Maintenance of the long-term effectiveness of tramadol in treatment of the pain of diabetic neuropathy

Enhanced Sensitivity to Tramadol in Diabetic Neuropathic Pain Compared to Nerve Compression Neuropathies: A Population PK/PD Model Analysis

Neuropathic pain, often associated with diabetic neuropathy or nerve compression injuries, arises from damage or dysfunction in the somatosensory nervous system. Tramadol, frequently prescribed for this pain, has its fraction unbound and that of its active metabolite (M1) significantly altered by diabetes. Yet, dosing adjustments for diabetic neuropathic pain remain underexplored. This study developed a comprehensive population pharmacokinetics/pharmacodynamics (PK/PD) model for tramadol and its major metabolites, focusing on diabetes's impact on PK and PK-PD relationship to identify optimal dosing regimens. Data from patients with chronic neuropathic pain on oral tramadol were used to develop enantiomer-specific population models, considering both total and unbound concentrations. Tramadol's PK was best described by a two-compartment model with Weibull absorption and linear elimination and a one-compartment model with enterohepatic circulation and first-pass metabolism for the active M1. Simulations showed higher unbound fractions of the active M1 in patients with type 1 and type 2 diabetes. Despite a 67% and 14% reduction in the AUC of total (1R,2R)-M1 in patients with type 1 and type 2 diabetes, respectively, the AUC of unbound (1R,2R)-M1 remained consistent. The unbound concentration of the active M1 required to achieve 50% of the maximum pain reduction (IC50) was lower in patients with diabetes, indicating increased sensitivity to the drug. This model-based approach provides valuable dosing guidance, suggesting once-daily dosing treatments in patients with diabetes and twice-daily dosing for patients with neuropathic pain secondary to nerve compression mechanisms.

Targeting Chemokines and Chemokine GPCRs to Enhance Strong Opioid Efficacy in Neuropathic Pain

Neuropathic pain (NP) originates from an injury or disease of the somatosensory nervous system. This heterogeneous origin and the possible association with other pathologies make the management of NP a real challenge. To date, there are no satisfactory treatments for this type of chronic pain. Even strong opioids, the gold-standard analgesics for nociceptive and cancer pain, display low efficacy and the paradoxical ability to exacerbate pain sensitivity in NP patients. Mounting evidence suggests that chemokine upregulation may be a common mechanism driving NP pathophysiology and chronic opioid use-related consequences (analgesic tolerance and hyperalgesia). Here, we first review preclinical studies on the role of chemokines and chemokine receptors in the development and maintenance of NP. Second, we examine the change in chemokine expression following chronic opioid use and the crosstalk between chemokine and opioid receptors. Then, we examine the effects of inhibiting specific chemokines or chemokine receptors as a strategy to increase opioid efficacy in NP. We conclude that strong opioids, along with drugs that block specific chemokine/chemokine receptor axis, might be the right compromise for a favorable risk/benefit ratio in NP management.

Management of diabetic neuropathy

Diabetic neuropathy is a neurodegenerative disorder that may alter both the somatic and autonomic peripheral nervous systems in the context of diabetes mellitus (DM). It is a prevalent and burdensome chronic complication of DM, that requires timely management. Optimized glycemic control (mainly for type 1 DM), multifactorial intervention (mainly for type 2 DM), with lifestyle intervention/physical exercise, and weight loss represent the basis of management for diabetic distal symmetrical polyneuropathy, and should be implemented early in the disease course. Despite better understanding of the pathogenetic mechanisms of diabetic peripheral neuropathy, there is still a stringent need for more pathogenetic-based agents that would significantly modify the natural history of the disease. The paper reviews the available drugs and current recommendations for the management of distal symmetrical polyneuropathy, including pain management, and for diabetic autonomic neuropathy. Evaluation of drug combinations that would perhaps be more efficient in slowing the progression of the disease or even reversing it, and that would provide a better pain management is still needed.

Evaluation of vitamin C protective effect on the cerebrocortical antioxidant defense, histopathological, pro-apoptotic p53 and anti-apoptotic Bcl2 expressions against tramadol neurotoxicity in rats

BACKGROUND

Reported tramadol toxicity emphasizes the necessity to recognize its mechanism of toxicity, particularly to the brain tissue.

AIM

This study aimed to evaluate the protective effect of vitamin C (Vit C) in cerebrocortical toxicity mediated by tramadol in rats using biochemical and histological parameters.

MATERIAL AND METHODS

Forty-eight albino rats were randomly divided into eight groups, (n = 6/group) as follow: the control group received normal saline and vitamin C group received vitamin C (200 mg/kg per oral). Tramadol 50, 100, 150 groups received tramadol in doses of (50, 100 and 150 mg/kg per oral, respectively); Tramadol 50+ Vit C, 100+ Vit C, 150+ Vit C groups received vitamin C (200 mg/kg per oral) plus tramadol in doses of (50, 100 and 150 mg/kg per oral, respectively). Rats had received vitamin C and tramadol daily for 30 days. Blood and brain tissues samples were harvested for biochemical, histopathological, immunohistochemical and electron microscopic examinations.

RESULTS

Tramadol administration leads to a significant elevation of MDA, NO levels and a significant decrease in antioxidants parameters (CAT, SOD and GSH) in the tissues of cerebral cortices in rats which were directly proportional to the dose of tramadol. In histological investigations, tramadol-treated groups showed pyknotic pyramidal cells, multiple red neurons and shrinking red neurons with hallows around it and apoptotic cells were detected. These biochemical abnormalities and histological impairment were ameliorated in groups with tramadol low doses by the co-treatment with vitamin C.

CONCLUSION

vitamin C has antioxidant and anti-apoptotic potentials against tramadol neurotoxicity via suppression of oxidative stress, lipid peroxidation, structural abnormalities, and down-regulation of p53 and overexpression of Bcl2 in the nervous tissues.

Loss of POMC-mediated antinociception contributes to painful diabetic neuropathy

Painful neuropathy is a frequent complication in diabetes. Proopiomelanocortin (POMC) is an endogenous opioid precursor peptide, which plays a protective role against pain. Here, we report dysfunctional POMC-mediated antinociception in sensory neurons in diabetes. In streptozotocin-induced diabetic mice the Pomc promoter is repressed due to increased binding of NF-kB p50 subunit, leading to a loss in basal POMC level in peripheral nerves. Decreased POMC levels are also observed in peripheral nervous system tissue from diabetic patients. The antinociceptive pathway mediated by POMC is further impaired due to lysosomal degradation of μ-opioid receptor (MOR). Importantly, the neuropathic phenotype of the diabetic mice is rescued upon viral overexpression of POMC and MOR in the sensory ganglia. This study identifies an antinociceptive mechanism in the sensory ganglia that paves a way for a potential therapy for diabetic neuropathic pain.

