Antinociception and the new COX inhibitors: research approaches and clinical perspectives

Anti-inflammatory, Analgesic, and Cytotoxic Effects of The Phytexponent: A Polyherbal Formulation

The Phytexponent is used to treat pain and inflammation in complementary and alternative medicine practices; however, empirical data supporting its pharmacological efficacy and safety is scanty, hence the present study. We used the carrageenan-induced paw oedema and the acetic acid-induced writhing techniques to determine the anti-inflammatory and analgesic efficacies, respectively, of the Phytexponent in Swiss albino mice models. The 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay technique was used to investigate the in vitro cytotoxic effects of the Phytexponent in the Vero E6 cell line. The Phytexponent exerted significant (P < .05) anti-inflammatory effects in the carrageenan-induced paw oedema mouse model in a dose- and time-dependent manner, with significantly higher efficacy at 250 mg/Kg BW, than indomethacin (4 mg/Kg BW), in the first, second, and third hour (P < .05). Besides, the Phytexponent significantly reduced the acetic acid-induced writhing frequency in mice (P < .05), in a dose-dependent manner, depicting its analgesic efficacy. Notably, the Phytexponent (at doses: 125 mg/Kg BW and 250 mg/Kg BW) exhibited significantly higher analgesic efficacy than the Indomethacin (P<.05). Moreover, the Phytexponent was not cytotoxic to Vero E6 cells (CC₅₀ >1000 µg/ml) compared to cyclophosphamide (CC₅₀ = 2.48 µg/ml). Thus, the Phytexponent has significant in vivo anti-inflammatory and analgesic efficacy in mice models and is not cytotoxic to Vero E6 cell line, depicting its therapeutic potential upon further empirical investigation.

Phytochemical profiling of bioactive compounds, anti-inflammatory and analgesic potentials of Habenaria digitata Lindl.: Molecular docking based synergistic effect of the identified compounds

ETHNOPHARMACOLOGICAL RELEVANCE

Members of Orchidaceae family has a long history in herbal and Chinese medicines. Members of this family are most commonly famous in the management of inflammation and analgesia in folk medicine. Habenaria digitata, an unexplored specie of Orchidaceae is found in North areas of Pakistan and is used by the local population for the management of analgesia and inflammation.

AIM OF THE STUDY

Based on the effective outcomes of the natural products as alternative therapies, we have evaluated Habenaria digitata for the management of analgesia and inflammation. The aim of the designed project is to provide a scientific basis of using this plant for the management of analgesia and inflammation.

MATERIALS AND METHODS

The H. digitata crude extract (Hd.Cr) and subfractions, i.e. n-hexane (Hd.Hex), chloroform (Hd.Chf), ethyl acetate (Hd.EtAc), n-butanol (Hd.Bt) and aqueous (Hd.Aq) were used. The GC-MS analysis was used for the identification of phytochemicals. The plants samples were subjected to cyclooxygenase (COX 2) and lipoxygenase (5-LOX) enzymes assays. The hot plate model, acetic acid induced writhing and formalin induced paw licking models were used for in-vivo analgesic studies. The in-vivo anti-inflammatory potential was determined with carrageenan induced paw edema test. Molecular docking studies of the identified compounds were carried out by using Molecular Operating Environment (MOE, 2016.08).

RESULTS

The GC-MS analysis confirmed sixty-five compounds in Hd.Cr. Among the fractions, Hd.Chf and Hd.EtAc displayed highest activities. The observed IC₅₀ values were 21.30 and 32.39 μg/ml against COX 2 while 14.42and 16.40 μg/ml for 5-LOX respectively. The in-vivo inflammatory and analgesic studies were pre-requisited with acute toxicity tests. In carrageenan induced inflammation, Hd.Chf excelled the standard drug aspirin by giving 62.92% inhibition of paw edema at 4^th h. Similarly, at highest concentration (75 mg/kg) of acetic acid induced analgesia, Hd.Chf was more potent than the standard drug. In formalin method, Hd.Chf exhibited 85.81% inhibition at phase-I and 74.15% at Phase-II. In hot plate model, Hd.Chf exhibited average reaction time of 10.90 at 15, 30, 45 and 60 min intervals. Docking studies supported our results and confirm the synergistic effects of phytochemicals.

