Intravenous Lidocaine: An Outdated or Underutilized Treatment for Pain?

Effectiveness of intracuff alkalinized lidocaine associated with intravenous dexamethasone in reducing laryngotracheal morbidity in children undergoing general anesthesia for tonsillectomy: a randomized controlled trial

BACKGROUND

Postoperative sore throat is one of the main postoperative complaints in patients undergoing tonsillectomy. As the primary outcome, we aimed to determine whether endotracheal tube cuffs filled with alkalinized lidocaine are associated with a lower incidence of postoperative sore throat and anesthesia emergence phenomena in children undergoing tonsillectomy or adenotonsillectomy. We also assessed the potential additional benefits of IV dexamethasone in reducing postoperative laryngotracheal morbidity.

METHODS

This is a clinical prospective, randomized, controlled trial. Patients were randomly allocated to one of four groups, as follows: air - endotracheal tube cuff filled with air; air/dex - endotracheal tube cuff filled with air and intravenous dexamethasone; lido - endotracheal tube cuff filled with alkalinized lidocaine; and lido/dex - endotracheal tube cuff filled with alkalinized lidocaine and intravenous dexamethasone. Perioperative hemodynamic parameters and the incidence of postoperative nausea and vomiting, coughing and hoarseness were recorded. Postoperative sore throat was assessed in the postanesthetic care unit and 24 hours post tracheal extubation.

RESULTS

In total, 154 children aged 4-12 years, ASA physical status I or II, undergoing general anesthesia for elective tonsillectomy and adenotonsillectomy, were assessed for postoperative sore throat in this study. The incidence of postoperative sore throat 24 hours after tracheal extubation was significantly lower in the lido/dex group compared to groups air and air/dex (p = 0.01). However, no additional reduction in these symptoms was observed from the intravenous administration of dexamethasone when comparing the lido and lido/dex groups. Similarly, there were no differences among groups regarding perioperative hemodynamic variables or postoperative nausea and vomiting, coughing, and hoarseness during the study period.

CONCLUSION

Intracuff alkalinized lidocaine, associated with intravenous dexamethasone, might be effective in reducing sore throat 24 hours post-tonsillectomy or adenotonsillectomy in children when compared to the use of air as the cuff insufflation media.

Patient Expectations and Therapeutic Alliance Affect Pain Reduction Following Lidocaine Infusion in an Interdisciplinary Chronic Pain Clinic

Pain experience is affected by both ascending nociceptive signals and descending modulation. Expectations can affect pain experience and augment treatment-induced analgesia through descending inhibitory modulation of pain. This open-label, prospective cohort study examined the association between participant expectation ratings and pain reduction in adult participants with chronic pain receiving an intravenous lidocaine infusion. We aimed to explore whether: 1) participants' expectations of treatment efficacy were associated with pain reduction over 8 weeks after infusion; and 2) participants' therapeutic alliance was associated with expectations and/or pain reduction. We recruited 70 participants with chronic pain scheduled for lidocaine infusion. Study measures included pain intensity (pre-treatment, post-treatment, and daily for 8 weeks), treatment expectations (EXPECT), and therapeutic alliance (Trust in Physician and Working Alliance Inventory-Short Revised). Baseline treatment expectations were significantly correlated with pain reduction (r = .42, P < .01). Therapeutic alliance was significantly correlated with expectations (r = .27, P < .05) and pain reduction (r = .38, P < .01). This study quantifies the contribution of: 1) treatment expectations; and 2) therapeutic alliance to the magnitude of lidocaine-induced pain reduction. Results generate the hypothesis that focused efforts to augment treatment expectations and therapeutic alliance could serve to improve pain treatment outcomes. PERSPECTIVE: This study evaluates the relationship between pain reduction and ratings of: 1) treatment expectations; and 2) therapeutic alliance following an intravenous lidocaine infusion. Results generate the hypothesis that focused efforts to augment treatment expectations and therapeutic alliance could serve to improve pain treatment outcomes.

