Pharmacogenetics of Opioids

Pharmacogenotyping disproves genetic cause of drug-related problems in family history: a case report

BACKGROUND

In clinical practice, family medication history is not routinely assessed as part of a patient's family health history (FHH). The information is self-reported and can depend on the individual's subjective perception. To illustrate how pharmacogenetic (PGx) testing results could be used to validate self-reported family medication history on drug-related problems (DRP), as well as to inform medication-related decisions, we herein present a case involving ten members of the same family.

CASE PRESENTATION

Prior to a planned surgery, a preemptive PGx panel test was performed for a nine-year-old girl due to self-reported family medication history. The PGx panel test was also performed for her three siblings, parents, and grandparents. The focus was directed to the paternal grandmother, as she reported DRP from the hypnotic agent propofol, and to the maternal grandmother, as she described DRP after the administration of codeine and tramadol. A commercial PGx panel test of 100 variations in 30 different genes was conducted and analyzed focusing on genetic variants in cytochrome P450 enzyme 2B6 (CYP2B6), and CYP2D6 as they are involved in the biotransformation of propofol and the bioactivation of codeine and tramadol, respectively. The girl was identified as (1) CYP2B6 intermediate metabolizer (IM) with reduced enzyme activity and (2) CYP2D6 poor metabolizer (PM) with no enzyme activity. Regarding the planned surgery, it was recommended (1) to carefully titrate propofol dosage with increased monitoring of potential DRP and (2) to avoid opioids whose activation is mediated by CYP2D6 (e.g. codeine and tramadol). Further PGx testing revealed (1) the paternal grandmother as CYP2B6 normal metabolizer (NM) and (2) the maternal grandmother as CYP2D6 NM.

CONCLUSION

The original trigger for PGx testing was the self-reported, conspicuous family medication history of DRP reported by the grandmothers. However, the girl's genotype predicted phenotypes of CYP2B6 IM and CYP2D6 PM, differed from the grandmothers'. With this exemplary case, we propose that hereditary concerns based on self-reported information on DRP should be verified by a PGx panel test, when the respective drug exhibits a PGx association. Also, the girl's PGx testing results provided important medication recommendations, which were considered perioperatively by the anesthetist suggesting to use PGx testing results preemptively to inform medication-related decisions.

In vitro inhibitory effects of selumetinib on activity of human UDP-glucuronosyltransferases and prediction of in vivo drug-drug interactions

Selumetinib is an oral, effective, and selective tyrosine kinase inhibitor targeting mitogen-activated protein kinase 1 and 2 (MEK1/2), which is clinically active in multiple tumor types, such as neurofibromatosis type 1 (NF1), melanoma, gliomas and non-small cell lung cancer (NSCLC). The purpose of this article was to assess the effects of selumetinib on the activities of twelve human UDP-glucosyltransferases (UGTs) including UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, and 2B17, and its potential for inducing clinical drug-drug interactions (DDIs). The results demonstrated that selumetinib potently inhibited the activity of UGT2B7 through the mechanism of mixed inhibition with the inhibition constant value of 5.79 ± 0.65 μM. Furthermore, the plasma concentration of UGT2B7 substrate as the co-administered drug was predicted to be increased by at least 84 % when patients took selumetinib 75 mg twice daily, suggesting a high potential to induce clinical DDIs. Selumetinib exhibited weak inhibitory effects on other human UGTs and was unlikely to trigger off UGTs-mediated DDIs except for UGT2B7. Therefore, the combination of selumetinib with the substrate drug of UGT2B7 requires additional attention to avoid adverse events in clinical treatment.

Protective effects of pistachio hydroalcoholic extract on morphine-induced analgesic tolerance and dependence: investigating the impact of oxidative stress

Background and purpose

Chronic consumption of morphine (Mor) induces tolerance and dependence. This study aimed to survey the effects of pistachio extract (PX) on the induction and expression of Mor analgesic tolerance and physical dependency in mice.

Experimental approach

Animals were randomly separated into six groups (n = 7): control, DMSO, Mor (10 mg/kg), Mor + saline, Mor + PX (10 mg/kg), and Mor + PX (100 mg/kg). Mor was injected (10 mg/kg, twice a day, s.c.) for 7 days to induce tolerance. PX was administered (10 and 100 mg/kg, orally) during the examination period. On each day and 20 min after Mor administration, a tail-flick test was done to measure the analgesic response and induction of tolerance. On day 7, naloxone (5 mg/kg, s.c.) was injected into the Mor-dependent animals to evaluate dependence, and animals were monitored for 30 min for jumping. Also, malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were assessed in the brain tissue.

Findings/Results

Our results indicated that co-administration of PX with Mor for 7 days diminished the induction of Mor tolerance. PX administration for 7 days alongside Mor reduced the frequency of withdrawal signs in naloxone-injected animals during dependence induction. Also, Mor increased the level of MDA and decreased the activities of SOD and GPx. Treatment with PX (100 mg/kg) restored all of the mentioned abnormalities.

Conclusion and implications

According to the results presented in this study, chronic administration of PX forbade the induction of Mor analgesic tolerance and dependency in mice.

The role of drug efflux and uptake transporters in the plasma pharmacokinetics and tissue disposition of morphine and its main metabolites

Morphine is a widely used opioid for the treatment of pain. Differences in drug transporter expression and activity may contribute to variability in morphine pharmacokinetics and response. Using appropriate mouse models, we investigated the impact of the efflux transporters ABCB1 and ABCG2 and the OATP uptake transporters on the pharmacokinetics of morphine, morphine-3-glucuronide (M3G), and M6G. Upon subcutaneous administration of morphine, its plasma exposure in Abcb1a/1b-/-;Abcg2-/--, Abcb1a/1b-/-;Abcg2-/-;Oatp1a/1b-/-;Oatp2b1-/- (Bab12), and Oatp1a/1b-/-;Oatp2b1-/- mice was similar to that found in wild-type mice. Forty minutes after dosing, morphine brain accumulation increased by 2-fold when mouse (m)Abcb1 and mAbcg2 were ablated. Relative recovery of morphine in small intestinal content was significantly reduced in all the knockout strains. In the absence of mOatp1a/1b and mOatp2b1, plasma levels of M3G were markedly increased, suggesting a lower elimination rate. Moreover, Oatp-deficient mice displayed reduced hepatic and intestinal M3G accumulation. Mouse Oatps similarly affected plasma and tissue disposition of subcutaneously administered M6G. Human OATP1B1/1B3 transporters modestly contribute to the liver accumulation of M6G. In summary, mAbcb1, in combination with mAbcg2, limits morphine brain penetration and its net intestinal absorption. Variation in ABCB1 activity due to genetic polymorphisms/mutations and/or environmental factors might, therefore, partially affect morphine tissue exposure in patients. The ablation of mOatp1a/1b increases plasma exposure and decreases the liver and small intestinal disposition of M3G and M6G. Since the contribution of human OATP1B1/1B3 to M6G liver uptake was quite modest, the risks of undesirable drug interactions or interindividual variation related to OATP activity are likely negligible.

Physiologically based pharmacokinetic modeling to predict the pharmacokinetics of codeine in different CYP2D6 phenotypes

Objectives

Codeine, a prodrug used as an opioid agonist, is metabolized to the active product morphine by CYP2D6. This study aimed to establish physiologically based pharmacokinetic (PBPK) models of codeine and morphine and explore the influence of CYP2D6 genetic polymorphisms on the pharmacokinetics of codeine and morphine.

Methods

An initial PBPK modeling of codeine in healthy adults was established using PK-Sim® software and subsequently extrapolated to CYP2D6 phenotype-related PBPK modeling based on the turnover frequency (Kcat) of CYP2D6 for different phenotype populations (UM, EM, IM, and PM). The mean fold error (MFE) and geometric mean fold error (GMFE) methods were used to compare the differences between the predicted and observed values of the pharmacokinetic parameters to evaluate the accuracy of PBPK modeling. The validated models were then used to support dose safety for different CYP2D6 phenotypes.