CONCLUSIONS

Our experimental results concluded that H. digitata contains several bioactive compounds. These bioactive compounds synergistically have therapeutic efficacy for the management of inflammation and analgesia. We have confirmed both of these potentials from the in-vitro and in-vivo experiments. Moreover, it is also obvious that the chloroform and ethyl acetate fractions are rich in these bioactive compounds. Specifically, the Hd.Chf is observed to be more practical in all the tested models of analgesia and inflammation. Computed binding energies of the compounds revealed that all the compounds have synergistic effect to prevent analgesia and inflammation.

A review of dexketoprofen trometamol in acute pain

OBJECTIVE

Dexketoprofen trometamol is a modified non-selective COX inhibitor with a rapid onset of action that is available as both oral and parenteral formulations. The aim of this narrative review was to assess the efficacy and tolerability/safety of dexketoprofen trometamol in acute pain states using the best available published scientific evidence (randomized controlled clinical trials and systematic reviews/meta-analyses).

METHODS

Literature retrieval was performed via Medline, Embase and the Cochrane Library (from inception up to March 2017) using combinations of the terms "randomized controlled trials", "dexketoprofen", "celecoxib", "etoricoxib", "parecoxib" and "acute pain".

RESULTS

Single-dose dexketoprofen trometamol provides effective analgesia in the treatment of acute pain, such as postoperative pain (dental and non-dental surgery), renal colic, acute musculoskeletal disorders and dysmenorrhea, and reduces opioid consumption in the postoperative setting. It has a rapid onset of action (within 30 minutes) and is well tolerated during short-term treatment. Direct comparisons with COX-2 inhibitors are lacking; however, the efficacy and tolerability of single-dose dexketoprofen trometamol appears to be consistent with that seen with celecoxib, etoricoxib and parecoxib in the acute pain setting.

CONCLUSION

In conclusion, dexketoprofen trometamol appears to provide similar analgesic efficacy to COX-2 inhibitors when used to treat acute pain, has a rapid onset of action, is well tolerated, and has an opioid-sparing effect when used as part of a multimodal regimen in the acute pain setting.

Single dose oral ketoprofen or dexketoprofen for acute postoperative pain in adults

BACKGROUND

This review is an update of "Single dose oral ketoprofen and dexketoprofen for acute postoperative pain in adults" last updated in Issue 4, 2009. Ketoprofen is a non-selective nonsteroidal anti-inflammatory drug (NSAID) used to treat acute and chronic painful conditions. Dexketoprofen is the (S)-enantiomer, which is believed to confer analgesia. Theoretically dexketoprofen is expected to provide equivalent analgesia to ketoprofen at half the dose, with a consequent reduction in gastrointestinal adverse events. This review is one of a series on oral analgesics for acute postoperative pain. Individual reviews have been brought together in two overviews to provide information about the relative efficacy and harm of the different interventions.

OBJECTIVES

To assess the efficacy and safety of single dose oral ketoprofen and oral dexketoprofen compared with placebo for acute postoperative pain, using methods that permit comparison with other analgesics evaluated in the same way, and criteria of efficacy recommended by an in-depth study at the individual patient level.

SEARCH METHODS

For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase from 2009 to 28 March 2017. We also searched the reference lists of retrieved studies and reviews, and two online clinical trial registries.

SELECTION CRITERIA

Randomised, double-blind, placebo-controlled trials of single dose orally administered ketoprofen or dexketoprofen in adults with moderate to severe acute postoperative pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently considered studies for inclusion in the review, examined issues of study quality and potential bias, and extracted data. For dichotomous outcomes, we calculated risk ratio (RR) and number needed to treat for an additional beneficial outcome (NNT) or harmful outcome (NNH) with 95% confidence intervals (CI) for ketoprofen and dexketoprofen, compared with placebo, where there were sufficient data. We collected information on the number of participants with at least 50% of the maximum possible pain relief over six hours, the median time to use of rescue medication, and the proportion of participants requiring rescue medication. We also collected information on adverse events and withdrawals. We assessed the quality of the evidence using GRADE, and created 'Summary of findings' tables.

