An update on analgesics

A Novel Ophthalmic Solution Containing Glicopro® Complex for the Treatment of Patients with Dry Eye Disease: Results from a Pilot Study

(1) Background: Dry eye disease (DED) is a multifactorial ocular surface disease characterized by an imbalance in ocular surface homeostasis, and tear substitutes constitute the first line of treatment. The present study aimed to evaluate the changes in the signs and symptoms of patients with DED treated with a novel tear substitute containing the GlicoPro® complex. (2) Methods: Patients with DED not successfully responding to other tear substitutes were enrolled and treated with a novel ophthalmic solution (two drops four times daily). Patients were examined before starting the study treatment (T0) and after 30 (T1) and 60 (T2) days of treatment by means of Keratograph for the evaluation of the following: (i) tear meniscus height (TMH); (ii) noninvasive Keratograph break-up time (NIKBUT); (iii) bulbar redness; and (iv) infrared meibography. The SANDE questionnaire was administered to assess ocular discomfort symptoms. Analysis of the tear content of proenkephalin and Met/Leu-enkephalin was also performed. (3) Results: At T2, a significant improvement in NIKBUT first, average, and class, TMH, and SANDE score was found. The tear content of proenkephalins was significantly higher at T1, whereas processed active Met/Leu-enkephalins increased at both T1 and T2. (4) Conclusions: Our novel tear substitute based on GlicoPro® resulted in a significant improvement in ocular discomfort symptoms, tear volume, and stability in the patients treated. The increase in active peptides processed in tears may represent the pathophysiological substrate underlying this finding.

The prevalence of self-medication and its associated factors among college students: Cross-sectional study from Saudi Arabia

Background

Self-medication with OTC or prescription drugs is widespread, may impair health, and leads to microbial resistance. Self-medication treats symptoms without a prescription. Self-medication is common among students across disciplines. Thus, this study evaluates medical and non-medical students' self-medication prevalence, knowledge, and variables.

Methods

352 people completed a verified 25-item online questionnaire from September 5 to November 17, 2021. Self-medication and demographic characteristics such as gender, professional college, and family income were examined using a chi-square test of independence.

Results

210 (59.6 %) participants were from the College of Medicine, and 142 (40.34 %) were from other professional health colleges. Health professional students self-medicated 55.9 %. This research found substantial connections between self-medication knowledge, gender, and family income. With a p-value of 0.0001, 32 % of women agreed that self-medication is safe, compared to 15.8 % of men. Female students were more likely than boys (61.9 % vs 38.1 %, p-value = 0.0291) to self-medicate as their initial therapy. Family income was also related to self-medication; 69.6 % of low-income pupils self-medicated to reduce doctor visits, p-value = 0.0477.

Conclusion

Students of all majors self-medicate. Medical students were more informed about generic drug safety and administration. There were substantial unfavorable sentiments regarding self-medication, highlighting the need for educational health activities to raise student understanding of its risks.

Comparison of Online Patient Reviews and National Pharmacovigilance Data for Tramadol-Related Adverse Events: Comparative Observational Study

BACKGROUND

Tramadol is known to cause fewer adverse events (AEs) than other opioids. However, recent research has raised concerns about various safety issues.

OBJECTIVE

We aimed to explore these new AEs related to tramadol using social media and conventional pharmacovigilance data.

METHODS

This study used 2 data sets, 1 from patients' drug reviews on WebMD (January 2007 to January 2021) and 1 from the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS; January 2016 to December 2020). We analyzed 2062 and 29,350 patient reports from WebMD and FAERS, respectively. Patient posts on WebMD were manually assigned the preferred terms of the Medical Dictionary for Regulatory Activities. To analyze AEs from FAERS, a disproportionality analysis was performed with 3 measures: proportional reporting ratio, reporting odds ratio, and information component.

RESULTS

From the 869 AEs reported, we identified 125 new signals related to tramadol use not listed on the drug label that satisfied all 3 signal detection criteria. In addition, 20 serious AEs were selected from new signals. Among new serious AEs, vascular disorders had the largest signal detection criteria value. Based on the disproportionality analysis and patients' symptom descriptions, tramadol-induced pain might also be an unexpected AE.

CONCLUSIONS

This study detected several novel signals related to tramadol use, suggesting newly identified possible AEs. Additionally, this study indicates that unexpected AEs can be detected using social media analysis alongside traditional pharmacovigilance data.