Treatment of Diabetic Cardiovascular Autonomic, Peripheral and Painful Neuropathy. Focus on the Treatment of Cardiovascular Autonomic Neuropathy with ACE Inhibitors

Neuropathies of the peripheral and autonomic nervous systems affect up to half of all people with diabetes mellitus, and are major risk factors for foot ulceration, amputation and cardiovascular dysfunction. Peripheral neuropathies manifest with either painful or painless symptoms, but many patients experience both. Once diagnosed appropriately, painful diabetic neuropathy management presents a unique challenge for physicians and should be considered as a syndrome, clinically distinct from diabetic peripheral neuropathy. The aetiology is multifactorial: metabolic changes in diabetes may directly affect neural tissue and neurodegenerative changes are precipitated by compromised nerve vascular supply. Metabolic changes include the elevated polyol pathway activity, the increased oxidative stress, the formation of advanced glycation and lipoxidation end products, and various pro-inflammatory changes. These mechanisms work in combination and interact in a mutually facilitatory fashion. This review focuses on the current therapies for the management of peripheral and cardiovascular autonomic neuropathy and of painful neuropathy as a distinct entity, based on the current knowledge of diabetic neuropathy. Moreover, the role of ACE inhibition has been explored in the treatment of Cardiovascular Autonomic Neuropathy.

Diabetic Peripheral Neuropathy: Diagnosis and Treatment

BACKGROUND

Diabetic peripheral neuropathy (DPN) is traditionally divided into large and small fibre neuropathy (SFN). Damage to the large fibres can be detected using nerve conduction studies (NCS) and often results in a significant reduction in sensitivity and loss of protective sensation, while damage to the small fibres is hard to reliably detect and can be either asymptomatic, associated with insensitivity to noxious stimuli, or often manifests itself as intractable neuropathic pain.

OBJECTIVE

To describe the recent advances in both detection, grading, and treatment of DPN as well as the accompanying neuropathic pain.

METHODS

A review of relevant, peer-reviewed, English literature from MEDLINE, EMBASE and Cochrane Library between January 1st 1967 and January 1st 2020 was used.

RESULTS

We identified more than three hundred studies on methods for detecting and grading DPN, and more than eighty randomised-controlled trials for treating painful diabetic neuropathy.

CONCLUSION

NCS remains the method of choice for detecting LFN in people with diabetes, while a gold standard for the detection of SFN is yet to be internationally accepted. In the recent years, several methods with huge potential for detecting and grading this condition have become available including skin biopsies and corneal confocal microscopy, which in the future could represent reliable endpoints for clinical studies. While several newer methods for detecting SFN have been developed, no new drugs have been accepted for treating neuropathic pain in people with diabetes. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors and anticonvulsants remain first line treatment, while newer agents targeting the proposed pathophysiology of DPN are being developed.

Efficacy and harms of long-term opioid therapy in chronic non-cancer pain: Systematic review and meta-analysis of open-label extension trials with a study duration ≥26 weeks

BACKGROUND AND OBJECTIVE

This updated systematic review evaluated the efficacy, acceptability and safety of long-term opioid therapy (LTOT) for chronic non-cancer pain (CNCP).

DATABASES AND DATA TREATMENT

Clinicaltrials.gov, CENTRAL and MEDLINE until June 2019. We included open-label extension trials with a study duration ≥26 weeks of RCTs with ≥2 weeks duration. Pooled estimates of event rates of categorical data and standardized mean differences (SMD) of continuous variables were calculated using a random effects model.

RESULTS

We added four new studies with 1,154 participants for a total of 15 studies with 3,590 participants. Study duration ranged between 26 and 156 weeks. Studies included patients with low back, osteoarthritis and neuropathic pain. The quality of evidence for every outcome was very low. 31.1% (95% Confidence interval [CI] 23.0%-40.7%) of patients randomized at baseline finished the open label period. 14.1% (95% CI 10.9%-19.4%) of patients dropped out to due adverse events. In 6.3% (95 CI 3.9%-10.1%) of patients serious adverse events and in 2.7% (95% CI 1.5%-4.7%) aberrant drug behaviour were noted. 0.5% (95% CI 0.2%-1.4%) of patients died.

CONCLUSIONS

Within the context of open-label extension studies, opioids maintain reduction of pain and disability and are rather well tolerated and safe. LTOT can be considered in carefully selected and monitored patients with low back, osteoarthritis and neuropathic pain who experience a clinically meaningful pain reduction with at least tolerable adverse events in short-term opioid therapy.

SIGNIFICANCE

There is very low quality evidence of the long-term efficacy, tolerability and safety of opioids for chronic low back, osteoarthritis and diabetic polyneuropathic pain within the context of open-label extension studies of randomized controlled trials. Drop out rate due to adverse events and deaths increase with study duration. One-third of patients profit from LTOT. Long-term opioid therapy can be considered in some carefully selected and monitored patients.

Diabetic neuropathy in children and adolescents with type 1 diabetes mellitus: Diagnosis, pathogenesis, and associated genetic markers

Diabetic neuropathy (DN) is a common long-term complication of type 1 (T1D) and type 2 (T2D) diabetes mellitus, with significant morbidity and mortality. DN is defined as impaired function of the autonomic and/or peripheral nervous system, often subclinical, particularly in children and adolescents with T1D. Nerve conduction studies (NCS) and skin biopsies are considered gold-standard methods in the assessment of DN. Multiple environmental and genetic factors are involved in the pathogenesis of DN. Specifically, the role of metabolic control and glycemic variability is of paramount importance. A number of recently identified genes, including the AKR1B1, VEGF, MTHFR, APOE, and ACE genes, contribute significantly in the pathogenesis of DN. These genes may serve as biomarkers to predict future DN development or treatment response. In addition, they may serve as the basis for the development of new medications or gene therapy. In this review, the diagnostic evaluation, pathogenesis, and associated genetic markers of DN in children and adolescents with T1D are presented and discussed.

Duplicated tramadol use in chronic low back pain: A nationwide cross-sectional study

Tramadol is a weak opioid that is commonly used for chronic low back pain (LBP). Despite its effectiveness, duplicated use of tramadol, which may indicate abuse or dependence, may exacerbate potential adverse reactions. This population-based, cross-sectional study aimed to investigate the prevalence of duplication of tramadol and its associated factors among patients with LBP. From a Korean nationwide claims database, non-hospitalized patients aged 40-99 years with LBP without malignancy were prescribed tramadol during 2014-2016. Duplication of tramadol was defined as overlapping of prescription days. Among them, we defined "extensive duplication (ED)" when days of tramadol duplication cover 10% or more of the days prescribed tramadol. Patient and healthcare utilization factors associated with ED were examined using a logistic regression model. The study population was 6 417 503 patients. Of these, 13.7% were ED users. The age- and sex-standardized prevalence of using tramadol twice or more a year was 14.06 per 100 people in 2014, 13.74 per 100 people in 2015 and 13.52 per 100 people in 2016. ED occurred more in those in the group aged 70-79 years (OR 1.12, 95% CI 1.11-1.13) than 40-49 years and in those with comorbidities, such as drug abuse (OR 2.99, 95% CI 2.05-4.36) or depression (OR 1.75, 95% CI 1.72-1.77). Based on the results of this study, a proper management system is needed to avoid tramadol duplication among older people and patients with drug abuse or depression.

Diabetic neuropathy

The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.

Diabetic neuropathy

The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.

