Current considerations for the treatment of severe chronic pain: the potential for tapentadol

Antinociceptive Effects of Sinomenine Combined With Ligustrazine or Paracetamol in Animal Models of Incisional and Inflammatory Pain

The management of postoperative and inflammatory pain has been a pressing challenge in clinical settings. Sinomenine (SN) is a morphinan derived alkaloid with remarkable analgesic properties in various kinds of pain models. The aim of the current study is to investigate if SN can enhance the effect of ligustrazine hydrochloride (LGZ) or paracetamol (PCM) in animal models of postoperative and inflammatory pain. And to determine if the combined therapeutic efficacies can be explained by pharmacokinetics changes. Pharmacological studies were performed using a rat model of incisional pain, and a mouse model of carrageenan induced inflammatory pain. Pharmacokinetic studies were performed using a microdialysis sampling and HPLC-MS/MS assay method to quantify SN, LGZ, and PCM levels in blood and extracellular fluid in brain. We found that SN plus LGZ or SN plus PCM produced marked synergistic analgesic effects. However, such synergy was subjected to pain modalities, and differed among pain models. Pharmacological discoveries could be partially linked to pharmacokinetic alterations in SN combinations. Though further evaluation is needed, our findings advocate the potential benefits of SN plus LGZ for postoperative pain management, and SN plus PCM for controlling inflammatory pain.

Repeated Administration of Clinically Relevant Doses of the Prescription Opioids Tramadol and Tapentadol Causes Lung, Cardiac, and Brain Toxicity in Wistar Rats

Tramadol and tapentadol, two structurally related synthetic opioid analgesics, are widely prescribed due to the enhanced therapeutic profiles resulting from the synergistic combination between μ-opioid receptor (MOR) activation and monoamine reuptake inhibition. However, the number of adverse reactions has been growing along with their increasing use and misuse. The potential toxicological mechanisms for these drugs are not completely understood, especially for tapentadol, owing to its shorter market history. Therefore, in the present study, we aimed to comparatively assess the putative lung, cardiac, and brain cortex toxicological damage elicited by the repeated exposure to therapeutic doses of both prescription opioids. To this purpose, male Wistar rats were intraperitoneally injected with single daily doses of 10, 25, and 50 mg/kg tramadol or tapentadol, corresponding to a standard analgesic dose, an intermediate dose, and the maximum recommended daily dose, respectively, for 14 consecutive days. Such treatment was found to lead mainly to lipid peroxidation and inflammation in lung and brain cortex tissues, as shown through augmented thiobarbituric acid reactive substances (TBARS), as well as to increased serum inflammation biomarkers, such as C reactive protein (CRP) and tumor necrosis factor-α (TNF-α). Cardiomyocyte integrity was also shown to be affected, since both opioids incremented serum lactate dehydrogenase (LDH) and α-hydroxybutyrate dehydrogenase (α-HBDH) activities, while tapentadol was associated with increased serum creatine kinase muscle brain (CK-MB) isoform activity. In turn, the analysis of metabolic parameters in brain cortex tissue revealed increased lactate concentration upon exposure to both drugs, as well as augmented LDH and creatine kinase (CK) activities following tapentadol treatment. In addition, pneumo- and cardiotoxicity biomarkers were quantified at the gene level, while neurotoxicity biomarkers were quantified both at the gene and protein levels; changes in their expression correlate with the oxidative stress, inflammatory, metabolic, and histopathological changes that were detected. Hematoxylin and eosin (H & E) staining revealed several histopathological alterations, including alveolar collapse and destruction in lung sections, inflammatory infiltrates, altered cardiomyocytes and loss of striation in heart sections, degenerated neurons, and accumulation of glial and microglial cells in brain cortex sections. In turn, Masson's trichrome staining confirmed fibrous tissue deposition in cardiac tissue. Taken as a whole, these results show that the repeated administration of both prescription opioids extends the dose range for which toxicological injury is observed to lower therapeutic doses. They also reinforce previous assumptions that tramadol and tapentadol are not devoid of toxicological risk even at clinical doses.