New Perspectives in the Pathophysiology and Treatment of Pain in Patients with Dry Eye Disease

Ocular discomfort and eye pain are frequently reported by patients with dry eye disease (DED), and their management remains a real therapeutic challenge for the Ophthalmologist. In DED patients, injury at the level of each structure of the ocular surface can determine variable symptoms, ranging from mild ocular discomfort up to an intolerable pain evoked by innocuous stimuli. In refractory cases, the persistence of this harmful signal is able to evoke a mechanism of maladaptive plasticity of the nervous system that leads to increased pain responsiveness. Peripheral and, subsequently, central sensitization cause nociceptor hyperexcitability and persistent pain perception that can culminate in the paradoxical situation of perceiving eye pain even in the absence of ocular surface abnormalities. Effective therapeutic strategies of these cases are challenging, and new options are desirable. Recently, a theoretical novel therapeutic approach concerns enkephalins thanks to the evidence that eye pain sensations are modulated by endogenous opioid peptides (enkephalins, endorphins and dynorphins). In this regard, new topical agents open up a new theoretical scenario in the treatment of ocular discomfort and eye pain in the setting of DED, such as, for example, a multimolecular complex based on proteins and glycosaminoglycans also containing opiorphin that may assist the physiological pain-relieving mechanism of the eye.

Repeated Administration of Clinical Doses of Tramadol and Tapentadol Causes Hepato- and Nephrotoxic Effects in Wistar Rats

Tramadol and tapentadol are fully synthetic and extensively used analgesic opioids, presenting enhanced therapeutic and safety profiles as compared with their peers. However, reports of adverse reactions, intoxications and fatalities have been increasing. Information regarding the molecular, biochemical, and histological alterations underlying their toxicological potential is missing, particularly for tapentadol, owing to its more recent market authorization. Considering the paramount importance of liver and kidney for the metabolism and excretion of both opioids, these organs are especially susceptible to toxicological damage. In the present study, we aimed to characterize the putative hepatic and renal deleterious effects of repeated exposure to therapeutic doses of tramadol and tapentadol, using an in vivo animal model. Male Wistar rats were randomly divided into six experimental groups, composed of six animals each, which received daily single intraperitoneal injections of 10, 25 or 50 mg/kg tramadol or tapentadol (a low, standard analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively). An additional control group was injected with normal saline. Following 14 consecutive days of administration, serum, urine and liver and kidney tissue samples were processed for biochemical, metabolic and histological analysis. Repeated administration of therapeutic doses of both opioids led to: (i) increased lipid and protein oxidation in liver and kidney, as well as to decreased total liver antioxidant capacity; (ii) decreased serum albumin, urea, butyrylcholinesterase and complement C3 and C4 levels, denoting liver synthesis impairment; (iii) elevated serum activity of liver enzymes, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and γ-glutamyl transpeptidase, as well as lipid profile alterations, also reflecting hepatobiliary commitment; (iv) derangement of iron metabolism, as shown through increases in serum iron, ferritin, haptoglobin and heme oxygenase-1 levels. In turn, elevated serum cystatin C, decreased urine creatinine output and increased urine microalbumin levels were detected upon exposure to tapentadol only, while increased serum amylase and urine N-acetyl-β-D-glucosaminidase activities were observed for both opioids. Collectively, these results are compatible with kidney injury. Changes were also found in the expression levels of liver- and kidney-specific toxicity biomarker genes, upon exposure to tramadol and tapentadol, correlating well with alterations in lipid profile, iron metabolism and glomerular and tubular function. Histopathological analysis evidenced sinusoidal dilatation, microsteatosis, mononuclear cell infiltrates, glomerular and tubular disorganization, and increased Bowman's spaces. Although some findings are more pronounced upon tapentadol exposure, our study shows that, when compared with acute exposure, prolonged administration of both opioids smooths the differences between their toxicological effects, and that these occur at lower doses within the therapeutic range.

ADME and toxicity considerations for tramadol: from basic research to clinical implications

INTRODUCTION

Tramadol is widely being used in chronic pain management for improving patients' life quality and reducing trauma. Although it is listed in several medicinal guidelines, its use is controversial because of the conflicting results obtained in pharmacokinetic/pharmacodynamic studies. This multi-receptor drug acts as µ₁ opioid receptor agonist, monoamine reuptake inhibitor, and inhibitor of ligand-gated ion channels and some special protein-coupled receptors.