MAIN RESULTS

This updated review included 24 studies; six additional studies added 1001 participants involved in comparisons of ketoprofen or dexketoprofen and placebo, with a 12% increase in participants taking ketoprofen and a 65% increase for dexketoprofen. Most participants (70%) were women. Dental studies typically involved young participants (mean age 20 to 30 years); other types of surgery involved older participants (mean age 37 to 68 years). Overall, we judged the studies at high risk of bias only for small size, which can lead to an overestimation of benefit.Ketoprofen doses ranged between 6.5 mg and 150 mg. The proportion of participants achieving at least 50% pain relief over six hours with the usual ketoprofen oral dose of 50 mg was 57%, compared to 23% with placebo, giving an NNT of 2.9 (95% CI 2.4 to 3.7) (RR 2.5, 95% CI 2.0 to 3.1; 594 participants; 8 studies; high quality evidence). Efficacy was significantly better in dental studies (NNT 1.8) than other surgery (NNT 4.2). The proportion of participants using rescue medication within six hours was lower with ketoprofen (32%) than with placebo (75%), giving a number needed to treat to prevent use of rescue medication (NNTp) of 2.3 (95% CI 1.8 to 3.1); 263 participants; 4 studies; high quality evidence). Median time to remedication estimates were poorly reported. Reports of any adverse event were similar with ketoprofen (18%) and placebo (11%) (RR 1.6, 95% CI 0.98 to 2.8; 342 participants; 5 studies; high quality evidence). No study reported any serious adverse events (very low quality evidence).Dexketoprofen doses ranged between 5 mg and 100 mg. The proportion of participants achieving at least 50% pain relief over six hours with the usual dexketoprofen oral dose of 20 mg or 25 mg was 52%, compared to 27% with placebo, giving an NNT of 4.1 (95% CI 3.3 to 5.2) (RR 2.0, 95% CI 1.6 to 2.2; 1177 participants; 8 studies; high quality evidence). Efficacy was significantly better in dental studies (NNT 2.7) than other surgery (NNT 5.7). The proportion of participants using rescue medication within six hours was lower with dexketoprofen (47%) than placebo (69%), giving an NNTp of 4.7 (95% CI 3.3 to 8.0); 445 participants; 5 studies; high quality evidence). Median time to remedication estimates were poorly reported. Reports of any adverse event were similar with dexketoprofen (14%) and placebo (10%) (RR 1.4, 95% CI 0.89 to 2.2; 536 participants, 6 studies; high quality evidence). No study reported any serious adverse events (very low quality evidence).

AUTHORS' CONCLUSIONS

Ketoprofen at doses of 25 mg to 100 mg is an effective analgesic in moderate to severe acute postoperative pain with an NNT for at least 50% pain relief of 2.9 with a 50 mg dose. This is similar to that of commonly used NSAIDs such as ibuprofen (NNT 2.5 for 400 mg dose) and diclofenac (NNT 2.7 for 50 mg dose). Dexketoprofen is also effective with an NNT of 4.1 in the dose range 10 mg to 25 mg. Differential efficacy between dental surgery and other types of surgery seen for both drugs is unusual. Both drugs were well tolerated in single doses.

