Management of opioid-induced pruritus: a role for 5-HT3 antagonists?

Interoception and Obsessive-Compulsive Disorder: A Review of Current Evidence and Future Directions

Disrupted interoceptive processes are present in a range of psychiatric conditions, and there is a small but growing body of research on the role of interoception in obsessive-compulsive disorder (OCD). In this review, we outline dimensions of interoception and review current literature on the processing of internal bodily sensations within OCD. Investigations in OCD utilizing objective measures of interoception are limited and results mixed, however, the subjective experience of internal bodily sensations appears to be atypical and relate to specific patterns of symptom dimensions. Further, neuroimaging investigations suggest that interoception is related to core features of OCD, particularly sensory phenomena and disgust. Interoception is discussed in the context of treatment by presenting an overview of existing interventions and suggesting how modifications aimed at better targeting interoceptive processes could serve to optimize outcomes. Interoception represents a promising direction for multi-method research in OCD, which we expect, will prove useful for improving current interventions and identifying new treatment targets.

Evaluation of Therapies for Peripheral and Neuraxial Opioid-induced Pruritus based on Molecular and Cellular Discoveries

Opioids are a mainstay of treatment for pain worldwide. Pruritus, a common side effect of opioids, is a patient dissatisfier that limits their use in many clinical settings. Both parenteral and neuraxial administration of opioids frequently evoke pruritus. The ability of opioids to suppress pain while causing itch continues to perplex clinicians and researchers alike. Several mechanisms have been proposed to explain how opioids can give rise to pruritus, but specific knowledge gaps perpetuate debate. This review summarizes the clinical burden of opioid-induced pruritus and emphasizes recent discoveries of peripheral and central mechanisms for opioid-induced pruritus, particularly with respect to scientific and conceptual advances in spinal cord circuitry and mast cell biology. The mechanisms and effectiveness of existing medications used for clinical management of pruritus will be evaluated, and we will highlight the emerging preclinical utility of selective κ-opioid receptor agonists, such as nalfurafine, for the management of opioid-induced pruritus.

Medications for the prevention of pruritus in women undergoing cesarean delivery with Intrathecal morphine: A systematic review and bayesian network meta-analysis of randomized controlled trials

PURPOSE

Intrathecal morphine-induced pruritus can cause significant discomfort in parturients and is refractory to conventional antipruritic treatment. This systematic review and network meta-analysis evaluates the effectiveness of the medications used for prevention of intrathecal (IT) morphine-induced pruritus after cesarean delivery under spinal anesthesia.

METHODS

A literature search was conducted from 1946 up to October 2019. We included all randomized controlled trials (RCTs) that compared medications used for prevention of pruritus with a control group in women undergoing cesarean delivery under spinal anesthesia with IT morphine. The primary outcome examined was the incidence of pruritus up to 24 h after cesarean delivery. Dichotomous data were extracted and summarized using odds ratios (OR) and 95% credible intervals (CrI) with Bayesian random effects network meta-analysis model. The GRADE approach was used to evaluate quality of the studies and effect evidence.

RESULTS

Of the 26 studies included in the systematic review, 21 studies with a total of 2594 patients were included in the network meta-analysis [prophylaxis, n = 1603 (62%) vs. control, n = 991 (38%)]. These studies investigated seven classes of drugs including serotonin-receptor antagonists, dopamine-receptor antagonists, opioid agonist-antagonists, opioid-receptor antagonists, histamine-receptor antagonists, propofol and celecoxib. The network meta-analysis showed that serotonin-receptor antagonists' prophylaxis [control vs. prophylaxis: 60% vs. 47%; OR (95% CrI): 2.69 (1.43-5.36)] and opioid agonist-antagonists prophylaxis [control vs. prophylaxis: 72% vs. 47%; OR (95% CrI): 4.57 (1.67-12.91)] decreased the incidence of pruritus compared to the control group. Although all included studies were at low risk of bias, the quality of the overall network meta-analysis pooled estimates was low.

CONCLUSION

This bayesian network meta-analysis of RCTs demonstrates serotonin-receptor antagonists and opioid agonist-antagonists may prevent pruritus in women undergoing cesarean delivery with intrathecal morphine compared to control group. However, further RCTs of adequate power and clearly defined end points are warranted.

Defining the role of mirtazapine in the treatment of refractory pruritus

BACKGROUND/OBJECTIVE

Mirtazapine has traditionally been used for the treatment of major depressive disorder, with an added benefit in patients who have comorbid insomnia or anxiety. Recent studies describe its usefulness in treating refractory pruritus of various causes as well. Our goal is to better define the use of mirtazapine in the treatment of refractory pruritus.

METHOD

Through a thorough literature review of PubMed, we identified all reports of the use of mirtazapine for pruritus.

RESULTS

Upon examination of 8 supporting articles, we found mirtazapine has quality evidence for the treatment of intra-thecal morphine-induced pruritus. Mirtazapine may also be effective in treating pruritus related to various other conditions, including psoriasis, atopic dermatitis, cutaneous malignancies (primary or metastatic), hematologic malignancies (lymphomas and leukemias), liver failure, renal failure, cholestasis, as well as pruritus of unknown origin.