AREAS COVERED

This review provides a comprehensive view on the pharmacokinetic, pharmacodynamic, and toxicity of tramadol with a deep look on its side effects, biochemical and pathological changes, and possible drug interactions. In addition, the main ways of tramadol poisoning management describe according to in vivo and clinical trial studies.

EXPERT OPINION

Given the broad spectrum of targets, increasing the cases of overdoses and toxicity, and probable drugs interaction, it is necessary to take another look at the pharmacology of tramadol. Regarding the adverse effects of tramadol on different tissues, especially the nervous system and liver tissue, more attentions to tramadol metabolites, their interaction with other drugs, and active agents seem critical. Seizure as the most cited effect of tramadol and its destructive effects on tissues would alleviate by co-administration with drugs with antioxidant properties.

Chronic use of tramadol after acute pain episode: cohort study

OBJECTIVE

To determine the risk of prolonged opioid use in patients receiving tramadol compared with other short acting opioids.

DESIGN

Observational study of administrative claims data.

SETTING

United States commercial and Medicare Advantage insurance claims (OptumLabs Data Warehouse) January 1, 2009 through June 30, 2018.

PARTICIPANTS

Opioid-naive patients undergoing elective surgery.

MAIN OUTCOME MEASURE

Risk of persistent opioid use after discharge for patients treated with tramadol alone compared with other short acting opioids, using three commonly used definitions of prolonged opioid use from the literature: additional opioid use (defined as at least one opioid fill 90-180 days after surgery); persistent opioid use (any span of opioid use starting in the 180 days after surgery and lasting ≥90 days); and CONSORT definition (an opioid use episode starting in the 180 days after surgery that spans ≥90 days and includes either ≥10 opioid fills or ≥120 days' supply of opioids).

RESULTS

Of 444 764 patients who met the inclusion criteria, 357 884 filled a discharge prescription for one or more opioids associated with one of 20 included operations. The most commonly prescribed post-surgery opioid was hydrocodone (53.0% of those filling a single opioid), followed by short acting oxycodone (37.5%) and tramadol (4.0%). The unadjusted risk of prolonged opioid use after surgery was 7.1% (n=31 431) with additional opioid use, 1.0% (n=4457) with persistent opioid use, and 0.5% (n=2027) meeting the CONSORT definition. Receipt of tramadol alone was associated with a 6% increase in the risk of additional opioid use relative to people receiving other short acting opioids (incidence rate ratio 95% confidence interval 1.00 to 1.13; risk difference 0.5 percentage points; P=0.049), 47% increase in the adjusted risk of persistent opioid use (1.25 to 1.69; 0.5 percentage points; P<0.001), and 41% increase in the adjusted risk of a CONSORT chronic opioid use episode (1.08 to 1.75; 0.2 percentage points; P=0.013).

CONCLUSIONS

People receiving tramadol alone after surgery had similar to somewhat higher risks of prolonged opioid use compared with those receiving other short acting opioids. Federal governing bodies should consider reclassifying tramadol, and providers should use as much caution when prescribing tramadol in the setting of acute pain as for other short acting opioids.

Patterns of regional variation of opioid prescribing in primary care in England: a retrospective observational study

BACKGROUND

Opioids are a widely prescribed class of drug with potentially harmful short-term and long-term side effects. There are concerns about the amounts of these drugs being prescribed in England given that they are increasingly considered ineffective in the context of long-term non-cancer pain, which is one of the major reasons for their prescription.

AIM

To assess the amount and type of opioids prescribed in primary care in England, and patterns of regional variation in prescribing.

DESIGN AND SETTING

Retrospective observational study using publicly available government data from various sources pertaining to opioids prescribed in primary practice in England and Indices of Social Deprivation.

METHOD

Official government data were analysed for opioid prescriptions from August 2010 to February 2014. The total amount of opioid prescribed was calculated and standardised to allow for geographical comparisons.

RESULTS

The total amount of opioid prescribed, in equivalent milligrams of morphine, increased (r = 0.48) over the study period. More opioids were prescribed in the north than in the south of England (r = 0.66, P<0.0001), and more opioids were prescribed in areas of greater social deprivation (r = 0.56, P<0.0001).