Results

The developed and validated CYP2D6 phenotype-related PBPK model successfully predicted codeine and morphine dispositions in different CYP2D6 phenotypes. Compared with EMs, the predicted AUC0-∞ value of morphine was 98.6% lower in PMs, 60.84% lower in IMs, and 73.43% higher in UMs. Morphine plasma exposure in IMs administered 80 mg of codeine was roughly comparable to that in EMs administered 30 mg of codeine. CYP2D6 UMs may start dose titration to achieve an optimal individual regimen and avoid a single dose of over 20 mg. Codeine should not be used in PMs for pain relief, considering its insufficient efficacy.

Conclusion

PBPK modeling can be applied to explore the dosing safety of codeine and can be helpful in predicting the effect of CYP2D6 genetic polymorphisms on drug-drug interactions (DDIs) with codeine in the future.

Perspectives on approaching pain management in patients with dementia

This paper presents a review of the latest literature and guidance regarding the assessment and management of pain in older adults with dementia. The size and nature of the problem will be presented, in terms of the increasing aging population across the globe and potential for a significant increase in adults with dementia, along with the reduction in younger counterparts who will be available to provide care in the future. We will present the latest recommendations regarding how to assess pain and which tools are recommended for use underpinned by the strongest evidence. Finally, we will present the findings of the latest national (UK) guidelines for the management of pain. Recommendations will be made for future research and clinical practice.

Endorphins, Sexuality, and Reproduction

Beta-endorphin is secreted from the hypothalamus and pituitary in both mother and newborn. The placenta produces numerous pituitary hormones from the third month of pregnancy, one of which is βE. It has been suggested that βE has a role in the appetitive and precopulatory phase of sexual behavior in animals. An increase in endorphin levels during sexual activity in humans may contribute to attachment and bonding between partners, but contradictory reports in the literature question the association between sexuality and βE levels. The level of βE also increases during pregnancy, rises in early labor, peaks in late labor, and drops in the postpartum period. This fluctuation provides natural analgesia, raises the pain threshold, decreases the sensation of pain, or suppresses pain, and decreases fear levels during labor and birth. Beta-endorphin also protects the fetus from hypoxia during labor and birth and potential neural damage by aiding blood flow to the brain under hypoxic conditions. It has been suggested that a variety of pharmacologic and nonpharmacologic complementary therapies, when used in pregnancy, labor, and birth, activate the opioid receptors in the CNS and alter the sensation of pain during labor and birth, affect the mother-child attachment and affect sexual function. These studies report contradictory results that will be discussed in this chapter.

A scoping review on the availability and utilization of essential opioid analgesics in Sub-Saharan Africa

BACKGROUND

Management of acute, post-operative, and chronic pain requires access to and availability of opioids. While often oversupplied in high-income countries, significant shortages exist in low- and middle-income countries. We conducted a scoping review on availability and usage of opioids in Sub-Saharan Africa (SSA).

METHODS

The five-stage approach of Arksey and O'Malley (2005) was used. MEDLINE via PubMed, EMBASE, and SCOPUS were search and results categorized into themes: 1) Local/regional availability and supply, 2) Consumption patterns, 3) Legislation and policy, 4) Costs and financing, 5) Knowledge and cultural beliefs, and 6) Education and training.

RESULTS

6923 studies were identified from which 69 (1%) met inclusion criteria. Five key findings were: 1) Significant shortages exist, especially in rural areas, 2) Non-opioid analgesics commonly used as first-line acute pain management, 3) Barriers to market entry and bureaucratic processes prevent local production, 4) Significant knowledge gaps/myths exist amongst healthcare practitioners on opioid use, and 5) Continuous education and short courses will be critical.

CONCLUSIONS

Major challenges significantly limit availability and utilization of essential opioids in SSA. Reforms needed to upscale training and education, increase uptake by professionals, and increase market entry.

Pharmacogenetics of pain management in Zimbabwean patients with sickle cell disease

Background: Pain is a common cause of hospitalization in sickle cell disease (SCD) patients. Failure to effectively control pain remains a challenge in patient care. Materials & methods: The authors conducted a cross-sectional study to determine the effect of CYP2D6 and UGT2B7 polymorphisms on pain management in 106 Zimbabwean SCD patients. Participant information was collected on a questionnaire. Genotyping was conducted using the GenoPharm® pharmacogenomics open array panel containing CYP2D6 and UGT genetic variants implicated in opioid response. Results: The reduced function alleles CYP2D6*17 and *29 had high frequencies of 15.9% and 12.9%, respectively. UGT2B7 rs73823859 showed a statistically significant correlation with pain levels (p = 0.0454). Conclusion: This study demonstrated the role of UGT2B7 polymorphism in SCD patient pain management.

Pharmacological data science perspective on fatal incidents of morphine treatment

Morphine prescribed for analgesia has caused drug-related deaths at an estimated incidence of 0.3% to 4%. Morphine has pharmacological properties that make it particularly difficult to assess the causality of morphine administration with a patient's death, such as its slow transfer between plasma and central nervous sites of action and the existence of the active metabolite morphine-6-glucuronide with opioid agonistic effects, Furthermore, there is no well-defined toxic dose or plasma/blood concentration for morphine. Dosing is often adjusted for adequate pain relief. Here, we summarize reported deaths associated with morphine therapy, including associated morphine exposure and modulating patient factors such as pharmacogenetics, concomitant medications, or comorbidities. In addition, we systematically analyzed published numerical information on the stability of concentrations of morphine and its relevant metabolites in biological samples collected postmortem. A medicolegal case is presented in which the causality of morphine administration with death was in dispute and pharmacokinetic modeling was applied to infer the administered dose. The results of this analytical review suggest that (i) inference from postmortem blood concentrations to the morphine dose administered has low validity and (ii) causality between a patient's death and the morphine dose administered remains a highly context-dependent and collaborative assessment among experts from different medical specialties.

Effects of Intraoperative Opioid Administration on Postoperative Pain and Pain Threshold: A Randomized Controlled Study

Fentanyl and short-acting remifentanil are often used in combination. We evaluated the effect of intraoperative opioid administration on postoperative pain and pain thresholds when the two drugs were used. Patients who underwent gynecological laparoscopic surgery were randomly assigned into two groups (15 patients each) to receive either sufficient (group A) or minimum (group B) fentanyl (maximum estimated effect site concentration: A: 7.86 ng/mL, B: 1.5 ng/mL). The estimated effect site concentration at the end of surgery was adjusted to the same level (1 ng/mL). Patients in both groups also received continuous intravenous remifentanil during surgery. The primary outcome was the pressure pain threshold, as evaluated by a pressure algometer 3 h postoperatively. The pressure pain threshold at 3 h postoperatively was 51.1% (95% CI: [44.4–57.8]) in group A and 56.6% [49.5–63.6] in group B, assuming a preoperative value of 100% (p = 0.298). There were no significant differences in pressure pain threshold and numeric rating scale scores between the groups after surgery. The pain threshold decreased significantly in both groups at 3 h postoperatively compared to preoperative values, and recovered at 24 h. Co-administration of both opioids caused hyperalgesia regardless of fentanyl dose.