Repeated Administration of Clinical Doses of Tramadol and Tapentadol Causes Hepato- and Nephrotoxic Effects in Wistar Rats

Tramadol and tapentadol are fully synthetic and extensively used analgesic opioids, presenting enhanced therapeutic and safety profiles as compared with their peers. However, reports of adverse reactions, intoxications and fatalities have been increasing. Information regarding the molecular, biochemical, and histological alterations underlying their toxicological potential is missing, particularly for tapentadol, owing to its more recent market authorization. Considering the paramount importance of liver and kidney for the metabolism and excretion of both opioids, these organs are especially susceptible to toxicological damage. In the present study, we aimed to characterize the putative hepatic and renal deleterious effects of repeated exposure to therapeutic doses of tramadol and tapentadol, using an in vivo animal model. Male Wistar rats were randomly divided into six experimental groups, composed of six animals each, which received daily single intraperitoneal injections of 10, 25 or 50 mg/kg tramadol or tapentadol (a low, standard analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively). An additional control group was injected with normal saline. Following 14 consecutive days of administration, serum, urine and liver and kidney tissue samples were processed for biochemical, metabolic and histological analysis. Repeated administration of therapeutic doses of both opioids led to: (i) increased lipid and protein oxidation in liver and kidney, as well as to decreased total liver antioxidant capacity; (ii) decreased serum albumin, urea, butyrylcholinesterase and complement C3 and C4 levels, denoting liver synthesis impairment; (iii) elevated serum activity of liver enzymes, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase, as well as lipid profile alterations, also reflecting hepatobiliary commitment; (iv) derangement of iron metabolism, as shown through increases in serum iron, ferritin, haptoglobin and heme oxygenase-1 levels. In turn, elevated serum cystatin C, decreased urine creatinine output and increased urine microalbumin levels were detected upon exposure to tapentadol only, while increased serum amylase and urine N-acetyl-β-D-glucosaminidase activities were observed for both opioids. Collectively, these results are compatible with kidney injury. Changes were also found in the expression levels of liver- and kidney-specific toxicity biomarker genes, upon exposure to tramadol and tapentadol, correlating well with alterations in lipid profile, iron metabolism and glomerular and tubular function. Histopathological analysis evidenced sinusoidal dilatation, microsteatosis, mononuclear cell infiltrates, glomerular and tubular disorganization, and increased Bowman's spaces. Although some findings are more pronounced upon tapentadol exposure, our study shows that, when compared with acute exposure, prolonged administration of both opioids smooths the differences between their toxicological effects, and that these occur at lower doses within the therapeutic range.

Do All Opioid Drugs Share the Same Immunomodulatory Properties? A Review From Animal and Human Studies

Suppression of the immune system has been constantly reported in the last years as a classical side effect of opioid drugs. Most of the studies on the immunological properties of opioids refer to morphine. Although morphine remains the "reference molecule," other semisynthetic and synthetic opioids are frequently used in the clinical practice. The primary objective of this review is to analyze the available literature on the immunomodulating properties of opioid drugs different from morphine in preclinical models and in the human. A search strategy was conducted in PubMed, Embase, and the Cochrane databases using the terms "immunosuppression," "immune system," "opioids," "Natural killer cells," "cytokines," and "lymphocytes." The results achieved concerning the effects of fentanyl, methadone, oxycodone, buprenorphine, remifentanil, tramadol, and tapentadol on immune responses in animal studies, in healthy volunteers and in patients are reported. With some limitations due to the different methods used to measure immune system parameters, the large range of opioid doses and the relatively scarce number of participants in the available studies, we conclude that it is not correct to generalize immunosuppression as a common side effect of all opioid molecules.

Tapentadol: an analgesic that differs from classic opioids due to its noradrenergic mechanism of action