A Review of the Lidocaine in the Perioperative Period

This review analyzes the controversies surrounding lidocaine (LIDO), a widely recognized local anesthetic, by exploring its multifaceted effects on pain control in the perioperative setting. The article critically analyzes debates about lidocaine's efficacy, safety, and optimal administration methods. While acknowledging its well-documented analgesic attributes, the text highlights the ongoing controversies in its application. The goal is to provide clinicians with a comprehensive understanding of the current discourse, enabling informed decisions about incorporating lidocaine into perioperative protocols. On the other hand, emphasizes the common uses of lidocaine and its potential role in personalized medicine. It discusses the medication's versatility, including its application in anesthesia, chronic pain, and cardiovascular diseases. The text recognizes lidocaine's widespread use in medical practice and its ability to be combined with other drugs, showcasing its adaptability for individualized treatments. Additionally, it explores the incorporation of lidocaine into hyaluronic acid injections and its impact on pharmacokinetics, signaling innovative approaches. The discussion centers on how lidocaine, within the realm of personalized medicine, can offer safer and more comfortable experiences for patients through tailored treatments.

Analgesic Effects and Adverse Reactions of Lidocaine for Patient-Controlled Intravenous Analgesia on Patients Undergoing Open Hepatectomy: A Retrospective Analysis

PURPOSE

The aim of this study was to investigate the effect of lidocaine for patient controlled intravenous analgesia (PCIA) in patients who underwent open hepatectomy.

DESIGN

A retrospective analysis.

METHODS

A total of 281 patients who underwent open hepatectomy from July 2018 to December 2018 were included. All patients were assigned into two groups: the lidocaine group (PCIA consisted of lidocaine, sufentanil, tramadol and granisetron) and the control group (PCIA consisted of sufentanil, tramadol and granisetron). The postoperative visual analogue scale (VAS) and complications (including respiratory depression, hypotension, nausea and vomiting, pruritus, numbness of the corners of the mouth, dizziness) between the groups were compared.

FINDINGS

There were no significant differences between the characteristics, duration of surgery and anesthesia, and recovery of postoperative activity between the two groups. In the first 3 days after the operation, the postoperative VAS score of the lidocaine group was lower than that of the control group at resting state, while after activity, the postoperative VAS contrast results were completely opposite. In particularly, the resting state at 48 hours (h) (1.05 ± 1.25 vs 1.57 ± 1.54) after surgery and the activity state at 72 h (3.02 ± 1.51 vs 2.2 ± 1.66) after surgery (P < 0.05). The incidence of mouth numbness and dizziness were significantly increased in the lidocaine group (P < 0.05).

CONCLUSION

The addition of lidocaine in PCIA was not beneficial to improve the pain during activities and increased the incidence of perioral numbness and dizziness.

Parenteral Lidocaine for Complex Cancer Pain in the Home or Inpatient Hospice Setting: A Review and Synthesis of the Evidence

Background: Cancer pain can remain refractory despite escalating opioids and adjuvants. Systemic Lidocaine is an option, but current approaches are hospital centered. While advantageous in advanced cancer, evidence is lacking for parenteral Lidocaine use in community-based care. Objectives: Review evidence for parenteral lidocaine in complex cancer pain outside the hospital setting. Design: Systematic review of peer-reviewed articles of any study design, including reviews. Search in four databases used keyword variations of "cancer," "pain," "Lidocaine," and "parenteral." Search was extended through reference lists of full texts assessed. Abstracted data from articles screened and selected were synthesized narratively by a palliative care clinician in Singapore. Results: Eight hundred eighty-three articles identified were screened by title and abstract. Twenty-eight full texts were assessed. Seven articles fulfilled criteria for synthesis of findings. A total of 73 patients received parenteral Lidocaine for mixed pains, reported collectively in 1 retrospective chart review, 3 practice guidelines, 2 case series, and 1 case study. Intravenous or subcutaneous Lidocaine was commenced in hospital or hospice and continued at home. Dosages and administration schedules varied, involving slow bolus with continuous infusion or the latter alone, for up to 240 days. All produced positive outcomes, with no severe adverse events. Monitoring included routine vital signs and conscious levels; electrocardiogram, liver, and renal function tests were uncommon. Lidocaine levels were not consistently assessed. Conclusion: Parenteral Lidocaine can be effective and safe in the community setting. More empirical studies are needed to inform patient selection and treatment protocol, and to validate expected outcomes.