Changes in CYP2D enzyme activity following induction of type 2 diabetes, and administration of cinnamon and metformin: an experimental animal study

1. Alterations in the activity of hepatic cytochrome P-450 isoenzymes result in changes in the pharmacokinetic behavior of drugs. This study was designed to explore the impact of type II diabetes, metformin and cinnamon on the activity of CYP2D isoenzyme. 2. Streptozotocin-nicotinamide-induced diabetic and normal rats were gavaged by cinnamon and/or metformin for 14 days. Using isolated perfusion of rat livers, the metabolic activity of CYP2D in the study groups was evaluated based on the oxidative biotransformation of tramadol hydrochloride. 3. The metabolic ratios of O-desmethyltramadol, the product of CYP2D-mediated metabolism of tramadol, in normal and diabetic control rats were found to be 0.33 ± 0.12 and 0.29 ± 0.07, respectively. Cinnamon significantly reduced the mentioned ratio in both normal and diabetic rats (0.13 ± 0.05 and 0.15 ± 0.04) and metformin increased the reduced activity in diabetic rats (0.37 ± 0.09 versus 0.29 ± 0.07). 4. In conclusion, it is evident that this study has shown the significant inhibitory effect of cinnamon on CYP2D. This finding suggests that it should be taken into consideration the possible metabolism-related pharmacokinetic drug-cinnamon interactions. 5. Additionally, type 2 diabetes condition reduced the enzyme activity and metformin consumption reversed this reduction; however, the significance of the latest is not clear.

Tramadol for neuropathic pain in adults

BACKGROUND

This review is an update of a review of tramadol for neuropathic pain, published in 2006; updating was to bring the review in line with current standards. Neuropathic pain, which is caused by a lesion or disease affecting the somatosensory system, may be central or peripheral in origin. Peripheral neuropathic pain often includes symptoms such as burning or shooting sensations, abnormal sensitivity to normally painless stimuli, or an increased sensitivity to normally painful stimuli. Neuropathic pain is a common symptom in many diseases of the peripheral nervous system.

OBJECTIVES

To assess the analgesic efficacy of tramadol compared with placebo or other active interventions for chronic neuropathic pain in adults, and the adverse events associated with its use in clinical trials.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase for randomised controlled trials from inception to January 2017. We also searched the reference lists of retrieved studies and reviews, and online clinical trial registries.

SELECTION CRITERIA

We included randomised, double-blind trials of two weeks' duration or longer, comparing tramadol (any route of administration) with placebo or another active treatment for neuropathic pain, with subjective pain assessment by the participant.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality and potential bias. Primary outcomes were participants with substantial pain relief (at least 50% pain relief over baseline or very much improved on Patient Global Impression of Change scale (PGIC)), or moderate pain relief (at least 30% pain relief over baseline or much or very much improved on PGIC). Where pooled analysis was possible, we used dichotomous data to calculate risk ratio (RR) and number needed to treat for an additional beneficial outcome (NNT) or harmful outcome (NNH), using standard methods. We assessed the quality of the evidence using GRADE and created 'Summary of findings' tables.

MAIN RESULTS

We identified six randomised, double-blind studies involving 438 participants with suitably characterised neuropathic pain. In each, tramadol was started at a dose of about 100 mg daily and increased over one to two weeks to a maximum of 400 mg daily or the maximum tolerated dose, and then maintained for the remainder of the study. Participants had experienced moderate or severe neuropathic pain for at least three months due to cancer, cancer treatment, postherpetic neuralgia, peripheral diabetic neuropathy, spinal cord injury, or polyneuropathy. The mean age was 50 to 67 years with approximately equal numbers of men and women. Exclusions were typically people with other significant comorbidity or pain from other causes. Study duration for treatments was four to six weeks, and two studies had a cross-over design.Not all studies reported all the outcomes of interest, and there were limited data for pain outcomes. At least 50% pain intensity reduction was reported in three studies (265 participants, 110 events). Using a random-effects analysis, 70/132 (53%) had at least 50% pain relief with tramadol, and 40/133 (30%) with placebo; the risk ratio (RR) was 2.2 (95% confidence interval (CI) 1.02 to 4.6). The NNT calculated from these data was 4.4 (95% CI 2.9 to 8.8). We downgraded the evidence for this outcome by two levels to low quality because of the small size of studies and of the pooled data set, because there were only 110 actual events, the analysis included different types of neuropathic pain, the studies all had at least one high risk of potential bias, and because of the limited duration of the studies.Participants experienced more adverse events with tramadol than placebo. Report of any adverse event was higher with tramadol (58%) than placebo (34%) (4 studies, 266 participants, 123 events; RR 1.6 (95% CI 1.2 to 2.1); NNH 4.2 (95% CI 2.8 to 8.3)). Adverse event withdrawal was higher with tramadol (16%) than placebo (3%) (6 studies, 485 participants, 45 events; RR 4.1 (95% CI 2.0 to 8.4); NNH 8.2 (95% CI 5.8 to 14)). Only four serious adverse events were reported, without obvious attribution to treatment, and no deaths were reported. We downgraded the evidence for this outcome by two or three levels to low or very low quality because of small study size, because there were few actual events, and because of the limited duration of the studies.

AUTHORS' CONCLUSIONS

There is only modest information about the use of tramadol in neuropathic pain, coming from small, largely inadequate studies with potential risk of bias. That bias would normally increase the apparent benefits of tramadol. The evidence of benefit from tramadol was of low or very low quality, meaning that it does not provide a reliable indication of the likely effect, and the likelihood is very high that the effect will be substantially different from the estimate in this systematic review.

The impact of black seed oil on tramadol-induced hepatotoxicity: Immunohistochemical and ultrastructural study

The natural herb, black seed (Nigella Sativa; NS) is one of the most important elements of folk medicine. The aim was to evaluate the impact of Nigella Sativa Oil (NSO) on the changes induced by tramadol in rat liver. Twenty four albino rats were used.

CONTROL GROUP

given intraperitoneal and oral saline for 30days. TR-group: given intraperitoneal tramadol (20, 40, 80mg/kg/day) in the first, middle and last 10days of the experiment, respectively. TR+NS group: administered intraperitoneal tramadol in similar doses to TR-group plus oral NSO (4ml/kg/day) for 30days. Immunohistochemical, electron microscopic, biochemical and statistical studies were performed. TR-group displayed disarranged hepatic architecture, hepatic congestion, hemorrhage and necrosis. Apoptotic hepatocytes, mononuclear cellular infiltration and a significant increase in the number of anti-CD68 positive cells were observed. Ultrastructurally, hepatocytes showed shrunken nuclei, swollen mitochondria, many lysosomes and autophagic vacuoles. Activated Ito and Von Kupffer cells were also demonstrated. Elevated serum levels of AST, ALT, ALP and bilirubin were noticed. NSO administration resulted in preservation of hepatic histoarchitecture and ultrastructure and significant reductions in the number of anti-CD68 positive cells and serum levels of liver seromarkers. In conclusion, NSO administration could mitigate the alterations induced by tramadol in rat liver.