CONCLUSION

Long-term opioid prescribing is increasing despite poor efficacy for non-cancer pain, potential harm, and incompatibility with best practice. Questions of equality of care arise from higher prescription rates in the north of England and in areas of greater social deprivation. A national registry of patients with high opioid use would improve patient safety for this high-risk demographic, as well as provide more focused epidemiological data regarding patterns of prescribing.

The influence of AMN082, metabotropic glutamate receptor 7 (mGlu7) allosteric agonist on the acute and chronic antinociceptive effects of morphine in the tail-immersion test in mice: Comparison with mGlu5 and mGlu2/3 ligands

Preclinical data indicated that the metabotropic glutamate receptors 5 (mGlu5) and glutamate receptors 2/3 (mGlu2/3) are involved in modulating morphine antinociception. However, little is known about the role of metabotropic glutamate receptors 7 (mGlu7) in this phenomenon. We compared the effects of AMN082 (0.1, 1 or 5mg/kg, ip), a selective mGlu7 allosteric agonist, LY354740 (0.1, 1 or 5mg/kg, ip), an mGlu2/3 agonist and MTEP (0.1, 1 or 5mg/kg, ip), a selective mGlu5 antagonist, on the acute antinociceptive effect of morphine (5mg/kg, sc) and also on the development and expression of tolerance to morphine analgesia in the tail-immersion test in mice. To determine the role of mGlu7 in morphine tolerance, and the association of the mGlu7 effect with the N-methyl-d-aspartate (NMDA) receptors regulation, we used MMPIP (10mg/kg, ip), a selective mGlu7 antagonist and MK-801, a NMDA antagonist. Herein, the acute administration of AMN082, MTEP or LY354740 alone failed to evoked antinociception, and did not affect morphine (5mg/kg, sc) antinociception. However, these ligands inhibited the development of morphine tolerance, and we indicated that MMPIP reversed the inhibitory effect of AMN082. When given together, the non-effective doses of AMN082 and MK-801 did not alter the tolerance to morphine. Thus, mGlu7, similarly to mGlu2/3 and mGlu5, are involved in the development of tolerance to the antinociceptive effects of morphine, but not in the acute morphine antinociception. Furthermore, while mGlu7 are engaged in the development of morphine tolerance, no interaction exists between mGlu7 and NMDA receptors in this phenomenon.

Acute administration of tramadol and tapentadol at effective analgesic and maximum tolerated doses causes hepato- and nephrotoxic effects in Wistar rats

Tramadol and tapentadol are two atypical synthetic opioid analgesics, with monoamine reuptake inhibition properties. Mainly aimed at the treatment of moderate to severe pain, these drugs are extensively prescribed for multiple clinical applications. Along with the increase in their use, there has been an increment in their abuse, and consequently in the reported number of adverse reactions and intoxications. However, little is known about their mechanisms of toxicity. In this study, we have analyzed the in vivo toxicological effects in liver and kidney resulting from an acute exposure of a rodent animal model to both opioids. Male Wistar rats were intraperitoneally administered with 10, 25 and 50mg/kg tramadol and tapentadol, corresponding to a low, effective analgesic dose, an intermediate dose and the maximum recommended daily dose, respectively, for 24h. Toxicological effects were assessed in terms of oxidative stress, biochemical and metabolic parameters and histopathology, using serum and urine samples, liver and kidney homogenates and tissue specimens. The acute exposure to tapentadol caused a dose-dependent increase in protein oxidation in liver and kidney. Additionally, exposure to both opioids led to hepatic commitment, as shown by increased serum lipid levels, decreased urea concentration, increased alanine aminotransferase and decreased butyrylcholinesterase activities. It also led to renal impairment, as reflected by proteinuria and decreased glomerular filtration rate. Histopathological findings included sinusoidal dilatation, microsteatosis, vacuolization, cell infiltrates and cell degeneration, indicating metabolic changes, inflammation and cell damage. In conclusion, a single effective analgesic dose or the maximum recommended daily dose of both opioids leads to hepatotoxicity and nephrotoxicity, with tapentadol inducing comparatively more toxicity. Whether these effects reflect risks during the therapeutic use or human overdoses requires focused attention by the medical community.