Analgesia in acute ischemic chest pain

Analgesics, particularly opioids, have been routinely used in the emergency treatment of ischemic chest pain for a long time. In the past two decades; however, several studies have raised the possibility of the harmful effects of opioid administration. In 2014, the American Heart Association (AHA)/American College of Cardiology Foundation (ACCF) changed the guidelines regarding the use of opioids from class IC to class IIb for non-ST elevation acute coronary syndrome. And in 2015, the European Society of Cardiology (ESC) guidelines incidentally noted the side effects of opioids. In ST-segment elevation myocardial infarction, both ESC and AHA/ACCF still recommend the use of opioids. Given the need for adequate pain relief in ischemic chest pain in the emergency setting, it is necessary to understand the adverse effects of analgesia, while still providing sufficiently potent options for analgesia. The primary purpose of this review is to quantify the effects of analgesics commonly used in the prehospital and emergency department in patients with ischemic chest pain.

The Analgesic and Emotional Response to Intravenous Lidocaine Infusion in the Treatment of Postherpetic Neuralgia: A Randomized, Double-Blinded, Placebo-controlled Study

OBJECTIVES

This study evaluated the analgesic efficacy and emotional response to intravenous lidocaine infusion compared with placebo in patients with postherpetic neuralgia (PHN).

METHODS

In this randomized, double-blinded study, patients with PHN received 5 mg/kg intravenous lidocaine infusion or placebo. The primary outcome was pain measured by Visual Analogue Scale, Von Frey, and area of allodynia. Moreover, emotional status of anxiety and depression were evaluated by Self-rating Anxiety Scale (SAS) and Self-rating Depression Scale (SDS). Quality of life was assessed by Short Form Health Survey 36.

RESULTS

In total, 197 patients were enrolled and eligible data were collected from 183 of those patients. The Visual Analogue Scale scores were reduced to a minimum at 2 weeks (2.74, 2.99) after infusion, but no significant difference was found between the lidocaine and placebo groups. Similar changes were also found in mechanical pain threshold and area of allodynia. However, the lidocaine group was associated with a statistically significant reduction in consumption of analgesics with a relative risk of 6.2 (95% confidence interval [CI], 2.24-17.16). Lidocaine infusion also significantly improved the anxiety and depression status; the values of mean change in anxiety and depression were 3.89 (95% CI, 1.43-6.35) and 4.3 (95% CI, 0.63-7.98), respectively, at 2 weeks. Moreover, improvement was exhibited in Short Form Health Survey 36 health status, with the mean change of 49.81 (95% CI, 28.17-71.46) at 1 week, in particular scores on vitality, physical and emotional role functioning, and mental health.

CONCLUSIONS

The analgesic response of 5 mg/kg lidocaine intravenous infusion is comparable to placebo in patients with PHN, but intravenous lidocaine infusion significantly reduced total analgesic consumption, and improved the overall emotional and health status.

Continuous Lidocaine Infusion as Adjunctive Analgesia in Intensive Care Unit Patients

Despite a paucity of data, the role of intravenous lidocaine (IVLI) as adjunctive analgesia in the intensive care unit (ICU) seems promising due to a low potential to contribute to respiratory depression. A retrospective chart review was conducted to evaluate the safety and effectiveness of IVLI for the treatment of pain in ICU patients with varying degrees of organ dysfunction from March 2014 to March 2016. The primary outcomes included the time to a ≥20% reduction in pain scores after the initiation of IVLI and the difference in opioid requirements as well as pain scores prior to and during IVLI therapy. Other variables included the presence of IVLI-related adverse events and the dosage and duration of IVLI. A total of 21 ICU patients were included from 2 different hospitals. The mean time to a ≥20% reduction in pain scores from the start of IVLI was 3.3 hours (SD = 2.2). The median morphine dose equivalents required during 6, 12, and 24 hours pre-IVLI were significantly higher compared to the same time periods after IVLI (18.3 vs 10 mg, P = .002; 41.8 vs 18.3 mg, P = .002; 93.5 vs 30.5 mg, P = .037). Neurological adverse effects of lidocaine were noted in 3 patients, but the effects were reversed on IVLI discontinuation. This report suggests that IVLI as an adjunctive agent in the treatment of acute pain may be a potential option in ICU patients who are refractory to opioids or those in whom opioid-induced respiratory depression is a concern.