Single fixed-dose oral dexketoprofen plus tramadol for acute postoperative pain in adults

BACKGROUND

Combining two different analgesics in fixed doses in a single tablet can provide better pain relief than either drug alone in acute pain. This appears to be broadly true across a range of different drug combinations, in postoperative pain and migraine headache. A new combination of dexketoprofen (a nonsteroidal anti-inflammatory drug) plus tramadol (an opioid) has been tested in acute postoperative pain conditions. It is not yet licensed for use. This review is one of a series on oral analgesics for acute postoperative pain. Individual reviews have been brought together in two overviews to provide information about the relative efficacy and harm of the different interventions.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of a single fixed-dose of oral dexketoprofen plus tramadol, compared with placebo, for moderate to severe postoperative pain in adults, using methods that permit comparison with other analgesics evaluated in standardised trials using almost identical methods and outcomes. A secondary objective was to compare the combination with the individual analgesics alone.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via CRSO, MEDLINE via Ovid, and Embase via Ovid from inception to 31 May 2016. We also searched the reference lists of retrieved studies and reviews, and two online clinical trial registries.

SELECTION CRITERIA

Randomised, double-blind trials of oral dexketoprofen plus tramadol administered as a single oral dose, for the relief of acute postoperative pain in adults, and compared to placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently considered trials for inclusion in the review, examined issues of study quality and potential bias, and extracted data. For dichotomous outcomes, we calculated risk ratio (RR) and number needed to treat for an additional beneficial outcome (NNT) for dexketoprofen plus tramadol, compared with placebo with 95% confidence intervals (CI). We collected information on the number of participants with at least 50% of the maximum possible pain relief over six hours, the median time to use of rescue medication, and the proportion of participants requiring rescue medication. We also collected information on adverse events and withdrawals. We assessed the quality of the evidence using GRADE and created a 'Summary of findings' table.We also collected information on the number of participants with at least 50% of the maximum possible pain relief over six hours for dexketoprofen alone and tramadol alone.

MAIN RESULTS

We included three studies with 1853 participants who had undergone surgical removal of impacted wisdom teeth, hip replacement, or hysterectomy. The overall risk of bias across the three included studies was low, with unclear risk of bias in relation to the size of the three studies. Two studies did not report all our prespecified outcomes, which limited the analyses we could do.The proportion of participants achieving at least 50% pain relief over six hours with dexketoprofen 25 mg plus tramadol 75 mg was 66%, compared to 32% with placebo, giving an NNT of 3.0 (95% CI 2.5 to 3.7) (RR 2.1 (95% CI 1.7 to 2.4); 748 participants; 3 studies) (moderate quality evidence). The response rate with dexketoprofen 25 mg alone was 53% (RR 1.3 (95% CI 1.1 to 1.4); 744 participants; 3 studies) and with tramadol alone was 45% (RR 1.5 (95% CI 1.3 to 1.7); 741 participants; 3 studies) (moderate quality evidence). We downgraded the evidence because of some inconsistency in the results.The median time to use of rescue medication could not be estimated exactly, but was probably eight hours or more, indicating a long duration of effect (moderate quality evidence). We downgraded the evidence because it was not possible to estimate the effect exactly in the two multiple dose studies, resulting in imprecision. Fewer participants used rescue medication with higher doses of active treatment (summary statistic not calculated; 123 participants; 1 study) (very low quality evidence). We downgraded the evidence because the data came from a single study with few participants and events.Adverse events and serious adverse events were not reported consistently for the single dose phase of the studies. In the single dose study, 11% of participants experienced adverse events with dexketoprofen 25 mg plus tramadol 75 mg, which were mostly mild or moderate nausea, vomiting, or dizziness, and typical with these medicines. Rates were lower with placebo and lower doses (very low quality evidence). We downgraded the evidence because the data came from a single study with few participants and events. Information on multiple dosing over three and five days supported a low event rate with the combination. Overall, rates were generally low in all treatment arms, as they were for withdrawals for adverse events or other reasons.

AUTHORS' CONCLUSIONS

A single oral dose of dexketoprofen 25 mg plus tramadol 75 mg provided good levels of pain relief with long duration of action to more people than placebo or the same dose of dexketoprofen or tramadol alone. The magnitude of the effect was similar to other good analgesics. Adverse event rates were low.There is modest uncertainty about the precision of the point estimate for efficacy, but the NNT of 3 is consistent with other analgesics considered effective and commonly used.