Chronic pain treatment represents one of the most complex clinical challenges and even though opioids exhibit particular efficacy on nociceptive pain, their use must be controlled to avoid the risk of adverse reactions. A useful approach, aimed at maintaining analgesia and mitigating side effects, is represented by the use of a new class of analgesics endowed of µ-opioid (MOR) receptor agonism and noradrenaline reuptake inhibition (NRI) mechanisms. Tapentadol is the progenitor of this new class of drugs called MOP-NRI. A literature review has been conducted to gain information about the efficacy and the tolerability profile of tapentadol shifting from MOR agonism (acute pain) to NRI activity (chronic pain). The tolerability and therapeutic safety of tapentadol in neuropathic pain models, as well as in clinical settings, has been analyzed showing a good gastrointestinal tolerability profile, a moderate effect on hormone levels (in healthy volunteers and in patients) and on cognitive performance, a lack of significant alteration of the electrocardiogram recording and no changes of the QT/QTc interval, a minimal effect on serotonin reuptake in vivo with a low risk of serotonin syndrome, a longer time for the onset of analgesic tolerance and a less occurrence of abuse liability compared to formulations containing other comparator compounds. Tapentadol represents a great innovation in chronic pain therapy with a unique analgesic profile different form classical opioids, therefore, thanks to its synergistic MOR-NRI action, it may be a good option for the treatment of chronic, neuropathic and mixed pain.

Does 'Strong Analgesic' Equal 'Strong Opioid'? Tapentadol and the Concept of 'µ-Load'

INTRODUCTION

The distinct properties of the centrally-acting analgesic tapentadol derive from the combined contributions of an opioid component and a nonopioid component. However, the opioid component's relative contribution to analgesic and adverse effects has not previously been elucidated. Tapentadol's analgesic effect derives from the combined contribution of an opioid mechanism and a nonopioid mechanism, the extent of which can vary for different pains. Likewise, the interaction can vary for various adverse effects. Hence, the contribution of each mechanism to adverse effects can be different from the contribution to analgesia. We here estimate the percent contribution of each component of the mechanism of action to analgesia and to adverse effects.

AREAS COVERED

Several approaches to in vitro and in vivo data to estimate the contribution of tapentadol's opioid component to analgesia and to the two important opioid adverse effects, respiratory depression and constipation. The results are then compared with clinical data.

EXPERT OPINION

Traditional opioids, such as morphine, oxycodone, and others, produce their analgesic effects primarily through a single mechanism-the activation of µ-opioid receptors (MOR). Therefore, the contribution of the opioid component to adverse effects is 100%. In contrast, the newer strong analgesic tapentadol produces its analgesic effect via two separate and complementary analgesic mechanisms, only one of which is µ-opioid. We applied standard drug-receptor theory and novel techniques to in vitro and in vivo data to estimate by several different ways the μ-load of tapentadol (the % contribution of the opioid component to the adverse effect magnitude relative to a pure/classical µ-opioid at equianalgesia) in respiratory depression and constipation, and we compared the results to clinical evidence. The estimate is remarkably consistent over the various approaches and indicates that the μ-load of tapentadol is ≤ 40% (relative to pure MOR agonists, which have, by definition, a µ-load of 100%).

FUNDING

Grünenthal GmbH.

Tapentadol Extended Release in the Treatment of Severe Chronic Low Back Pain and Osteoarthritis Pain

Tapentadol is a novel pain reliever with apparently synergistic dual mechanisms of action, capable of addressing both nociceptive and neuropathic components of chronic pain. As an effective analgesic with good tolerability, tapentadol may be appropriate for patients suffering from severe chronic pain associated with low back pain (LBP) or osteoarthritis (OA). Efficacy studies of tapentadol in populations of patients with severe chronic LBP or OA pain suggest that tapentadol is non-inferior to oxycodone. Its tolerability, especially with respect to gastrointestinal (GI) side effects, may be better than that of other strong opioids in clinical trials and analyses of multiple trials. Patient satisfaction with tapentadol extended release for chronic noncancer pain syndromes is good. Although tapentadol has an opioid component with abuse liability, it appears to be a difficult opioid for tampering with less appeal to abusers than other opioids. For patients with severe LBP and OA pain, tapentadol appears to hold promise as a safe, effective therapeutic option.

Chronic maladaptive pain in cats: A review of current and future drug treatment options

Despite our increasing understanding of the pathophysiology underlying chronic or maladaptive pain, there is a significant gap in our ability to diagnose and treat the condition in domestic cats. Newer techniques being used to identify abnormalities in pain processing in the cat include validated owner questionnaires, measurement of movement and activity, and measurement of sensory thresholds and somatomotor responses. While some data are available evaluating possible therapeutics for the treatment of chronic pain in the cat, most data are limited to normal cats. This review details our current understanding of chronic or maladaptive pain, techniques for the detection and measurement of the condition and the associated central nervous changes, as well as an overview of the data evaluating potential therapeutics in cats.