Association of polymorphisms in ARRB2 and clinical response to methadone for pain in advanced cancer

Background: The prescription of methadone in advanced cancer poses multiple challenges due to the considerable interpatient variation seen in effective dose and toxicity. Previous reports have suggested that ARRB2 influences the response to methadone in opioid substitution therapy. Associations with opioid response for pain management in advanced cancer are conflicting, with no studies including methadone as the primary intervention. Methods: In a prospective, multicenter, open-label dose individualization study, we investigated whether polymorphisms in ARRB2 were associated with methadone dose requirements and pain severity. Results: Significant associations were found for rs3786047, rs1045280, rs2036657 and pain score. Conclusion: While studies are few and the sample size small, ARRB2 genotyping may assist in individualized management of the most feared symptom in advanced cancer.

A non-injected opioid analgesia protocol for acute pain crisis in adolescents and adults with sickle cell disease

Initial management of the acute pain crisis (APC) of sickle cell disease (SCD) is often unsatisfactory, and might be improved by developing a standardised analgesia protocol. Here, we report the first stages in developing a standard oral protocol for adolescents and adults. Initially, we performed a dose finding study to determine the maximal tolerated dose of sublingual fentanyl (MTD SLF) given on arrival in the acute care facility, when combined with repeated doses of oral oxycodone. We used a dose escalation algorithm with two dosing ranges based on patient’s weight (<50 kg or >50 kg). We also made a preliminary evaluation of the safety and efficacy of the protocol. The study took place in a large tertiary centre in London, UK. Ninety patients in the age range 14–60 years were pre-consented and 31 treatment episodes were evaluated. The first 21 episodes constituted the dose escalation study, establishing the MTD SLF at 600 mcg (>50 kg) or 400 mcg (<50 kg). Further evaluation of the protocol indicated no evidence of severe opioid toxicity, nor increased incidence of acute chest syndrome (ACS). Between 0 and 6 hours, the overall gradient of reduction of visual analogue pain score (visual analogue scale (VAS)) was 0.32 centimetres (cm) per hour (95% confidence interval (CI) = 0.20 to 0.44, p < 0.001). For episodes on MTD SLF, there was median (interquartile range (IQR)) reduction in VAS score of 2.8 cm (0–4.2) and 59% had at least a 2.6-cm reduction. These results are supportive of further evaluation of this protocol for acute analgesia of APC in a hospital setting and potentially for supervised home management.

Effects of valsartan on morphine tolerance and dependence in rats

Background and purpose:

Opiates are traditionally used for the treatment of pain. Chronic consumption of opiates such as morphine (MOR) induces tolerance and dependence. This study aimed to investigate the effects of valsartan (VAL), as an angiotensin II receptor blocker, on the induction and expression of MOR analgesic tolerance and physical dependence in rats.

Experimental approach:

MOR 10 mg/kg was injected s.c. twice a day for 7 days to induce tolerance and dependence. For evaluating the effect of VAL on the induction of MOR analgesic tolerance and physical dependence, 20 mg/kg VAL was administered orally (once a day) during the 7 days of the examination period. The tail-flick test was performed every day. On day 7, 5 mg/kg naloxone () was injected s.c. into the morphine-dependent rats and the rats were monitored for 30 min for the frequency of withdrawal signs such as jumping, diarrhea, defecation, head tremor, rearing, scratching, sniffing, teeth chattering, and wet-dog shake. For evaluating the effect of VAL on the expression of MOR-analgesic tolerance and physical dependence, 45 min before the last MOR injection, VAL was administered only on day 7. The tail-flick test was performed and naloxone was injected into the addicted rats and they were monitored for 30 min for the frequency of withdrawal signs such as jumping, diarrhea, defecation, head tremor, rearing, scratching, sniffing, teeth chattering, and wet-dog shake.

Findings/Results:

Our results revealed that the co-administration of VAL with MOR for 7 consecutive days reduced the induction of MOR tolerance. Moreover, VAL administration for 7 days along with MOR reduced the frequency of diarrhea and defecation in naloxone-injected animals.

Conclusion and implications:

According to the results presented in this study, chronic administration of VAL prevented the induction of MOR-analgesic tolerance and dependence in rats.

Clinical outcomes of concomitant rifamycin and opioid therapy: A systematic review

Opioids are one of the most prescribed classes of analgesic medications. Their narrow therapeutic index and metabolism through cytochrome p450 (CYP) enzymes can result in a drug interaction when used concomitantly with rifamycins. In clinical scenarios where concurrent therapy with an opioid and a rifamycin occurs, there is no standardized guidance for managing the interaction. The objective of this review was to examine literature which evaluates the concomitant use of opioids and rifamycins with clinically relevant CYP-inducing properties. A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria was performed. PubMed, Scopus, and OVID Embase were queried for studies from database inception to January 2020 related to rifamycin and opioid medications. Only full-text, peer-reviewed, English language articles addressing clinical outcomes from concomitant rifamycin and opioid therapy were included. The review isolated 12 articles for data extraction from an original 2260 citations identified. Rifampin (11; 92%) and rifabutin (2; 17%) were the rifamycins studied along with seven different opioids. Decreased effect of opioids with concomitant rifampin therapy manifested as withdrawal in numerous patients on methadone and a decreased analgesic effect from tramadol, morphine, and, most notably, oxycodone. Only the combinations of rifampin with buccal fentanyl and rifabutin with buprenorphine and methadone were found to have no clinically measurable interaction. Available literature suggests that a decrease in opioid clinical effects is appreciated with concomitant rifamycin therapy. Further research is needed to focus on specific mitigation strategies beyond opioid agent selection, such as dosing adjustment recommendations.

Influence of Genetic Polymorphisms on the Response to Tramadol, Ibuprofen, and the Combination in Patients With Moderate to Severe Pain After Dental Surgery

PURPOSE

We aimed to elucidate the influence on analgesic effect of genetic polymorphisms in enzymes responsible for biotransformation of tramadol and ibuprofen or other possible genes involved in their mechanism of action.

METHODS

The study population comprised 118 patients from a multicenter, randomized, double-blind, placebo-controlled, Phase III clinical trial that assessed the analgesic efficacy and tolerability of a single dose of ibuprofen (arginine)/tramadol 400/37.5 mg compared with ibuprofen arginine 400 mg alone, tramadol 50 mg alone, and placebo in patients with moderate to severe pain after dental surgery. We analyzed 32 polymorphisms in the cytochrome P450 (CYP) enzymes COMT, ABCB1, SLC22A1, OPRM1, and SLC22A1.

FINDINGS

We did not find any statistically significant difference among CYP2C9 phenotypes related to ibuprofen response, although CYP2C9 poor metabolizers had a longer effect (higher pain relief at 6 hours). Likewise, we did not find any statistically significant difference among PTGS2 genotypes, contradicting previously publications.

IMPLICATIONS

There was not a clear effect of CYP2D6 phenotype on tramadol response, although CYP2D6 poor metabolizers had a slower analgesic effect. Concerning the transport of CYP2D6, we observed a better response in individuals carrying ABCB1 mutated alleles, which might correlate with higher tramadol plasma levels. Finally, we found a statistically significant better response in patients carrying the OPRM1 A118G G allele, which contradicts the previous reports. Measuring the active metabolite O-desmethyl-tramadol formation would be of great importance to better evaluate this association because O-desmethyl-tramadol has a higher μ-opioid receptor affinity compared with the parent drug. EudraCT.ema.europa.eu identifier: 2013-004637-33.