Flavonoids as Cytokine Modulators: A Possible Therapy for Inflammation-Related Diseases

High levels of cytokines, such as interleukin (IL)-1β, tumor necrosis factor (TNF)-α and IL-6, are associated with chronic diseases like rheumatoid arthritis, asthma, atherosclerosis, Alzheimer's disease and cancer; therefore cytokine inhibition might be an important target for the treatment of these diseases. Most drugs used to alleviate some inflammation-related symptoms act by inhibiting cyclooxygenases activity or by blocking cytokine receptors. Nevertheless, these drugs have secondary effects when used on a long-term basis. It has been mentioned that flavonoids, namely quercetin, apigenin and luteolin, reduce cytokine expression and secretion. In this regard, flavonoids may have therapeutical potential in the treatment of inflammation-related diseases as cytokine modulators. This review is focused on current research about the effect of flavonoids on cytokine modulation and the description of the way these compounds exert their effect.

Design, synthesis and biological evaluation of novel analgesic agents targeting both cyclooxygenase and TRPV1

Multitarget-directed ligands might offer certain advantages over traditional single-target drugs and/or drug combinations. In the present study, a series of novel analgesic agents targeting both cyclooxygenase and TRPV1 were prepared and evaluated in an effort to optimize properties of previously described lead compounds from piperazine, ethanediamine cores. These compounds were evaluated for antagonism of hTRPV1 activation by capsaicin and the ability to inhibit Ovine COX-1 and human recombinant COX-2 in vitro. The favorable potentials of these test compounds were further characterized in preliminary analgesic and side-effects tests in vivo. On the basis of comprehensive evaluations, compound 8d which showed strong TRPV1 antagonistic activity, middle COX-2 inhibition, weak ulcerogenic action and had no hyperthermia side-effect was considered as a safe candidate for the further development of analgesic drugs.

Potent anti-inflammatory effect of a novel furan-2,5-dione derivative, BPD, mediated by dual suppression of COX-2 activity and LPS-induced inflammatory gene expression via NF-κB inactivation

BACKGROUND AND PURPOSE

We previously reported that 3-(benzo[d]-1,3-dioxol-5-yl)-4-phenylfuran-2,5-dione (BPD) showed strong inhibitory effects on PGE(2) production. However, the exact mechanism for the anti-inflammatory effect of BPD is not completely understood. In this study, we investigated the molecular mechanism involved in the effects of BPD on inflammatory mediators in LPS-stimulated macrophages and animal models of inflammation.

EXPERIMENTAL APPROACH

The expressions of COX-2, inducible NOS (iNOS), TNF-α, IL-6 and IL-1β, in LPS-stimulated RAW 264.7 cells and murine peritoneal macrophages, were determined by Western blot and/or qRT-PCR, respectively. NF-κB activation was investigated by EMSA, reporter gene assay and Western blotting. Anti-inflammatory effects of BPD were evaluated in vivo in carrageenan-induced paw oedema in rats and LPS-induced septic shock in mice.

KEY RESULTS

BPD not only inhibited COX-2 activity but also reduced the expression of COX-2. In addition, BPD inhibited the expression of iNOS, TNF-α, IL-6 and IL-1β at the transcriptional level. BPD attenuated LPS-induced DNA-binding activity and the transcription activity of NF-κB; this was associated with a decrease in the phosphorylation level of inhibitory κB-α (IκB-α) and reduced nuclear translocation of NF-κB. Furthermore, BPD suppressed the formation of TGF-β-activated kinase-1 (TAK1)/TAK-binding protein1 (TAB1), which was accompanied by a parallel reduction of phosphorylation of TAK1 and IκB kinase (IKK). Pretreatment with BPD inhibited carrageenan-induced paw oedema and LPS-induced septic death.

CONCLUSION AND IMPLICATIONS

Taken together, our data indicate that BPD is involved in the dual inhibition of COX-2 activity and TAK1-NF-κB pathway, providing a molecular basis for the anti-inflammatory properties of BPD.