CONCLUSIONS

Mirtazapine plays a role in treatment for intra-thecel morphine-induced pruritis yet high-quality trials are needed to confirm its efficacy in other dermatologic conditions.

Brain allopregnanolone induces marked scratching behaviour in diet-induced atopic dermatitis mouse model

Allopregnanolone (ALLO) is a neurosteroid produced in the brain, but so far, no study has explored its link with itching. Herein, we used a diet-induced atopic dermatitis mouse model to examine whether exogenously administered and endogenously produced ALLO contribute to inducing scratching. Systemic administration of ALLO elicited robust scratching in the atopic dermatitis model, while it did not affect spontaneous and pruritogen-induced scratching in normal mice. ALLO caused scratching when administered intracisternally, but not when administered intrathecally or intradermally, suggesting the involvement of supraspinal mechanisms. Pharmacological analyses suggested that both γ-aminobutyric acid type A receptor activation and serotonin type 3 receptor inhibition were involved in ALLO-induced scratching. We next examined whether endogenously produced ALLO is involved in ethanol-induced scratching in atopic dermatitis mice, because ethanol administration increases ALLO in rodent brain. Acute ethanol administration increased brain ALLO levels, which coincided with increased scratching. Pre-treatment with finasteride, a synthetic ALLO inhibitor, suppressed ethanol-induced scratching and ALLO production in the brain. Collectively, our results demonstrated for the first time that ALLO administration caused marked scratching in atopic dermatitis mice, and ethanol-induced scratching may be mediated through endogenously produced brain ALLO.

High-dose ondansetron reduces activation of interoceptive and sensorimotor brain regions

Several psychiatric disorders involve abnormalities of interoception and associated neural circuitry centered on the insula. The development of interventions modulating interoceptive circuits could lead to novel treatment approaches for these disorders. The 5-HT3 receptor antagonist ondansetron is a good candidate for the modulation of interoceptive circuits, as 5-HT3 receptors are located abundantly on sensory pathways and ondansetron has shown some clinical utility in disorders characterized by sensory and interoceptive abnormalities. The present study tested the ability of three different doses of ondansetron to engage neural regions involved in interoception to determine the drug's utility as a therapeutic agent to target circuit abnormalities in patients. Fifty-three healthy subjects were randomized to receive a single 8-mg (n = 18), 16-mg (n = 17), or 24-mg (n = 18) dose of ondansetron and placebo before MRI scanning on separate days. Subjects performed an fMRI task previously shown to engage interoceptive circuitry in which they viewed videos depicting body movements/sensation and control videos. The results revealed a highly significant relationship between dosage and activation in bilateral insula, somatosensory and premotor regions, cingulate cortex, and temporal cortex for control but not body-focused videos. These effects were driven by a robust reduction in activation for ondansetron compared to placebo for the 24-mg group, with weaker effects for the 16-mg and 8-mg groups. In conclusion, high-dose ondansetron reduces activation of several areas important for interoception, including insula and sensorimotor cortical regions. This study reveals the potential utility of this drug in modulating hyperactivity in these regions in patients.

Is There a Role for 5-HT3 Receptor Antagonists in the Treatment of Opioid-Induced Pruritus?

Pruritus is an unpleasant irritation symptom that can be related to various systemic and dermatological conditions. Although underreported, pruritus is a common adverse event noted after use of opioid pain medications. This article reviews the current understanding of the mechanism of opioid-induced pruritus (OIP) and various pharmacological therapies. 5-Hydroxytryptamine 3 (5-HT₃) receptor antagonists are potentially effective for treating OIP and may be a valuable treatment option if further controlled studies are encouraging.

Comparison of intrathecal morphine and surgical-site infusion of ropivacaine as adjuncts to intravenous patient-controlled analgesia in living-donor kidney transplant recipients

INTRODUCTION

This prospective observational study compared the postoperative analgesic effectiveness of intrathecal morphine (ITM) and surgical-site infusion (SSI) of ropivacaine as adjuncts to intravenous (IV) patient-controlled analgesia (PCA) (fentanyl) in living-donor kidney transplant recipients.

METHODS

Patients undergoing living-donor kidney transplantation who received ITM or SSI in addition to IV PCA were included. Rescue analgesia was achieved with IV meperidine as required. The primary outcome, measured using the Numeric Pain Rating Scale (NRS), was pain at rest and when coughing. Patients were assessed for 48 hours after surgery.

RESULTS

A total of 53 patients (32 ITM, 21 SSI) were included in the study. The ITM group showed significantly lower NRS scores, at rest and when coughing, for up to 12 and eight hours. NRS scores were comparable between the groups at other times. The ITM group had significantly less postoperative systemic opioid requirement in the first 24 hours, but there was no significant difference between the systemic opioid consumption of the groups on postoperative Day 2. In the ITM group, 3 (9.4%) patients presented with bradypnoea and 1 (3.1%) with excessive sedation in the first 12 postoperative hours. More patients in the ITM group developed pruritus requiring treatment during the first 24 hours. There were no differences between the groups in other outcomes (e.g. nausea/vomiting, change in pulmonary or kidney functions).

