Topical and Peripheral Ketamine as an Analgesic

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Systemic ketamine toxicity following dermal application of a compounded pain cream

Ketamine is an NMDA receptor antagonist commonly used as a dissociative anesthetic and analgesic. Though it is conventionally administered via the intravenous, intramuscular, or intranasal route, use as a compounded analgesic cream is becoming increasingly common. This is a case report of a 61-year-old man who was detained by the police for erratic driving. He was transported to the emergency department for bizarre behavior and altered mental status. Upon arrival, he was agitated and had torsional nystagmus. He had just applied a large amount of an analgesic cream containing 10 % ketamine, 5 % lidocaine, and 5 % amitriptyline to numerous ulcerations in his perineal and sacral region from pyoderma gangrenosum. His clinical presentation was consistent with ketamine toxicity, and mass spectrometry demonstrated an elevated urine ketamine concentration (32,300 ng/mL). His symptoms resolved spontaneously within a few hours and he was discharged. This is a unique case of systemic toxicity following dermal application of a ketamine pain cream in a patient with impaired skin barrier function due to pyoderma gangrenosum.

Effectiveness of preoperative ketamine gargle to reduce postoperative sore throat in adult patients undergoing surgery with endotracheal tube; systematic review and meta-analysis of randomized control trials

BACKGROUND

Postoperative sore throat is a frequent and distressing complication caused by airway instrumentation during general anesthesia. The discomfort can lead to immediate distress, delayed recovery and reduce patient satisfaction. The objective of this study was to determine the effectiveness of preoperative ketamine gargle on the occurrence of postoperative sore throat among adult patients who underwent surgery under general anesthesia with endotracheal tube.

METHOD

PubMed, Cochrane Library, Google Scholar, and World Clinical Trial Registry were searched to find the eligible randomized control trials comparing the effect of preoperative ketamine gargle and placebo gargle on the occurrence of postoperative sore throat after surgery with endotracheal tube in adult patients. We utilized Review Manager Version 5.4 to perform statistical analyses. Cochrane risk of bias tool for randomized control trials was used to assess the risk of bias of included studies. We explored heterogeneity using the I2 test. In addition to this, subgroup analysis, and sensitivity analysis was conducted to confirm the robustness of findings. The risk of publication bias was tested using funnel plot Pooled risk ratio along with 95% confidence interval (CI) was used to analyze the outcome.

RESULT

In the present systematic review and metanalysis, seventeen [17] randomized controlled trials (RCTs) with 1552 participants were included. Compared with placebo, preoperative ketamine gargle is effective to reduce postoperative sore throat (RR = 0.48; 95%CI [0.45, 0.52] in adult patients undergoing surgery under general anesthesia with endotracheal tube.

CONCLUSION

Preoperative ketamine gargle before induction of general anesthesia is effective to reduce the occurrence of postoperative sore throat in adult patients undergoing surgery under general anesthesia with an endotracheal tube. Further studies with large sample size, better study quality and optimal reporting could be conducted to determine the long-term efficacy and safety of ketamine gargle in different surgical populations.

Solid Metal Chemical and Thermal Injury Management

INTRODUCTION

Solid metals may create a variety of injuries. White phosphorous (WP) is a metal that causes both caustic and thermal injuries. Because of its broad use in munitions and smoke screens during conflicts and wars, all military clinicians should be competent at WP injury identification and acute therapy, as well as long-term consequence recognition.

MATERIALS AND METHODS

English-language manuscripts addressing WP injuries were curated from PubMed and Medline from inception to January 31, 2024. Data regarding WP injury identification, management, and sequelae were abstracted to construct a Scale for the Assessment of Narrative Review Articles guideline-consistent narrative review.

RESULTS

White phosphorous appears to be ubiquitous in military conflicts. White phosphorous creates a characteristic wound appearance accompanied by smoke, a garlic aroma, and spontaneous combustion on contact with air. Decontamination and burning prevention or cessation are key and may rely on aqueous irrigation and submersion or immersion in substances that prevent air contact. Topical cooling is a key aspect of preventing spontaneous ignition as well. Disposal of all contaminated clothing and gear is essential to prevent additional injury, especially to rescuers. Long-term sequelae relate to phosphorous absorption and may lead to death. Chronic or repeated exposure may induce jaw osteonecrosis. Tactical Combat Casualty Care recommendations do not currently address WP injury management.

CONCLUSIONS

Education and management regarding WP acute injury and late sequelae is essential for acute battlefield and definitive facility care. Resource-replete and resource-limited settings may use related approaches for acute management and ignition prevention. Current burn wound management recommendations should incorporate specific WP management principles and actions for military clinicians at every level of skill and environment.

A shea butter-based ketamine ointment: The antidepressant effects of transdermal ketamine in rats

The delayed onset of monoaminergic antidepressants and disadvantages of traditional administration routes created the need for alternative non-invasive delivery methods with rapid onset therapeutic effect. Ketamine attracted attention as a fast-acting glutamatergic antidepressant with ideal physiochemical properties for alternative routes of administration. However, there is no sufficient data for its transdermal use in depression. In this proof-of-concept study, we investigated the antidepressant effects of transdermal ketamine delivered via a novel ointment with skin protective, emulsifying and permeation enhancing properties. A shea butter-based 5% (w/w) ketamine ointment or a drug-free vehicle ointment were applied to the shaved dorsal skin of male Wistar rats for 2 days, twice a day. Behavioral despair, locomotor activity and anxiety-like behavior were respectively assessed in the forced swim test (FST), open field test (OFT), and elevated plus maze (EPM). The pharmacokinetic profile of the ointment was analyzed with high-performance liquid chromatography. Transdermal ketamine ameliorated behavioral despair without altering general locomotor activity and anxiety-like behavior, showing that skin-friendly drug carriers like shea butter may constitute promising alternatives to current routes of delivery for ketamine. Tested transdermal method aims to provide more sustainable drug delivery for long-term treatment schedules. Future studies can investigate its long-term use, side effects and abuse liability.