The Analgesic Effect of Dexketoprofen When Added to Lidocaine for Intravenous Regional Anaesthesia: A Prospective, Randomized, Placebo-Controlled Study

This prospective, randomized, placebo-controlled study evaluated the effects of dexketoprofen as an adjunct to lidocaine in intravenous regional anaesthesia (IVRA) or as a supplemental intravenous (i.v.) analgesic. Patients scheduled for elective hand or forearm soft-tissue surgery were randomly divided into three groups. All 45 patients received 0.5% lidocaine as IVRA. Dexketoprofen was given either i.v. or added into the IVRA solution and the control group received an equal volume of saline both i.v. and as part of the IVRA. The times of sensory and motor block onset, recovery time and postoperative analgesic consumption were recorded. Compared with controls, the addition of dexketoprofen to the IVRA solution resulted in more rapid onset of sensory and motor block, longer recovery time, decreased intra- and postoperative pain scores and decreased paracetamol use. It is concluded that coadministration of dexketoprofen with lidocaine in IVRA improves anaesthetic block and decreases postoperative analgesic requirements.

Influence of COX-inhibiting analgesics on the platelet function of patients with subarachnoid hemorrhage

BACKGROUND

Platelet function of patients with subarachnoid hemorrhage (SAH) may play an important part in both rebleeding and delayed cerebral ischemia, but little is known about aggregation pathways during the acute phase of stroke. Analgesics are used regularly in the first days after bleeding, and some can potentially inhibit the cyclooxygenase (COX) enzyme. We examined the platelet function of patients with SAH in order to describe their basal situation and determine whether the administration of intravenous nonsteroidal antiinflammatory drugs (NSAIDs) affected platelet aggregation.

METHODS

Arachidonic acid (AA)-induced aggregation and the platelet function analyzer (PFA)-100 test with collagen/epinephrine cartridges were used to study a group of SAH patients that was treated with dexketoprofen and dipyrone and to compare them to patients that had received no analgesia.

RESULTS

Ninety-six consecutive SAH patients prospectively enrolled in platelet studies. Twenty-seven patients were taking NSAIDs (10 on dexketoprofen and 17 on dipyrone), and there were 15 cases in the control group. AA-induced aggregation was 10% ± 3.2% for NSAIDs (mean ± standard error), specifically 17.2% ± 7% for dexketoprofen and 5.7% ± 1% for dipyrone. Aggregation in the control group was 72.4% ± 6% (P = .001). Both analgesics slowed the platelet plug formation during the PFA-100 test, with closure times of 237.2 ± 25 seconds for dexketoprofen and 198.4 ± 22 seconds for dipyrone and 138.1 ± 21 seconds in controls (P = .02).

CONCLUSIONS

The administration of COX-inhibiting analgesics leads to an hypoaggregability state in the first days of SAH. Further insight into their impact on complications such as rebleeding and delayed cerebral ischemia is needed in order to optimize the headache treatment of SAH.

Single dose oral ketoprofen and dexketoprofen for acute postoperative pain in adults

BACKGROUND

Ketoprofen is a non-selective non-steroidal anti-inflammatory drug (NSAID) used to treat acute and chronic painful conditions. Dexketoprofen is the (S)-enantiomer, which is believed to confer analgesia. Theoretically dexketoprofen is expected to provide equivalent analgesia to ketoprofen at half the dose, with a consequent reduction in gastrointestinal adverse events.

OBJECTIVES

To assess efficacy, duration of action, and associated adverse events of single dose oral ketoprofen and dexketoprofen in acute postoperative pain in adults.

SEARCH STRATEGY

We searched Cochrane CENTRAL, MEDLINE, EMBASE and the Oxford Pain Relief Database for studies to August 2009.

SELECTION CRITERIA

Randomised, double blind, placebo-controlled trials of single dose orally administered ketoprofen and dexketoprofen in adults with moderate to severe acute postoperative pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. Pain relief or pain intensity data were extracted and converted into the dichotomous outcome of number of participants with at least 50% pain relief over 4 to 6 hours, from which relative risk and number-needed-to-treat-to-benefit (NNT) were calculated. Numbers of participants using rescue medication over specified time periods, and time to use of rescue medication, were sought as additional measures of efficacy. Information on adverse events and withdrawals was collected.

