients (80%) requiring only a single dose of opioid in 24 hours. There was no incidence of infection at site of catheter insertion one week after the procedure.

CONCLUSION

Regional techniques if used properly can provide superior pain control in the post-operative period. There is reduction in the requirements of opioids in the immediate post-operative when regional techniques are used for pain management. We need to encourage the use of these techniques especially in our setting where resources are sparse and potent analgesics are not always available.

Prescriptions for schedule II opioids and benzodiazepines increase after the introduction of computer-generated prescriptions

BACKGROUND

Prescriptions for controlled substances decrease when regulatory barriers are put in place. The converse has not been studied.

OBJECTIVES

The objective was to determine whether a less complicated prescription writing process is associated with a change in the prescribing patterns of controlled substances in the emergency department (ED).

METHODS

The authors conducted a retrospective nonconcurrent cohort study of all patients seen in an adult ED between April 19, 2005, and April 18, 2007, who were discharged with a prescription. Prior to April 19, 2006, a specialized prescription form stored in a locked cabinet was obtained from the nursing staff to write a prescription for benzodiazepines or Schedule II opioids. After April 19, 2006, New York State mandated that all prescriptions, regardless of schedule classification, be generated on a specialized bar-coded prescription form. The main outcome of the study was to compare the proportion of Schedule III-V opioids to Schedule II opioids and benzodiazepines prescribed in the ED before and after the introduction of a less cumbersome prescription writing process.

RESULTS

Of the 26,638 charts reviewed, 2.1% of the total number of prescriptions generated were for a Schedule II controlled opioid before the new system was implemented compared to 13.6% after (odds ratio [OR] = 7.3, 95% confidence interval [CI] = 6.4 to 8.4). The corresponding percentages for Schedule III-V opioids were 29.9% to 18.1% (OR = 0.52, 95% CI = 0.49 to 0.55) and for benzodiazepines 1.4% to 3.9% (OR = 2.8, 95% CI = 2.4 to 3.4).

CONCLUSIONS

Patients were more likely to receive a prescription for a Schedule II opioid or a benzodiazepine after a more streamlined computer-generated prescription writing process was introduced in this ED.

[The role of strong opioids in the treatment of the chronic musculoskeletal pain]

This article concentrates on recent evidence about opioid analgesics for persistent musculoskeletal pain. Chronic musculoskeletal pain is a major health problem for which opioids provide one treatment option. Pain is an experience that affects all aspects of a patient's life and effective pain management with strong opioids may help the patient to focus on the positive aspects of life, decreasing the focus on pain. This therapy should be reserved for patients who fail to respond to other lower-risk options and only after proper consideration is given to the long-term consequences of strong opioid use according to the WHO three-step ladder. Several reviews and our experience have shown that opioids are typically reserved for moderate to severe musculoskeletal pain that cannot be relieved by other drugs. In this article are presented the strong opioid drugs, routes of administration, dosage guidelines and potential adverse effects. The management of patients with chronic musculoskeletal pain is a common clinical challenge.

[Efficacy comparison between morphine sulfate controlled-released tablet and morphine hydrochloride sustained-released tablet in treating cancer pain]

BACKGROUND & OBJECTIVE

Morphine sulfate controlled-released tablet and morphine hydrochloride sustained-released tablet are preferred medicines for treating moderate-severe cancer pain. There are some differences between the two medicines in their efficacy, metabolism and adverse events. This study was to compare the efficacy and toxicities between morphine sulfate controlled-released tablet and morphine hydrochloride sustained-released tablet in treating moderate-severe cancer pain.

METHODS

A total of 121 patients with moderate-severe cancer pain were randomized into two groups: 61 were treated with morphine sulfate controlled-released tablet and 60 were treated with morphine hydrochloride sustained-released tablet. Analgesic efficacy and toxicities of the two medicines were observed.

RESULTS

Of the 61 patients treated with morphine sulfate controlled-released tablet, 12 had moderate pain, 49 had severe pain; the total response rate was 91.80%. Of the 60 patients treated with morphine hydrochloride sustained-released tablet, 13 had moderate pain, 47 had severe pain; the total response rate was 91.67%. There was no significant difference in the efficacy between the two medicines. Digestive system adverse events, including nausea, vomiting and constipation, were more common in morphine hydrochloride sustained-released tablet group than in morphine sulfate controlled-released tablet group (66.66% vs. 34.43%, P<0.05).

