Effectiveness of Duloxetine versus Other Therapeutic Modalities in Patients with Diabetic Neuropathic Pain: A Systematic Review and Meta-Analysis

Objectives: Diabetic peripheral neuropathy (DPN) is a chronic complication of diabetes mellitus (DM) with symptoms like intense pain and impaired quality of life. This condition has no treatment; instead, the pain is managed with various antidepressants, including duloxetine. The aim of this study is to analyze the evidence on the efficacy of duloxetine in the management of DPN. Methods: A systematic search in different databases was conducted using the keywords "diabetic neuropathy", "duloxetine therapy", "neuropathic pain", and "Diabetes Mellitus". Finally, eight studies were included in this meta-analysis. Results: All articles comparing duloxetine at different doses vs. a placebo reported significant differences in favor of duloxetine on pain scales like 24 h Average Pain Severity (standardized mean difference [SMD] = -1.06, confidence interval [CI] = -1.09 to -1.03, and p < 0.00001) and BPI Severity (SMD = -0.70, CI = -0.72 to -0.68, and p < 0.00001), among others. A total of 75% of the meta-analyses of studies comparing duloxetine at different doses showed a tendency in favor of the 120 mg/d dose. There were significant differences in favor of duloxetine when compared to routine care on the Euro Quality of Life (SMD = -0.04, CI = -0.04 to -0.03, and p < 0.00001) and SF-36 Survey (SMD = -5.86, CI = -6.28 to -5.44, and p < 0.00001) scales. There were no significant differences on the visual analog scale (VAS) when comparing duloxetine and gabapentin. Conclusions: Duloxetine appears to be effective in the management of DPN in different pain, symptom improvement, and quality of life scales.

Evolving data analysis of an Oral Lipid Tolerance Test toward the standard for the Oral Glucose Tolerance Test: Cross species modeling effects of AZD7687 on plasma triacylglycerol

We have developed a novel mechanistic pharmacokinetic-pharmacodynamic (PK/PD) model to describe the time course of plasma triglyceride (TAG) after Oral Lipid Tolerance Test (OLTT) and the effects of AZD7687, an inhibitor of diacylglycerol acyltransferase 1 (DGAT1), in humans, rats, and mice. Pharmacokinetic and plasma TAG data were obtained both in animals and in two phase I OLTT studies. In the PK/PD model, the introduction of exogenous TAG is represented by a first order process. The endogenous production and removal of TAG from plasma are described with a turnover model. AZD7687 inhibits the contribution of exogenous TAG into circulation. One or two compartment models with first order absorption was used to describe the PK of AZD7687 for the different species. Nonlinear mixed effect modeling was used to fit the model to the data. The effects of AZD7687 on the plasma TAG time course during an OLTT as well as interindividual variability were well described by the model in all three species. Meal fat content or data from single vs repeated dosing did not affect model parameter estimates. Body mass index was found to be a significant covariate on the plasma TAG baseline. The system parameters of the model will facilitate analysis for other compounds and provide tools to bring the standard of OLTT data analysis closer to the analyses of Oral Glucose Tolerance Test data maximizing knowledge gain.

Neuropathic pain: treatment guidelines and updates

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the diagnosis, treatment, and prevention of neuropathic pain.

RECENT FINDINGS

Neuropathic pain can be debilitating, leading to poor quality of life and functional status. Neuropathic pain results from numerous mechanisms of nerve injury including infectious diseases, complication of medical diseases, and mechanical damage. As a result of the lack of class I evidence for the treatment of numerous neuropathic pain conditions, those diseases without such evidence are often managed, as though neuropathic pain is a singular condition. In diseases such as diabetes, HIV, and herpes infections, the resultant neuropathic pain is often modifiable with prevention strategies. In one of the more prevalent neuropathic pain conditions, radiculopathy, the commonly used treatments lack sufficient evidence to explain their widespread use.

SUMMARY

The literature reveals that neuropathic pain is underdiagnosed and often undertreated or treated with ineffective or untested modalities. Evolving definitions of neuropathic pain has broadened the range of therapeutic approaches and brought current treatment paradigms under increased scrutiny. The lack of a mechanism-based approach to treatment may be responsible for the lackluster responses seen in most neuropathic pain conditions.

Are there different predictors of analgesic response between antidepressants and anticonvulsants in painful diabetic neuropathy?

BACKGROUND

To investigate baseline demographics and disease characteristics as predictors of the analgesic effect of duloxetine and pregabalin on diabetic peripheral neuropathic pain (DPNP).

METHODS

Based on data from the COMBO-DN study, a multinational clinical trial in DPNP, the potential impact of baseline characteristics on pain relief after 8-week monotherapy with 60 mg/day duloxetine or 300 mg/day pregabalin was assessed using analyses of covariance. Subgroups of interest were characterized regarding their baseline characteristics and efficacy outcomes.

RESULTS

A total of 804 patients were evaluated at baseline. A significant interaction with treatment was observed in the mood symptom subgroups with a larger pain reduction in duloxetine-treated patients having no mood symptoms [Hospital Anxiety and Depression Scale (HADS) depression or anxiety subscale score <11; -2.33 (duloxetine); -1.52 (pregabalin); p = 0.024]. There were no significant interactions between treatment for subgroups by age (<65 or ≥65 years), gender, baseline pain severity [Brief Pain Inventory Modified Short Form (BPI-MSF) average pain <6 or ≥6], diabetic neuropathy duration (≤2 or >2 years), baseline haemoglobin A1c (HbA1c) (<8% or ≥8%), presence of comorbidities and concomitant medication use.

CONCLUSIONS

Our analyses suggest that the efficacy of duloxetine and pregabalin for initial 8-week treatment in DPNP was consistent across examined subgroups based on demographics and disease characteristics at baseline except for the presence of mood symptoms. Duloxetine treatment appeared to be particularly beneficial in DPNP patients having no mood symptoms.

Handling missing data in a duloxetine population pharmacokinetic/pharmacodynamic model - imputation methods and selection models

PURPOSE

In pharmacokinetic (PK)/pharmacodynamic (PD) modelling and simulations (M&S), omitting dropouts can cause inaccuracies in parameter estimation and clinical trial simulations (CTS). This study examines the impact of different imputation methods for missing data on the interpretation of model results, as well as develops a selection model (where dropout and efficacy are jointly modelled) for use in CTS.

METHODS

Missing data were imputed using single and multiple imputation and pattern mixtures methods for a previously reported duloxetine PK/PD model. The probability of dropout was described in the selection model and CTS was conducted with a hypothetical drug to examine the impact of dropout on trial results.

RESULTS

The study completion rate was 75% and dropouts were not random. Model parameters obtained with different imputation methods were mostly within 40% (range 0 to 63%) compared to the model without dropouts. CTS showed 0.3 points lower median pain scores and 3% lower coefficient of variation over the 12-week simulations when dropout was included.

CONCLUSIONS

Missing data had little impact on the original population PK/PD analyses. Sensitivity analyses for dropouts should be conducted in M&S exercises. The utility of selection models in CTS was explored via a hypothetical case study.