CONCLUSION

Compared with SSI, ITM reduced immediate postoperative pain and IV opioid consumption on postoperative Day 1 after living-donor kidney transplantation, but at the cost of increased pruritus and respiratory depression.

Building a 5-HT3A Receptor Expression Map in the Mouse Brain

Of the many serotonin receptors, the type 3 receptors (5-HT3R) are the only ionotropic ones, playing a key role in fast synaptic transmission and cognitive and emotional brain function through controlled neuronal excitation. To better understand the various functions of 5-HT3Rs, it is very important to know their expression pattern in the central nervous system (CNS). To date, many distributional studies have shown localized 5-HT3R expression in the brain and spinal cord. However, an accurate pattern of 5-HT3R expression in the CNS remains to be elucidated. To investigate the distribution of 5-HT3R in the mouse brain in detail, we performed immunofluorescent staining using 5-HT3AR-GFP transgenic mice. We found strong 5-HT3AR expression in the olfactory bulb, cerebral cortex, hippocampus, and amygdala; and partial expression in the pons, medulla, and spinal cord. Meanwhile, the thalamus, hypothalamus, and midbrain exhibited a few 5-HT3AR-expressing cells, and no expression was detected in the cerebellum. Further, double-immunostaining using neural markers confirmed that 5-HT3AR is expressed in GABAergic interneurons containing somatostatin or calretinin. In the present study, we built a 5-HT3AR expression map in the mouse brain. Our findings make significant contributions in elucidating the novel functions of 5-HT3R in the CNS.

Intravenous Midazolam as More Effective Than Propofol for Preventing Pruritus After Intrathecal Sufentanil in Surgical Patients: A Randomized Blinded Trial

Background

Pruritus is a troublesome side effect of intrathecal opioids. Midazolam can reinforce GABA-mediated inhibition of the medullary dorsal horn neurons, and thus theoretically has potential to suppress opioid-induced pruritus.

Objectives

This prospective double-blinded randomized trial aimed at comparing the effects of propofol, midazolam, and a combination of the two on the prevention of pruritus induced by intrathecal sufentanil.

Methods

Eighty-four patients undergoing spinal anesthesia with 3 mL hyperbaric bupivacaine 0.5% and 5 μg sufentanil (1 mL) were randomly allocated to one of the three study groups: Group 1, who were administered 20 mg intravenous (IV) propofol bolus, then 50 μg/kg/min IV infusion; Group 2, who were administered 0.03 mg/kg IV midazolam bolus, then 0.02 mg/kg/h IV infusion; and Group 3, who were administered 10 mg IV propofol and 0.015 mg/kg IV midazolam bolus, then 25 μg/kg/min propofol and 0.01 mg/kg/h midazolam IV infusion. The incidence rates and severity of pruritus were assessed intraoperatively and postoperatively for 24 hours.

Results

The Ramsay Sedation Score was highest for the propofol group throughout the duration of the anesthetic process. Overall, 17 patients in the propofol group (60.7%), eight patients in the midazolam group (28.6%), and nine patients in the propofol-midazolam group (32.1%) developed pruritus (P = 0.027). Intraoperative pruritus was observed in seven patients in the propofol group (25%), two patients in the midazolam group (7.1%), and five patients in the midazolam-propofol group (17.9%) (P = 0.196). Postoperative pruritus developed in 12 patients in the propofol group (42.9%), six patients in the midazolam group (21.4%), and four patients in the midazolam-propofol group (14.3%) (P = 0.041). There was no significant difference between the groups with respect to the severity of pruritus (P > 0.05).

Conclusions

This study showed that in comparison with propofol, the administration of 0.03 mg/kg IV midazolam bolus followed by 0.02 mg/kg/h could be more effective in the prevention of intrathecal sufentanil-induced pruritus without increasing sedation and other side effects.

A randomised controlled trial comparing the effect of adjuvant intrathecal 2 mg midazolam to 20 micrograms fentanyl on postoperative pain for patients undergoing lower limb orthopaedic surgery under spinal anaesthesia

BACKGROUND

Intrathecal adjuvants are added to local anaesthetics to improve the quality of neuraxial blockade and prolong the duration of analgesia during spinal anaesthesia. Used intrathecally, fentanyl improves the quality of spinal blockade as compared to plain bupivacaine and confers a short duration of post-operative analgesia. Intrathecal midazolam as an adjuvant has been used and shown to improve the quality of spinal anaesthesia and prolong the duration of post-operative analgesia. No studies have been done comparing intrathecal fentanyl with bupivacaine and intrathecal 2 mg midazolam with bupivacaine.

OBJECTIVE

To compare the effect of intrathecal 2mg midazolam to intrathecal 20 micrograms fentanyl when added to 2.6 ml of 0.5% hyperbaric bupivacaine, on post-operative pain, in patients undergoing lower limb orthopaedic surgery under spinal anaesthesia.