Endomorphin-2 Inhibition of Substance P Signaling within Lamina I of the Spinal Cord Is Impaired in Diabetic Neuropathic Pain Rats

Opiate analgesia in the spinal cord is impaired in diabetic neuropathic pain (DNP), but until now the reason is unknown. We hypothesized that it resulted from a decreased inhibition of substance P (SP) signaling within the dorsal horn of the spinal cord. To investigate this possibility, we evaluated the effects of endomorphin-2 (EM2), an endogenous ligand of the μ-opioid receptor (MOR), on SP release within lamina I of the spinal dorsal horn (SDH) in rats with DNP. We established the DNP rat model and compared the analgesic efficacy of EM2 between inflammation pain and DNP rat models. Behavioral results suggested that the analgesic efficacy of EM2 was compromised in the condition of painful diabetic neuropathy. Then, we measured presynaptic SP release induced by different stimulating modalities via neurokinin-1 receptor (NK1R) internalization. Although there was no significant change in basal and evoked SP release between control and DNP rats, EM2 failed to inhibit SP release by noxious mechanical and thermal stimuli in DNP but not in control and inflammation pain model. We also observed that EM2 decreased the number of FOS-positive neurons within lamina I of the SDH but did not change the amount of FOS/NK1R double-labeled neurons. Finally, we identified a remarkable decrease in MORs within the primary afferent fibers and dorsal root ganglion (DRG) neurons by Western blot (WB) and immunohistochemistry (IHC). Taken together, these data suggest that reduced presynaptic MOR expression might account for the loss of the inhibitory effect of EM2 on SP signaling, which might be one of the neurobiological foundations for decreased opioid efficacy in the treatment of DNP.

[Long-term opioid therapy in chronic noncancer pain. A systematic review and meta-analysis of efficacy, tolerability and safety in open-label extension trials with study duration of at least 26 weeks]

BACKGROUND

The efficacy and safety of long-term (≥ 6 months) opioid therapy (LtOT) in chronic noncancer pain (CNCP) is under debate. A systematic review with meta-analysis of the efficacy and harms of opioids in open-label extension studies of randomized controlled trials (RCTs) has not been conducted until now.

METHODS

We screened MEDLINE and clinicaltrials.gov (through to December 2013), as well as reference sections of systematic reviews of long-term RCTs of opioids in CNCP. We included open-label extension trials with a study duration ≥ 26 weeks of RCTs of ≥ 2 weeks duration. Using a random effects model, pooled estimates of event rates for categorical data and standardized mean differences (SMD) for continuous variables were calculated.

RESULTS

We included 11 open-label extension studies with 2445 participants with nociceptive (low back, osteoarthritis) and neuropathic (radicular, polyneuropathy) pain. Median study duration was 26 (range 26-108) weeks. Four studies tested oxycodone, two studies tramadol and buprenorphine; hydromorphone, morphine, oxymorphone and tapentadol were each tested in one study. Of the patients randomized at baseline, 28.5 % (95 % confidence interval, CI, 17.9-39.2 %) finished the open-label period; 53.5 % (95 % CI 38.1-68.2 %) of patients entering the open-label period finished the open-label period. In sum, the total loss was 71.5 % (95 % CI 60.9-83.1 %) of all patients primarily included into the RCT. A total of 4.9 % (95 % CI 2.9-8.2 %) of patients dropped out due lack of efficacy; 16.8 % (95 % CI 11.0-24.8 %) dropped out to due adverse events (AE) in the open-label period and 0.08 % (95 % CI 0.001-0.05 %) of patients died during the open-label period. Only one study systematically assessed aberrant drug behavior of the patients: 5.7 % (95 % CI 3.4-9.6 %) showed aberrant drug behavior in the opinion of the investigators and 2.6 % (95 % CI 1.2-5.8 %) were judged to show aberrant drug behavior by independent expert assessment. There was no significant change (p = 0.50) in pain intensity between the end of the randomized period and the end of open-label phase (SMD 0.19 [- 0.03, 0.41]; six studies with 1360 participants).

CONCLUSION

Only a minority of patients selected for opioid therapy at randomization finished the long-term open-label study. However, sustained effects of pain reduction could be demonstrated in these patients. LtOT can be considered in carefully selected and monitored CNCP patients who experience clinically meaningful pain reduction with at least tolerable AE in short-term opioid therapy. The English full-text version of this article is freely available at SpringerLink (under "Supplementary Material").

Painful diabetic neuropathy — current understanding and management for the primary care team

Primary care has an increasing role in the diagnosis and treatment of painful diabetic neuropathy (PDN), and early accurate diagnosis and intervention can greatly improve the prognosis. With the incidence of diabetes predicted to increase dramatically, the number of patients with PDN is set to soar. PDN can have a serious impact on quality of life, leading to severe depression and even suicide. The evolution of a schematic approach to the diagnosis and treatment of PDN can offer new hope to many patients. This review focuses on PDN and current treatment strategies. Many leading pain clinics have adopted a multidisciplinary approach to the pharmacological and non-pharmacological management of PDN.

Incidence of tramadol shopping behavior in a retrospective cohort of chronic non-cancer pain patients in France

PURPOSE

Opioid analgesic use in chronic non-cancer pain (CNCP) is increasingly prevalent, but the benefits and risks are inadequately understood. In France, tramadol is one of the most used prescription opioids, but studies on its misuse liability in CNCP are still lacking. The aim was to assess the incidence of tramadol shopping behavior in CNCP patients and to identify the associated risk factors.

METHODS

A retrospective cohort of CNCP patients aged 18 years and older treated by tramadol for at least six consecutive months between 2005 and 2013 from a sample of the French Health Insurance database was established. Doctor shopping was defined as at least 1 day of overlapping prescriptions written by two or more different prescribers and filled in at least three different pharmacies.

RESULTS

A total of 3505 CNCP patients were included with a majority of women (66.4%) and a mean age of 66.4 ± 14.7 years. The median tramadol treatment duration was 260 [interquartile range: 211-356] days. The 1-year incidence rate of tramadol shopping behavior was 1.0% [95%CI: 0.7-1.5]. On multivariate analysis, risk factors associated with tramadol shopping behavior were age (hazard ratio [HR] = 7.4 [95%CI: 2.8-19.7] for age <40, HR = 2.8 [95%CI: 1.0-7.7] for 40 ≤ age < 50, versus age ≥50), low-income status (HR = 8.5 [95%CI: 3.6-20.5]), and prior use of strong opioids (HR = 5.7 [95%CI: 1.9-17.0]).

CONCLUSION

Tramadol shopping behavior incidence appears low in CNCP patients but may represent a public health concern given the widespread use of tramadol. Education and best monitoring of high-risk patients are needed to reduce doctor shopping. Copyright © 2016 John Wiley & Sons, Ltd.

Design, synthesis and biological evaluation of N-phenylalkyl-substituted tramadol derivatives as novel μ opioid receptor ligands

AIM

Tramadol is an atypical opioid analgesic with low potential for tolerance and addiction. However, its opioid activity is much lower than classic opiates such as morphine. To develop novel analgesic and further explore the structure activity relationship (SAR) of tramadol skeleton.