Opioid Treatment for Neonatal Opioid Withdrawal Syndrome: Current Challenges and Future Approaches

Chronic intrauterine exposure to psychoactive drugs often results in neonatal opioid withdrawal syndrome (NOWS). When nonpharmacologic measures are insufficient in controlling NOWS, morphine, methadone, and buprenorphine are first-line medications commonly used to treat infants with NOWS because of in utero exposure to opioids. Research suggests that buprenorphine may be the leading drug therapy used to treat NOWS when compared with morphine and methadone. Currently, there are no consensus or standardized treatment guidelines for medications prescribed for NOWS. Opioids used to treat NOWS exhibit large interpatient variability in pharmacokinetics (PK) and pharmacodynamic (PD) response in neonates. Organ systems undergo rapid maturation after birth that may alter drug disposition and exposure for any given dose during development. Data regarding the PK and PD of opioids in neonates are sparse. Pharmacometric methods such as physiologically based pharmacokinetic and population pharmacokinetic modeling can be used to explore factors predictive of some of the variability associated with the PK/PD of opioids in newborns. This review discusses the utility of pharmacometric techniques for enhancing precision dosing in infants requiring opioid treatment for NOWS. Applying these approaches may contribute to optimizing the outcome by reducing cumulative drug exposure, mitigating adverse drug effects, and reducing the burden of NOWS in neonates.

Relative addictive potential of opioid analgesic agents

Opioid overdoses and deaths continue to be a problem in the USA with a significant portion related to prescribed opioid analgesic agents. The role of pharmacogentic factors in opioid addiction is an active area of research. While all opioid analgesic agents have some addictive potential, it is clear that there are some with greater addictive potential. Oxycodone is the most widely abused opioid analgesic and it appears to predispose to chronic use with high likability by users. Fentanyl and hydromorphone are both very lipophilic allowing rapid penetration into the CNS, but are not rated as highly as other agents. Providers should consider the risk of addiction with the opioids they prescribe and give those with a lower addictive potential.

Pharmacological Chaperones Attenuate the Development of Opioid Tolerance

Opioids are potent analgesics widely used to control acute and chronic pain, but long-term use induces tolerance that reduces their effectiveness. Opioids such as morphine bind to mu opioid receptors (MORs), and several downstream signaling pathways are capable of inducing tolerance. We previously reported that signaling from the endoplasmic reticulum (ER) contributed to the development of morphine tolerance. Accumulation of misfolded proteins in the ER induced the unfolded protein response (UPR) that causes diverse pathological conditions. We examined the effects of pharmacological chaperones that alleviate ER stress on opioid tolerance development by assessing thermal nociception in mice. Pharmacological chaperones such as tauroursodeoxycholic acid and 4-phenylbutyrate suppressed the development of morphine tolerance and restored analgesia. Chaperones alone did not cause analgesia. Although morphine administration induced analgesia when glycogen synthase kinase 3β (GSK3β) was in an inactive state due to serine 9 phosphorylation, repeated morphine administration suppressed this phosphorylation event. Co-administration of chaperones maintained the inactive state of GSK3β. These results suggest that ER stress may facilitate morphine tolerance due to intracellular crosstalk between the UPR and MOR signaling. Pharmacological chaperones may be useful in the management of opioid misuse.

A theoretical framework and nomenclature to characterize the iatrogenic contribution of therapeutic opioid exposure to opioid induced hyperalgesia, physical dependence, and opioid use disorder

Opioid use, misuse, and risky use contribute to a critically important and complex crisis in current healthcare. Consequences of long-term opioid use, including opioid induced hyperalgesia, physical dependence, and opioid use disorder, can be considered iatrogenic, or partially iatrogenic, in cases where therapeutic opioid exposures were contributory. Research investigation and presumptive clinical action are needed to attenuate the iatrogenic component of the opioid crisis; treatment of individuals already suffering from opioid use disorder will not prevent incident cases. This work will be challenged by a remarkably high degree of complexity involving myriad and highly variable factors along the continuum from initial opioid exposure to long-term opioid use. An organized view of this complex problem should accelerate the pace of innovation and facilitate clinical implementation of research findings. Herein, we propose a theoretical framework and modern nomenclature for characterizing therapeutic opioid exposure and the degree to which it contributes iatrogenically to adverse outcomes. In doing so, we separate the role of exposure from other factors contributing to long-term opioid use, clarify the relationship between opioid exposure and outcomes, emphasize that exposure source is an important consideration for health services research and practice in the areas of pain treatment and opioid prevention, and recommend terminology necessary to quantify therapeutic opioid exposure separately from nonmedical exposure.

Simultaneous and Sensitive Determination of Amphetamine, Codeine and Morphine in Exhaled Breath Condensate, Using Capillary Electrophoresis Coupled with On-line and Off-line Enhancing Methods

Background:

Abuse of drugs is associated with several medical, forensic, toxicology and social challenges. “Drugs of abuse” testing is therefore an important issue.

Objective:

We propose a simple CE-based method for the quantification of amphetamine, codeine and morphine after direct injection of Exhaled Breath Condensate (EBC) by the aid of simple stacking mode and an off-line pre-concentration method.

Methods:

Using graphene oxide adsorbents, amphetamine, codeine and morphine were extracted from EBC in order to eliminate the proteins and other interferences. In addition to off-line method, an online stacking mode was applied to improve the analytical signal obtained from the instrument.

Results:

The validation parameters were experimented on the developed method based on the FDA guideline over concentration ranges of 12.5-100, 30-500 and 10-1250 ng/mL associated with amphetamine, codeine and morphine, respectively. Small volumes (around 100 μL) of EBC were collected using a lab-made setup and successfully analyzed using the proposed method where precisions and accuracies (within day and between days) were in accordance with the guideline (recommended less than 15 % for biological samples). The recovery tests were used to evaluate the matrix effect and data (94 to 105 %) showed that the proposed method can be applied in different EBC matrix samplings of subjects.

Conclusion:

The proposed method is superior for simultaneous determination of amphetamine, codeine and morphine over chromatographic analyses because it is fast and consumes fewer chemicals, with no derivatization step.

Mortality Following Nonfatal Opioid and Sedative/Hypnotic Drug Overdose

INTRODUCTION

Opioid and sedative/hypnotic drug overdoses are major causes of morbidity in the U.S. This study compares 12-month incidence of fatal unintentional drug overdose, suicide, and other mortality among emergency department patients presenting with nonfatal opioid or sedative/hypnotic overdose.

METHODS

This is a retrospective cohort study using statewide, longitudinally linked emergency department patient record and mortality data from California. Participants comprised all residents presenting to a licensed emergency department at least once in 2009-2011 with nonfatal unintentional opioid overdose, sedative/hypnotic overdose, or neither (a 5% random sample). Participants were followed for 1 year after index emergency department presentation to assess death from unintentional overdose, suicide, or other causes, ascertained using ICD-10 codes. Absolute death rates per 100,000 person years and standardized mortality ratios relative to the general population were calculated. Data were analyzed February-August 2019.

RESULTS

Following the index emergency department visit, unintentional overdose death rates per 100,000 person years were 1,863 following opioid overdose, 342 following sedative/hypnotic overdose, and 31 for reference patients without an index overdose (respective standardized mortality ratios of 106.1, 95% CI=95.2, 116.9; 24.5, 95% CI=21.3, 27.6; and 2.6, 95% CI=2.2, 3.0). Suicide mortality rates per 100,000 were 319, 174, and 32 following opioid overdose, sedative/hypnotic overdose, and reference visits, respectively. Natural causes mortality rates per 100,000 were 8,058 (opioid overdose patients), 17,301 (sedative/hypnotic overdose patients), and 3,097 (reference patients).

CONCLUSIONS

Emergency department patients with nonfatal opioid or sedative/hypnotic drug overdose have exceptionally high risks of death from unintentional overdose, suicide, and other causes. Emergency department-based interventions offer potential for reducing these patients' overdose and other mortality risks.