METHODS

A total of 40 patients undergoing lower limb orthopaedic surgery under spinal anaesthesia were randomized to two groups. Group 1: 2.6mls 0.5% hyperbaric bupivacaine with 0.4mls (20micrograms) fentanyl Group 2: 2.6mls of 0.5% hyperbaric bupivacaine with 0.4mls (2mg) midazolam.

RESULTS

The duration of effective analgesia was longer in the midazolam group (384.05 minutes) as compared to the fentanyl group (342.6 minutes). There was no significant difference (P 0.4047). The time to onset was significantly longer in midazolam group 17.1 minutes as compared to the fentanyl group 13.2 minutes (P 0.023). The visual analogue score at rescue was significantly lower in the midazolam group (5.55) as compared to the fentanyl group 6.35 (P - 0.043).

CONCLUSION

On the basis of the results of this study, there was no significant difference in the duration of effective analgesia between adjuvant intrathecal 2 mg midazolam as compared to intrathecal 20 micrograms fentanyl for patients undergoing lower limb orthopaedic surgery.

Efficacy of intrathecal morphine for postoperative pain management following open nephrectomy

Objective

To evaluate the efficacy and safety of intrathecal morphine (ITM) for postoperative pain control in patients with renal cell carcinoma undergoing open nephrectomy.

Methods

Forty-five patients scheduled for open nephrectomy were randomised to receive 300 µg ITM and intravenous patient-controlled analgesia (IV-PCA) (n = 22) or IV-PCA alone (n = 23) for postoperative analgesia. The numeric pain score (NPS), postoperative IV-PCA requirements and opioid-related complications including nausea, vomiting, dizziness, headache, and pruritus were compared between groups.

Results

NPS was significantly lower in the ITM group up to 24 h postoperatively. Upon coughing, NPS at 24 h postoperatively was 50 (interquartile range (IQR) 30–60) in the ITM group and 60 (45–70) in the IV-PCA group. Cumulative morphine consumption at 72 h postoperatively was significantly lower in the ITM group compared with the IV-PCA group (20 (9–33) mg vs. 31 (21–49) mg, respectively). Opioid-related complications were similar in both groups with the exception of pruritus (ITM, 77% vs. IV-PCA, 26%).

Conclusions

ITM was associated with greater analgesia without serious complications in patients undergoing open nephrectomy.

HTR7 Mediates Serotonergic Acute and Chronic Itch

Chronic itch is a prevalent and debilitating condition for which few effective therapies are available. We harnessed the natural variation across genetically distinct mouse strains to identify transcripts co-regulated with itch behavior. This survey led to the discovery of the serotonin receptor HTR7 as a key mediator of serotonergic itch. Activation of HTR7 promoted opening of the ion channel TRPA1, which in turn triggered itch behaviors. In addition, acute itch triggered by serotonin or a selective serotonin reuptake inhibitor required both HTR7 and TRPA1. Aberrant serotonin signaling has long been linked to a variety of human chronic itch conditions, including atopic dermatitis. In a mouse model of atopic dermatitis, mice lacking HTR7 or TRPA1 displayed reduced scratching and skin lesion severity. These data highlight a role for HTR7 in acute and chronic itch and suggest that HTR7 antagonists may be useful for treating a variety of pathological itch conditions.

Neuraxial opioid-induced pruritus: An update

Pruritus is a troublesome side-effect of neuraxial (epidural and intrathecal) opioids. Sometimes it may be more unpleasant than pain itself. The prevention and treatment still remains a challenge. A variety of medications with different mechanisms of action have been used for the prevention and treatment of opioid-induced pruritus, with mixed results. The aim of this article is to review the current body of literature and summarize the current understanding of the mechanisms and the pharmacological therapies available to manage opioid-induced pruritus. The literature source of this review was obtained via PubMed, Medline and Cochrane Database of Systematic Reviews until 2012. The search results were limited to the randomized controlled trials, systemic reviews and non-systemic reviews.

Opioid side effects and their treatment in patients with chronic cancer and noncancer pain

Opioids are the foundation of standard analgesic regimens for moderate to severe pain due to life-threatening illnesses such as cancer, and are increasingly employed in chronic noncancer pain of the same severity. Opioids are frequently used for long periods in these populations, sometimes for years. However, side effects are common and may reduce quality of life, or become life threatening, and frequently cause patients to discontinue opioid therapy. Successful opioid therapy dictates that benefits of analgesia outweigh safety concerns. The mechanisms, incidence, and treatment or prevention of commonly reported side effects in chronic pain populations are reviewed, employing best available evidence along with empiric practice. General management strategies include switching opioids ("opioid rotation"), discontinuation of concurrent medications that exacerbate side effects, and symptomatic treatment. In addition, recently recognized adverse events that occur after long-term opioid therapy are discussed. High-quality evidence is lacking for the treatment of most side effects, and the true incidence, underlying mechanisms, and clinical implications of long-term responses to opioid therapy are not yet fully understood.