Acute administration of tramadol and tapentadol at effective analgesic and maximum tolerated doses causes hepato- and nephrotoxic effects in Wistar rats

Tramadol and tapentadol are two atypical synthetic opioid analgesics, with monoamine reuptake inhibition properties. Mainly aimed at the treatment of moderate to severe pain, these drugs are extensively prescribed for multiple clinical applications. Along with the increase in their use, there has been an increment in their abuse, and consequently in the reported number of adverse reactions and intoxications. However, little is known about their mechanisms of toxicity. In this study, we have analyzed the in vivo toxicological effects in liver and kidney resulting from an acute exposure of a rodent animal model to both opioids. Male Wistar rats were intraperitoneally administered with 10, 25 and 50mg/kg tramadol and tapentadol, corresponding to a low, effective analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively, for 24h. Toxicological effects were assessed in terms of oxidative stress, biochemical and metabolic parameters and histopathology, using serum and urine samples, liver and kidney homogenates and tissue specimens. The acute exposure to tapentadol caused a dose-dependent increase in protein oxidation in liver and kidney. Additionally, exposure to both opioids led to hepatic commitment, as shown by increased serum lipid levels, decreased urea concentration, increased alanine aminotransferase and decreased butyrylcholinesterase activities. It also led to renal impairment, as reflected by proteinuria and decreased glomerular filtration rate. Histopathological findings included sinusoidal dilatation, microsteatosis, vacuolization, cell infiltrates and cell degeneration, indicating metabolic changes, inflammation and cell damage. In conclusion, a single effective analgesic dose or the maximum recommended daily dose of both opioids leads to hepatotoxicity and nephrotoxicity, with tapentadol inducing comparatively more toxicity. Whether these effects reflect risks during the therapeutic use or human overdoses requires focused attention by the medical community.

Antinociceptive Effect of the Essential Oil from Croton conduplicatus Kunth (Euphorbiaceae)

Medicinal plants have been widely used in the treatment of chronic pain. In this study, we describe the antinociceptive effect of the essential oil from Croton conduplicatus (the EO 25, 50, and 100 mg/kg, i.p.), a medicinal plant native to Brazil. Antinociceptive activity was investigated by measuring the nociception induced by acetic acid, formalin, hot plate and carrageenan. A docking study was performed with the major constituents of the EO (E-caryophyllene, caryophyllene oxide, and camphor). The EO reduced nociceptive behavior at all doses tested in the acetic acid-induced nociception test (p < 0.05). The same was observed in both phases (neurogenic and inflammatory) of the formalin test. When the hot-plate test was conducted, the EO (50 mg/kg) extended the latency time after 60 min of treatment. The EO also reduced leukocyte migration at all doses, suggesting that its antinociceptive effect involves both central and peripheral mechanisms. Pretreatment with glibenclamide and atropine reversed the antinociceptive effect of the EO on the formalin test, suggesting the involvement of K_ATP channels and muscarinic receptors. The docking study revealed a satisfactory interaction profile between the major components of the EO and the different muscarinic receptor subtypes (M2, M3, and M4). These results corroborate the medicinal use of C. conduplicatus in folk medicine.

Investigation of the presence and antinociceptive function of muscarinic acetylcholine receptors in the African naked mole-rat (Heterocephalus glaber)

The present study investigated the cholinergic system in the African naked mole-rat (Heterocephalus glaber) with focus on the muscarinic acetylcholine receptor subtypes M₁ and M₄. The protein sequences for the subtypes m_1–5 of the naked mole-rat were compared to that of the house mouse (Mus musculus) using basic local alignment search tool (BLAST). The presence and function of M₁ and M₄ was investigated in vivo, using the formalin test with the muscarinic receptor agonists xanomeline and VU0152100. Spinal cord tissue from the naked mole-rat was used for receptor saturation binding studies with [³H]-N-methylscopolamine. The BLAST test revealed 95 % protein sequence homology showing the naked mole-rat to have the genetic potential to express all five muscarinic acetylcholine receptor subtypes. A significant reduction in pain behavior was demonstrated after administration of 8.4 mg/kg in the formalin test. Administration of 50 mg/kg VU0152100 resulted in a non-significant tendency towards antinociception. The antinociceptive effects were reversed by the muscarinic acetylcholine receptor antagonist atropine. Binding studies indicated presence of muscarinic acetylcholine receptors with a radioligand affinity comparable to that reported in mice. In conclusion, muscarinic acetylcholine receptor subtypes are present in the naked mole-rat and contribute to antinociception in the naked mole-rat.