METHODS

Based on a three-dimensional (3D) structure superimposition and molecular docking study, we found that M1 (the active metabolite of tramadol) and morphine have common pharmacophore features and similar binding modes at the μ opioid receptor in which the substituents on the nitrogen atom of both compounds faced a common hydrophobic pocket formed by Trp2936.48 and Tyr3267.43. In this study, N-phenethylnormorphine was docked to the μ opioid receptor. It was found that the N-substituted group of N-phenethylnormorphine extended into a hydrophobic pocket formed by Trp2936.48 and Tyr3267.43. This hydrophobic interaction may contribute to the improvement of its opioid activities as compared with morphine. The binding modes of M1, morphine and N-phenethylnormorphine overlapped, indicating that the substituent on the nitrogen atoms of the three compounds may adopt common orientations. A series of N-phenylalkyl derivatives from the tramadol scaffold were designed, synthesized and assayed in order to generate a new type of analgesics.

RESULTS

As a result, compound 5b was identified to be an active candidate from these compounds. Furthermore, the binding modes of 5b and morphine derivatives in the μ opioid receptor were comparatively studied.

CONCLUSION

Unlike morphine-derived structures in which bulky N-substitution is associated with improved opioid-like activities, there seems to be a different story for tramadol, suggesting the potential difference of SAR between these compounds. A new type of interaction mechanism in tramadol analogue (5b) was discovered, which will help advance potent tramadol-based analgesic design.

Effect of Nigella sativa Linn oil on tramadol-induced hepato- and nephrotoxicity in adult male albino rats

The present study was carried out to evaluate the role of Nigella sativa Linn (NsL) oil against subacute tramadol-induced hepatotoxicity, nephrotoxicity as well as oxidative stress in adult male albino rats. Sixty adult male albino rats were divided into four groups. Group I: control group; 30 rats equally subdivided into: Ia; −ve control group, Ib; +ve control group received saline, Ic; +ve control group received corn oil. Group II: 10 rats received NsL oil; 1 mg/kg in 1 ml corn oil/day, group III: 10 rats received tramadol; 30 mg/kg/day, group IV: 10 rats received tramadol + NsL oil in the previous doses. Treatments were given by gavage for 30 days. Then rats were sacrificed and specimens from the livers and kidneys were taken for biochemical and histopathological study. Biochemical data showed elevated liver enzymes; alanine transaminase (ALT), aspartate transaminase (AST), gamma glutamyltransferase (GGT), bilirubin as well as urea and creatinine in tramadol group. A significant increase in hepatic and renal malondialdehyde (MDA) and a decrease in glutathione peroxidase (GPx) levels were also noticed. Histological analysis of the liver showed vacuolated hepatocyte cytoplasm indicating hydropic degeneration with binucleated cells, apoptotic nuclei, congested central veins, cellular infiltration and hemorrhage. Kidney sections revealed atrophied glomeruli with collapsed tufts and wide Bowman's space, degenerated tubules, hemorrhage and mononuclear cellular infiltration. There was also an increase in area % of collagen fibers in both organs. Concomitant use of NsL oil with tramadol induced partial improvement in the hepato- and nephrotoxic effects. In conclusion, this study suggested that concomitant use of NsL oil with tramadol proved to be capable of ameliorating tramadol-induced hepato- and nephrotoxicity which might be due to its antioxidant potential.

Effects of type 1 and type 2 diabetes on the pharmacokinetics of tramadol enantiomers in patients with neuropathic pain phenotyped as cytochrome P450 2D6 extensive metabolizers

Objectives

The aim of this study was to evaluate the influence of poorly controlled type 1 (T1DM) and type 2 diabetes mellitus (T2DM) on the pharmacokinetics and metabolism of tramadol enantiomers in patients with neuropathic pain.

Methods

Nondiabetic patients (control group, n = 12), patients with T1DM (n = 9) or T2DM (n = 9), all with neuropathic pain and phenotyped as cytochrome P450 2D6 extensive metabolizers, received a single oral dose of 100 mg racemic tramadol. Serial blood samples were collected over a 24-h period.

Key findings

Patients with T1DM showed reduced Cmax of both tramadol enantiomers. The plasma concentrations of the active (+)-M1 were significantly reduced in T1DM (area under the curve plasma concentration versus time (AUC∞): 313.1 ng·h/ml) when compared with nondiabetic patients (AUC∞: 1246.6 ng·h/ml). The fraction unbound of (+)-M1 was increased in patients with T1DM. Patients with T1DM and T2DM showed reduced AUC and increased fraction unbound of (−)-M1.

Conclusions

The reduced total plasma concentrations of the active (+)-M1 in patients with T1DM may not be of clinical relevance because they are counterbalanced by the increased fraction unbound.

Duloxetine in the long-term management of diabetic peripheral neuropathic pain: An open-label, 52-week extension of a randomized controlled clinical trial

BACKGROUND

Duloxetine hydrochloride, a selective serotonin (5-HT) and norepinephrine (NE) reuptake inhibitor, is relatively balanced in its affinity for both 5-HT and NE reuptake inhibition and is the first US Food and Drug Administration-approved prescription drug for the management of diabetic peripheral neuropathic pain (DPNP).

OBJECTIVES

The aim of this study was to determine whether management of DPNP with duloxetine interferes with the treatment of diabetes. It also examined the tolerability of long-term exposure to duloxetine with regard to the progression of diabetic complications, and assessed the impact of DPNP management with duloxetine versus routine care.

METHODS

This was a 52-week, multicenter, re-randomized, open-label extension of a parallel, double-blind, randomized, placebo-controlled, acute (12-week) study. Patients who completed the duloxetine or placebo acute treatment period were randomly reassigned in a 2:1 ratio to treatment with duloxetine 60 mg BID or routine care for an additional 52 weeks. The study included male and female outpatients aged ≥18 years with a diagnosis of DPNP caused by type 1 or type 2 diabetes. Over the course of the 52-week study, visits were scheduled on the following weeks (of the extension phase of the study): 1 (via phone only), 2, 4, 8, 12, 20, 28, 40, and 52. Tolerability was assessed by review and analyses of discontinuation rates, adverse events (AEs), laboratory data, vital signs, electrocardiographic results, concomitant medications, and diabetic complications. Treatment-emergent AEs (TEAEs) were defined as AEs that appeared during therapy (were not present at baseline) or were exacerbated during treatment. Data on AEs and concomitant medications were collected at every visit. Data on blood pressure, heart rate, and significant hypoglycemic events were collected at every visit starting from week 2. Fasting clinical chemistry and electrolyte group laboratory assessments were done at every visit, starting from week 4. Electrocardiographic data was collected at weeks 4 and 52, and glycosylated hemoglobin and lipid profile data were collected at weeks 20 and 52. Hematology and urinalysis laboratory assessments and diabetic complication assessments were done at week 52. All safety data was assessed in cases of early discontinuation. Treatment differences on quality of life (QOL) were compared using the Short Form-36 Health Status Survey (SF-36) and the EQ-5D instrument of the European Health-Related Quality of Life Measures. This was assessed at the last visit or at early discontinuation.