Lidocaine Infusion: A Promising Therapeutic Approach for Chronic Pain

Opioid abuse is a national epidemic in the United States, where it is estimated that a prescription drug overdose death occurs every 19 minutes. While opioids are highly effective in acute and subacute pain control, their use for treatment of chronic pain is controversial. Chronic opioids use is associated with tolerance, dependency, hyperalgesia. Although there are new strategies and practice guidelines to reduce opioid dependence and opioid prescription drug overdose, there has been little focus on development of opioid-sparing therapeutic approaches. Lidocaine infusion has been shown to be successful in controlling pain where other agents have failed. The opioid sparing properties of lidocaine infusion added to its analgesic and antihyperalgesic properties make lidocaine infusion a viable option for pain control in opioid dependent patients. In this review, we provide an overview of the opioid abuse epidemic, and we outline current evidence supporting the potential use of lidocaine infusion as an adjuvant therapeutic approach for management of chronic pain.

The effects of tracheal tube cuffs filled with air, saline or alkalinised lidocaine on haemodynamic changes and laryngotracheal morbidity in children: a randomised, controlled trial

We studied the effects of tracheal tube cuffs filled with air, saline or alkalinised lidocaine on haemodynamic changes during tracheal extubation and postoperative laryngotracheal morbidity in children. We randomly allocated 164 children aged 3-13 years undergoing general anaesthesia to one of four groups; tracheal tube cuffs filled with air (n = 41); saline (n = 41); alkalinised lidocaine 0.5% (n = 41); or alkalinised lidocaine 1% (n = 41). Intracuff pressure was monitored and maintained below 20 cmH₂ O. The mean (SD) increases in systolic blood pressure after tracheal extubation compared with before extubation were 10.9 (10.8) mmHg, 7.3 (17.7) mmHg, 4.1 (10.5) mmHg and 1.9 (9.5) mmHg in the air, saline, 0.5% and 1% alkalinised lidocaine groups, respectively (p = 0.021). The mean (SD) increases in diastolic blood pressure after tracheal extubation compared with before extubation were 3.9 (9.7) mmHg, 7.9 (14.6) mmHg, 0.7 (10.4) mmHg and 3.6 (6.9) mmHg in the air, saline, 0.5% and 1% alkalinised lidocaine groups, respectively (p = 0.019). The mean (SD) increases in heart rate after tracheal extubation compared with before extubation were 14.2 (7.6) beats.min^-1 , 15.5 (13.1) beats.min^-1 , 5.2 (9.6) beats.min^-1 and 4.1 (6.6) beats.min^-1 in the air, saline, 0.5% and 1% alkalinised lidocaine groups, respectively (p < 0.001). The incidence of sore throat 8 h after tracheal extubation was 22.0% in the air-filled group, 9.8% in the saline group, 4.9% in the 0.5% alkalinised lidocaine group and 2.4% in the 1% alkalinised lidocaine group, p = 0.015. We conclude that filling the tracheal tube cuff with alkalinised lidocaine-filled reduces the haemodynamic response to tracheal extubation and postoperative laryngotracheal morbidity in children.

Intravenous lidocaine for the treatment of acute pain in the emergency department

Objective

To evaluate intravenous lidocaine’s safety and efficacy as an analgesic agent in the treatment of a variety of painful conditions presenting to the emergency department.

Methods

This case series identified seventeen patients who received lidocaine over a six month period and recorded demographic data, amount of lidocaine administered, the amount of opioid medication administered before and after lidocaine, pre- and post-lidocaine pain scores, and any qualitative descriptors of the patient’s pain recorded in the record. Side effects and adverse events were also recorded.

Results

Of the seven patients who had a pre- and post-lidocaine pain score recorded, the mean reduction was 3 points on a 10 point scale. Patients who received lidocaine used less opioid medication. One patient received an improperly high dose of lidocaine and suffered a brief seizure and cardiac arrest, but was quickly resuscitated.

Conclusion

This series suggests that lidocaine may be a useful adjunct in the treatment of acutely painful conditions in the emergency department.