CONCLUSIONS

Both morphine sulfate controlled-released tablet and morphine hydrochloride sustained-released tablet are safety in treating moderate-severe cancer pain and the toxicities are tolerable. We recommend to take morphine sulfate controlled-released tablet for older patients and the patients with digestive disorders.

Internet surveillance: content analysis and monitoring of product-specific internet prescription opioid abuse-related postings

OBJECTIVES

This study describes the development of a systematic approach to the analysis of Internet chatter as a means of monitoring potentially abusable opioid analgesics.

METHODS

Message boards dedicated to drug abuse were selected using specific inclusion criteria. Threaded discussions containing 48,293 posts were captured. A coding system was created to compare content of posts related to 3 opioid analgesics: Kadian, Vicodin, and OxyContin.

RESULTS

The number of posts containing mentions of the target drugs were significantly different [OxyContin (1813)>Vicodin (940)>Kadian (27), P<0.001]. Analyses revealed that these differences were not simply a reflection of the availability of each product (ie, number of prescriptions written). Reliability tests indicated that the content coding system achieved good interrater reliability coefficients (average kappa across all categories=0.76, range=0.52 to 1.0). Content analysis of a sample of 234 randomly selected posts indicated that the proportion of Internet posts endorsing abuse of Kadian was statistically significantly less than OxyContin (45.5% vs. 68.4%, P=0.036, not adjusted for multiple comparisons).

DISCUSSION

These results suggest that a systematic approach to postmarketing surveillance of Internet chatter related to pharmaceutical products is feasible and yields reliable information about the quantity of discussion of specific products and qualitative information regarding the nature of the discussions. Kadian was associated with fewer Internet mentions than either OxyContin or Vicodin. This investigation stands as a first attempt to establish systematic methods for conducting Internet surveillance.

Distinct effects of individual opioids on the morphology of spines depend upon the internalization of mu opioid receptors

This study has examined the relationship between the effects of opioids on the internalization of mu opioid receptors (MORs) and the morphology of dendritic spines. Several opioids (morphine, etorphine, DAMGO or methadone) were applied to cultured hippocampal neurons. Live imaging and biochemical techniques were used to examine the dynamic changes in MOR internalization and spine morphology. This study reveals that MOR internalization can regulate opioid-induced morphological changes in dendritic spines: (1) Chronic treatment with morphine, which induced minimal receptor internalization, caused collapse of dendritic spines. In contrast, "internalizing" opioids such as DAMGO and etorphine induced the emergence of new spines. It reveals that opioid-induced changes in spines vary greatly depending on how the applied opioid agonist affects MOR internalization. (2) The blockade of receptor internalization by dominant negative mutant of dynamin, K44E, reversed the effects of DAMGO and etorphine. It indicates that receptor internalization is necessary for the distinct effects of DAMGO and etorphine on spines. (3) In neurons that were cultured from MOR knock-out mice and had been co-transfected with DsRed and MOR-GFP, morphine caused collapse of spines whereas DAMGO induced emergence of new spines, indicating that opioids can alter the structure of spines via postsynaptic MORs. (4) Methadone at a low concentration induced minimal internalization and had effects that were similar to morphine. At a high concentration, methadone induced robust internalization and had effects that are opposite to morphine. The concentration-dependent opioid-induced changes in dendritic spines might also contribute to the variation in the effects of individual opioids.

Rational Use of Sublingual Opioids in Palliative Medicine

The sublingual administration of opioid analgesics has been a mainstay in the pain management of homebound dying hospice patients who are no longer able to swallow. It is also a potentially useful route of administration in other situations in which the oral route is not available and other routes are impractical or inappropriate. Potential advantages of the sublingual route include rapid analgesic onset and avoidance of hepatic first-pass metabolism. Pharmacokinetic and pharmacodynamic studies have yielded widely disparate data on sublingual morphine. Other opioids have been less studied. Available data suggests limited sublingual availability of hydrophilic opioids (e.g., morphine, oxycodone, and hydromorphone) and superior absorption of the lipophilic opioids (e.g., methadone and the fentanils). Buprenorphine, a potent, lipophilic, partial mu-opioid receptor agonist, appears promising but awaits further study.