MAIN RESULTS

Fourteen studies compared ketoprofen (968 participants) at mainly 25 mg and 50 mg with placebo (520 participants). Seven studies compared dexketoprofen (681 participants) at mainly 10 mg to 25 mg with placebo (289 participants). Studies were of adequate reporting quality, and participants had pain following dental, orthopaedic, obstetric, gynaecological and general surgery. There was considerable clinical heterogeneity between studies in dental and other types of surgery, particularly bunionectomy, which limited analysis.Ketoprofen at doses between 12.5 mg and 100 mg produced NNTs for at least 50% pain relief over 4 to 6 hours of 2.4 to 3.3. For dental studies only there was a trend to more efficacy at higher doses, with NNT decreasing from 2.4 at 12.5 mg to 1.6 at 100 mg. Dexketoprofen at doses of 10/12.5 mg and 20/25 mg produced NNTs for at least 50% pain relief over 4 to 6 hours of 3.2 and 3.6, with no obvious dose response. Significantly fewer participants used rescue medication with ketoprofen and dexketoprofen than placebo. The median time to remedication was about 5 hours with ketoprofen and 4 hours with dexketoprofen. The expected equivalent efficacy with a half dose of dexketoprofen compared to ketoprofen was not demonstrated.Adverse events were uncommon with both drugs, and not significantly different from placebo.

AUTHORS' CONCLUSIONS

Ketoprofen at doses of 25 mg to 100 mg is an effective analgesic in moderate to severe acute postoperative pain with an NNT for at least 50% pain relief of 3.3 with a 50 mg dose. This is similar to that of commonly used NSAIDs such as ibuprofen (NNT 2.5 for 400 mg dose) and diclofenac (NNT 2.7 at 50 mg dose). Duration of action is about 5 hours. Dexketoprofen is also effective with NNTs of 3.2 to 3.6 in the dose range 10 mg to 25 mg. Both drugs were well tolerated in single doses.

Systematic review of dexketoprofen in acute and chronic pain

BACKGROUND

Dexketoprofen, an NSAID used in the management of acute and chronic pains, is licensed in several countries but has not previously been the subjected of a systematic review. We used published and unpublished information from randomised clinical trials (RCTs) of dexketoprofen in painful conditions to assess evidence on efficacy and harm.

METHODS

PubMed and Cochrane Central were searched for RCTs of dexketoprofen for pain of any aetiology. Reference lists of retrieved articles and reviews were also searched. Menarini Group produced copies of published and unpublished studies (clinical trial reports). Data were abstracted into a standard form. For studies reporting results of single dose administration, the number of patients with at least 50% pain relief was derived and used to calculate the relative benefit (RB) and number-needed-to-treat (NNT) for one patient to achieve at least 50% pain relief compared with placebo.

RESULTS

Thirty-five trials were found in acute pain and chronic pain; 6,380 patients were included, 3,381 receiving dexketoprofen. Information from 16 trials (almost half the total patients) was obtained from clinical trial reports from previously unpublished trials or abstracts. Almost all of the trials were of short duration in acute conditions or recent onset pain.All 12 randomised trials that compared dexketoprofen (any dose) with placebo found dexketoprofen to be statistically superior. Five trials in postoperative pain yielded NNTs for 12.5 mg dexketoprofen of 3.5 (2.7 to 4.9), 25 mg dexketoprofen of 3.0 (2.4 to 3.9), and 50 mg dexketoprofen of 2.1 (1.5 to 3.5). In 29/30 active comparator trials, dexketoprofen at the dose used was at least equivalent in efficacy to comparator drugs. Adverse event withdrawal rates were low in postoperative pain and somewhat higher in trials of longer duration; no serious adverse events were reported.