[Effect of intraoperative intravenous lidocaine on pain and plasma interleukin-6 in patients undergoing hysterectomy]

BACKGROUND AND OBJECTIVES

Interleukin-6 (IL-6) is a predictor of trauma severity. The purpose of this study was to evaluate the effect of intravenous lidocaine on pain severity and plasma IL-6 after hysterectomy.

METHOD

A prospective, randomized, comparative, double-blind study with 40 patients, aged 18-60 years. G1 received lidocaine (2mg.kg(-1).h(-1)) or G2 received 0.9% saline solution during the operation. Anesthesia was induced with O2/isoflurane. Pain severity (T0: awake and 6, 12, 18 and 24hours), first analgesic request, and dose of morphine in 24hours were evaluated. IL-6 was measured before starting surgery (T0), five hours after the start (T5), and 24hours after the end of surgery (T24).

RESULTS

There was no difference in pain severity between groups. There was a decrease in pain severity between T0 and other measurement times in G1. Time to first supplementation was greater in G2 (76.0±104.4min) than in G1 (26.7±23.3min). There was no difference in supplemental dose of morphine between G1 (23.5±12.6mg) and G2 (18.7±11.3mg). There were increased concentrations of IL-6 in both groups from T0 to T5 and T24. There was no difference in IL-6 dosage between groups. Lidocaine concentration was 856.5±364.1 ng.mL(-1) in T5 and 30.1±14.2 ng.mL(-1) in T24.

CONCLUSION

Intravenous lidocaine (2mg.kg(-1).h(-1)) did not reduce pain severity and plasma levels of IL-6 in patients undergoing abdominal hysterectomy.

Brief review: Neuraxial analgesia in refractory malignant pain

PURPOSE

This narrative review aims to inform health care practitioners of the current literature surrounding the use of intrathecal (IT) and epidural analgesia in cancer patients with refractory pain at end of life. Topics discussed and reviewed include: patient selection, treatment planning, procedure, equipment, medications, complications, policies and procedures, as well as directions for future research.

PRINCIPAL FINDINGS

Cancer pain is inadequately treated in an estimated 10% of patients with malignant pain despite the implementation of the World Health Organization three-step analgesic ladder. This has prompted some to advocate for the addition of a fourth step that would include neuraxial interventions. There is moderate evidence supporting the safety and efficacy of IT drug therapy in cancer patients with refractory pain. A detailed assessment and interdisciplinary team approach is necessary to develop and implement care plans for patients requiring neuraxial analgesia. Neuraxial analgesia can significantly improve pain and reduce side effects, but this must be balanced against the increased complexity of care and the risk of uncommon but serious complications.

CONCLUSION

Neuraxial drug delivery gives clinicians more options to manage refractory pain at end of life and should be offered to patients with intractable cancer pain. Teams should be interprofessional with clear delineation of roles and responsibilities. They should discuss advanced discharge planning with the patient prior to implantation as well as provide on-call support.

Interaction of local anesthetics with biomembranes consisting of phospholipids and cholesterol: mechanistic and clinical implications for anesthetic and cardiotoxic effects

Despite a long history in medical and dental application, the molecular mechanism and precise site of action are still arguable for local anesthetics. Their effects are considered to be induced by acting on functional proteins, on membrane lipids, or on both. Local anesthetics primarily interact with sodium channels embedded in cell membranes to reduce the excitability of nerve cells and cardiomyocytes or produce a malfunction of the cardiovascular system. However, the membrane protein-interacting theory cannot explain all of the pharmacological and toxicological features of local anesthetics. The administered drug molecules must diffuse through the lipid barriers of nerve sheaths and penetrate into or across the lipid bilayers of cell membranes to reach the acting site on transmembrane proteins. Amphiphilic local anesthetics interact hydrophobically and electrostatically with lipid bilayers and modify their physicochemical property, with the direct inhibition of membrane functions, and with the resultant alteration of the membrane lipid environments surrounding transmembrane proteins and the subsequent protein conformational change, leading to the inhibition of channel functions. We review recent studies on the interaction of local anesthetics with biomembranes consisting of phospholipids and cholesterol. Understanding the membrane interactivity of local anesthetics would provide novel insights into their anesthetic and cardiotoxic effects.