Melatonin and morphine: potential beneficial effects of co-use

Morphine is a potent analgesic agent used to control acute or chronic pain. Chronic administration of morphine results in analgesic tolerance, hyperalgesia, and other side effects including dependence, addiction, respiratory depression, and constipation, which limit its clinical usage. Therefore, identifying the new analgesics with fewer side effects which could increase the effect of morphine and reduce its side effects is crucial. Melatonin, a multifunctional molecule produced in the body, is known to play an important role in pain regulation. The strong anti-inflammatory effect of melatonin is suggested to be involved in the attenuation of the pain associated with inflammation. Melatonin also increases the anti-nociceptive actions of opioids, such as morphine, and reverses their tolerance through regulating several cellular signaling pathways. In this review, published articles evaluating the effect of the co-consumption of melatonin and morphine in different conditions were investigated. Our results show that melatonin has pain-killing properties when administered alone or in combination with other anti-nociceptive drugs. Melatonin decreases morphine consumption in different pathologies. Furthermore, attenuation of morphine intake can be accompanied by reduction of morphine-associated side-effects, including physical dependence, morphine tolerance, and morphine-related hyperalgesia. Therefore, it is reasonable to believe that the combination of melatonin with morphine could reduce morphine-induced tolerance and hyperalgesia, which may result from anti-inflammatory and antioxidant properties of melatonin. Overall, we underscore that, to further ameliorate patients' life quality and control their pain in various pathological conditions, melatonin deserves to be used with morphine by anesthesiologists in clinical practice.

Involvement of CYP2D6 and CYP2B6 on tramadol pharmacokinetics

This study included 24 healthy volunteers who received a single 37.5 mg oral dose of tramadol. We analyzed 18 polymorphisms within CYP2D6, CYP2B6, CYP3A, COMT, ABCB1, SLC22A1 and OPRM1 genes by quantitative PCR, to study whether these polymorphisms affect its pharmacokinetics, pharmacodynamics and safety. CYP2D6 intermediate metabolizers (n = 6) showed higher tramadol plasma concentrations and lower clearance compared with normal and ultrarapid metabolizers. CYP2B6 G516T T/T (n = 2) genotype was also associated to higher tramadol plasma levels. No other polymorphism affected tramadol pharmacokinetics. Three volunteers experienced a prolonged QTc not associated with the genetic variants studied or altered phamacokinetic parameters. The correlation of CYP2B6 genotype with higher tramadol concentrations is remarkable since its influence on its elimination is also relevant and has been less studied to date. However, given our small sample size, it is important to interpret our results with caution.

Electroacupuncture for post-thoracotomy pain: Protocol for a systematic review and meta-analysis

BACKGROUND

Thoracotomy is a common surgical procedure used in cases such as trauma and cancer resection. It is an invasive procedure in which incisions are made in the chest wall to gain access to the chest. Therefore, it often produces intense postoperative pain. Electroacupuncture has been known for its analgesic effects in various conditions, including cases of postoperative pain. This protocol design is for a systematic review and meta-analysis to gather evidence and investigate the analgesic effects of electroacupuncture in pain after thoracotomy.

METHODS

The studies for the systematic review will be searched with keywords on the following 10 databases: PubMed, Cochrane Library (CENTRAL), EMBASE, MEDLINE, Google Scholar, CNKI, KoreaMed, KMBASE, KISS, and OASIS. The search will be done without language restrictions. Only the randomized controlled trials that meet the eligibility criteria will be finally included in the study. The quality of the study will be assessed using the Cochrane Collaborations' risk-of-bias tool, and Cochrane's software RevMan 5.3 will be used for meta-analysis.

RESULTS

The designed study will provide a systematic review and meta-analysis of the searched and randomized controlled trials that meet the eligibility criteria. Meta-analysis will be performed with pain scores as the main outcome measure, and they may also be performed with additional outcomes. The qualitative and quantitative data synthesis is expected to provide high quality evidence to judge the pain management effect of electroacupuncture for patients who underwent thoracotomy.

CONCLUSION

The conclusion of this systematic review and meta-analysis will provide evidence to judge whether electroacupuncture is an effective analgesic treatment option for patients suffering with post-thoracotomy pain.

PROSPERO REGISTRATION NUMBER

CRD42019142157.

Prediction of Drug-Drug Interactions Between Opioids and Overdosed Benzodiazepines Using Physiologically Based Pharmacokinetic (PBPK) Modeling and Simulation

Background

Researchers have long been interested in the potential drug–drug interactions (DDIs) between opioids and benzodiazepines. However, much remains unknown concerning the interactions between these two drug classes. The objective of this work is to study the mechanism underlying the DDIs between opioids and benzodiazepines from the perspective of their pharmacokinetic (PK) interactions. A PK interaction occurs when two drugs are metabolized by the same cytochrome P450 enzymes and is one of the most common reasons for DDIs.

Methods

We quantitatively predicted the DDIs between three opioids (fentanyl, oxycodone and buprenorphine) and four benzodiazepines (alprazolam, diazepam, midazolam and triazolam) using a physiologically based pharmacokinetic (PBPK) modeling approach. A set of PBPK models was first constructed for these common opioids and benzodiazepines using SimCYP software, and the DDIs between them were then explored at various dosages.

Results

Our simulation results suggested there were no PK interactions between normal doses of opioids and benzodiazepines; but weak interactions can be expected with the combination of opioids and overdosed benzodiazepines. Particular attention should be given to the combination of fentanyl and overdosed alprazolam since a PK interaction can be observed between them.

Conclusion

Our results appear to indicate that pharmacodynamics may play a more important role than PKs in causing DDIs between opioids and benzodiazepines. This study also demonstrated that molecular modeling can be a very useful tool to mitigate the problem of “missing metabolic reaction parameters” in PK modeling and simulation.

Electronic supplementary material

The online version of this article (10.1007/s40268-019-00282-3) contains supplementary material, which is available to authorized users.

Improving the therapeutic window of conventional opioids: novel differential signaling modulators

Conventional opioids are widely used for acute pain management in the postoperative setting. However, a primary concern with conventional opioids is their therapeutic window-the range between doses that produce the desired therapeutic effect (analgesia) and doses that produce unwanted opioid-related adverse events (ORAEs). Conventional µ receptor opioids have a narrow therapeutic window in part because of their mechanism of action (MoA): they bind to µ receptors and non-selectively activate two intracellular signaling pathways, leading to analgesia and to ORAEs. This review explores the clinical potential of µ receptor ligands with differential signaling. Agents with a 'differential signaling" MoA represent an innovative approach that may enhance the therapeutic window. These agents modulate µ receptor activity to selectively engage downstream signaling pathways associated with analgesia while limiting activity in downstream signaling pathways that lead to ORAEs. Differential signaling may fulfill an unmet need in the management of postoperative pain.

Multimodal Analgesia for Perioperative Management of Patients presenting for Spinal Surgery

Multimodal, non-opioid based analgesia has become the cornerstone of ERAS protocols for effective analgesia after spinal surgery. Opioid side effects, dependence and legislation restricting long term opioid use has led to a resurgence in interest in opioid sparing techniques. The increasing array of multimodal opioid sparing analgesics available for spinal surgery targeting novel receptors, transmitters, and altering epigenetics can help provide an optimal perioperative experience with less opioid side effects and long-term dependence. Epigenetic mechanisms of pain may enhance or suppress gene expression, without altering the genome itself. Such mechanisms are complex, dynamic and responsive to environment. Alterations that occur can affect the pathophysiology of pain management at a DNA level, modifying perceived pain relief. In this review, we provide a brief overview of epigenetics of pain, systemic local anesthetics and neuraxial techniques that continue to remain useful for spinal surgery, neuropathic agents, as well as other common and less common target receptors for a truly multimodal approach to perioperative pain management.