5-HT(3) receptors: role in disease and target of drugs

Serotonin type 3 (5-HT(3)) receptors are pentameric ion channels belonging to the superfamily of Cys-loop receptors. Receptor activation either leads to fast excitatory responses or modulation of neurotransmitter release depending on their neuronal localisation. 5-HT(3) receptors are known to be expressed in the central nervous system in regions involved in the vomiting reflex, processing of pain, the reward system, cognition and anxiety control. In the periphery they are present on a variety of neurons and immune cells. 5-HT(3) receptors are known to be involved in emesis, pain disorders, drug addiction, psychiatric and GI disorders. Progress in molecular genetics gives direction to personalised medical strategies for treating complex diseases such as psychiatric and functional GI disorders and unravelling individual drug responses in pharmacogenetic approaches. Here we discuss the molecular basis of 5-HT(3) receptor diversity at the DNA and protein level, of which our knowledge has greatly extended in the last decade. We also evaluate their role in health and disease and describe specific case-control studies addressing the involvement of polymorphisms of 5-HT3 subunit genes in complex disorders and responses to drugs. Furthermore, we focus on the actual state of the pharmacological knowledge concerning not only classical 5-HT(3) antagonists--the setrons--but also compounds of various substance classes targeting 5-HT(3) receptors such as anaesthetics, opioids, cannabinoids, steroids, antidepressants and antipsychotics as well as natural compounds derived from plants. This shall point to alternative treatment options modulating the 5-HT(3) receptor system and open new possibilities for drug development in the future.

Pain management principles in the critically ill

This article addresses conventional pharmacologic and nonpharmacologic treatment of pain in patients in ICUs. For the critically ill patient, opioids have been the mainstay of pain control. The optimal choice of opioid and dosing regimen for a specific patient varies depending on factors such as the pharmacokinetics and physicochemical characteristics of an opioid and the body's handling of the opioid, concomitant sedative regimen, potential or actual adverse drug events, and development of tolerance. The clinician must appreciate that favorable pharmacokinetic properties such as a short-elimination half-life do not necessarily translate into clinical advantages in the ICU setting. A variety of medications have been proposed as alternatives or adjuncts to the opioids for pain control that have unique considerations when contemplated for use in the critically ill patient. Most have been relatively unstudied in the ICU setting, and many have limitations with respect to availability of the GI route of administration in patients with questionable GI absorptive function. Nonpharmacologic, complementary therapies are low cost, easy to provide, and safe, and many clinicians can implement them with little difficulty or resources. However, the evidence base for their effectiveness is limited. At present, insufficient research evidence is available to support a broad implementation of nonpharmacologic therapies in ICUs.

Effect of prophylactic 5-HT3 receptor antagonists on pruritus induced by neuraxial opioids: a quantitative systematic review

Pruritus is a frequent adverse event observed after neuraxial administration of opioids. Central 5-hydroxytryptamine subtype 3 (5-HT3) receptors may be activated in this process. This systematic review aimed to evaluate the efficacy of prophylactic 5-HT3 receptor antagonists on neuraxial opioid-induced pruritus. We searched Medline, Embase, and Cochrane Collaboration Library databases. Studies were evaluated with the Oxford Validity Scale. Studies with a score of 3 or more and reporting prophylactic administration of 5-HT3 receptor antagonists vs placebo were included. Fifteen randomized double-blind controlled trials (n=1337) were selected. 5-HT3 antagonists (n=775) significantly reduced pruritus [odds ratio (OR) 0.44 (95% confidence interval, 95% CI, 0.29-0.68), P=0.0002, number-needed-to-treat (NNT) 6 (95% CI, 4-14)], the treatment request for pruritus [OR 0.58 (95% CI, 0.43-0.78), P=0.0003, NNT 10 (95% CI, 7-20)], the intensity of pruritus [weighted mean difference (WMD) -0.35 (95% CI, -0.59 to -0.10), P=0.007], the incidence and the intensity of postoperative nausea and vomiting (PONV), and the need of rescue treatment [respectively, Peto odds ratio (Peto OR) 0.43 (95% CI, 0.31-0.58), P<0.00001, NNT 7 (95% CI, 6-10); WMD -0.12 (95% CI, -0.24 to 0.00), P=0.05 and OR 0.42 (95% CI, 0.20-0.86), P=0.02, NNT 8 (95% CI, 5-35)]. However, the funnel plot was asymmetric, suggesting a risk of publication bias. 5-HT3 receptor antagonists may be an effective strategy in preventing neuraxial opioid-induced pruritus and PONV. Further large randomized controlled trials are required to confirm these findings.

The role of intrathecal drugs in the treatment of acute pain

Intrathecal opioids are widely used as useful adjuncts in the treatment of acute and chronic pain, and a number of non-opioid drugs show promise as analgesic drugs with spinal selectivity. In this review we examine the historical development and current use of intrathecal opioids and other drugs that show promise for treating pain in the perioperative period. The pharmacology and clinical use of intrathecal morphine and other opioids is reviewed in detail, including dosing guidelines for specific surgical procedures and the incidence and treatment of side effects associated with these drugs. Available data on the use of non-opioid drugs that have been tested intrathecally for use as analgesics are also reviewed. Evidence-based guidelines for dosing of intrathecal drugs for specific surgical procedures and for the treatment of the most common side effects associated with these drugs are presented.