RESULTS

The open-label extension-phase study included 337 patients (duloxetine, n = 222; routine care, n = 115). For the duloxetine group, mean age was 60.2 years, 61.3% were male, and 78.4% were white. For the routine-care group, mean age was 58.9 years, 60.0% were male, and 74.8% were white. Mean weight was 95.3 kg for both groups. None of the TEAEs occurred significantly more often in the duloxetine-treated group than in the routine-care-treated group. No TEAEs were reported by >10% of patients in the duloxetine group. The TEAEs reported by >10% of patients in the routine-care group included dizziness (11.3%), somnolence (13.0%), headache (10.4%), and vomiting (10.4%). No significant differences were found between treatment groups in the occurrence of serious AEs or in the number of patients discontinuing because of AEs. Duloxetine was significantly better than routine care on the bodily pain subscale of the SF-36 (mean change: 1.5 vs -4.1; P= 0.021) and on the EQ-5D (mean change: -0.00 vs -0.09; P = 0.001).

CONCLUSIONS

Over 52 weeks of follow-up, treatment of these diabetic patients with duloxetine for peripheral neuropathic pain was associated with outcomes similar to, or significantly better than, that of routine care on most measures of tolerability, diabetic complications, and QOL.

Alloxan-induced diabetic thermal hyperalgesia, prophylaxis and phytotherapeutic effects of Rheum ribes L. in mouse model

Rheum ribes L., known as Syrian rhubarb, is used in traditional Lebanese folk medicine for the treatment of diabetes. The present study aims to investigate the activities of R. ribes aqueous extract for glucose homeostasis, in vivo antioxidant and diabetic neuropathy protection in mice. The acute and the subacute effects of various doses of R. ribes on blood glucose and in vivo antioxidant activity utilizing serum catalase level (CAT) were studied in alloxan-diabetic mice. The high doses significantly lowered glucose level and increased serum CAT in alloxan-diabetic mice. Pretreatment with the extract prior to alloxination, protected the mice from acquiring diabetes and diabetic neuropathy. Treatment with the extract for 8 weeks alleviated hyperalgesia in diabetic mice. Our findings provide clinicians with promising drugs intended for the management of the symptoms of diabetic complications. The protective activity of R. ribes against acquiring diabetes and diabetic neuropathy might pave the way for preparing a prophylactic treatment for diabetes risk groups.

Pharmacokinetic considerations for therapies used to treat interstitial cystitis

INTRODUCTION

Interstitial cystitis (IC) or bladder pain syndrome (BPS) is defined as supra-pubic pain related to bladder filling. IC is characterized by a particular symptom complex with no identifiable causes; as with bladder hypersensitivity it is usually associated with urinary frequency and urgency with bladder pain. No current treatments have a significant impact on symptoms over time.

AREAS COVERED

This systematic review examines the pharmacokinetic aspects and adverse event of present IC therapy to highlight appropriate treatment to improve the symptoms of IC. This article reviews material obtained via Medline, PubMed, and EMBASE literature searches up to October 2013.

EXPERT OPINION

The correct approach to IC should consider a multidisciplinary team of specialists and a multimodal treatment package that include psychotherapy, behavior change, physical activation, and analgesic treatment. Unfortunately, a single therapeutic target for IC is not yet known. With regard to pathophysiology and therapy, there is more to discover. The first insult damages the bladder urothelium, hence vehicles that lead the drug to penetrate the wall of the bladder might be a novel strategic approach.

Diabetic neuropathy

Diabetic neuropathy (DN) is the most common and troublesome complication of diabetes mellitus, leading to the greatest morbidity and mortality and resulting in a huge economic burden for diabetes care. The clinical assessment of diabetic peripheral neuropathy and its treatment options are multifactorial. Patients with DN should be screened for autonomic neuropathy, as there is a high degree of coexistence of the two complications. A review of the clinical assessment and treatment algorithms for diabetic neuropathy, painful neuropathy, and autonomic dysfunction is provided.

Long-term opioid treatment of chronic nonmalignant pain: unproven efficacy and neglected safety?

BACKGROUND

For the past 30 years, opioids have been used to treat chronic nonmalignant pain. This study tests the following hypotheses: (1) there is no strong evidence-based foundation for the conclusion that long-term opioid treatment of chronic nonmalignant pain is effective; and (2) the main problem associated with the safety of such treatment - assessment of the risk of addiction - has been neglected.

METHODS

Scientometric analysis of the articles representing clinical research in this area was performed to assess (1) the quality of presented evidence (type of study); and (2) the duration of the treatment phase. The sufficiency of representation of addiction was assessed by counting the number of articles that represent (1) editorials; (2) articles in the top specialty journals; and (3) articles with titles clearly indicating that the addiction-related safety is involved (topic-in-title articles).

RESULTS

Not a single randomized controlled trial with opioid treatment lasting >3 months was found. All studies with a duration of opioid treatment ≥6 months (n = 16) were conducted without a proper control group. Such studies cannot provide the consistent good-quality evidence necessary for a strong clinical recommendation. There were profound differences in the number of addiction articles related specifically to chronic nonmalignant pain patients and to opioid addiction in general. An inadequate number of chronic pain-related publications were observed with all three types of counted articles: editorials, articles in the top specialty journals, and topic-in-title articles.

CONCLUSION

There is no strong evidence-based foundation for the conclusion that long-term opioid treatment of chronic nonmalignant pain is effective. The above identified signs indicating neglect of addiction associated with the opioid treatment of chronic nonmalignant pain were present.

CYP2D6*2 Polymorphism as a Predictor of Failed Outpatient Tramadol Therapy in Postherpetic Neuralgia Patients

Human cytochrome P4502D6 (CYP2D6) gene is highly polymorphic, leading to wide interindividual ethnic differences in CYP2D6-mediated drug metabolism. Its activity ranges from complete deficiency to excessive activity, potentially causing toxicity of the medication or therapeutic failure with recommended drug dosages. The aim of the study was to find the association of CYP2D6*2 polymorphisms with demographic characters (age, sex, and weight), pain intensity scales [numerical rating scale (NRS) sleep, global perceived effect (GPE)], and adverse drug effects in postherpetic neuralgia (PHN) patients receiving tramadol. The study comprised 246 patients [including 123 nonresponders (NRs) and 123 responders (Rs)] with PHN undergoing analgesic treatment at the pain clinic, Out Patient Department, University College of Medical Sciences, Guru Teg Bahadur Hospital, Delhi, India. Patients with any history of diabetes mellitus, human immunodeficiency virus, malignancy, hematological or liver disease, psychiatric illness, alcohol abuse, and tramadol sensitivity were excluded from the study. The NRSs of (resting and movement), NRS-sleep, and GPE were evaluated by the treating physician. Adverse drug effects during the time of the study were recorded. All samples were analyzed for CYP2D6*2 polymorphism using the polymerase chain reaction-restriction fragment length polymorphism method. The genotype distribution did not vary significantly among genders [NR (P = 0.723); R (P = 0.947)] and different age groups in NRs (P = 0.763) and Rs (P = 0.268). Clinically, statistically significant (P < 0.001) results were obtained in both the groups when compared with baseline in the NRS-sleep and GPE scores, whereas no association was found between NRS-sleep and GPE scores when compared with CYP2D6*2 genotype (P > 0.05). In addition, CYP2D6*2 genotype was not related to the adverse effects of analgesic therapy. The overall results suggested that CYP2D6*2 polymorphism plays no role in the PHN patients receiving tramadol treatment. The CYP2D6*2 polymorphism may not be a predictor of treatment outcome of patients with respect to PHN-receiving tramadol.