Fentanyl-induced hyperalgesia in acute pain management

There are safety concerns with the use of fentanyl, including respiratory depression, nausea, constipation, and possibly opioid-induced hyperalgesia (OIH). The purpose of this review is to evaluate the occurrence and significance of opioid-induced hyperalgesia (OIH) after acute fentanyl exposure. A literature search was conducted from October 1995 through January 2015 using MEDLINE, Embase, and Scopus with the terms hyperalgesia, fentanyl, pronociceptive, acute tolerance, and acute. Published articles evaluating the adverse effects of fentanyl during acute pain management (≤96 hours) in humans were included. Opioid-induced hyperalgesia is a phenomenon defined by increasing pain after opioid exposure with the worsening of pain occurring when opioid doses are increased. Hyperalgesia has been described following remifentanil and morphine use, but the question remains about the associated risk with acute fentanyl exposure. Six randomized, controlled trials evaluating the effect of fentanyl on pain in the acute setting have been conducted. Two trials oppose whereas four trials support the occurrence of fentanyl-induced hyperalgesia. The data on OIH after acute fentanyl exposure are limited and conflicting. Hyperalgesia should be considered in patients with uncontrolled pain despite escalating fentanyl doses, since the possibility of fentanyl-induced OIH exists in the acute setting. Well-designed trials are needed to determine the clinical significance of this phenomenon.

Comparison of tapentadol with tramadol for analgesia after cardiac surgery

Background:

Tapentadol is a relatively new analgesic. We decided to compare it with tramadol for their various effects after cardiac surgery.

Setting:

A study in a tertiary care hospital.

Materials and Methods:

Sixty adults undergoing cardiac surgery were divided into 2 groups of 30 each by computerized random allotment (Group X = tapentadol 50 mg oral and Group Y = tramadol 100 mg oral). Informed Consent and Institutional Ethics Committee approval were obtained. The patients were given either drug X or drug Y after extubation in this single blinded study, wherein the data collectors and analyzers were blinded to the study. All patients received oral paracetamol qds and either drug X or drug Y tds. The pain score was noted on a Visual Analog Scale before each drug dose, 3 h later and on coughing. Heart rate, respiratory rate, and blood pressure were recorded before the drug dose and 3 h later. Postoperative nausea or vomiting (PONV), temperature, and modified Glasgow Coma Scale readings were recorded. The above readings were obtained for 6 doses (up to 48 h after extubation).

Statistics:

t-test, Pearson Chi-square test, Fisher exact test, and Mantel–Haenszel test were used for statistics.

Results:

Tapentadol group patients had significantly better analgesia 3 h after the drug and “on coughing” than tramadol group. The difference in their effects on blood creatinine levels, temperature, hemodynamics, oxygen saturation, and respiratory rate were not clinically significant. Tapentadol produced lesser drowsiness and lesser vomiting than tramadol.

Conclusions:

Tapentadol, due to its norepinephrine reuptake inhibition properties, in addition to mu agonist, is a better analgesic than tramadol and has lesser PONV.

Effects of parecoxib on analgesia benefit and blood loss following open prostatectomy: a multicentre randomized trial

Background

This multi-centre, prospective, randomized, double-blind, placebo-controlled study was designed to test the hypotheses that parecoxib improves patients’ postoperative analgesia without increasing surgical blood loss following radical open prostatectomy.

Methods

105 patients (64 ± 7 years old) were randomized to receive either parecoxib or placebo with concurrent morphine patient controlled analgesia. Cumulative opioid consumption (primary objective) and the overall benefit of analgesia score (OBAS), the modified brief pain inventory short form (m-BPI-sf), the opioid-related symptom distress scale (OR-SDS), and perioperative blood loss (secondary objectives) were assessed.

Results

In each group 48 patients received the study medication for 48 hours postoperatively. Parecoxib significantly reduced cumulative opioid consumption by 24% (43 ± 24.1 mg versus 57 ± 28 mg, mean ± SD, p=0.02), translating into improved benefit of analgesia (OBAS: 2(0/4) versus 3(1/5.25), p=0.01), pain severity (m-BPI-sf: 1(1/2) versus 2(2/3), p < 0.01) and pain interference (m-BPI-sf: 1(0/1) versus 1(1/3), p=0.001), as well as reduced opioid-related side effects (OR-SDS score: 0.3(0.075/0.51) versus 0.4(0.2/0.83), p=0.03). Blood loss was significantly higher at 24 hours following surgery in the parecoxib group (4.3 g⋅dL⁻¹ (3.6/4.9) versus (3.2 g⋅dL⁻¹ (2.4/4.95), p=0.02).