The pharmacogenetics of natural products: A pharmacokinetic and pharmacodynamic perspective

Natural products have represented attractive alternatives for disease prevention and treatment over the course of human history and have contributed to the development of modern drugs. These natural products possess beneficial efficacies as well as adverse efffects, which vary largely among individuals because of genetic variations in their pharmacokinetics and pharmacodynamics. As with other synthetic chemical drugs, the dosing of natural products can be optimized to improve efficacy and reduce toxicity according to the pharmacogenetic properties. With the emergence and development of pharmacogenomics, it is possible to discover and identify the targets/mechanisms of pharmacological effects and therapeutic responses of natural products effectively and efficiently on the whole genome level. This review covers the effects of genetic variations in drug metabolizing enzymes, drug transporters, and direct and indirect interactions with the pharmacological targets/pathways on the individual response to natural products, and provides suggestions on dosing regimen adjustments of natural products based on their pharmacokinetic and pharmacogenetic paratmeters. Finally, we provide our viewpoints on the importance and necessity of pharmacogenetic and pharmacogenomic research of natural products in natural medicine's rational development and clinical application of precision medicine.

Opioids in the treatment of non-specific acute and chronic pain

After reading this article, the reader will be familiar with the general classes of opioid agonists and partial agonists, the basics of the pharmacokinetics and pharmacodynamics of opioids, the risks of opioid therapy and the requirements for the safe and effective use of opioids in acute and chronic pain. The use of opioids during surgical procedures or anesthesia is not discussed. Also, there is no discussion about various available opioid antagonists that are used to treat overdose and the various disorders associated with their use (including naloxone and naltrexone). Opioids are available, the most powerful and effective analgesics, and have become acceptable drugs for the treatment of acute and cancerous pain. However, there is concern about their use in case of chronic pain, if there is no cancer, because they are long-range ineffective but best suited for stopping this pain. Opioid prescription must be monitored for better use. Chronic pain creates discomfort for these patients, reducing their productivity and efficiency, which, in turn, can lead to economic problems in the country. The choice of Nalbuphine is due to the following reasons: the opioid, which is comparable to morphine by its analgesic potential, but has a better safety profile for nausea, vomiting and respiratory depression; not subject to strict quantitative accounting (extract on prescription form 1); the choice of opioid analgesics is significantly limited in Ukraine.

Pharmacogenomics in Papua New Guineans: unique profiles and implications for enhancing drug efficacy while improving drug safety

Papua New Guinea (PNG) can be roughly divided into highland, coastal and island peoples with significant mitochondrial DNA differentiation reflecting early and recent distinct migrations from Africa and East Asia, respectively. Infectious diseases such as tuberculosis, malaria and HIV severely impact on the health of its peoples for which drug therapy is the major treatment and pharmacogenetics has clinical relevance for many of these drugs. Although there is generally little information about known single nucleotide polymorphisms in the population, in some instances, their frequencies have been shown to be higher than anywhere worldwide. For example, CYP2B6*6 is over 50%, and CYP2C19*2 and *3 are over 40 and 25%, respectively. Conversely, CYP2A6*9, 2B6*2, *3, *4 and *18, and 2C8*3 appear to be much lower than in Whites. CYP2D6 known variants are unclear, and for phase II enzymes, only UGT2B7 and UGT1A9 data are available, with variant frequencies either slightly lower than or similar to Whites. Although almost all PNG people tested are rapid acetylators, but which variant(s) define this phenotype is not known. For HLA-B*13:01, HLA-B*35:05 and HLA-C*04:01, the frequencies show some regioselectivity, but the clinical implications with respect to adverse drug reactions are not known. There are minimal phenotype data for the CYPs and nothing is known about drug transporter or receptor genetics. Determination of genetic variants that are rare in Whites or Asians but common in PNG people is a topic of both scientific and clinical importance, and further research needs to be carried out. Optimizing the safety and efficacy of infectious disease drug therapy through pharmacogenetic studies that have translation potential is a priority.

Melatonin and their analogs as a potential use in the management of Neuropathic pain

Melatonin (N-acetyl-5-methoxytryptamine), secreted by the pineal gland is known to perform multiple functions including, antioxidant, anti-hypertensive, anti-cancerous, immunomodulatory, sedative and tranquilizing functions. Melatonin is also known to be involved in the regulation of body mass index, control the gastrointestinal system and play an important role in cardioprotection, thermoregulation, and reproduction. Recently, several studies have reported the efficacy of Melatonin in treating various pain syndromes. The current paper reviews the studies on Melatonin and its analogs, particularly in Neuropathic pain. Here, we first briefly summarized research in preclinical studies showing the possible mechanisms through which Melatonin and its analogs induce analgesia in Neuropathic pain. Second, we reviewed research indicating the role of Melatonin in attenuating analgesic tolerance. Finally, we discussed the recent studies that reported novel Melatonin agonists, which were proven to be effective in treating Neuropathic pain.

Pharmacokinetics and physiologic/behavioral effects of buprenorphine administered sublingually and intravenously to neonatal foals

Buprenorphine is absorbed following sublingual administration, which would be a low-stress delivery route in foals. However, the pharmacokinetics/pharmacodynamics are not described in foals. Six healthy foals <21 days of age participated in a blinded, randomized, 3-period, 5-sequence, 3-treatment crossover prospective study. Foals received 0.01-0.02 mg/kg buprenorphine administered SL or IV with an equivalent volume of saline administered by the opposite route. Blood was collected from the cephalic vein for pharmacokinetic analysis. Physiologic parameters (HR, RR, body temperature, GI sounds), locomotion (pedometer), and behavioral data (activity level, nursing time, response to humans) were recorded. Plasma concentration of buprenorphine exceeded a presumed analgesic level (0.6 ng/ml) in five foals in the IV group and one in the SL group but only for a very brief time. Pharmacokinetic analysis following IV administration demonstrated a short elimination half-life (t_1/2β 1.95 ± 0.7 hr), large volume of distribution (6.46 ± 1.54 L/kg), and a high total clearance (55.83 ± 23.75 ml/kg/min), which differs from adult horses. Following SL administration, maximum concentrations reached were 0.61 ± 0.11 ng/ml and bioavailability was 25.1% ± 10.9%. In both groups, there were minor statistical differences in HR, RR, body temperature, locomotion, and time spent nursing. However, these differences were clinically insignificant in this single dose study, and excitement, sedation, or colic did not occur.

Novel Roles of Non-Coding RNAs in Opioid Signaling and Cardioprotection

Cardiovascular disease (CVD) is a significant cause of morbidity and mortality across the world. A large proportion of CVD deaths are secondary to coronary artery disease (CAD) and myocardial infarction (MI). Even though prevention is the best strategy to reduce risk factors associated with MI, the use of cardioprotective interventions aimed at improving patient outcomes is of great interest. Opioid conditioning has been shown to be effective in reducing myocardial ischemia-reperfusion injury (IRI) and cardiomyocyte death. However, the molecular mechanisms behind these effects are under investigation and could provide the basis for the development of novel therapeutic approaches in the treatment of CVD. Non-coding RNAs (ncRNAs), which are functional RNA molecules that do not translate into proteins, are critical modulators of cardiac gene expression during heart development and disease. Moreover, ncRNAs such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are known to be induced by opioid receptor activation and regulate opioid signaling pathways. Recent advances in experimental and computational tools have accelerated the discovery and functional characterization of ncRNAs. In this study, we review the current understanding of the role of ncRNAs in opioid signaling and opioid-induced cardioprotection.

The effect of acute morphine on obstructive sleep apnoea: a randomised double-blind placebo-controlled crossover trial

Objective

Anaesthesiology guidelines suggest that opioids worsen obstructive sleep apnoea (OSA) despite no randomised controlled trial evidence. We therefore conducted a randomised controlled trial to evaluate the effects of a common clinical dose of morphine on OSA, and to identify clinical phenotype and genotype vulnerability to opioid-respiratory depression.