Remifentanil as a Single Drug for Extracorporeal Shock Wave Lithotripsy: A Comparison of Infusion Doses in Terms of Analgesic Potency and Side Effects

This randomized, double-blind study was designed to evaluate analgesic effectiveness and side effects of two remifentanil infusion rates in patients undergoing extracorporeal shock wave lithotripsy (ESWL) for renal stones. We included 200 patients who were administered remifentanil either 0.05 microg x kg(-1) x min(-1) (n = 100) or 0.1 microg x kg(-1) x min(-1) (n = 100) plus demand bolus of 10 microg of remifentanil via a patient-controlled analgesia (PCA) device. No other sedating drugs were given. The frequencies of PCA demands and deliveries were recorded. Arterial blood pressure, oxygen saturation, and respiratory rate were recorded throughout the procedure; postoperative nausea and vomiting (PONV), dizziness, itching, agitation, and respiratory depression were measured posttreatment. Visual analog scale (VAS) scores were taken preoperatively, directly postoperatively, and 30 min after finishing the procedure. There were no statistically significant differences in the frequency of PCA demands and delivered boluses or among perioperative VAS scores. The extent of PONV and frequency of dizziness and itching immediately after and dizziness 30 min after the end of treatment were significantly reduced in the smaller dose group. We conclude that a remifentanil regimen of 0.05 microg x kg(-1) x min(-1) plus 10 microg demands is superior to 0.1 microg x kg(-1) x min(-1) plus demands, as there was no difference in the VAS scores recorded between groups and it has a less frequent incidence of side effects in patients receiving ESWL.

IMPLICATIONS

Remifentanil is an appropriate analgesic choice for patients undergoing extracorporeal shock wave lithotripsy (ESWL) therapy, as it has both fast onset and offset times. We studied remifentanil as a sole drug for ESWL and have shown that an infusion rate of 0.05 microg x kg-1 x min-1 plus patient-controlled analgesia demands of 10 microg provides adequate analgesia and has significantly less side effects than a dose of 0.1 microg x kg-1 x min-1 plus 10 microg demands.

Intrathecal fentanyl-induced pruritus during labour: the effect of prophylactic ondansetron

Fentanyl is commonly used for spinal analgesia during labour but it is associated with a high incidence of pruritus. This randomised, double-blind, placebo-controlled study was performed to evaluate the effect of prophylactic ondansetron on the incidence and severity of pruritus among parturients receiving intrathecal fentanyl as part of combined spinal-epidural analgesia. Seventy-three women were randomised to receive either saline placebo (group P, n = 25), ondansetron 4 mg (group O4, n = 23) or ondansetron 8 mg (group O8, n = 25) intravenously before intrathecal fentanyl 25 micrograms and bupivacaine 2 mg. The incidence and severity of pruritus were measured using a verbal rating and a visual analogue scale, and by the requirement for rescue anti-pruritic medication (naloxone). The overall incidence of pruritus was 95% (group P 100%, group O4 95%, group O8 90%). There were no significant differences between groups for severity of pruritus or requirement for treatment (naloxone given to 45%, 28% and 35% of groups P, O4 and O8 respectively). Secondary outcomes such as the incidence of headache, pain and nausea were not significantly different between groups. We conclude that prophylactic ondansetron 4 or 8 mg intravenously was ineffective in reducing the incidence or severity of intrathecal fentanyl-induced pruritus during labour.

Paroxetine in the treatment of severe non-dermatological pruritus: a randomized, controlled trial

Severe pruritus may be an idiopathic phenomenon or associated with advanced systemic disease. It is one of the most distressing and difficult to treat symptoms. Uncontrolled studies have suggested that, in patients experiencing severe pruritus, paroxetine appeared to have a rapid anti-pruritic effect. This study was a prospective double-blind, randomized within patient comparison of paroxetine and placebo. The intensity of pruritus was measured subjectively with a numerical analogue scale. The primary endpoint of the trial was the mean pruritus score, measured for seven days after randomization and after cross-over. The secondary endpoint was individual global response to the treatment. Response was defined as at least 50% reduction of intensity of pruritus in the last three days of the treatment period vs. baseline. Adverse effects and patient satisfaction and preferences were also recorded. Twenty-six patients were included in the study; 17 of them had solid tumors, 4 had hematological malignancies and 5 had various nonmalignant or idiopathic conditions. Eight patients had drug-induced pruritus (none opioid-induced), 7 patients had paraneoplastic pruritus and 3 had cholestatic pruritus. After a run-in period, patients were randomly assigned to treatment with 20 mg paroxetine or placebo. The crossover took place after 7 days. Two patients discontinued treatment because of adverse effects of paroxetine. Twenty-four patients treated with paroxetine had lower pruritus intensity scores over the 7 treatment periods (mean+/-SE=5.2+/-0.32) as compared to placebo (mean+/-SE=6.0+/-0.32). Mean difference between placebo and paroxetine was 0.78 (95% CI=0.37-1.19). Nine of twenty-four patients (37.5%) fulfilled criteria of response. The onset of anti-pruritic action was observed usually after 2-3 days, irrespective of the order of treatment. The outcome of this study indicates that paroxetine is effective in the treatment of severe pruritus of non-dermatological origin.