Comparison of Real-world Outcomes Between Patients Treated with Tapentadol ER or Oxycodone CR

Background: The objective of this study was to compare health care utilization and costs between matched cohorts of chronic pain patients treated with the opioids tapentadol extended release (ER) or oxycodone controlled release (CR). Methods: This retrospective study used claims data from the Optum Research Database. Commercial and Medicare Advantage adult patients with ≥1 prescription fill for oxycodone CR or tapentadol ER between September 1, 2011 and September 30, 2012 were eligible. The date of the first observed oxycodone CR or tapentadol ER claim was the index date. Patients had continuous health plan enrollment for 6 months before and after the index date, ≥ 90 days supply of opioid therapy, and no index drug claims in the preindex period. Patients were propensity score matched in a 1:2 ratio (tapentadol ER : oxycodone CR). Results: The attributes of the matched cohorts (1,120 tapentadol ER and 2,240 oxycodone CR patients) appeared similar. In the 6 month post-index period, lower proportions of the tapentadol ER cohort than the oxycodone CR cohort had ≥1 inpatient stay (14.6% versus 20.5%; p<0.001) and ≥1 emergency department visit (33.4% versus 37.5%; p=0.021). The tapentadol ER compared with the oxycodone CR cohort had higher mean pharmacy costs ($4,263 versus $3,694; p <0.001), lower mean inpatient costs ($3,625 versus $6,309; p<0.001), and lower mean total healthcare costs ($16,510 versus $19,330; p=0.004). Conclusions: During follow-up, total mean healthcare costs were lower among tapentadol ER patients than oxycodone CR patients, and tapentadol ER patients were less likely to have an inpatient admission or emergency department visit.

Lasting Prolonged-Release Tapentadol for Moderate/Severe Non-Cancer Musculoskeletal Chronic Pain

Introduction

Despite opioids’ recognized role in the treatment of moderate/severe musculoskeletal chronic pain, their long-term benefits need investigation. We explored the lasting analgesic efficacy, tolerability, influence on life quality, and chronicity stage of the novel prolonged release (PR) opioid, tapentadol, in 30 outpatients.

Methods

We evaluated patients’ pain intensity and relief (Numerical Rating Scale; NRS), adverse effects, sleep quality, treatment satisfaction, health status (12-questions Health-Survey; SF-12), chronicity stage (Italian Mainz Pain-Staging System; I-MPSS) at 10, 30, 60, and 90 days after tapentadol prescription.

Results

At follow-ups, the investigated outcomes showed an overall statistically significant (Wilcoxon signed-rank test) improvement and remained stable over time, as did the health status and chronicity stage. Adverse effects were limited, transitory, and tolerable.

Conclusions

Twelve weeks of PR tapentadol in outpatients with moderate/severe chronic musculoskeletal pain showed satisfactory analgesic efficacy and tolerability, and had a positive influence on life quality and chronicity stage. The results are robust enough to warrant a subsequent study with a larger sample and a longer observation period.

Tapentadol at medium to high doses in patients previously receiving strong opioids for the management of cancer pain

OBJECTIVE

The aim of this study was to assess the efficacy and tolerability of tapentadol (TP) for a period of 4 weeks in patients who were already treated by opioids.

METHODS

A convenience sample of 30 patients was selected for a prospective observational cohort study. Cancer patients who were receiving at least 60 mg of oral morphine equivalents were selected. Patients discontinued their previous opioid analgesics before starting TP, in doses calculated according the previous opioid consumption (1:3.3 ratio with oral morphine equivalents). The subsequent doses were changed according to the patients' needs for a period of 4 weeks. Oral morphine was offered as a breakthrough pain medication. Pain and symptom intensity were recorded at weekly intervals. Distress score (DS) was calculated from the sum of symptom intensities. TP opioid escalation indexes (TPEI) for the study period were calculated.