Intravenous lidocaine and magnesium for management of intractable trigeminal neuralgia: a case series of nine patients

Most patients suffering from trigeminal neuralgia (TN) benefit from medical therapy, for example carbamazepin, gabapentin, and pregabalin, individually or in combination. Nonetheless, some patients experience severe and intractable pain despite such medication, or the medication eliminates their pain but they experience intolerable side effects sufficient to warrant discontinuation. Intravenous magnesium and lidocaine have been used for management of intractable neuropathic pain. We treated nine patients with TN by using an intravenous infusion of a combination of 1.2 g magnesium and 100 mg lidocaine for 1 hour, once a week for 3 weeks. All patients experienced sound pain relief after the combined intravenous infusion therapy. Two patients experienced short and mild dizziness after the therapy, but no severe side effects were reported.

Medication Repurposing: New Uses for Old Drugs

Background:

Medication repurposing, the practice of using old drugs in new ways, is becoming more common. Old drugs that had previously fallen out of favor due to safety concerns, lack of efficacy, or development of more desirable therapeutic alternatives have been resurfacing in the literature and on pharmacy shelves. Developing new uses for old drugs may provide patients with access to helpful therapies but may also present challenges and risks.

Objective:

To explore the rationale for, and historical context of, the developing trend of recycling existing drugs for new, innovative uses, and to provide pharmacy practitioners with information about how to find clinical evidence regarding these new uses.

Data Synthesis:

The process of obtaining marketing approval for new drugs can take an average of over 10 years and exceed $1 billion. Repurposing old drugs (both approved and unapproved) for new uses requires considerably fewer resources since information about production needs, pharmacology, and pharmacokinetics is already known. Other advantages of using old drugs include faster availability for patient use and known safety concerns for the original indication. Disadvantages of new uses for old drugs may include lack of clinical evidence, unknown safety for the new clinical context, limited availability of information about new uses, and liability or legal concerns. Several methods of identifying potential new uses exist, including the observance of previously unknown desirable pharmacologic effects during clinical use, new knowledge of a mechanism of action leading to exploration of innovative therapeutic areas, or screening compound libraries for targeted clinical activity.

Conclusions:

There are many examples of recycling existing medications for new purposes. Pharmacy practitioners should be aware of this developing trend and know how to find information about utilizing old drugs in new ways.

Intravenous lidocaine reduces ischemic pain in healthy volunteers

BACKGROUND AND OBJECTIVES

Lidocaine, a local anesthetic and antiarrhythmic drug that alters depolarization in neurons by blocking the fast voltage-gated sodium (Na+) channels in the cell membrane, is used for regional anesthesia, as antiarrhythmic drug, and as analgesic for various painful conditions. It is unclear whether monotherapy with intravenous lidocaine has an analgesic effect in healthy individuals. To address this important question, we studied pain perception before, during, and after the administration of intravenous lidocaine in 16 human volunteers. Our hypothesis was that lidocaine, administered as a short intravenous infusion, does not have an analgesic effect in healthy volunteers.

METHODS

Sixteen healthy human volunteers received systemic lidocaine at plasma concentration 2 mg/mL using a computer-assisted infusion. Participants underwent a series of sensory tests-thermal, electrical, and ischemic pain and normal pinprick sensation-at baseline, during, and 30 mins after administration of a 20-min lidocaine infusion at a 2 mg/mL effect site concentration.

RESULTS

We found a sustained decrease in ischemic pain ratings and a limited analgesic effect for electrical pain, whereas thermal pain and normal sensation did not change.

CONCLUSIONS

The observed sustained analgesic effect of systemic lidocaine in the ischemic pain model suggests that lidocaine may be used to treat acute pain.

A role for intravenous lidocaine in severe cancer-related neuropathic pain at the end-of-life

BACKGROUND

Systemic administration of lidocaine has been widely reported to provide effective analgesia in both cancer and non-malignant pain.

CASE REPORT

We report the use of intravenous lidocaine in the management of cancer-related neuropathic pain and its pivotal role in restoring function and facilitating end-of-life care at home.