Pharmacogenetics of Opioids

Opioids are used for acute and chronic pain and dependency. They have a narrow therapeutic index and large interpatient variability in response. Genetic factors regulating their pharmacokinetics (metabolizing enzymes, transporters) and pharmacodynamics (receptors and signal transduction elements) are contributors to such variability. The polymorphic CYP2D6 regulates the O-demethylation of codeine and other weak opioids to more potent metabolites with poor metabolizers having reduced antinociception in some cases. Some opioids are P-glycoprotein substrates, whereas, ABCB1 genotypes inconsistently influence opioid pharmacodynamics and dosage requirements. Single-nucleotide polymorphisms in the mu opioid receptor gene are associated with increasing morphine, but not methadone dosage requirements and altered efficacy of mu opioid agonists and antagonists. As knowledge regarding the interplay between genes affecting opioid pharmacokinetics including cerebral kinetics and pharmacodynamics increases, our understanding of the role of pharmacogenomics in mediating interpatient variability in efficacy and side effects to this important class of drugs will be better informed. Opioid drugs as a group have withstood the test of time in their ability to attenuate acute and chronic pain. Since the isolation of morphine in the early 1800s by Friedrich Sertürner, a large number of opioid drugs beginning with modification of the 4,5-epoxymorphinan ring structure were developed in order to improve their therapeutic margin, including reducing dependence and tolerance, ultimately without success.

Adverse effects of opioids on the central nervous systems of palliative care patients

Opioids, defined as drugs that stimulate opioid receptors, are primarily used in the treatment of moderate to severe pain. They induce central nervous system (CNS) adverse effects which can be divided into three groups. The first group includes effects that lower the level of consciousness-sedation, drowsiness and sleep disturbance. The second group affects the thinking process and the ability to react-cognitive impairment, psychomotor impairment, delirium, hallucinations, dreams and nightmares. The third group is of the direct toxic effects of opioids on neurons and includes myoclonus (perhaps), hyperalgesia and tolerance. This review addresses the incidence, possible mechanisms, and treatment of each of these groups of opioid-induced adverse effects.

Incomplete Recovery of Prescription Opioids in Urine using Enzymatic Hydrolysis of Glucuronide Metabolites

Confirmation of opioids in urine samples of clinical patients requires liberation of opioids from their glucuronide conjugates. Both acid hydrolysis and enzyme hydrolysis using beta-glucuronidase from various sources have been reported, with the latter approach prevailing in most clinical toxicology laboratories. The goal of this study was to compare the efficiency of acid versus different enzyme hydrolysis methods in recovering morphine and common semisynthetic opioids from glucuronide standards and 78 patient urine samples that were screened positive for opioids as a class. Specimens were analyzed with a validated gas chromatography-mass spectrometry (GC-MS) procedure. With the exception of oxycodone, the results indicated that the majority of opioids tested were extensively glucuronide-conjugated in urine. Significantly, acid hydrolysis liberated > 90% of morphine and hydromorphone from their glucuronide standards but enzyme hydrolysis had lower and variable efficiency, depending on the opiate type and the enzyme source. In patient specimens, much higher concentrations of free codeine, morphine, hydromorphone, and oxymorphone were obtained with acid hydrolysis than with various enzyme methods. Incomplete hydrolysis using beta-glucuronidase could lead to false-negative results for many opioids when urine is tested for drugs of abuse. We conclude that acid hydrolysis is the method of choice for GC-MS confirmation of urine opioids.

Geographic variation in the prescription of schedule II opioid analgesics among outpatients in the United States

OBJECTIVE

To measure geographic variation in opioid use in a large, commercially insured, outpatient population in the United States.

DATA SOURCES

Outpatient prescription drug claims database of a national pharmaceutical benefit manager for 7,873,337 subjects with at least one prescription drug claim in 2000.

STUDY DESIGN

We measured the period prevalence of claims for opioid analgesics and controlled-release oxycodone at the state level. We measured geographic variation using the weighted coefficient of variation and systematic component of variation. In county-level multivariable regression, we explored associations between potential explanatory variables and claims for opioid analgesics and controlled-release oxycodone.

PRINCIPAL FINDINGS

A total of 567,778 (64.2 per 1,000 total claims) were for oral opioid analgesics. Claim rates by state ranged from <20 to >100 claims per 1,000 total claims. States with long-standing prescription monitoring programs had among the lowest rates. In the county-level data, presence of a statewide prescription monitoring program and proportions of the population aged 15-24 and 65 years and older were independently and negatively associated with claim rates for all opioid analgesics. Surgeons per 1,000, proportion of the population reporting illicit drug use, and proportion who were female were independently and positively associated with claim rates for all opioid analgesics. Only the proportion of the population aged 25-34 and number of surgeons per 1,000 were independently and positively associated with claim rates for oxycodone.