Intraoperative Low-Dose S-Ketamine Reduces Depressive Symptoms in Patients with Crohn's Disease Undergoing Bowel Resection: A Randomized Controlled Trial

Background: Patients with Crohn's disease (CD) undergoing bowel resection often suffer from depression and acute pain, which severely impairs their recovery. We aimed to investigate the effects of S-ketamine preconditioning on postoperative depression in patients with CD undergoing a bowel resection with mild to moderate depression and to observe whether it can relieve postoperative pain and anti-inflammation. Methods: A total of 124 adult patients were randomized into one of the two groups. Patients in the S-ketamine group received a 0.25 mg/kg S-ketamine intravenous drip under general anesthesia induction, followed by a continuous infusion of S-ketamine with 0.12 mg/kg/h for more than 30 min through target-controlled infusion. Patients in the placebo group received 0.9% saline at an identical volume and rate. The primary outcome measure was the 17-item Hamilton depression Scale (HAMD-17). The secondary outcomes were scores on the following questionnaires: a nine-item patient health questionnaire (PHQ-9); a quality of recovery (QoR-15) form; and a numeric rating scale (NRS). Additional secondary outcomes included the levels of C-reactive protein (CRP) and interleukin 6 (IL-6) on postoperative days (PODs) 1, 3, and 5, the length of hospital stay, and opioid use throughout the hospital stay. Results: The scores of PHQ-9 and HAMD-17 in the S-ketamine group were lower than those in the placebo group on postoperative days (PODs) 1, 2, and 7 (p < 0.05). The scores of QoR-15 in the S-ketamine group were higher than those in the placebo group on postoperative days (PODs) 3 and 5 (p < 0.05). The NRS scores of PACU, postoperative days 1 and 2 in the S-ketamine group were lower than those in the placebo group (p < 0.05). There was no significant difference in the CRP and IL-6 levels on postoperative days (PODs) 1, 3, and 5, postoperative complications, and hospital stay between the two groups (p > 0.05). Conclusions: The trial indicated that the intraoperative administration of low-dose S-ketamine could alleviate mild-to-moderate depressive symptoms and postoperative pain in patients with Crohn's disease undergoing bowel resection without worsening their safety.

N-Ethylnorketamine has anesthetic and analgesic effects with abuse liability

Arylcyclohexylamines is an ever-growing class of new psychoactive substances, including an increasing number of ketamine analogs. N-Ethylnorketamine (NENK) is a new synthetic ketamine analog that has emerged as an abused drug, but little is known about the pharmacological profile of NENK. In this study, we investigated the anesthetic and analgesic activity, abuse liability of NENK compared with ketamine. The ED₅₀ values of anesthetic activity for NENK and ketamine were 96.9, 69.4 mg/kg, respectively. The ED₅₀ values of analgesic activity for NENK and ketamine were 45.9 and 23.6 mg/kg, respectively. NENK induced significant conditioned place preference at a minimum dose of 10.0 mg/kg in mice, an effect comparable to that of ketamine (3.0 mg/kg). Acute injections of NENK or ketamine at 30.0 mg/kg enhanced locomotor activity, and repeated treatments with this dose induced locomotor sensitization after withdrawal. Taken together, these results clearly demonstrated that NENK has lower anesthetic and analgesic activity compared to ketamine, but has significant abuse liability.

An overview of painful diabetic peripheral neuropathy: Diagnosis and treatment advancements

Diabetes mellitus remains a public health problem, affecting 422 million people worldwide. Currently, there is no consensus around treating painful diabetic peripheral neuropathy in a step-wise manner. Among the non-pharmacological interventions, neuromodulation has become a promising alternative. Over the past decade, significant clinical trials have paved the way for prompt inclusion of high-frequency spinal cord stimulation within the painful diabetic peripheral neuropathy treatment algorithm. This article aims to provide an updated evidence-based approach for the management of painful diabetic peripheral neuropathy.

Pain in the Cancer Survivor

Recent decades have demonstrated significant strides in cancer screening, diagnostics and therapeutics. As such there have been dramatic changes in survival following a diagnosis of cancer.

Topical ketamine as a local anesthetic agent in reducing venipuncture pain: A randomized controlled trial

AIM

Pain control is an important aspect of ED patient management, and there are many different protocols used around the world influenced by both availability of local resources as well as staff competency and experience. This study aims to evaluate the use of topical ketamine in acute pain reduction by directly comparing it to lidocaine-prilocaine (EMLA) cream.

MATERIALS AND METHODS

In this randomized clinical trial, 300 adult patients classified as level 4 or 5 by ESI triage system were enrolled. These patients were divided randomly into three groups. The site of venipuncture was covered with 2 g of topical ketamine cream 10% in group one, 2 g of 5% EMLA cream in group two, and finally, in group 3 (control group), was covered with placebo (2 g of cold cream). The primary end point of the study was reported pain severity with secondary end points being onset of local anesthesia as well as any side effects noted.

RESULTS

The data gathered showed pain score during venipuncture in both intervention groups were significantly lower when compared to the control group (P < 0.05). However, pain score did not differ between the 2 intervention groups (P = 0.395). There was no statistically significant difference between the ketamine or EMLA in onset of local anesthesia (P = 0.419). We noted itching and irritation was significantly higher in the EMLA group when compared to ketamine(P < 0.05).

CONCLUSION

This study showed that local cutaneous ketamine is as effective as EMLA in relieving pain during venipuncture.

A randomized controlled trial of infraorbital block using ketamine 1% for intra- and postoperative analgesia in children for ambulatory cleft lip correction

BACKGROUND In Indonesia, cleft lip correction surgery is often done as a social program in remote areas with limited resources. This study aimed to assess the effectiveness of ketamine, a cheaper and more accessible alternative, as a local analgesia in infraorbital block and to determine the possibility of ketamine as an alternative local analgesic drug for intraoperative and postoperative periods. METHODS This was a randomized controlled trial in children aged 2 months to 5 years who underwent cleft lip correction surgery at Cipto Mangunkusumo Hospital in 2016. Subjects were randomly divided into two groups: ketamine and bupivacaine. Standard general anesthesia with endotracheal intubation was performed in each group. Bilateral intraoral infraorbital block was performed using ketamine 1% 0.5 ml or bupivacaine 0.25% 0.5 ml. Postoperative evaluation includes pain scores based on the face, leg, activity, cry, and consolability (FLACC) scale and analgesic duration. RESULTS A total of 36 subjects were enrolled in this study, with 18 in each group. Both groups received the same total amount of fentanyl addition intraoperatively (p = 1). The postoperative FLACC pain scale scores between the two groups were not different, with p>0.05 in every measurement. The mean duration of postoperative analgesia in the ketamine group was longer than the bupivacaine group (15–13.49 hours, p = 0.031). CONCLUSIONS Infraorbital block with 1% ketamine 0.5 mg/kg was similarly effective for intraoperative and postoperative analgesia but had a longer duration than that with 0.25% bupivacaine 0.5 ml in ambulatory cleft lip correction.