Targeting primary afferent nerves for novel antitussive therapy

The best available data support the hypothesis that there are at least two types of vagal nerves responsible for initiating coughing reflexes. One type of nerve conducts action potentials in the A-range and is characterized by rapidly adapting responses to mechanical probing or acidification of the large airway epithelium. Stimulation of these nerves can evoke cough in unconscious experimental animals and humans. These nerves are important in immediate cough evoked by aspiration and as such perform a critical role in airway defense. The other type of primary afferent nerve involved in cough is the vagal C-fiber. Inhalation of selective C-fiber stimulants leads to cough only in conscious animals. In clinical studies, inhalation of a low concentration of a C-fiber stimulant causes an irritating, itchy urge-to-cough sensation that mimics the urge-to-cough sensations associated with respiratory tract infection, post-infection, gastroesophageal reflux disorders, and inflammatory airway diseases. Here we discuss the recent advances in sensory neurobiology that allow for the targeting of vagal C-fibers for novel antitussive therapy. No attempts are made to be all-inclusive with respect to the numerous possible molecular targets being considered to accomplish this goal. Rather, two general strategies are discussed: decreasing generator potential amplitude and decreasing the efficiency by which a generator potential evokes action-potential discharge. For the first category we focus on two targets, transient receptor potential vanilloid 1 and transient receptor potential A1. For the latter category we focus on recent advances in voltage-gated sodium (Na(V)) channel biology.

A phase II pilot study to evaluate use of intravenous lidocaine for opioid-refractory pain in cancer patients

Opioid-refractory pain is distressing because it is notoriously difficult to treat. Relief from adjuvant therapies often occurs after a lag time. Retrospective evidence points to a role for intravenous (IV) lidocaine in this setting for pain relief. This study was planned as a randomized, double-blind, placebo-controlled, crossover study in which eligible patients received both lidocaine and placebo infusions separated by two weeks. Primary endpoints were magnitude and duration of pain relief. Fifty patients were included in the study. Pain relief was significantly better (P<0.001) and more patients reported a decrease in analgesic requirements (P=0.0012) after lidocaine infusion than after placebo. Onset of analgesia was noted at a mean of 40+/-16.28 minutes after initiation of infusion of IV lidocaine. Mean duration of this analgesia, 9.34+/-2.58 days after the single infusion, was significantly longer than that for placebo (P<0.01). Side effects observed were tinnitus, perioral numbness, sedation, light-headedness, and headache. All side effects were self-limited and did not require any intervention except termination of lidocaine infusion in one case. These data demonstrate that a single IV infusion of lidocaine provided a significantly greater magnitude and duration of pain relief than placebo infusion in opioid-refractory patients with cancer pain. Side effects were tolerable. It is thus a promising modality worth investigating further to establish guidelines for its use in cancer patients with opioid-refractory pain.

The pharmacology of voltage-gated sodium channels in sensory neurones

Voltage-gated sodium channels (VGSCs) are vital for the normal functioning of most excitable cells. At least nine distinct functional subtypes of VGSCs are recognized, corresponding to nine genes for their pore-forming alpha-subunits. These have different developmental expression patterns, different tissue distributions in the adult and are differentially regulated at the cellular level by receptor-coupled cell signalling systems. Unsurprisingly, VGSC blockers are found to be useful as drugs in diverse clinical applications where excessive excitability of tissue leads to pathological dysfunction, e.g. epilepsy or cardiac tachyarrhythmias. The effects of most clinically useful VGSC blockers are use-dependent, i.e. their efficacy depends on channel activity. In addition, many natural toxins have been discovered that interact with VGSCs in complex ways and they have been used as experimental probes to study the structure and function of the channels and to better understand how drugs interact with the channels. Here we have attempted to summarize the properties of VGSCs in sensory neurones, discuss how they are regulated by cell signalling systems and we have considered briefly current concepts of their physiological function. We discuss in detail how drugs and toxins interact with archetypal VGSCs and where possible consider how they act on VGSCs in peripheral sensory neurones. Increasingly, drugs that block VGSCs are being used as systemic analgesic agents in chronic pain syndromes, but the full potential for VGSC blockers in this indication is yet to be realized and other applications in sensory dysfunction are also possible. Drugs targeting VGSC subtypes in sensory neurones are likely to provide novel systemic analgesics that are tissue-specific and perhaps even disease-specific, providing much-needed novel therapeutic approaches for the relief of chronic pain.