Serotonin-norepinephrine reuptake inhibitors and the influence of binding affinity (Ki) on analgesia

Pharmacological Methods of Pain Management: Narrative Review of Medication Used

Background

Pain management is a critical aspect of healthcare, aimed at alleviating discomfort and improving the quality of life for individuals experiencing acute or chronic pain. Pharmacological methods constitute a primary approach to pain management, including a diverse array of drugs that work through different mechanisms.

Aim

Identifying medications commonly employed in pain management, focusing on their mechanism of actions, uses, efficacy and pharmacological applications.

Methods

The methodology involved a systematic search of scientific literature using various databases, including PubMed, Scopus, and Google Scholar. Relevant articles published between 2000 and 2023 were screened for inclusion. The selected studies encompassed original research, review articles, therapeutic guidelines and randomized controlled trials.

Results

The findings of this review suggest that a multimodal approach combining various analgesics can enhance pain relief while minimizing adverse effects. It emphasizes the importance of assessing pain intensity, determining the underlying etiology, and utilizing evidence-based guidelines to optimize pain management outcomes.

Conclusion

Pharmacological methods of pain management are an essential component of pain management strategies to achieve optimal pain relief while minimizing adverse effects. The article concludes with a discussion on emerging trends and future directions in pharmacological pain management, including novel drug targets and advances in drug delivery systems.

Rosuvastatin Synergistically Enhances the Antinociceptive Efficacy of Duloxetine in Paclitaxel-Induced Neuropathic Pain in Mice

Paclitaxel, a widely used cancer chemotherapeutic agent, has high incidence of neurotoxicity associated with the production of neuropathic pain, for which only duloxetine has shown significant but moderate analgesic effect. Since statins, classically used to reduce hypercholesterolemia, have shown antinociceptive effect in preclinical studies on neuropathic pain, we studied whether the antinociceptive efficacy of duloxetine could be synergistically potentiated by rosuvastatin in a model of paclitaxel-induced neuropathy in mice. The astrocytic and microglial responses in the spinal cord of paclitaxel-treated mice were also assessed by measuring GFAP and CD11b proteins, respectively. Paclitaxel treatment did not impair motor coordination and balance in rotarod testing. Rosuvastatin, duloxetine, and the rosuvastatin/duloxetine combination (combined at equieffective doses) dose-dependently decreased mechanical allodynia (ED₃₀, von Frey testing) and thermal hyperalgesia (ED₅₀, hot plate testing) in paclitaxel-treated mice. Isobolographic analysis showed a superadditive interaction for rosuvastatin and duloxetine, as both the ED₃₀ and ED₅₀ for the rosuvastatin/duloxetine combination contained only a quarter of each drug compared to the individual drugs. The rosuvastatin/duloxetine combination reversed paclitaxel-induced GFAP overexpression, indicating that such effects might depend in part on astrocyte inactivation. Results suggest that statins could be useful in synergistically enhancing the efficacy of duloxetine in some chemotherapy-induced neuropathic conditions.

Pharmacological treatments of fibromyalgia in adults; overview of phase IV clinical trials

Background: Fibromyalgia is a chronic neurological condition characterized by widespread pain. The effectiveness of current pharmacological treatments is limited. However, several medications have been approved for phase IV trials in order to evaluate them.

Aim: To identify and provide details of drugs that have been tested in completed phase IV clinical trials for fibromyalgia management in adults, including the primary endpoints and treatment outcomes. This article was submitted to Neuropharmacology, a section of the journal Frontiers in Pharmacology.

Method: Publicly available and relevant phase IV trials registered at ClinicalTrials.gov were analyzed. The uses of the trialed drugs for fibromyalgia were reviewed.

Results: As of 8 August 2022, a total of 1,263 phase IV clinical trials were identified, of which 121 were related to fibromyalgia. From these, 10 clinical trials met the inclusion criteria for the current study. The drugs used in phase IV trials are milnacipran, duloxetine, pregabalin, a combination of tramadol and acetaminophen, and armodafinil. The effectiveness of the current pharmacological treatments is apparently limited.

Conclusion: Due to its complexity and association with other functional pain syndromes, treatment options for fibromyalgia only are limited and they are designed to alleviate the symptoms rather than to alter the pathological pathway of the condition itself. Pain management specialists have numerous pharmacologic options available for the management of fibromyalgia.