Behandlung von Pruritus als Symptom von Hauterkrankungen mit dem Serotonin-Rezeptorantagonisten Ondansetron. Therapy of pruritus associated with skin diseases with the serotonin receptor antagonist ondansetron

BACKGROUND

Pruritus is often a stressing symptom and a therapeutic challenge. We report our experience with the serotonin receptor antagonist ondansetron in the symptomatic treatment of pruritus accompanying various skin diseases.

PATIENTS AND METHODS

The influence of ondansetron (8-12 mg orally per day) on pruritus was assessed in twelve patients with various skin disorders. The intensity of pruritus was quantitated daily by a visual analogue scale over the time period of one week before, during, and one week after treatment.

RESULTS

Ondansetron decreased pruritus intensity in prurigo simplex (four patients), asteatotic eczema (two patients), parapsoriasis en plaques, and pruritus of unknown origin (one patient each). One of two patients with atopic dermatitis experienced relief, whereas no benefit was observed in urticaria factitia and notalgia paraesthetica (one patient each).

CONCLUSIONS

Ondansetron may ameliorate the concomitant pruritus of some dermatologic diseases.

5-Hydroxytryptamine (5-HT)2 receptor involvement in acute 5-HT-evoked scratching but not in allergic pruritus induced by dinitrofluorobenzene in rats

We investigated the role of serotonin (5-hydroxytryptamine; 5-HT)2 and 5-HT3 receptor subtypes in acute itch-associated scratching behavior as well as in an allergic pruritus model in rats. Intradermal 5-HT evoked hind limb scratching directed toward the injection site in naïve rats. Scratching behavior was significantly reduced by pretreatment with the 5-HT2 receptor antagonist ketanserin. Intradermal injection of alpha-methylserotonin, a 5-HT2 receptor agonist, also elicited scratching behavior in a dose-dependent manner, indicating that acute 5-HT-induced scratching is mediated via peripheral 5-HT2 receptors. To produce a model of allergic pruritus, skin was sensitized by topical application of 5% dinitrofluorobenzene (DNFB). One month later, repeated challenge of the skin with 0.2% DNFB at weekly intervals elicited scratching as part of the immediate allergic response. Scratching was not affected by ketanserin or by the 5-HT3 receptor antagonist ondansetron, indicating that neither 5-HT2 nor 5-HT3 receptors is involved in itch-associated scratching behavior caused by allergic skin dermatitis in rats.

Management of opioid side effects in cancer-related and chronic noncancer pain: a systematic review

Side effects can limit opioid dosage and reduce quality of life. The purpose of this systematic review was to assess the management of opioid side effects in the context of cancer pain management or, in the event that no evidence was available for cancer pain, for chronic noncancer pain. The side effects studied were constipation, pruritus, nausea and vomiting, myoclonus, sedation, respiratory depression, and delirium. Opioid rotation to manage side effects was also studied. For each side effect, we searched MEDLINE and the Cochrane Controlled Trials Register and identified 657 possible titles for inclusion. Of these, 67 studies met inclusion criteria for analysis. The lack of well-designed, randomized controlled trials and the heterogeneity of populations and study designs made the drawing of firm conclusions difficult and precluded performance of meta-analysis. The type, strength, and consistency of evidence for available interventions to manage opioid side effects vary from strong (eg, on the use of naloxone to reverse respiratory depression or constipation) to weak (eg, changing from the oral to epidural route of morphine administration to manage sedation). Well-designed trials in the specified populations are required to furnish clinicians with secure evidence on managing opioid side effects successfully.

Neuraxial opioid-induced pruritus: a review

When intrathecal and epidural opioids are administered, pruritus occurs as an unwanted and troublesome side effect. The reported incidence varies between 30% and 100%. The exact mechanisms of neuraxial opioid-induced pruritus remain unclear. Postulated mechanisms include the presence of an "itch center" in the central nervous system, medullary dorsal horn activation, and antagonism of inhibitory transmitters. The treatment of intrathecal opioid-induced pruritus remains a challenge. Many pharmacological therapies, including antihistamines, 5-HT(3)-receptor antagonists, opiate-antagonists, propofol, nonsteroid antiinflammatory drugs, and droperidol, have been studied. In this review, we will summarize pathophysiological and pharmacological advances that will improve understanding and ultimately the management of this troublesome problem.