Topical agents: a thoughtful choice for multimodal analgesia

For over a thousand years, various substances have been applied to the skin to treat pain. Some of these substances have active ingredients that we still use today. However, some have been discontinued due to their harmful effect, while others have been long forgotten. Recent concerns regarding the cardiovascular and renal risk from nonsteroidal anti-inflammatory drugs, and issues with opioids, have resulted in increasing demand and attention to non-systemic topical alternatives. There is increasing evidence of the efficacy and safety of topical agents in pain control. Topical analgesics are great alternatives for pain management and are an essential part of multimodal analgesia. This review aims to describe essential aspects of topical drugs that physicians should consider in their practice as part of multimodal analgesia. This review describes the mechanism of popular topical analgesics and also introduces the most recently released and experimental topical medications.

Topical application of ketamine to prevent postoperative sore throat in adults: A systematic review and meta-analysis

BACKGROUND

Postoperative sore throat is a leading undesirable postoperative outcome. Ketamine is an N-methyl-d-aspartate receptor antagonist and its topical application is used for chronic pain and oral/throat indications. We conducted a systematic review to assess the efficacy of preoperative, topical ketamine application for preventing postoperative sore throat.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL through September 23, 2019 for randomized controlled trials in which at least one intervention was topical ketamine to prevent postoperative sore throat in adults undergoing endotracheal intubation. The primary outcome was the incidence of sore throat at 24 hours postoperatively. The comparators were non-analgesic controls (placebo, no treatment, or usual care) or active agents. We pooled the data using a random-effects model.

RESULTS

We included 41 randomized controlled trials involving 3784 participants. Topical ketamine was associated with reduced incidence of sore throat at 24 hours postoperatively compared to non-analgesic methods (risk ratio, 0.45; 95% CI, 0.37-0.54; P < .001). We found significant publication bias, but the results remained unchanged with a trim-and-fill analysis. Trial sequential analysis (TSA) suggested that the efficacy of topical ketamine was adequate (TSA-adjusted 95% CI, 0.33-0.56). The GRADE quality for this evidence was moderate. Topical ketamine was inferior to a combination of nebulized ketamine and clonidine in preventing postoperative sore throat.

CONCLUSIONS

Preoperative, topical ketamine application may be more effective than non-analgesic methods in preventing postoperative sore throat. The number of studies did not suffice to determine the place of topical ketamine among agents to prevent postoperative sore throat.

Topical Ketamine with Other Adjuvants: Underutilized for Refractory Cancer Pain? A Case Series and Suggested Revision of the World Health Organization Stepladder for Cancer Pain

Background: Uncontrolled cancer pain is a significant problem in palliative medicine. Opioids are often first-line treatment that increase risks of analgesic tolerance and hyperalgesia. Topical ketamine with other adjuvant pain medications is an often-overlooked treatment, yet may be most effective in difficult-to-treat cancer pain.

Objective: We report a case series of hospice patients with uncontrolled cancer pain who were suboptimally treated with opioids and nerve blocks, whose symptoms responded to topical ketamine with other adjuvants. We review the pronociceptive properties of opioids and how topical multimodal treatment of cancer pain can be more effective than standard opioids, other topical adjuvant medications, and nerve blocks. We discuss the shortcomings of the World Health Organization (WHO) stepladder for the treatment of cancer pain and suggest an adjuvant treatment algorithm, directing physicians to appropriate adjuvant pain agents based on pain type and distinct receptor actions.

Design: This is a retrospective case series of patients who responded to topical multimodal pain treatment with implementation of findings into an addendum to the WHO stepladder.

Subjects: Subjects were from a case series of community-based hospice patients with previously uncontrolled cancer pain.

Measurement: Measurement was made by self-report of pain levels using the 10-point numeric pain rating scale.

Results: Patients' pain was controlled with topical adjuvant medications with return to previously lost function and prevention of otherwise escalating opioid dosing.

Conclusions: These patient cases reveal how ketamine-based topical treatment for cancer pain can be more effective than standard opioids, other topical adjuvant medications, and nerve blocks with no noted side effects and observed reduction in opioid consumption.

An Update on the Basic and Clinical Science of Ketamine Analgesia

OBJECTIVE

In the context of the current opioid epidemic, there has been a renewed interest in the use of ketamine as an analgesic agent.

METHODS

We reviewed ketamine analgesia.

RESULTS

Ketamine is well-known as an antagonist for N-methyl-D-aspartate receptors. In addition, it can regulate the function of opioid receptors and sodium channels. Ketamine also increases signaling through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. These myriad of molecular and cellular mechanisms are responsible for a number of pharmacological functions including pain relief and mood regulation. Clinically, a number of studies have investigated the role of ketamine in the setting of acute and chronic pain, and there is evidence that ketamine can provide analgesia in a variety of pain syndromes.

DISCUSSION

In this review, we examined basic mechanisms of ketamine and its current clinical use and potential novel use in pain management.

Itch: From mechanism to (novel) therapeutic approaches

Itch is a common sensory experience that is prevalent in patients with inflammatory skin diseases, as well as in those with systemic and neuropathic conditions. In patients with these conditions, itch is often severe and significantly affects quality of life. Itch is encoded by 2 major neuronal pathways: histaminergic (in acute itch) and nonhistaminergic (in chronic itch). In the majority of cases, crosstalk existing between keratinocytes, the immune system, and nonhistaminergic sensory nerves is responsible for the pathophysiology of chronic itch. This review provides an overview of the current understanding of the molecular, neural, and immune mechanisms of itch: beginning in the skin, proceeding to the spinal cord, and eventually ascending to the brain, where itch is processed. A growing understanding of the mechanisms of chronic itch is expanding, as is our pipeline of more targeted topical and systemic therapies. Our therapeutic armamentarium for treating chronic itch has expanded in the last 5 years, with developments of topical and systemic treatments targeting the neural and immune systems.

Local Ketamine Improves Postoperative Analgesia After Third Molar Surgery

PURPOSE

Evidence exists to support the peripheral analgesic effect of local administration of ketamine (LAK) after third molar surgery. The aim of the present systematic review and meta-analysis was to determine the efficacy of LAK in the control of pain, swelling, and trismus after third molar surgery.