RESULTS

Nineteen patients were male, and the mean age was 63.5 years (±11.5). The mean Karnofsky status was 62.9 (±10). The mean dose of oral morphine equivalents before switching to TP was 112 mg (±57) and the initial mean dose of TP was 343 mg (±150). Pain intensity significantly decreased. Tapentadol escalation index in percentage was 1.26 (TPEI% ± 2.6) and Tapentadol escalation index in mg was 2.76 (TPEImg ± 4.96). No significant relationships were found with primary tumor (TPEI%, p = 0.204; TPEImg, p = 0.180), pain mechanism (TPEI%, p = 0.863; TPEImg, p = 0.846), age (TPEI%, p = 0.882; TPEImg, p = 0.884), or gender (TPEI%, p = 0.287; TPEImg, p = 0.325). DS decreased, but non-significantly (p = 0.1). Ten patients did not complete the study period: five patients discontinued TP for uncontrolled pain, despite increasing doses of TP over 600 mg/day. Two patients discontinued TP for adverse effects and three patients dropped out, one patient for poor compliance and two patients for unrecorded reasons.

CONCLUSION

In our sample, TP used in doses of 350-450 mg/day was well tolerated and effective in opioid tolerant patients with cancer pain and could be considered as a flexible drug to be used for the management of moderate to severe cancer pain. Like most studies in patients with cancer pain, it was limited by its open-label, uncontrolled design, the number of patients lost in follow-up, and discontinuation of the treatment for several reasons. Further studies in a large number of patients should confirm these preliminary results.

μ-Opioid receptor activation and noradrenaline transport inhibition by tapentadol in rat single locus coeruleus neurons

BACKGROUND AND PURPOSE

Tapentadol is a novel analgesic that combines moderate μ-opioid receptor agonism and noradrenaline reuptake inhibition in a single molecule. Both mechanisms of action are involved in producing analgesia; however, the potency and efficacy of tapentadol in individual neurons has not been characterized.

EXPERIMENTAL APPROACH

Whole-cell patch-clamp recordings of G-protein-coupled inwardly rectifying K(+) (KIR 3.x) currents were made from rat locus coeruleus neurons in brain slices to investigate the potency and relative efficacy of tapentadol and compare its intrinsic activity with other clinically used opioids.

KEY RESULTS

Tapentadol showed agonist activity at μ receptors and was approximately six times less potent than morphine with respect to KIR 3.x current modulation. The intrinsic activity of tapentadol was lower than [Met]enkephalin, morphine and oxycodone, but higher than buprenorphine and pentazocine. Tapentadol inhibited the noradrenaline transporter (NAT) with potency similar to that at μ receptors. The interaction between these two mechanisms of action was additive in individual LC neurons.

CONCLUSIONS AND IMPLICATIONS

Tapentadol displays similar potency for both µ receptor activation and NAT inhibition in functioning neurons. The intrinsic activity of tapentadol at the μ receptor lies between that of buprenorphine and oxycodone, potentially explaining the favourable profile of side effects, related to μ receptors.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

[Pain management in patients with liver cirrhosis]

Pain management in patients with liver cirrhosis is a real challenge and is often inadequate due to a lack of therapeutic efficacy or the high incidence of adverse effects. The focus of treatment differs depending on whether the pain is acute or chronic and involves understanding the causative pathophysiological mechanism. Analgesics should be started with the minimum effective dose and should be titrated slowly with avoidance of polypharmacy. Adverse effects must be monitored, especially sedation and constipation, which predispose the patient to the development of hepatic encephalopathy. The first-line drug is paracetamol, which is safe at doses of 2-3g/day. Non-steroidal anti-inflammatory agents are contraindicated because they can cause acute renal failure and/or gastrointestinal bleeding. Tramadol is a safe option for moderate-severe pain. The opioids with the best safety profile are fentanyl and hydromorphone, with methadone as an alternative. Topical treatment can reduce oral drug consumption. In neuropathic pain the first-line therapeutic option is gabapentin. The use of antidepressants such as amitriptyline can be considered in some patients. Interventional techniques are a valuable tool in moderate to severe pain, since they allow a reduction in drug therapy and consequently its adverse effects. Psychological treatment, physical therapy and rehabilitation should be considered as part of multimodality therapy in the management of chronic pain.