Conclusions

Following major abdominal surgery, parecoxib significantly improves patients’ perceived analgesia. Parecoxib may however increase perioperative blood loss. Further trials are needed to evaluate the effects of selective cyclooxygenase-2 inhibitors on blood loss.

Trial registration

ClinicalTrials.gov Identifier: NCT00346268

Differential scanning calorimetry approach to investigate the transfer of the multitarget opioid analgesic LP1 to biomembrane model

An emerging approach in pain management is the use of multitarget opioid ligands, owing an improved analgesic effect coupled to a reduced incidence of side effects. With a mu opioid receptor agonist/delta opioid receptor antagonist profile, the benzomorphan-based compound LP1 belongs to multitarget ligands class. Previous in vivo investigations showed that LP1 - subcutaneously administered as oxalate salt - was an antinociceptive agent as potent as morphine with a low tolerance-inducing capability. Because the renal toxicity of oxalate is known, an alternative approach allowing the administration of LP1 freebase could be more biocompatible. In this study the interaction of LP1 freebase and LP1 oxalate salt with multilamellar vesicles, as membrane model, was evaluated using differential scanning calorimetry technique. Despite the good membrane interaction showed by LP1 freebase, it was not capable to diffuse in the aqueous medium and to be uptaken by multilamellar vesicles. On the other hand, LP1 freebase possessed a good transfer profile by a liposomal carrier to a biomembrane model. Considering our findings and the need of safe formulations, studies for the development of a suitable carrier for a systemic administration of LP1 freebase are in progress.

NSAIDs and opioids in management of fragility fractures

Fragility fractures and their care are a major burden on individuals, health systems, and social care systems in industrialized countries. Fragility fracture can lead to long lasting painful and disabling condition. The level of pain is a major determinant for the outcome of any treatment of these fractures regardless of its location. The treatment of pain in patient with fragility fracture is rarely considered a priority in the care pathway.

The multitarget opioid ligand LP1's effects in persistent pain and in primary cell neuronal cultures

Persistent pain states, such as those caused by nerve injury or inflammation, are associated with altered sensations, allodynia and hyperalgesia, that are resistant to traditional analgesics. A contribution to development and maintenance in altered pain perception comes from nociceptive processing and descending modulation from supraspinal sites. A multitarget ligand seems to be useful for pain relief with a decreased risk of adverse events and a considerable analgesic efficacy. The multitarget MOR agonist-DOR antagonist LP1, (3-[(2R,6R,11R)-8-hydroxy-6,11-dimethyl-1,4,5,6-tetrahydro-2,6-methano-3-benazocin-3(2H)-yl]-N-phenylpropanamide, is a central acting antinociceptive agent with low potential to induce tolerance. LP1 was tested in models of neuropathic pain - induced by chronic constriction injury (CCI) of the left sciatic nerve - and inflammatory pain - produced by intraplantar injection of carrageenan. In CCI rats, subcutaneous (s.c.) LP1 (3 mg/kg) showed a significant antiallodynic effect, measured with von Frey filaments, and antihyperalgesic effect, evoked in response to a radiant heat stimulus with plantar test. Analogously, LP1 significantly reduced allodynic and hyperalgesic thresholds in a model of inflammatory pain induced by carrageenan. To evaluate the contribution of opioid receptor subtypes in LP1 antinociceptive effects, the multitarget LP1 profile was assessed using selective opioid antagonists. Moreover, functional electrophysiological in vitro assays, using primary cortical and spinal cord networks, allowed to define the "pharmacological fingerprint" of LP1. The EC₅₀ values in this functional screening seem to confirm LP1 as a potent opioid ligand (EC₅₀ = 0.35 fM and EC₅₀ = 44 pM in spinal cord and frontal cortex, respectively). Using a NeuroProof data-base of well characterised reference compounds, a similarity profile of LP1 to opioid and non-opioid drugs involved in pain modulation was detected. Our studies seem to support that multitarget ligand approach should be useful for persistent pain conditions in which mechanical allodynia and thermal hyperalgesia are significant components of the nociceptive response.