MATERIALS AND METHODS

The study design was a systematic review with a meta-analysis of the effect of LAK after third molar surgery. A search in electronic databases was performed from September 2017 to February 2019. Only prospective clinical trials and randomized controlled trials that had evaluated LAK after third molar surgery were included. The meta-analysis was based on the random effects model. The outcome measures evaluated were postoperative acute pain, swelling, and trismus. The estimated overall effect size was a standardized mean difference (SMD).

RESULTS

A total of 110 study subjects (men and women aged 18 to 50 years) were evaluated for the analgesic effect. The SMD showed a significant analgesic effect (postoperative pain control) favoring LAK (SMD, -1.7403; 95% confidence interval [CI], -2.45 to -1.04). Evaluation of the anti-inflammatory effect of LAK included 105 study subjects and resulted in significantly less swelling in the first postoperative day (SMD, -0.6169; 95% CI, -1.1654 to -0.0683). However, LAK did not reduce the incidence of trismus after third molar surgery (SMD, -0.7241; 95% CI, -2.2765 to 0.8284).

CONCLUSIONS

The use of LAK can reduce the incidence and severity of postoperative pain after third molar surgery and had an anti-inflammatory effect, although only in the first postoperative day. However, LAK had no effect on trismus reduction after third molar surgery.

Opioid-Sparing Effects of Topical Ketamine in Treating Severe Pain From Decubitus Ulcers

Pain from pressure ulcers can severely impact a patient's quality of life. Evidence-based treatment of ulcer-related pain typically relies on systemic opioids with limiting side effects. Literature exists on the use of topical ketamine for neuropathic pain, but not for tissue injury in general and for decubitus ulcer pain specifically. Ketamine has a number of actions including blocking of the glutamate NMDA ionophore in the periphery. Preclinical evidence suggests that NMDA receptors located on peripheral sensory afferent terminals may play a role in initiating pain signaling in inflamed tissues. Topical ketamine, therefore, has the potential to provide analgesia when applied to decubitus ulcers. Here a case is reported of a 54-year-old female with diffuse large B-cell lymphoma who during a critical period in her illness experienced gangrene leading to chronic bilateral stage IV decubitus heel ulcers. The severe pain reported by the patient was poorly managed using high doses of systemic opioids and resulted in intermittent systemic side effects. Adding a compounded ketamine gel to her wound dressings twice daily over an interval of several months drastically reduced her opioid use and, more important, her pain, with minimal side effects.

Topical drug therapeutics for neuropathic pain

INTRODUCTION

Neuropathic pain (NP) is a particularly severe and intractable chronic condition that is not well treated by commonly recommended systemic pharmacological therapies, partly due to dose-limiting side effects or adverse events. The use of topical therapeutics for NP is growing and benefits from the reduced potential for adverse effects, as well as the ability to directly target peripheral pathological processes.

AREAS COVERED

The current review defines and describes the limitations of various commonly prescribed systemic pharmacological therapies for NP. It also provides a justification for increased research aimed at developing topical therapeutics for NP, particularly localized and peripheral NP. The review discusses the various classes of topical treatments used for NP, including agents that: block sensory inputs; activate inhibitory systems; provide mechanism-based therapeutics; are used in mucosal tissues; and include combinations that produce multimodal therapeutic effects.

EXPERT OPINION

There are arguments that the current topical therapeutics for NP rely too heavily on the use of local anesthetics and capsaicinoids, and more research is certainly needed on topical therapies that are multimodal and/or are targeted at the peripheral sources of pathology. The potential for novel topical therapeutics may be enhanced by further research on topical co-drugs, drug-drug salts, co-crystals and hydrates, and ionic liquids.

Management of chronic neuropathic pain with single and compounded topical analgesics

The goal of our review was to emphasize important aspects that physicians should take into consideration when prescribing topical analgesics as part of chronic neuropathic pain treatment. We discuss the dermatopharmacokinetics and microstructural components of the skin, differences between topical and transdermal drug delivery, and topical medication effects on peripheral neuropathy and central sensitization. Even though the US FDA approved topical analgesics are 8%-capsaicin and 5%-lidocaine patches for treating postherpetic neuralgia, there are many other studies conducted on the efficacy of topical ketamine cream, clonidine gel, topical gabapentin, topical baclofen and topical phenytoin for peripheral neuropathic pain, either alone or in combination with other formulations. Furthermore, we discuss new compounded topical analgesics that are becoming more popular and that are showing promising results in the management of chronic peripheral neuropathies. However, more studies are needed for elucidation of the role of topical analgesics and their effects, especially when combined with other treatments.

Drug repurposing may generate novel approaches to treating depression

Objectives

The breakthrough advancements in scientific medical research have greatly improved our understanding of the pathogenesis of depression, encouraging drug discoverers to take a shorter path than ever through drug repurposing to generate new antidepressant medications. In addition to reduced noradrenergic and serotonergic neurotransmission in the brain, other coincidence features such as glutamate neurotoxicity, inflammation and/or cerebrovascular insufficiency are implicated in the pathogenesis of major depressive disorder and late-life depression. This short review discusses the progress made in repurposing drugs for antidepressant actions.

Key findings

Drugs being repurposed as antidepressants act on novel drug targets, thereby treating resistant depression and improving remission rate. Drugs such as ketamine, dextromethorphan/quinidine and scopolamine are rapidly acting antidepressants targeting glutamate receptors. Nimodipine and quetiapine are efficient add-on therapy for late-life depression. Anti-inflammatory drugs, statins, insulin sensitizers, minocycline could remarkably contribute to treating refractory depression.

Summary

Drug repurposing represents an alternative approach to cope with major obstacles, including financial insufficiency and unavoidable long lag evaluation time, undermining the classical pathway of developing new hit compounds into clinically approved antidepressants.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

This is an update of a review first published in 2003 and updated in 2012.Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of refractory cancer pain, when opioids alone or in combination with appropriate adjuvant analgesics prove to be ineffective. Ketamine is known to have psychomimetic (including hallucinogenic), urological, and hepatic adverse effects.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids for refractory cancer pain in adults.

SEARCH METHODS

For this update, we searched MEDLINE (OVID) to December 2016. We searched CENTRAL (CRSO), Embase (OVID) and two clinical trial registries to January 2017.