Rab7 silencing prevents μ-opioid receptor lysosomal targeting and rescues opioid responsiveness to strengthen diabetic neuropathic pain therapy

Painful diabetic neuropathy is poorly controlled by analgesics and requires high doses of opioids, triggering side effects and reducing patient quality of life. This study investigated whether enhanced Rab7-mediated lysosomal targeting of peripheral sensory neuron μ-opioid receptors (MORs) is responsible for diminished opioid responsiveness in rats with streptozotocin-induced diabetes. In diabetic animals, significantly impaired peripheral opioid analgesia was associated with a loss in sensory neuron MOR and a reduction in functional MOR G-protein-coupling. In control animals, MORs were retained mainly on the neuronal cell membrane. In contrast, in diabetic rats, they were colocalized with upregulated Rab7 in LampI-positive perinuclear lysosome compartments. Silencing endogenous Rab7 with intrathecal Rab7-siRNA or, indirectly, by reversing nerve growth factor deprivation in peripheral sensory neurons not only prevented MOR targeting to lysosomes, restoring their plasma membrane density, but also rescued opioid responsiveness toward better pain relief. These findings elucidate in vivo the mechanisms by which enhanced Rab7 lysosomal targeting of MORs leads to a loss in opioid antinociception in diabetic neuropathic pain. This is in contrast to peripheral sensory neuron MOR upregulation and antinociception in inflammatory pain, and provides intriguing evidence that regulation of opioid responsiveness varies as a function of pain pathogenesis.

Treatment of painful peripheral neuropathy

Neuropathic pain management is an important aspect in the management of painful peripheral neuropathy. Anticonvulsants and antidepressants have been studied extensively and are often used as first-line agents in the management of neuropathic pain. In this article, data from multiple randomized controlled studies on painful peripheral neuropathies are summarized to guide physicians in treating neuropathic pain. Treatment is a challenge given the diverse mechanisms of pain and variable responses in individuals. However, most patients derive pain relief from a well-chosen monotherapy or well-designed polypharmacy that combines agents with different mechanisms of action.

Guidelines in the management of diabetic nerve pain: clinical utility of pregabalin

Diabetic peripheral neuropathy is a common complication of diabetes. It presents as a variety of syndromes for which there is no universally accepted unique classification. Sensorimotor polyneuropathy is the most common type, affecting about 30% of diabetic patients in hospital care and 25% of those in the community. Pain is the reason for 40% of patient visits in a primary care setting, and about 20% of these have had pain for greater than 6 months. Chronic pain may be nociceptive, which occurs as a result of disease or damage to tissue with no abnormality in the nervous system. In contrast, neuropathic pain is defined as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system." Persistent neuropathic pain interferes significantly with quality of life, impairing sleep and recreation; it also significantly impacts emotional well-being, and is associated with depression, anxiety, and noncompliance with treatment. Painful diabetic peripheral neuropathy is a difficult-to-manage clinical problem, and patients with this condition are more apt to seek medical attention than those with other types of diabetic neuropathy. Early recognition of psychological problems is critical to the management of pain, and physicians need to go beyond the management of pain per se if they are to achieve success. This evidence-based review of the assessment of the patient with pain in diabetes addresses the state-of-the-art management of pain, recognizing all the conditions that produce pain in diabetes and the evidence in support of a variety of treatments currently available. A search of the full Medline database for the last 10 years was conducted in August 2012 using the terms painful diabetic peripheral neuropathy, painful diabetic peripheral polyneuropathy, painful diabetic neuropathy and pain in diabetes. In addition, recent reviews addressing this issue were adopted as necessary. In particular, reports from the American Academy of Neurology and the Toronto Consensus Panel on Diabetic Neuropathy were included. Unfortunately, the results of evidence-based studies do not necessarily take into account the presence of comorbidities, the cost of treatment, or the role of third-party payers in decision-making. Thus, this review attempts to give a more balanced view of the management of pain in the diabetic patient with neuropathy and in particular the role of pregabalin.

A randomized, prospective study of efficacy and safety of oral tramadol in the management of post-herpetic neuralgia in patients from north India

OBJECTIVE

To evaluate the safety and efficacy of oral tramadol therapy (50 to 200 mg/day) in the treatment for post-herpetic neuralgia (PHN).

METHODS

The study was a prospective, single-blind, non-responder vs. responder, randomized trial conducted in 100 outpatients of PHN after oral administration of tramadol for 4 weeks. Those patients who had achieved 50% or greater pain relief after 14 days of oral tramadol treatment were categorized as responders and those reporting < 50% pain relief were categorized as non-responders. Rescue analgesia was provided by the topical application of a cream consisting of the combination of 3.33% doxepin and 0.05% capsaicin to the affected areas of PHN patients of both groups for at least 14 days, along with tramadol therapy. The rescue analgesia was extended to 4 weeks in patients of the non-responder group. The primary endpoints were measured using a numerical rating scale (NRS) at rest and with movement. Secondary endpoints included additional pain ratings such as global perceived effect (GPE), Neuropathic Pain Symptom Inventory scores (NPSI), daily sleep interference score (DSIS), quality of life (QOL) as per WHO QOL-BREF Questionnaire scores, patient and clinician ratings of global improvement. The 2 groups were compared on the basis of pain intensity scores, encompassing primary as well as secondary endpoints, and QOL after 28 days of the treatment regimen.

RESULTS

Pain intensity scores measured by NRS (at resting and with movement), NPSI, and DSIS were consistently reduced (P < 0.001) over 28 days at varying intervals in both the groups, but the magnitude of reduction was higher in responders than non-responders. A concomitant improvement (P < 0.001) was observed in GPE on days 3, 14, and 28 as compared to the respective baseline scores in both the groups. Although the WHO QOL-BREF scores showed significant (P < 0.001) improvement in QOL of PHN patients at days 14 and 28 in both the groups, the magnitude of improvement was higher in responders as compared to non-responders. Significant improvement in pain intensity scores and QOL in non-responders is mainly attributed to the use of rescue analgesia for 28 days rather than recommended tramadol therapy.

CONCLUSIONS

Treatment with tramadol 50 to 200 mg per day was associated with significant pain reduction in terms of enhanced pain relief, reduced sleep interference, greater global improvement, diminished side-effect profile, and improved QOL in PHN patients from North India. Further categorization of PHN patients may be helpful so that additional or alternative therapy may be prescribed to non-responders.