CONCLUSIONS

Claim rates for opioid analgesics vary significantly by state. Presence of a statewide prescription monitoring program is associated with lower claim rates at the county level. Future research should use individual-level data to assess whether these findings reflect a reduction in abuse and diversion or suboptimal treatment of pain.

[Clinical pharmacology of analgesics: outlook and risks]

Despite that many drugs are available for pain treatment, many patients are still suffering because of wrong choice or wrong use of analgesics. Both are determined by the degree and the nature of pain to be treated. Non-opioid drugs, especially COX-2-inhibitors are extensively evaluated. If treatment with these drugs is not sufficient, opioids have to be used. Their efficiency is outstanding and their side effects are appropriate. However, doctors and nurses are still reluctant to use opioids because of overestimation of respiratory depression and addiction.

Opioid guidelines in the management of chronic non-cancer pain

BACKGROUND

Opioid abuse has increased at an alarming rate. However, available evidence suggests a wide variance in the use of opioids, as documented by different medical specialties, medical boards, advocacy groups, and the Drug Enforcement Administration (DEA).

OBJECTIVES

The objective of these opioid guidelines by the American Society of Interventional Pain Physicians (ASIPP) is to provide guidance for the use of opioids for the treatment of chronic non-cancer pain, to bring consistency in opioid philosophy among the many diverse groups involved, to improve the treatment of chronic non-cancer pain, and to reduce the incidence of drug diversion.

DESIGN

A policy committee evaluated a systematic review of the available literature regarding opioid use in managing chronic non-cancer pain. This resulted in the formulation of the essentials of guidelines, a series of potential evidence linkages representing conclusions, followed by statements regarding relationships between clinical interventions and outcomes.

METHODS

Consistent with the Agency for Healthcare Research and Quality (AHRQ) hierarchical and comprehensive standards, the elements of the guideline preparation process included literature searches, literature synthesis, systematic review, consensus evaluation, open forum presentations, formal endorsement by the Board of Directors of the American Society of Interventional Pain Physicians (ASIPP), and blinded peer review. Evidence was designated based on scientific merit as Level I (conclusive), Level II (strong), Level III (moderate), Level IV (limited), or Level V (indeterminate).

RESULTS

After an extensive review and analysis of the literature, the authors utilized two systematic reviews, two narrative reviews, 32 studies included in prior systematic reviews, and 10 additional studies in the synthesis of evidence. The evidence was limited.

CONCLUSION

These guidelines evaluated the evidence for the use of opioids in the management of chronic non-cancer pain and recommendations for management. These guidelines are based on the best available scientific evidence and do not constitute inflexible treatment recommendations. Because of the changing body of evidence, this document is not intended to be a "standard of care."

Opioid dosing trends and mortality in Washington State workers' compensation, 1996-2002

BACKGROUND

The use of opioids for chronic non-cancer pain has increased in the United States since state laws were relaxed in the late 1990s. These policy changes occurred despite scanty scientific evidence that chronic use of opioids was safe and effective.

METHODS

We examined opiate prescriptions and dosing patterns (from computerized databases, 1996 to 2002), and accidental poisoning deaths attributable to opioid use (from death certificates, 1995 to 2002), in the Washington State workers' compensation system.

RESULTS

Opioid prescriptions increased only modestly between 1996 and 2002. However, prescriptions for the most potent opioids (Schedule II), as a percentage of all scheduled opioid prescriptions (II, III, and IV), increased from 19.3% in 1996 to 37.2% in 2002. Among long-acting opioids, the average daily morphine equivalent dose increased by 50%, to 132 mg/day. Thirty-two deaths were definitely or probably related to accidental overdose of opioids. The majority of deaths involved men (84%) and smokers (69%).

CONCLUSIONS

The reasons for escalating doses of the most potent opioids are unknown, but it is possible that tolerance or opioid-induced abnormal pain sensitivity may be occurring in some workers who use opioids for chronic pain. Opioid-related deaths in this population may be preventable through use of prudent guidelines regarding opioid use for chronic pain.