SELECTION CRITERIA

The intervention considered by this review was the addition of ketamine, given by any route of administration, in any dose, to pre-existing opioid treatment given by any route and in any dose, compared with placebo or active control. We included studies with a group size of at least 10 participants who completed the trial.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results and performed 'Risk of bias' assessments. We aimed to extract data on patient-reported pain intensity, total opioid consumption over the study period; use of rescue medication; adverse events; measures of patient satisfaction/preference; function; and distress. We also assessed participant withdrawal (dropout) from trial. We assessed the quality of the evidence using GRADE (Grading of Recommendations Assessment, Development and Evaluation).

MAIN RESULTS

One new study (185 participants) was identified by the updated search and included in the review. We included a total of three studies in this update.Two small studies, both with cross-over design, with 20 and 10 participants respectively, were eligible for inclusion in the original review. One study with 20 participants examined the addition of intrathecal ketamine to intrathecal morphine, compared with intrathecal morphine alone. The second study with 10 participants examined the addition of intravenous ketamine bolus in two different doses to ongoing morphine therapy, compared with placebo. Both of these studies reported reduction in pain intensity and reduction in morphine requirements when ketamine was added to opioid for refractory cancer pain. The new study identified by the updated search had a parallel group design and 185 participants. This placebo-controlled study examined rapid titration of subcutaneous ketamine to high dose (500 mg) in participants who were using different opioids. There were no differences between groups for patient-reported pain intensity.Pooling of the data from the three included trials was not appropriate because of clinical heterogeneity.The study examining intrathecal drug administration reported no adverse events related to ketamine. In the study using intravenous bolus administration, ketamine caused hallucinations in four of 10 participants. In the rapid dose escalation/high-dose subcutaneous ketamine study, there was almost twice the incidence of adverse events in the ketamine group, compared to the placebo group, with the most common adverse events being needle site irritation and cognitive disturbance. Two serious adverse events (bradyarrhythmia and cardiac arrest) thought to be related to ketamine were also reported in this trial.For all three studies there was an unclear risk of bias overall. Using GRADE, we judged the quality of the evidence to be very low due to study limitations and imprecision due to the small number of participants in all comparisons.

AUTHORS' CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of refractory cancer pain. The evidence was of very low quality, meaning that it does not provide a reliable indication of the likely effect, and the likelihood that the effect will be substantially different is high. Rapid dose escalation of ketamine to high dose (500 mg) does not appear to have clinical benefit and may be associated with serious adverse events. More randomised controlled trials (RCTs) examining specific low-dose ketamine clinical regimens in current use are needed.

Comparison of topical ropivacaine with and without ketamine on post-surgical pain in children undergoing tonsillectomy: a randomized controlled double-blind study

PURPOSE

Tonsillectomy in pediatric patients may cause severe postoperative pain. Topical local anesthetics are an easy and safe way to control post-tonsillectomy pain, but there is no benefit during the early postoperative stage. Topical ketamine shows a good effect on early stage postoperative pain. We compared the effect of topical ropivacaine with and without ketamine on post-tonsillectomy pain.

METHODS

Patients aged 3-7 years undergoing tonsillectomy were selected to participate in the study. Our study was performed in a randomized, placebo-controlled, double-blind manner. Patients were randomly assigned to one of two groups using computer-generated random numbers. The researchers who assessed the pain score, the caregivers, and the patient were blinded to group assignment. One group received topical ropivacaine with saline (RS group) and the other group received topical ropivacaine with 20 mg ketamine (RK group) on the tonsillar bed. Pain scores using the modified Children's Hospital of Eastern Ontario Pain Scale (mCHEOPS) at 15 min and 30 min, and at 1, 2, 4, 8, 16 and 24 h were recorded. Rescue analgesic requirement and complications were also recorded.

RESULTS

A total of 66 patients were randomly assigned to the RS group (n = 33) and the RK group (n = 33). The mCHEOPS scores were significantly lower in the RK group at 15 min (P = 0.046). The mCHEOPS scores of the two groups decreased with time, but there was no intergroup interaction. The RS group received more analgesics until 1 h after surgery and the RK group received more analgesics during 1-24 h after surgery. There were no differences in adverse outcomes.

CONCLUSIONS

Topical ropivacaine with ketamine can reduce immediate postoperative pain and analgesic requirement better than ropivacaine alone.

Urinary Concentrations of Topically Administered Pain Medications

A common treatment for chronic pain is prescription of analgesics, but their long-term use entails risk of morbidity, addiction and misuse. One way to reduce the risk of abuse is prescribing of analgesics in a topical form. Physicians are urged to perform urine drug testing to ensure that patients are compliant with their medication regimens. However, there is little data on the efficiency of transdermal delivery for many analgesic drugs, and no data on expected urine drug levels. This study includes data from over 29,000 specimens tested for gabapentin, ketamine, cyclobenzaprine or amitriptyline used orally or topically. Gabapentin and amitriptyline concentrations were more likely to be below the limits of detection (25-40 ng/mL) in the urine of patients using them topically as compared with patients using them orally. Levels in gabapentin-positive topical specimens were much lower than in gabapentin-positive oral specimens (261 ng/mL vs >10,000 ng/mL). In contrast, ketamine and cyclobenzaprine were more readily detectable in the urine of topical users. Ketamine topical specimens were positive 12% more often than oral specimens, and mean topical specimen levels were 68-100% those of oral specimens. Cyclobenzaprine specimens were equally likely to be positive whether the dose was oral or topical, although mean levels after topical dosing were approximately 13-21% those after oral dosing. These findings are consistent with the reported percutaneous absorption efficiencies of gabapentin and ketamine, and are likely to be related to the absorption efficiencies of cyclobenzaprine and amitriptyline.

Topical versus caudal ketamine/bupivacaine combination for postoperative analgesia in children undergoing inguinal herniotomy

Background:

Multiple studies claim that caudal administration of ketamine causes effective postoperative analgesia. The aim of this study was to assess the clinical effectiveness of ketamine after caudal or topical administration in pediatric patients undergoing inguinal herniotomy.

Patients and Methods:

This randomized, comparative, double-blind study included eighty children (aged 6 months to 6 years) received either 1 ml/kg of 0.25% bupivacaine/ketamine 0.5 mg/kg for caudal analgesia (caudal group) or 0.3 ml/kg of 0.25% bupivacaine/ketamine 0.5 mg/kg sprayed by the surgeon around the spermatic cord and upon the ilioinguinal nerve before wound closure for topical analgesia (topical group). The duration of postoperative analgesia, pain scores, rescue analgesic consumption, sedation score, hemodynamic monitoring, and side-effects were evaluated 48 h postoperative.