Prophylactic ondansetron reduces the incidence of intrathecal fentanyl-induced pruritus

We investigated the effectiveness of prophylactic IV ondansetron in preventing intrathecal fentanyl-induced pruritus. One-hundred-fifty ASA status I-II patients undergoing spinal anesthesia with 7-10 mg of hyperbaric bupivacaine and 25 micro g of fentanyl were randomized to receive ondansetron 8 mg IV or normal saline IV before the commencement of spinal anesthesia. Evaluations were performed every 15 min in the first hour after the injection of study drugs and at 1, 2, 3, 4, 5, and 6 h after the administration of the study drug. Statistical analysis was performed by using chi(2) tests and Student's t-test, as appropriate. The incidence of pruritus was significantly more frequent in the placebo group compared with the ondansetron group (68% versus 39%) (P = 0.001). Time to pruritus was similar in both groups (placebo group, 55 +/- 32 min versus ondansetron group, 50 +/- 31 min). Duration of pruritus was also similar in both groups (placebo group, 98 +/- 60 min versus ondansetron group, 103 +/- 58 min). Ondansetron prophylaxis significantly reduced the incidence of intrathecal fentanyl-induced pruritus in patients undergoing surgery under bupivacaine spinal anesthesia.

IMPLICATIONS

Pruritus is a commonly reported side effect after intrathecal fentanyl administration during spinal anesthesia. This study was performed in a prospective, randomized, double-blinded, placebo-controlled manner to investigate the efficacy of prophylactic IV ondansetron in the prevention of pruritus after intrathecal fentanyl administration during spinal anesthesia. The incidence of pruritus was significantly more frequent in the placebo group compared with the ondansetron group (68% versus 39%) (P = 0.001).

Continuous epidural, not intravenous, droperidol inhibits pruritus, nausea, and vomiting during epidural morphine analgesia

PURPOSE

To investigate whether continuous epidural droperidol and intravenous (IV) intraoperative droperidol inhibit pruritus and postoperative nausea and vomiting (PONV) during epidural morphine analgesia.

DESIGN

Randomized, double-blinded, controlled study.

SETTING

Metropolitan cancer center.

PATIENTS

120 ASA physical status I and II patients undergoing thoracic or abdominal surgery with general anesthesia combined with epidural anesthesia.

INTERVENTIONS

Patients received an intraoperative epidural injection of 2 mg morphine hydrochloride, followed postoperatively by a continuous epidural infusion of morphine hydrochloride 4 mg/day for 4 days. Patients were randomly allocated to four groups: Group A = control group, Group B = intraoperative single IV injection of droperidol (2.5 mg), Group C = postoperative continuous epidural droperidol infusion (2.5 mg/day), and Group D = intraoperative IV injection of droperidol (2.5 mg) and postoperative continuous epidural droperidol infusion (2.5 mg/day).

MEASUREMENTS AND MAIN RESULTS

The frequency and severity of pruritus and PONV in each group were evaluated during the postoperative period. Continuous epidural infusion of droperidol significantly reduced the frequency and severity of pruritus and PONV induced by epidural morphine without causing significant side effects. Intraoperative single IV injection of droperidol was effective for PONV (p < 0.05) but not for pruritus.

CONCLUSION

Postoperative epidural droperidol infusion significantly decreased both the frequency and severity of pruritus and PONV during postoperative continuous epidural morphine analgesia. IV intraoperative droperidol significantly reduced the frequency and the severity of PONV but not pruritus.

Ondansetron: a selective 5-HT(3) receptor antagonist and its applications in CNS-related disorders

Ondansetron is a selective 5-hydroxytryptamine(3) (5-HT(3)) receptor antagonist that has been introduced to clinical practice as an antiemetic for cancer treatment-induced and anesthesia-related nausea and vomiting. Its use under these circumstances is both prophylactic and therapeutic. It has a superior efficacy, safety and pharmacoeconomic profile compared with other groups of antiemetics, namely antidopaminergics, antihistamines and anticholinergics. However, its place in the management of anticipatory and delayed vomiting in cancer treatment and as a rescue antiemetic in surgical patients needs to be further explored. Furthermore, recent animal and human research also reflects its possible novel application in the treatment of other disease states, such as alcoholism, cocaine addiction, opioid withdrawal syndrome, anxiety disorders, gastrointestinal motility disorders, Tourette's syndrome and pruritus. This review revisits the widespread physiological and pathological effects of 5-HT and discusses both the basic science literature and the clinical developments responsible for the conventional and novel uses of ondansetron. In addition, new discoveries relating to the effects of ondansetron on other receptors/channels and their possible therapeutic applications are presented.

Understanding pruritus in systemic disease

Many pruritic conditions do not originate in the skin, but are the result of systemic abnormality. Among the diseases that can cause pruritus are renal insufficiency, cholestasis, Hodgkin's lymphoma, polycythemia vera, solid tumors, and many others. Other pruritic conditions appear to be iatrogenic; opioid-induced pruritus may be the most important in palliative medicine. Successful treatment of the underlying condition usually relieves itch. But, with time, many diseases progress and treatment of the cause will be impossible. Topical treatments may be of limited value. Strategies involving systemic treatments include use of antidepressants, oral opioid antagonists, or cholestyramine. There is no one cure for all pruritic symptoms. Better understanding of mechanisms of pruritus may help develop better treatments.