Methods

Under a double-blind, randomised, crossover design, 60 male patients with OSA attended two visits to the hospital sleep laboratory, at least 1 week apart. Either 40 mg controlled-release oral morphine or placebo was administered. Awake ventilatory chemoreflex tests were performed post dose and prior to overnight polysomnography monitoring. Blood was sampled before sleep and the next morning for toxicology and genotype analyses. Sleep time with oxygen saturation (SpO2) <90% (T90) was the primary outcome.

Results

Despite a large inter-individual variability, 40 mg morphine did not worsen T90 and apnoea–hypopnoea index, and only decreased the SpO2 nadir by 1.3%. In patients with severe OSA, a lower baseline CO2ventilatory response threshold correlated with the worsening of T90, apnoea–hypopnoea index and oxygen desaturation index with morphine use. Patients with OSA and the A118G OPRM1 polymorphism of A/A and A/G had a significantly different morphine effect on awake ventilatory chemosensitivity and T90 during sleep.

Conclusions

40 mg oral controlled-release morphine did not worsen OSA in men, challenging traditional thinking that OSA will be worsened by opioids. Individual opioid response in patients with OSA may relate to baseline CO2 response threshold and OPRM1 genotype. Our study findings may pave the way for a precision medicine approach to avoid opioid-related risks.

Trial registration number

The Australian and New Zealand Clinical Trial Registry, ACTRN12613000858796.

Pharmacogenomics and Patient Treatment Parameters to Opioid Treatment in Chronic Pain: A Focus on Morphine, Oxycodone, Tramadol, and Fentanyl

Objective

Opioids are one of the most commonly prescribed medicines for chronic pain. However, their use for chronic pain has been controversial. The objective of this literature review was to identify the role of genetic polymorphisms on patient treatment parameters (opioid dose requirements, response, and adverse effects) for opioids used in malignant and nonmalignant chronic pain. The opioids that this review focuses on are codeine, morphine, oxycodone, tramadol, and fentanyl.

Method

A literature search of databases Medline and Embase was carried out, and studies up to April 2016 were included in this review. Studies were included based on a combination of key words: chronic pain and related terms, pharmacogenetics and related terms, and opioids and related terms.

Results

Among the 1,408 individual papers retrieved from the search in Medline and Embase, 32 original articles were included in this review, with none related to codeine. The 32 papers reported various study designs, opioids, and polymorphisms being studied for associations with treatment outcomes. This literature review reveals that variants in ABCB1, OPRM1, and COMT have been replicated for opioid dosing and variants in ABCB1 have been replicated for both treatment response and adverse effects.

Conclusions

Currently, there are few validated studies to form a strong evidence base to support pharmacogenomics testing when initiating opioid therapy. However, the field of pharmacogenomics in chronic pain is likely to expand over the coming years, with the increasing number of treatment options available and larger cohorts being assembled in order to identify true associations.

Opioid prescribing for chronic musculoskeletal pain in UK primary care: results from a cohort analysis of the COPERS trial

OBJECTIVE

To establish the level of opioid prescribing for patients with chronic musculoskeletal pain in a sample of patients from primary care and to estimate prescription costs.

DESIGN

Secondary data analyses from a two-arm pragmatic randomised controlled trial (COPERS) testing the effectiveness of group self-management course and usual care against relaxation and usual care for patients with chronic musculoskeletal pain (ISRCTN 24426731).

SETTING

25 general practices and two community musculoskeletal services in the UK (London and Midlands).

PARTICIPANTS

703 chronic pain participants; 81% white, 67% female, enrolled in the COPERS trial.

MAIN OUTCOME MEASURES

Anonymised prescribing data over 12 months extracted from GP electronic records.

RESULTS

Of the 703 trial participants with chronic musculoskeletal pain, 413 (59%) patients were prescribed opioids. Among those prescribed an opioid, the number of opioid prescriptions varied from 1 to 52 per year. A total of 3319 opioid prescriptions were issued over the study period, of which 53% (1768/3319) were for strong opioids (tramadol, buprenorphine, morphine, oxycodone, fentanyl and tapentadol). The mean number of opioid prescriptions per patient prescribed any opioid was 8.0 (SD=7.9). A third of patients on opioids were prescribed more than one type of opioid; the most frequent combinations were: codeine plus tramadol and codeine plus morphine. The cost of opioid prescriptions per patient per year varied from £3 to £4844. The average annual prescription cost was £24 (SD=29) for patients prescribed weak opioids and £174 (SD=421) for patients prescribed strong opioids. Approximately 40% of patients received >3 prescriptions of strong opioids per year, with an annual cost of £236 per person.

CONCLUSIONS

Long-term prescribing of opioids for chronic musculoskeletal pain is common in primary care. For over a quarter of patients receiving strong opioids, these drugs may have been overprescribed according to national guidelines.

TRIAL REGISTRATION NUMBER

ISRCTN24426731; Post-results.

The ACTTION-APS-AAPM Pain Taxonomy (AAAPT) Multidimensional Approach to Classifying Acute Pain Conditions

Objective

With the increasing societal awareness of the prevalence and impact of acute pain, there is a need to develop an acute pain classification system that both reflects contemporary mechanistic insights and helps guide future research and treatment. Existing classifications of acute pain conditions are limiting, with a predominant focus on the sensory experience (e.g., pain intensity) and pharmacologic consumption. Consequently, there is a need to more broadly characterize and classify the multidimensional experience of acute pain.

Setting

Consensus report following expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM).

Methods

As a complement to a taxonomy recently developed for chronic pain, the ACTTION public-private partnership with the US Food and Drug Administration, the APS, and the AAPM convened a consensus meeting of experts to develop an acute pain taxonomy using prevailing evidence. Key issues pertaining to the distinct nature of acute pain are presented followed by the agreed-upon taxonomy. The ACTTION-APS-AAPM Acute Pain Taxonomy will include the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms. Future efforts will consist of working groups utilizing this taxonomy to develop diagnostic criteria for a comprehensive set of acute pain conditions.

Perspective

The ACTTION-APS-AAPM Acute Pain Taxonomy (AAAPT) is a multidimensional acute pain classification system designed to classify acute pain along the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms.

Conclusions

Significant numbers of patients still suffer from significant acute pain, despite the advent of modern multimodal analgesic strategies. Mismanaged acute pain has a broad societal impact as significant numbers of patients may progress to suffer from chronic pain. An acute pain taxonomy provides a much-needed standardization of clinical diagnostic criteria, which benefits clinical care, research, education, and public policy. For the purposes of the present taxonomy, acute pain is considered to last up to seven days, with prolongation to 30 days being common. The current understanding of acute pain mechanisms poorly differentiates between acute and chronic pain and is often insufficient to distinguish among many types of acute pain conditions. Given the usefulness of the AAPT multidimensional framework, the AAAPT undertook a similar approach to organizing various acute pain conditions.

The ACTTION-APS-AAPM Pain Taxonomy (AAAPT) Multidimensional Approach to Classifying Acute Pain Conditions

OBJECTIVE

With the increasing societal awareness of the prevalence and impact of acute pain, there is a need to develop an acute pain classification system that both reflects contemporary mechanistic insights and helps guide future research and treatment. Existing classifications of acute pain conditions are limiting, with a predominant focus on the sensory experience (eg, pain intensity) and pharmacologic consumption. Consequently, there is a need to more broadly characterize and classify the multidimensional experience of acute pain.

SETTING

Consensus report following expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM).

METHODS

As a complement to a taxonomy recently developed for chronic pain, the ACTTION public-private partnership with the US Food and Drug Administration, the APS, and the AAPM convened a consensus meeting of experts to develop an acute pain taxonomy using prevailing evidence. Key issues pertaining to the distinct nature of acute pain are presented followed by the agreed-upon taxonomy. The ACTTION-APS-AAPM Acute Pain Taxonomy will include the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms. Future efforts will consist of working groups utilizing this taxonomy to develop diagnostic criteria for a comprehensive set of acute pain conditions.