Results:

Kaplan–Meier survival analysis of analgesia free time demonstrated a significant advantage of topical ketamine (TK) group over caudal ketamine (CK) group. The duration of postoperative analgesia was longer in TK group than in CK group (28.74 ± 2.88 vs. 21.43 ± 5.01 h, P = 0.000). Fewer children asked for oral analgesics in the topical group (24 of 36, 66.7%) than in the caudal one (28 of 32, 87.5%; P < 0.01). Postoperative pain scores at the 6^th till 48^th h were lower in topical group with comparable analgesic consumption between two groups. In the caudal group, four subjects suffered from retention of urine: Two presented with a residual motor block and two had photophobia.

Conclusion:

Wound instillation of bupivacaine/ketamine is a simple, noninvasive, and effective technique that could be a safe alternative to CK for postoperative analgesia in children undergoing inguinal hernia repair.

Prospective, randomized, and controlled trial on ketamine infusion during bilateral axillo-breast approach (BABA) robotic or endoscopic thyroidectomy: Effects on postoperative pain and recovery profiles: A consort compliant article

BACKGROUND

Robotic or endoscopic thyroidectomy using bilateral axillo-breast approach (BABA) is frequently performed for excellent cosmesis. However, postoperative pain is remained as concerns due to the extent tissue dissection and tension during the operation. Ketamine is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist that reduces acute postoperative pain. We evaluated the effects of intraoperative ketamine infusion on postoperative pain control and recovery profiles following BABA robotic or endoscopic thyroidectomy.

METHODS

Fifty-eight adult patients scheduled for BABA robotic or endoscopic thyroidectomy were randomized into a control group (n = 29) and ketamine group (n = 29). Following induction of anesthesia, patients in each group were infused with the same volume of saline or ketamine solution (1 mg/kg bolus, 60 μg/kg/h continuous infusion). Total intravenous anesthesia with propofol and remifentanil was used to induce and maintain anesthesia. Pain scores (101-point numerical rating scale, 0 = no pain, 100 = the worst imaginable pain), the consumption of rescue analgesics, and other postoperative adverse effects were assessed at 1, 6, 24, and 48 hours postoperatively.

RESULTS

Patients in the ketamine group reported lower pain scores than those in the control group at 6 hours (30 [30] vs 50 [30]; P = 0.017), 24 hours (20 [10] vs 30 [20]; P < 0.001), and 48 hours (10 [10] vs 20 [15]; P < 0.001) in neck area. No statistically significant differences were found between the 2 groups in terms of the requirements for rescue analgesics or the occurrence of adverse events.

CONCLUSION

Intravenous ketamine infusion during anesthesia resulted in lower postoperative pain scores following BABA robotic or endoscopic thyroidectomy, with no increase in adverse events.

Chemogenomics knowledgebase and systems pharmacology for hallucinogen target identification-Salvinorin A as a case study

Drug abuse is a serious problem worldwide. Recently, hallucinogens have been reported as a potential preventative and auxiliary therapy for substance abuse. However, the use of hallucinogens as a drug abuse treatment has potential risks, as the fundamental mechanisms of hallucinogens are not clear. So far, no scientific database is available for the mechanism research of hallucinogens. We constructed a hallucinogen-specific chemogenomics database by collecting chemicals, protein targets and pathways closely related to hallucinogens. This information, together with our established computational chemogenomics tools, such as TargetHunter and HTDocking, provided a one-step solution for the mechanism study of hallucinogens. We chose salvinorin A, a potent hallucinogen extracted from the plant Salvia divinorum, as an example to demonstrate the usability of our platform. With the help of HTDocking program, we predicted four novel targets for salvinorin A, including muscarinic acetylcholine receptor 2, cannabinoid receptor 1, cannabinoid receptor 2 and dopamine receptor 2. We looked into the interactions between salvinorin A and the predicted targets. The binding modes, pose and docking scores indicate that salvinorin A may interact with some of these predicted targets. Overall, our database enriched the information of systems pharmacological analysis, target identification and drug discovery for hallucinogens.

Differential Efficacy of Ketamine in the Acute versus Chronic Stages of Complex Regional Pain Syndrome in Mice

BACKGROUND

Complex regional pain syndrome (CRPS) is a painful, disabling, and often chronic condition, where many patients transition from an acute phase with prominent peripheral neurogenic inflammation to a chronic phase with evident central nervous system changes. Ketamine is a centrally acting agent believed to work through blockade of N-methyl-D- aspartate receptors and is being increasingly used for the treatment of refractory CRPS, although the basis for the drug's effects and efficacy at different stages of the syndrome remains unclear.

METHODS

The authors used a mouse model of CRPS (n = 8 to 12/group) involving tibia fracture/cast immobilization to test the efficacy of ketamine (2 mg kg day; 7 days) or vehicle infusion during acute (3 weeks after fracture) and chronic (7 weeks after fracture) stages.

RESULTS

Acute-phase fracture mice displayed increased limb temperature, edema, and nociceptive sensitization that were not reduced by ketamine. Fracture mice treated with ketamine during the chronic phase showed reduced nociceptive sensitization that persisted beyond completion of the infusion. During this chronic phase, ketamine also reduced latent nociceptive sensitization and improved motor function at 18 weeks after fracture. No side effects of the infusions were identified. These behavioral changes were associated with altered spinal astrocyte activation and expression of pain-related proteins including N-methyl-D-aspartate receptor 2b, Ca/calmodulin-dependent protein kinase II, and brain-derived neurotrophic factor.

CONCLUSIONS

Collectively, these results demonstrate that ketamine is efficacious in the chronic, but not acute, stage of CRPS, suggesting that the centrally acting drug is relatively ineffective in early CRPS when peripheral mechanisms are more critical for supporting nociceptive sensitization.

Effects of the noncompetitive N-methyl-d-aspartate receptor antagonists ketamine and MK-801 on pain-stimulated and pain-depressed behaviour in rats

BACKGROUND

Pain is a significant public health concern, and current pharmacological treatments have problematic side effects and limited effectiveness. N-methyl-d-aspartate (NMDA) glutamate receptor antagonists have emerged as one class of candidate treatments for pain because of the significant contribution of glutamate signalling in nociceptive processing.