Activity dependent inhibition of TRPC1/4/5 channels by duloxetine involves voltage sensor-like domain

Transient receptor potential canonical 5 (TRPC5) is a polymodal, calcium-permeable, nonselective ion channel that is expressed in the brain and 75 % of human sensory neurons. Its pharmacological or genetic inhibition leads to the relief of neuropathic and inflammatory pain. The clinically approved drug duloxetine is superior to other serotonin and norepinephrine reuptake inhibitors at managing painful neuropathies, but it is not known why. Here we ask whether the TRPC5 receptor is modulated by duloxetine and may contribute to its analgesic effect. Electrophysiological measurements of heterologously expressed human TRPC5 in HEK293T cells were performed to evaluate the effect of duloxetine. The interaction site was identified by molecular docking and molecular dynamics simulations in combination with point mutagenesis. We found that duloxetine inhibits TRPC5 in a concentration-dependent manner with a high potency (IC₅₀ = 0.54 ± 0.03 µM). Our data suggest that duloxetine binds into a voltage sensor-like domain. For the interaction, Glu⁴¹⁸ exhibited particular importance due to putative hydrogen bond formation. Duloxetine effectively inhibits TRPC5 currents induced by cooling, voltage, direct agonists and by the stimulation of the PLC pathway. The finding that this TRPC5 inhibitor is widely used and well tolerated provides a scaffold for new pain treatment strategies.

Pharmacological treatment of major depressive disorder according to severity in psychiatric inpatients: results from the AMSP pharmacovigilance program from 2001-2017

The International Classification of Diseases (10^th Version) categorizes major depressive disorder (MDD) according to severity. Guidelines provide recommendations for the treatment of MDD according to severity. Aim of this study was to assess real-life utilization of psychotropic drugs based on severity of MDD in psychiatric inpatients. Drug utilization data from the program “Drug Safety in Psychiatry” (German: Arzneimittelsicherheit in der Psychiatrie, AMSP) were analyzed according to the severity of MDD. From 2001 to 2017, 43,868 psychiatric inpatients with MDD were treated in participating hospitals. Most patients were treated with ≥ 1 antidepressant drug (ADD; 85.8% of patients with moderate MDD, 89.8% of patients with severe MDD, and 87.9% of patients with psychotic MDD). More severely depressed patients were more often treated with selective serotonin–norepinephrine reuptake inhibitors and mirtazapine and less often with selective serotonin reuptake inhibitors (p < 0.001 each). Use of antipsychotic drugs (APDs), especially second-generation APDs, increased significantly with severity (37.0%, 47.9%, 84.1%; p < 0.001 each). APD + ADD was the most used combination (32.8%, 43.6%, 74.4%), followed by two ADDs (26.3%, 29.3%, 24.9%). Use of lithium was minimal (3.3%, 6.1% ,7.1%). The number of psychotropic drugs increased with severity of MDD—patients with psychotic MDD had the highest utilization of psychotropic drugs (93.4%, 96.5%, 98.7%; p < 0.001). ADD monotherapy was observed to a lesser extent, even in patients with non-severe MDD (23.2%, 17.1%, 4.4%). Findings reveal substantial discrepancies between guideline recommendations and real-life drug utilization, indicating that guidelines may insufficiently consider clinical needs within the psychiatric inpatient setting.

Incidence of Drug-Induced Delirium During Treatment With Antidepressants or Antipsychotics: A Drug Surveillance Report of German-Speaking Countries Between 1993 and 2016

OBJECTIVES

Successful treatment of delirium depends on the detection of the reversible contributors. Drugs with delirogenic properties are the most prevalent reversible cause of delirium.

METHODS

This observational study is based on data from Arzneimittelsicherheit in der Psychiatrie, a multicenter drug surveillance program in German-speaking countries recording severe adverse drug reactions (ADRs) in psychiatric inpatients. The present study analyzes drug-induced delirium (DID) during treatment with antidepressants and antipsychotics.