PERSPECTIVE

The ACTTION-APS-AAPM Acute Pain Taxonomy (AAAPT) is a multidimensional acute pain classification system designed to classify acute pain along the following dimensions: 1) core criteria, 2) common features, 3) modulating factors, 4) impact/functional consequences, and 5) putative pathophysiologic pain mechanisms.

CONCLUSIONS

Significant numbers of patients still suffer from significant acute pain, despite the advent of modern multimodal analgesic strategies. Mismanaged acute pain has a broad societal impact as significant numbers of patients may progress to suffer from chronic pain. An acute pain taxonomy provides a much-needed standardization of clinical diagnostic criteria, which benefits clinical care, research, education, and public policy. For the purposes of the present taxonomy, acute pain is considered to last up to seven days, with prolongation to 30 days being common. The current understanding of acute pain mechanisms poorly differentiates between acute and chronic pain and is often insufficient to distinguish among many types of acute pain conditions. Given the usefulness of the AAPT multidimensional framework, the AAAPT undertook a similar approach to organizing various acute pain conditions.

The impact of UGT2B7 C802T and CYP3A4*1G polymorphisms on pain relief in cancer patients receiving oxycontin

BACKGROUND

Single nucleotide polymorphisms (SNPs) in UGT2B7 C802T and CYP3A4*1G impact drug metabolism. This study aimed to investigate the impact of these SNPs on the efficacy of oxycontin for pain relief in cancer patients.

METHODS

A total of 57 Han Chinese cancer patients (age range 20-70 years) who received oxycontin to ease pain for the first time were enrolled and divided into two groups (refractory group and remission group) according to pain relief. Peripheral blood samples were collected from each patient for sequencing analysis. The genotype and allele frequency between the two groups were analyzed using the chi-square test.

RESULTS

The T allele frequency of UGT2B7 C802T was 25% among all participants, but was higher (32%) in the refractory group (P = 0.047). The variant allele frequency of CYP3A4*1G was 27% and did not differ between the refractory group and remission group.

CONCLUSION

The palliative effect of oxycontin is better in patients with UGT2B7 802CC than in those with 802TT. CYP3A4*1G SNP is unlikely to affect pain relief efficacy of oxycontin.

4218T/C polymorphism associations with post-cesarean patient-controlled epidural fentanyl consumption and pain perception

BACKGROUND

The utilization of intrathecal opioids is an efficacious component of post-cesarean section pain management. Given that growing evidence indicates that calcitonin gene-related peptide (CGRP) plays a key role in the development of peripheral sensitization and is associated with enhanced pain, we hypothesized that CGRP 4218T/C polymorphism is associated with the variability in fentanyl consumption for post-cesarean analgesia.

METHODS

We recruited 548 patients who presented for elective cesarean delivery, and used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to analyze CGRP 4218T/C polymorphism. We examined the association of CGRP 4218T/C polymorphism and post-operative fentanyl consumption for analgesia as well as adverse reactions to fentanyl in those patients who received cesarean section surgeries.

RESULTS

We found that the CGRP 4218T/C polymorphism has a significant effect on pain perception, analgesic requirement, and nausea and vomiting for the first 24 h after cesarean delivery in patients who received PCEA fentanyl. Individuals with the C/C genotype had more pain, required more PCEA fentanyl, and experienced a lower incidence of nausea and vomiting.

CONCLUSION

These results indicated that patients with C/C genotype may have reduced sensitivity to fentanyl analgesia and/or increased pain perception, and were more willing to use PCEA fentanyl to manage their pain.

Using Genome Sequence to Enable the Design of Medicines and Chemical Probes

Rapid progress in genome sequencing technology has put us firmly into a postgenomic era. A key challenge in biomedical research is harnessing genome sequence to fulfill the promise of personalized medicine. This Review describes how genome sequencing has enabled the identification of disease-causing biomolecules and how these data have been converted into chemical probes of function, preclinical lead modalities, and ultimately U.S. Food and Drug Administration (FDA)-approved drugs. In particular, we focus on the use of oligonucleotide-based modalities to target disease-causing RNAs; small molecules that target DNA, RNA, or protein; the rational repurposing of known therapeutic modalities; and the advantages of pharmacogenetics. Lastly, we discuss the remaining challenges and opportunities in the direct utilization of genome sequence to enable design of medicines.

The effect of metformin on morphine analgesic tolerance and dependence in rats

Opiate tolerance and dependence is a worldwide public health problem and gives a significant burden to society. The aim of this study was to evaluate the effects of metformin (MET) on development and expression of morphine tolerance and dependence in rats. For induction of tolerance, morphine sulfate was injected (10 mg/kg, twice a day, s.c.) for 7 days. Animals received metformin (5 and 50 mg/kg, orally, daily) during the examination period for assessing the development of morphine tolerance and dependence. In order to evaluate the expression of morphine tolerance and dependence, single doses of MET (5 and 50 mg/kg, orally) were administered on day 7. Tail flick test was performed to assess the induction of morphine tolerance. For evaluation of morphine dependence, naloxone-induced jumping (5 mg/kg, s.c.) was monitored. Our results showed that 7 days coadministration of 50 mg/kg of MET significantly reduced the development of morphine analgesic tolerance versus morphine + saline treated rats (P < 0.001). Treatment with 50 mg/kg MET reduced the incidence and frequency of jumping in naloxone injected animals (P < 0.01). It is notable that single dose administration of MET, did not prevent the expression of analgesic tolerance and physical dependence to morphine. Based on these results, it can be concluded that MET attenuates the development of morphine analgesic tolerance and dependence in rats.

A randomized, Phase IIb study investigating oliceridine (TRV130), a novel µ-receptor G-protein pathway selective (μ-GPS) modulator, for the management of moderate to severe acute pain following abdominoplasty

Background

Oliceridine (TRV130), a novel μ-receptor G-protein pathway selective (μ-GPS) modulator, was designed to improve the therapeutic window of conventional opioids by activating G-protein signaling while causing low β-arrestin recruitment to the μ receptor. This randomized, double-blind, patient-controlled analgesia Phase IIb study was conducted to investigate the efficacy, safety, and tolerability of oliceridine compared with morphine and placebo in patients with moderate to severe pain following abdominoplasty (NCT02335294; oliceridine is an investigational agent not yet approved by the US Food and Drug Administration).

Methods

Patients were randomized to receive postoperative regimens of intravenous oliceridine (loading/patient-controlled demand doses [mg/mg]: 1.5/0.10 [regimen A]; 1.5/0.35 [regimen B]), morphine (4.0/1.0), or placebo with treatment initiated within 4 hours of surgery and continued as needed for 24 hours.

Results

Two hundred patients were treated (n=39, n=39, n=83, and n=39 in the oliceridine regimen A, oliceridine regimen B, morphine, and placebo groups, respectively). Patients were predominantly female (n=198 [99%]) and had a mean age of 38.2 years, weight of 71.2 kg, and baseline pain score of 7.7 (on 11-point numeric pain rating scale). Patients receiving the oliceridine regimens had reductions in average pain scores (model-based change in time-weighted average versus placebo over 24 hours) of 2.3 and 2.1 points, respectively (P=0.0001 and P=0.0005 versus placebo); patients receiving morphine had a similar reduction (2.1 points; P<0.0001 versus placebo). A lower prevalence of adverse events (AEs) related to nausea, vomiting, and respiratory function was observed with the oliceridine regimens than with morphine (P<0.05). Other AEs with oliceridine were generally dose-related and similar in nature to those observed with conventional opioids; no serious AEs were reported with oliceridine.

Conclusion

These results suggest that oliceridine may provide effective, rapid analgesia in patients with moderate to severe postoperative pain, with an acceptable safety/tolerability profile and potentially wider therapeutic window than morphine.