Differences between opioids: pharmacological, experimental, clinical and economical perspectives

Clinical studies comparing the response and side effects of various opioids have not been able to show robust differences between drugs. Hence, recommendations of the regulatory authorities have been driven by costs with a general tendency in many countries to restrict physician's use of opioids to morphine. Although this approach is recognized as cost-effective in most cases there is solid evidence that, on an individual patient basis, opioids are not all equal. Therefore it is important to have an armamentarium of strong analgesics in clinical practice to ensure a personalized approach in patients who do not respond to standard treatment. In this review we highlight differences between opioids in human studies from a pharmacological, experimental, clinical and health economics point of view. We provide evidence that individuals respond differently to opioids, and that general differences between classes of opioids exist. We recommend that this recognition is used to individualize treatment in difficult cases allowing physicians to have a wide range of treatment options. In the end this will reduce pain and side effects, leading to improved quality of life for the patient and reduce the exploding pain related costs.

Tapentadol extended release for chronic pain patients

INTRODUCTION

Chronic pain reduces quality of life, utilizes healthcare resources, and increases healthcare costs. It is widespread, but generally inadequately treated or managed, partly due to several obstacles, including a limited number of mechanistic options for long-term pharmacologic agents. Opioids are generally the primary class of analgesic prescribed, but because of associated side effects during long-term treatment, many patients become noncompliant or discontinue treatment. A long-term use analgesic with a good benefit/risk ratio is advantageous.

METHODS

A literature search for randomized trials using tapentadol extended release (ER) for noncancer chronic pain patients was conducted. Databases searched included PubMed, MEDLINE, EMBASE, and Google Scholar, using key terms "tapentadol," "prolonged release," "extended release," and "chronic pain" individually or in combination. The results were synthesized and evaluated.

RESULTS

A total of six randomized, controlled studies were identified. Chronic pain conditions analyzed included low back, osteoarthritis, and diabetic peripheral neuropathy. Treatment arms consisted most often of placebo, tapentadol ER (100-250 mg twice daily [b.i.d.]), and/or oxycodone CR (controlled release) (20-50 mg b.i.d.). Subjects treated with tapentadol ER had significant reduction in pain intensity compared to placebo controls and similar efficacy to oxycodone CR. Overall, the safety profile was superior to that of oxycodone CR in regards to reduction in side effects, reduced severity of side effects (particularly gastrointestinal related), and lower study discontinuation rates.

CONCLUSION

The two mechanisms of analgesic action of tapentadol, combined with an ER, appears to provide equal efficacy to a strong controlled-release opioid while providing greater gastrointestinal tolerability. The reduction in incidence and severity of gastrointestinal side effects correlated with a higher compliance rate. These findings suggest that tapentadol ER might be a viable alternative to conventional strong opioids for pain management for chronic pain patients.

Tapentadol in cancer pain management: a prospective open-label study

OBJECTIVES

The aim of this prospective, open-label study was to evaluate the efficacy and tolerability of tapentadol (TP) in the management of cancer pain.

METHODS

A 4 weeks' prospective study was carried out in 50 opioid-naive cancer patients with moderate-severe pain. Each patient initially received twice-daily doses of slow-release TP 50 mg. Doses were then managed to maintain adequate relief or dose-limiting toxicity, on the basis of the clinical response. The following parameters were recorded at weekly intervals for 4 weeks: pain and opioid-related adverse effects, quality of life measured with the Spitzer score, TP escalation index percent (TPEI%) and TP escalation index in mg (TPEImg), calculated at the end of the study, pain mechanisms, and PainDETECT at baseline.

RESULTS

Of 50 patients, 39 completed the entire study and 11 discontinued the treatment for different reasons. Pain intensity significantly decreased from baseline to all the week intervals (p < 0.0005), and adverse effects did not changed significantly, while quality of life improved. TP escalation indexes were low and no relationship was found with age, gender, and pain mechanisms.

CONCLUSION

Tapentalol started in doses of 100 mg/day was well-tolerated and effective in opioid-naive patients with cancer pain, regardless of the pain mechanism. It can be considered as a flexible drug to be used in patients with moderate-severe pain.

LIMITATIONS

This was an open-label study for exploratory purposes. Data should be confirmed in controlled studies with a larger number of patients.