RESULTS

A total of 436 565 psychiatric inpatients were treated with antidepressants and/or antipsychotics during the observation period from 1993 to 2016 in the participating 110 hospitals. Overall, 254 cases (0.06% of all patients treated with antidepressants and/or antipsychotics) of DID were detected. Implicated either in combination or alone (multiple drugs were implicated in 70.1% of DID), clomipramine (0.24%), amitriptyline (0.21%), and clozapine (0.18%) showed the highest incidence rates of DID. When implicated alone (98 cases overall), clozapine (0.11%) followed by amitriptyline (0.05%) were most likely causally associated with the occurrence of DID. Drugs with strong antimuscarinic properties generally exhibited higher risk of DID.

CONCLUSIONS

With an incidence rate of <0.1%, the use of antidepressants and antipsychotics was rarely associated with DID within the Arzneimittelsicherheit in der Psychiatrie program. Tricyclic antidepressants and clozapine were the most commonly implicated psychotropic drugs. These data support the specific role of antimuscarinic properties in DID.

Depression Part 3: Medication Related Problems

When selecting and managing psychoactive medications in older people, it is equally important to focus on avoidance of toxicity as it is to focus on efficacy. Higher psychoactive medication load is associated with increased rate and risk of all cause hospitalization. The medication classes used to treat depression and related comorbidities include antidepressants, antipsychotics, stimulants, mood stabilizers, lithium, anxiolytics and sedative hypnotics. This discussion will examine considerations to help avoid medication related problems relevant to medications used to treat depression in the antidepressant pharmacological class.

A Real-World, Prospective, Multicenter, Single-Arm Observational Study of Duloxetine in Patients With Major Depressive Disorder or Generalized Anxiety Disorder

Background: Suboptimal treatment response during anti-depressive treatment is fairly common with the first antidepressant (AD) choice, followed by switching to another agent in the majority of cases. However, the efficacy of this strategy over continuation of the original agent is less solidly documented in real-life studies. The aim of our present study was to ascertain the effects of switching to duloxetine following inadequate response to prior ADs on general illness severity, pain, and health-related quality of life in a large sample of major depressive disorder (MDD) and generalized anxiety disorder (GAD) patients in a prospective, real-world, multicenter, observational study. Methods: A total of 578 participants with MDD or GAD were enrolled in 58 outpatient sites in an 8-week, single-arm, open-label, flexible-dose trial with duloxetine. Severity of symptoms [with Clinical Global Impression-Severity (CGI-S) and Clinical Global Impression-Improvement (CGI-I)], severity of pain (with a Visual Analog Scale), satisfaction with current treatment, and health-related quality of life [with the three-level version of the EuroQol five-dimensional questionnaire (EQ-5D-3L)] measures were recorded at baseline and at follow-up visits 4 and 8 weeks after initiation of treatment. Data were analyzed using ANOVA and mixed linear models. Results: 565 patients completed the study and comprised the analyzed dataset. Results indicated that severity of illness significantly decreased over the 8 weeks of the study and already at 4 weeks in both patient groups. Overall quality of life and all of its subindicators also significantly improved in both patient groups and so did subjective experience of pain. Satisfaction with current treatment also significantly increased during the study period. Frequency of side effects was low. In both GAD and MDD groups, two patients dropped out of the study due to adverse effects, leading to treatment termination in four cases (0.7%). Conclusions: This 8-week, multicenter, flexible-dosing, single-arm, open-label, observational real-life study in MDD and GAD patients switched to duloxetine after inadequate response or low tolerability to other ADs showed a significant positive effect on all outcome measures, including a significant decrease in illness severity as well as significant overall symptomatic improvement, with good tolerability.