Antinociceptive effects of two deltorphins analogs in the tail-immersion test in rats

The antinociceptive effects of analogs of deltorphins: cyclo(Nδ,Nδ-carbonyl-D-Orn2, Orn4)deltorphin (DEL-6) and deltorphin II N-(ureidoethyl)amide (DK-4) after intracerebroventricular (i.c.v.) administration were investigated in the tail-immersion test in rats. Morphine, the most commonly used μ-opioid receptors (MOR) agonist, was employed as a reference compound. The contribution of the MOR, δ-(DOR) and κ-opioid receptors (KOR) in antinociceptive effects of the deltorphins analogs was studies using selective antagonists of these receptors. The results indicated that DK-4 (5, 10 and 20 nmol) and DEL-6 (5, 10 and 20 nmol) were the most effective in alleviating thermal pain at the dose of 20 nmol. The antinociceptive potency of DEL-6 at the dose of 20 nmol was approximately equal but DK-4 at the dose of 20 nmol was less effective than morphine at the dose of 13 nmol. DOR antagonist - naltrindole (NTI, 5 nmol) very strongly and, to the lower extent MOR antagonist - β-funaltrexamine (β-FNA, 5 nmol), inhibited antinociceptive effect of DK-4 (20 nmol). In turn, β-FNA was more potent than NTI in inhibition of the antinociceptive effects of DEL-6. Co-administration of DEL-6 and morphine at doses of 5 nmol, which do not produce measurable antinociception, generated additive antinociceptive effect. Chronic intraperitoneal (i.p.) injection of morphine (9 days) displayed a marked analgesic tolerance to the challenge dose of morphine and a slight cross-tolerance to challenge doses of DEL-6 and DK-4, given i.c.v. These findings indicate that the new deltorphin analogs recruit DOR and MOR to attenuate the nociceptive response to acute thermal stimuli.

[Undesired side effects of tapentadol in comparison to oxycodone. A meta-analysis of randomized controlled comparative studies]

OBJECTIVE

Tapentadol is a new centrally acting analgesic with a dual mode of action as an agonist of the µ-opioid receptor and as a norepinephrine reuptake inhibitor. The aim of the present study was to evaluate the results from randomized controlled trials investigating the relative amount of adverse effects using tapentadol or oxycodone for the treatment of pain.

METHODS

A quantitative systematic review was carried out according to the PRISMA recommendations on randomized controlled trials comparing tapentadol and oxycodone in pain treatment. The incidences of typical adverse side effects of opioid-based analgesic therapy (e.g. nausea, vomiting, obstipation or pruritus) were extracted and the pooled relative risks (RR) with corresponding 95% confidence intervals (CI) were calculated.

RESULTS

A total of 9 trials involving 7,948 patients were included and of these 2,810 patients were treated with oxycodone and 5,138 were treated with tapentadol in equivalent analgesic dosages as documented by an equivalent analgesic effect. The risk of typical opioid-based adverse effects, such as nausea (RR 0.61; 95% CI 0.57-0.66), vomiting (RR 0.50, 95% CI: 0.41-0.60), obstipation (RR 0.47, 95%-CI 0.40-0.56), dizziness (RR 0.86, 95% CI 0.78-0.95), somnolence (RR 0.76, 95% CI 0.67-0.86) and pruritus (RR 0.46, 95% CI 0.37-0.58) was reduced when tapentadol was used for analgesic treatment. These adverse effects were investigated in all nine trials. The risk for dryness of the mouth (6 trials, 6,218 patients, RR 1.79, 95% CI 1.40-2.29) and dyspepsia (1 trial, 646 patients, RR 2.75, 95% CI 1.09-6.94) was increased when tapentadol was used instead of oxycodone. There were no significant differences in the relative risk for any other investigated adverse effect such as dysentery, headache or fatigue.

CONCLUSION

The results show that using tapentadol significantly reduces the risk of the typical opioid-based adverse effects compared with oxycodone while providing equivalent analgesic treatment.