CYP2D6*4 polymorphism, tramadol treatment and its clinical impact in patients with postherpetic neuralgia

Aim: The aim of this study was to investigate the associations between the CYP2D6*4 polymorphism, interindividual differences in CYP2D6 activity and adverse drug effects in postherpetic neuralgia (PHN) patients receiving tramadol. Patients & methods: The study comprised 158 patients (including 78 nonresponders and 80 responders) with PHN who were undergoing analgesic treatment at the Pain Clinic in the Out Patient Department of the University College of Medical Sciences, Guru Teg Bahadur Hospital (New Delhi, India). The numerical rating scale scores were measured at the resting and movement stages; Neuropathic Pain Symptom Inventory scores were evaluated by the treating physician. WHO-brief questionnaire scores for quality of life and adverse drug effects during the time of study were recorded. All samples were analyzed for the CYP2D6*4 polymorphism using the PCR-restriction fragmentation length polymorphism method. Results: The genotype distribution did not vary significantly among different age groups in nonresponders and responders. The CYP2D6*4 polymorphism was significantly associated with lower Neuropathic Pain Symptom Inventory (burning, squeezing stabbing and pressure) scores. The quality-of-life (sociological, psychological and environmental domains) scores correlated with CYP2D6*4 and showed significant results (p < 0.05) using a generalized linear model. No association was found between the physiological domain compared with the CYP2D6*4 allele (p > 0.05). In addition, the homozygous mutated CYP2D6*4 allele was not related to adverse effects of analgesic therapy. Conclusion: The CYP2D6*4 polymorphism may not be a predictor for treatment outcome of patients with PHN receiving tramadol. However, further investigation is required to confirm these findings in a larger sample size.

Evidence-based guideline: Treatment of painful diabetic neuropathy: report of the American Academy of Neurology, the American Association of Neuromuscular and Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation

OBJECTIVE

To develop a scientifically sound and clinically relevant evidence-based guideline for the treatment of painful diabetic neuropathy (PDN).

METHODS

We performed a systematic review of the literature from 1960 to August 2008 and classified the studies according to the American Academy of Neurology classification of evidence scheme for a therapeutic article, and recommendations were linked to the strength of the evidence. The basic question asked was: "What is the efficacy of a given treatment (pharmacological: anticonvulsants, antidepressants, opioids, others; and non-pharmacological: electrical stimulation, magnetic field treatment, low-intensity laser treatment, Reiki massage, others) to reduce pain and improve physical function and quality of life (QOL) in patients with PDN?"

RESULTS AND RECOMMENDATIONS

Pregabalin is established as effective and should be offered for relief of PDN (Level A). Venlafaxine, duloxetine, amitriptyline, gabapentin, valproate, opioids (morphine sulphate, tramadol, and oxycodone controlled-release), and capsaicin are probably effective and should be considered for treatment of PDN (Level B). Other treatments have less robust evidence or the evidence is negative. Effective treatments for PDN are available, but many have side effects that limit their usefulness, and few studies have sufficient information on treatment effects on function and QOL.

Adherence and long-term effect of oxycodone/paracetamol in chronic noncancer pain: a retrospective study

INTRODUCTION

Long-term administration of opiates in patients with chronic noncancer pain (CNCP) is subject to debate due to insufficient clinical evidence to support efficacy and tolerability.

METHODS

This retrospective analysis used hospital records to investigate the effects of low doses of the combination of oxycodone/paracetamol on CNCP in an outpatient clinic setting to verify adherence to therapy and long-term efficacy. All patients receiving therapy for CNCP were examined between May and September 2010 and information was collected on medication, duration of therapy, and static and dynamic pain measured using numeric rating scales (NRS) from relevant charts.

RESULTS

Two hundred and thirty-one patients (157 men, 68%) with a mean (± SD) age of 66.4±15.5 years were analyzed. Pain indexes at baseline revealed a mean (± SD) static NRS (sNRS) of 3.5±1.77 and a mean dynamic NRS (dNRS) of 7.24±1.33. At last follow-up, mean (± SD) pain reductions versus baseline were 1.58±1.42 for sNRS and 3.04±1.43 for dNRS (P<0.0001 for both). Regarding the duration of therapy, 54 patients (23.4%) were treated for <4 months, and 177 patients (76.6%) for 4 months up to 23 months. Pain reduction was significant in all groups (P<0.0001) but was greatest in patients who had been receiving therapy for ≥4 months. Improvements in pain relief were not associated with an increase in daily dose, which remained stable or decreased slightly over time.

DISCUSSION

The results of this study support the hypothesis that an opiate-based combination at low doses improves tolerability and adherence and results in patients obtaining long-term efficacy. Larger studies of the use of opiates in this setting and clinical monitoring on the regional and national level may convince clinicians to view opiates as efficacious analgesics and not as dangerous substances of abuse.

Clinical Approach to the Treatment of Painful Diabetic Neuropathy

Painful neuropathy is a common and often progressive complication of diabetes. Patients frequently report symptoms of tingling, burning, lancinating pain, hyperesthesia and allodynia. The natural history of the disease may vary from intermittent mild symptoms to severe chronic daily pain; the latter is often associated with diminished quality of life. There are a variety of pharmaceutical agents from different medicinal categories available for the symptomatic treatment of painful diabetic neuropathy, however selecting an agent is often challenging given the breadth of choices and lack of consistent guidelines. As a result, many patients remain untreated or undertreated.This article presents a practical clinical approach to the treatment of pain in diabetic neuropathy. Recommendations for first, second and third line medications are based on specific evidence for the treatment of painful diabetic neuropathy as well as safety, tolerability, drug interactions and cost. Additional topics of discussion include breakthrough pain, opioid use and topical therapies. This review does not comprehensively discuss all possible treatments for painful neuropathy, but provides a systematic approach designed to guide clinicians in tailoring therapies to the individual patient.

Comparison of the efficacy and safety of tramadol/acetaminophen combination therapy and gabapentin in the treatment of painful diabetic neuropathy

AIMS

This study compared the efficacy and safety of tramadol/acetaminophen (T/A) and gabapentin in the management of painful diabetic neuropathy.

METHODS

An open, randomized, comparative study was conducted. Subjects with painful symmetric neuropathy in the lower limbs and mean pain-intensity score > or = 4 on a numeric rating scale were eligible. Subjects were randomized to receive either tramadol (37.5 mg)/acetaminophen (325 mg) or gabapentin (300 mg) for 6 weeks. After 2 weeks of the titration period (1200 mg/day for gabapentin and three tablets/day for T/A), the doses were maintained if the pain was relieved. The primary efficacy outcome was a reduction in pain intensity. Secondary measures evaluated a pain relief scale, a Brief Pain Inventory, a 36-item Short Form Health Survey, average pain intensity and sleep disturbance.

RESULTS

One hundred and sixty-three subjects (T/A 79; gabapentin 84) were included. At the final visit, the mean doses were 1575 mg/day for gabapentin and 4.22 tablets/day for T/A. Both groups were similar in terms of baseline pain intensity (mean intensity: T/A 6.7 +/- 1.6; gabapentin 6.3 +/- 1.6, P = 0.168). At the final visit, the mean reductions in pain intensity were similar in both groups (T/A -3.1 +/- 2.0; gabapentin -2.7 +/- 2.1, P = 0.744). Both groups had similar improvements in every Short Form Health Survey category and Brief Pain Inventory subcategory, and in the mean pain relief scores.

CONCLUSION

This study suggests that the T/A combination treatment is as effective as gabapentin in the treatment of painful diabetic neuropathy in patients with Type 2 diabetes.