METHODS

This study compared effects of the NMDA receptor antagonists ketamine and MK-801 in assays of pain-stimulated and pain-depressed behaviour in rats. The nonsteroidal anti-inflammatory drug ketoprofen was examined for comparison as a positive control. Intraperitoneal injection of dilute acid served as an acute visceral noxious stimulus to stimulate a stretching response or depress intracranial self-stimulation (ICSS) in male Sprague-Dawley rats.

RESULTS

Ketamine (1.0-10.0 mg/kg) blocked acid-stimulated stretching but failed to block acid-induced depression of ICSS, whereas MK-801 (0.01-0.1 mg/kg) blocked both acid-stimulated stretching and acid-induced depression of ICSS. These doses of ketamine and MK-801 did not alter control ICSS in the absence of the noxious stimulus; however, higher doses of ketamine (10 mg/kg) and MK-801 (0.32 mg/kg) depressed all behaviour. Ketoprofen (1.0 mg/kg) blocked both acid-induced stimulation of stretching and depression of ICSS without altering control ICSS.

CONCLUSION

These results support further consideration of NMDA receptor antagonists as analgesics; however, some NMDA receptor antagonists are more efficacious at attenuating pain-depressed behaviours.

WHAT DOES THIS STUDY ADD

NMDA receptor antagonists produce dissociable effects on pain-depressed behaviour. Provides evidence that pain-depressed behaviours should be considered and evaluated when determining the antinociceptive effects of NMDA receptor antagonists.

An Ethical Exploration of Barriers to Research on Controlled Drugs

We examine the ethical, social, and regulatory barriers that may hinder research on therapeutic potential of certain controversial controlled substances like marijuana, heroin, or ketamine. Hazards for individuals and society and potential adverse effects on communities may be good reasons for limiting access and justify careful monitoring of these substances. Overly strict regulations, fear of legal consequences, stigma associated with abuse and populations using illicit drugs, and lack of funding may, however, limit research on their considerable therapeutic potential. We review the surprisingly sparse literature and address the particular ethical concerns pertinent to research with illicit and addictive substances, such as undue inducement, informed consent, therapeutic misconception, and risk to participants, researchers, and institutions. We consider the perspectives of key research stakeholders and explore whether they may be infected with bias. We conclude by proposing an empirical research agenda to provide an evidentiary basis for ethical reasoning.

Treatment of Neuropathic Pain

OPINION STATEMENT

Neuropathic pain is notoriously variable in its severity and impact on patients, as well as in its response to treatment. Certain therapies for neuropathic pain have better evidence for their use; however, it is apparent that although some therapies provide relief for only a minority of patients, the relief may be significant. Without a trial of therapy, there is no way to know if that relief is achievable. Our treatment experiences have shown that occasionally unexpected benefit is obtained through a thorough investigation of all options, even in the setting of failure of those with the most compelling evidence or indication. Chronic neuropathic pain is generally best treated with regularly dosed medications, balancing efficacy and tolerability. Evidence supports first-line trials of anticonvulsants, tricyclic antidepressants, and serotonin-norepinephrine reuptake inhibitors, alone or in certain combinations. While opioid medications, particularly methadone, can be effective in treating neuropathic pain, they are best used only in refractory cases and by experienced clinicians, due to concerns for both short- and long-term safety. Some therapies have a long history of successful use for certain syndromes (e.g., carbamazepine for trigeminal neuralgia pain), but these should not be considered to the exclusion of other more recent, less-supported therapies (e.g., botulinum toxin A for the same), particularly in refractory cases. We find the principles of palliative care highly applicable in the treatment of chronic neuropathic pain, including managing expectations, mutually agreed-upon meaningful outcomes, and a carefully cultivated therapeutic relationship.

Topical treatment in pain medicine: from ancient remedies to modern usage

Over several millennia, substances have been applied to the skin for treatment of pain. Some ingredients are in current use; others have been discontinued. Mechanisms of action include interactions with nociceptive neural networks and inflammatory processes. Substances must penetrate the stratum corneum barrier and vehicles that enhance penetration have been developed. Topical drugs with links to the past include menthol, capsaicin, some opioids, local anesthetic agents and NSAIDs. Mandragora is also described as an example of a herbal remedy that has been discontinued due to its toxicity. The future for topical drugs is promising, with the advent of new drugs tailored for specific pain mechanisms and the development of both penetration enhancers and sterile preparation methods.

Ketamine Affects In Vitro Differentiation of Monocyte into Immature Dendritic Cells

Background:

Monocytes (MOs) have the unique ability to differentiate into immature dendritic cells (iDCs) (MO→iDC) under the influence of interleukin-4 and granulocyte–monocyte colony-stimulating factor (IL-4&GM-CSF). In this study, the authors investigated the influence of ketamine on the process of MO→iDC.

Methods:

iDCs were cultured from MO obtained from 36 subjects in the presence of IL-4 and GM-CSF and ketamine at 100, 10, and 1 μg/ml for 5 days. In some of the experiments, the authors used nonspecific N-methyl-d-aspartate (NMDA) receptor antagonist MK-801, NMDA, or a neutralizing antibody for transforming growth factor β (TGFβ). The expression of surface markers and functional assays were used to assess the effect of ketamine on IL-4&GM-CSF-stimulated MO. IL-4&GM-CSF-stimulated MO’s supernatants were assessed for cytokine levels.

Results:

Ketamine at 10 μg/ml, and higher concentrations, diminished the expression of CD1a on IL-4&GM-CSF-stimulated MO and retarded both their ability to process DQ ovalbumin and mixed lymphocyte reaction stimulation. The addition of ketamine to IL-4&GM-CSF-differentiated MO resulted in the persistent expression of CD14 and unchanged expression of CD86 and CD206. The phagocytic abilities of IL-4&GM-CSF-differentiated MO were not changed by ketamine. MK-801, a nonselective NMDA agonist, mimicked ketamine’s effect on MO→iDC differentiation. Adding exogenous NMDA to IL-4&GM-CSF-stimulated MO in the presence of ketamine partially restored the level of CD1a+. TGFβ was elevated in supernatants of IL-4&GM-CSF-stimulated MO in the presence of ketamine. Adding neutralizing TGFβ antibody or TGFβR1 blocker (SB431542) resulted in the full recovery of MO→iDC, despite the presence of ketamine.

Conclusions:

Ketamine diminishes the process of MO→iDC in vitro. This is mediated via NMDA-dependent mechanisms and TGFβ.