Tapentadol extended-release: a recent addition to our analgesic armamentarium

SUMMARY In the never-ending process of providing therapy with diminishing side effects, pain medicine stands out as an important area of work. Ever since the introduction of opioids and elucidation of their mechanisms pharmaceutical researchers have sought a compound that provides long-term analgesia with none of the side effects that include somnolence, lethargy, tolerance, addiction, gastrointestinal symptoms and so on. This article reviews one of the latest improvements in analgesia, the formulation of tapentadol as an extended-release medication. Despite not claiming to have eliminated all the negatives of narcotics tapentadol extended-release seems to have made inroads to that goal.

Development of 5-Substituted N-Methylmorphinan-6-ones as Potent Opioid Analgesics with Improved Side-Effect Profile

One of the most important functions of the opioid system is the control of pain. Among the three main opioid receptor classes (μ, δ, κ), the μ (MOR) is the main type targeted for pharmacotherapy of pain. Opioid analgesics such as morphine, oxycodone and fentanyl are agonists at the MOR and are the mainstay for the treatment of moderate-to-severe pain. However, adverse effects related to opioid use are severe and often lead to early discontinuation and inadequate analgesia. The development of more effective and safer medications for the management of pain still remains a major direction in pharmaceutical research. Chemical approaches towards the identification of novel MOR analgesics with reduced side effects include structural modifications of 14-alkoxy-N-methylmorphinan-6-ones in key positions that are important for binding, selectivity, potency, and efficacy at opioid receptors. This paper describes a representative strategy to improve the therapeutic usefulness of opioid analgesics from the morphinan class of drugs by targeting position 5. The focus is on chemical and biological studies and structure-activity relationships of this series of ligands. We report on 14-alkoxymorphinan-6-ones having a methyl and benzyl group at position 5 as strong opioid antinociceptive agents with reduced propensity to cause undesired effects compared to morphine although interacting selectively with MORs.

Antinociceptive profile of LP1, a non-peptide multitarget opioid ligand

AIMS

Opioid drugs are the principal treatment option for moderate to severe pain and exert their biological effects through interactions with opioid receptors that are widely distributed throughout the CNS and peripheral tissues. Ligands capable of simultaneously targeting different receptors could be successful candidates for the treatment of chronic pain. Enhanced antinociception coupled with a low incidence of side effects has been demonstrated for ligands possessing mixed mu-opioid receptor (MOR) and delta-opioid receptor (DOR) activity. We previously reported that 3-[(2R,6R,11R)-8-hydroxy-6,11-dimethyl-1,4,5,6-tetrahydro-2,6-methano-3-benzazocin-3(2H)-yl]-N-phenylpropanamide (LP1) acted as a MOR-DOR ligand in in vitro functional assays and moreover this drug produced a valid antinociception that was longer lasting than that of morphine. The aim of this work was to determine whether the antinociceptive effect produced by LP1 was central or peripheral and to assess which opioid receptor subtypes are involved in its effects.

MAIN METHODS

We explored the effects of naloxone methiodide (NX-M), a quaternary opioid antagonist, administered either intracerebroventricularly (i.c.v.) or subcutaneously (s.c.), on LP1-mediated antinociception in male Sprague-Dawley rats. In addition, we administered s.c. selective antagonists for MOR, DOR and kappa-opioid receptor (KOR) to investigate the effects of LP1. To characterise this drug's DOR profile better, we also investigated the effects of LP1 on DPDPE, a selective DOR agonist.

KEY FINDINGS

Data obtained by tail flick test showed that LP1 induced predominantly MOR-mediated supraspinal antinociception and was able to counteract DPDPE analgesia.

SIGNIFICANCE

LP1, a multitarget opioid ligand, is a supraspinal acting antinociceptive agent that is useful for the treatment of chronic pain.

New formulations of local anaesthetics-part I

Part 1 comments on the types of local anaesthetics (LAs); it provides a better understanding of the mechanisms of action of LAs, and their pharmacokinetics and toxicity. It reviews the newer LAs such as levobupivacaine, ropivacaine, and articaine, and examines the newer structurally different LAs. The addition of adjuvants such as adrenaline, bicarbonate, clonidine, and corticosteroids is explored. Comment is made on the delivery of topical LAs via bioadhesive plasters and gels and controlled-release local anaesthetic matrices. Encapulation matrices such as liposomes, microemulsions, microspheres and nanospheres, hydrogels and liquid polymers are discussed as well. New innovations pertaining to LA formulations have indeed led to prolonged action and to novel delivery approaches.