Desvenlafaxine-associated hyperglycemia: A case report and literature review

Desvenlafaxine is a potent selective serotonin and norepinephrine reuptake inhibitor used to treat depression and anxiety. Several antidepressants have been associated with drug-induced hyperglycemia, but currently there are no reports for desvenlafaxine. A case of suspected desvenlafaxine-induced hyperglycemia is presented involving a 59-year-old female with type 2 diabetes whose average blood glucose increased by 30 mg/dL for fasting blood glucose and 75 mg/dL for postprandial blood glucose 1 month after switching from venlafaxine to desvenlafaxine. Prior to starting desvenlafaxine, she was stable on metformin 1000 mg twice daily, insulin glargine 8 units daily, and dulaglutide 1.5 mg once weekly. Over the course of 3 months after desvenlafaxine initiation, insulin glargine was increased and insulin lispro was initiated as the patient refused alternative antidepressant therapy due to favorable improvements in anxiety and depression. No other cause for elevated blood glucose could be elucidated. The Naranjo scale resulted in a score of 3, indicating a possible cause for the adverse drug reaction. Antidepressants have been associated with glucose dysregulation. However, literature also demonstrates improved glycemic control in treated versus untreated depression. If altered glucose levels are noted, all potential causative factors should be evaluated and risks and benefits weighed to guide therapy.

Distinguishing analgesic drugs from non-analgesic drugs based on brain activation in macaques with oxaliplatin-induced neuropathic pain

The antineoplastic agent oxaliplatin is a first-line treatment for colorectal cancer. However, neuropathic pain, characterized by hypersensitivity to cold, emerges soon after treatment. In severe instances, dose reduction or curtailing treatment may be necessary. While a number of potential treatments for oxaliplatin-induced neuropathic pain have been proposed based on preclinical findings, few have demonstrated efficacy in randomized, placebo-controlled clinical studies. This failure could be related, in part, to the use of rodents as the primary preclinical species, as there are a number of distinctions in pain-related mechanisms between rodents and humans. Also, an indicator of preclinical pharmacological efficacy less subjective than behavioral endpoints that is translatable to clinical usage is lacking. Three days after oxaliplatin treatment in Macaca fascicularis, a significantly reduced response latency to cold (10 °C) water was observed, indicating cold hypersensitivity. Cold-evoked bilateral activation of the secondary somatosensory (SII) and insular (Ins) cortex was observed with functional magnetic resonance imaging. Duloxetine alleviated cold hypersensitivity and significantly attenuated activation in both SII and Ins. By contrast, neither clinically used analgesics pregabalin nor tramadol affected cold hypersensitivity and cold-evoked activation of SII and Ins. The current findings suggest that suppressing SII and Ins activation leads to antinociception, and, therefore, could be used as a non-behavioral indicator of analgesic efficacy in patients with oxaliplatin-induced neuropathic pain.

LPM580098, a Novel Triple Reuptake Inhibitor of Serotonin, Noradrenaline, and Dopamine, Attenuates Neuropathic Pain

Background and Purpose: Sedation and somnolence remain serious adverse effects of the existing analgesics (e.g., pregabalin, duloxetine) for neuropathic pain. The available evidence indicates that serotonin (5-HT), noradrenaline (NE), and dopamine (DA) play important roles in modulating the descending inhibitory pain pathway and sleep-wake cycle. The aim of this work was to test the hypothesis that LPM580098, a novel triple reuptake inhibitor (TRI) of 5-HT, NE, and DA, has analgesic effect, and does not induce significant adverse effects associated with central inhibition, such as sedation and somnolence. Methods: The analgesic activity of LPM580098 was assessed on formalin test and spinal nerve ligation (SNL)-induced neuropathic pain model. Locomotor activity, pentobarbital sodium-induced sleeping and rota-rod tests were also conducted. In vitro binding and uptake assays, and Western blotting were performed to examine the potential mechanisms. Results: LPM580098 suppressed the nocifensive behaviors during phase II of the formalin test in mice. In SNL rats, LPM580098 (16 mg kg^-1) inhibited mechanical allodynia, thermal hyperalgesia and hyperexcitation of wide-dynamic range (WDR) neurons, in which the effect of LPM580098 was similar to pregabalin (30 mg kg^-1). However, pregabalin altered the spontaneous locomotion, affected pentobarbital sodium-induced sleep, and showed a trend to perform motor dysfunction, which were not induced by LPM580098. Mechanistically, LPM580098 inhibited the uptake of 5-HT, NE, and DA, improved pain-induced changes of the synaptic functional plasticity and structural plasticity possibly via downregulating the NR2B/CaMKIIα/GluR1 and Rac1/RhoA signaling pathways. Conclusion: Our results suggest that LPM580098, a novel TRI, is effective in attenuating neuropathic pain without producing unwanted sedation and somnolence associated with central nervous system (CNS) depressants.