Topical analgesics for neuropathic pain in the elderly: current and future prospects

Neuropathic pain (NeP) is a significant medical and socioeconomic burden with limited therapeutic options. Elderly patients exhibit a higher incidence of several NeP conditions and pose a particular challenge due to age-related pharmacokinetic and pharmacodynamic issues, comorbid conditions, and polypharmacy, as well as frailty and cognitive decline. Topical analgesics are of interest because of their comparable efficacy to oral agents, good tolerability and safety, and potential to be add-on therapies to oral treatments. In recent years, two topical formulations for NeP have been approved (5% lidocaine medicated plaster, 8% capsaicin patch) but are not available in all countries. There are controlled trials and a growing body of open-label reports on their use in clinical care. Some studies provide a post hoc analysis of data in relation to older age (≥65 years), which is useful. The body of evidence relating to topical investigational agents is growing and involves controlled trials as well as individual cases. The largest single body of information is for topical ketamine, administered either alone or combined with other agents (particularly amitriptyline), and some large randomized controlled trials report efficacy. Other large trials involve topical clonidine and further ketamine combinations. Compounding analgesics involves challenges, including uncertain composition (two to five ingredients are used) and concentrations (range 0.5-5%), as well as the heterogeneity of data that support choices. Nevertheless, case reports and acceptable response rates in larger cohorts are intriguing, and this area merits further investigation in controlled settings as well as continued documentation of clinical experiences.

Analgesic Response to Intravenous Ketamine Is Linked to a Circulating microRNA Signature in Female Patients With Complex Regional Pain Syndrome

Although ketamine is beneficial in treating complex regional pain syndrome (CRPS), a subset of patients respond poorly to therapy. We investigated treatment-induced microRNA (miRNA) changes and their predictive validity in determining treatment outcome by assessing miRNA changes in whole blood from patients with CRPS. Blood samples from female patients were collected before and after 5 days of intravenous ketamine administration. Seven patients were responders and 6 were poor responders. Differential miRNA expression was observed in whole blood before and after treatment. In addition, 33 miRNAs differed between responders and poor responders before therapy, suggesting the predictive utility of miRNAs as biomarkers. Investigation of the mechanistic significance of hsa-miR-548d-5p downregulation in poor responders showed that this miRNA can downregulate UDP-glucuronosyltransferase UGT1A1 mRNA. Poor responders had a higher conjugated/unconjugated bilirubin ratio, indicating increased UGT1A1 activity. We propose that lower pretreatment levels of miR-548d-5p may result in higher UDP-GT activity, leading to higher levels of inactive glucuronide conjugates, thereby minimizing the therapeutic efficacy of ketamine in poor responders. Differences in miRNA signatures can provide molecular insights distinguishing responders from poor responders. Extending this approach to other treatment and outcome assessments might permit stratification of patients for maximal therapeutic outcome. Perspective: This study suggests the usefulness of circulating miRNAs as potential biomarkers. Assessing miRNA signatures before and after treatment demonstrated miRNA alterations from therapy; differences in miRNA signature in responders and poor responders before therapy indicate prognostic value. Mechanistic studies on altered miRNAs can provide new insights into disease.

Alternative methods of pain management for the older adult population: Review of topical pain medications

The older adult population is one of the fastest growing age groups in the United States. As this population continues to expand, determining the safest way to provide pain management has become increasingly important. More than 50% of community-dwelling older adults experience pain on a daily basis, and up to 83% of those in assisted living facilities experience persistent pain. Pain is exceedingly challenging to treat safely and effectively in the elderly because of the physiologic changes that occur as people age. In addition, many nonnarcotic medications with analgesic properties are listed in both the 2012 American Geriatrics Society Beers Criteria for Potentially Inappropriate Medication Use in Older Adults and the Pharmacy Quality Alliance high-risk medications lists. An approach to the growing challenge of managing pain in the elderly that is gaining popularity among community-dwelling patients is the use of topical pain medications. The goal of this article is to review some of the available literature regarding the use of various topical analgesics alone or in combination, and to discuss their known or theoretical mechanisms of peripheral pain modulation. Commercially available or compounded topical pain medications may be used to replace or augment doses of oral medications in an effort to decrease the risk of adverse drug events for older adult patients. When prescribing topical pain medications physicians should consider the nature of the pain targeted, the type of analgesia expected from each ingredient, the potential for systemic absorption, and related side effects.

Topical and Intranasal Analgesic Therapy in a Woman with Refractory Postherpetic Neuralgia

A patient-specific, stepped approach to topical and intranasal analgesic pharmacotherapy was effective in reducing refractory postherpetic neuralgia (PHN) not responding to the current standard of care for PHN. The use of topical analgesic therapy allowed for higher concentrations of medication locally while reducing the likelihood of systemic side effects common to the drugs used. No adverse effects were noted for either topical or intranasal drug therapy. The patient-specific, stepped approach resulted in clinically significant decreases in pain on visual analog scale (VAS), with the use of intranasal ketamine 10% solution and topical gabapentin 6%, ketoprofen 10%, lidocaine 5%, and ketamine 10% cream.

Acute effect of topical menthol on chronic pain in slaughterhouse workers with carpal tunnel syndrome: triple-blind, randomized placebo-controlled trial

Topical menthol gels are classified “topical analgesics” and are claimed to relieve minor aches and pains of the musculoskeletal system. In this study we investigate the acute effect of topical menthol on carpal tunnel syndrome (CTS). We screened 645 slaughterhouse workers and recruited 10 participants with CTS and chronic pain of the arm/hand who were randomly distributed into two groups to receive topical menthol (Biofreeze) or placebo (gel with a menthol scent) during the working day and 48 hours later the other treatment (crossover design). Participants rated arm/hand pain intensity during the last hour of work (scale 0–10) immediately before 1, 2, and 3 hours after application. Furthermore, global rating of change (GROC) in arm/hand pain was assessed 3 hours after application. Compared with placebo, pain intensity and GROC improved more following application of topical menthol (P = 0.026 and P = 0.044, resp.). Pain intensity of the arm/hand decreased by −1.2 (CI 95%: −1.7 to −0.6) following topical menthol compared with placebo, corresponding to a moderate effect size of 0.63. In conclusion, topical menthol acutely reduces pain intensity during the working day in slaughterhouse workers with CTS and should be considered as an effective nonsystemic alternative to regular analgesics in the workplace management of chronic and neuropathic pain.