CONCLUSION

Dexketoprofen was at least as effective as other NSAIDs and paracetamol/opioid combinations. While adverse event withdrawal was not different between dexketoprofen and comparator analgesics, the different conditions and comparators studies precluded any formal analysis. Exposure was limited, and no conclusions could be drawn about safety in terms of serious adverse events like gastrointestinal bleeding or cardiovascular events.

Paracetamol (Acetaminophen): mechanisms of action

Paracetamol has a central analgesic effect that is mediated through activation of descending serotonergic pathways. Debate exists about its primary site of action, which may be inhibition of prostaglandin (PG) synthesis or through an active metabolite influencing cannabinoid receptors. Prostaglandin H(2) synthetase (PGHS) is the enzyme responsible for metabolism of arachidonic acid to the unstable PGH(2). The two major forms of this enzyme are the constitutive PGHS-1 and the inducible PGHS-2. PGHS comprises of two sites: a cyclooxygenase (COX) site and a peroxidase (POX) site. The conversion of arachidonic acid to PGG(2) is dependent on a tyrosine-385 radical at the COX site. Formation of a ferryl protoporphyrin IX radical cation from the reducing agent Fe(3+) at the POX site is essential for conversion of tyrosine-385 to its radical form. Paracetamol acts as a reducing cosubstrate on the POX site and lessens availability of the ferryl protoporphyrin IX radical cation. This effect can be reduced in the presence of hydroperoxide-generating lipoxygenase enzymes within the cell (peroxide tone) or by swamping the POX site with substrate such as PGG(2). Peroxide tone and swamping explain lack of peripheral analgesic effect, platelet effect, and anti-inflammatory effect by paracetamol. Alternatively, paracetamol effects may be mediated by an active metabolite (p-aminophenol). p-Aminophenol is conjugated with arachidonic acid by fatty acid amide hydrolase to form AM404. AM404 exerts effect through cannabinoid receptors. It may also work through PGHS, particularly in areas of the brain with high concentrations of fatty acid amide hydrolase.

Nitroparacetamol (NCX-701) and pain: first in a series of novel analgesics

The combination of numerous classic drugs with nitric oxide donors has led to the development of new compounds with promising therapeutic activities in a great variety of situations, including cardiovascular and respiratory systems, ocular pressure, inflammation, and pain. One of the first compounds developed was NCX-701 or nitroparacetamol, resulting from the combination of paracetamol, a classic and popular analgesic used in a great number of over-the-counter medications because of its antipyretic and analgesic properties, and a nitrooxybutyroyl moiety, which releases nitric oxide at a low but steady level. Although paracetamol is devoid of most of the gastrointestinal toxicity associated with aspirin-like drugs, this type of compounds was first designed to take advantage of the cytoprotective properties of nitric oxide when released at low concentrations. However, the combination of these molecules also resulted in an unexpected enhancement of the analgesic activity of paracetamol. In fact, NCX-701 has been shown to be effective in acute nociception as well as in neuropathic pain, situations in which paracetamol and other COX inhibitors are devoid of any effect. In addition, NCX-701 is more potent and, in some circumstances, more effective than its parent compound in different models of inflammatory pain. Furthermore, whereas paracetamol lacks any effective antiinflammatory action, NCX-701 might reduce inflammation. All these results taken together imply that the mechanism of action of NCX-701 is different from that of paracetamol, although it is not yet established for either molecule. NCX-701 appears to be a promising compound in the treatment of different types of pain, with a likely better profile of side effects than its parent molecule, paracetamol. Although recent clinical trials provided data consistent with the preclinical profile of NCX-701, further studies are needed to support its clinical use.

First “hybrid” ligands of vanilloid TRPV1 and cannabinoid CB2receptors and non-polyunsaturated fatty acid-derived CB2-selective ligands

12-Phenylacetyl-ricinoleoyl-vanillamide (phenylacetylrinvanil, PhAR, IDN5890), is an ultra-potent agonist of human vanilloid TRPV1 receptors also endowed with moderate affinity for human cannabinoid CB(2) receptors. To improve its CB(2) affinity and temper its potency at TRPV1, the modification of the polar headgroup and the lipophilic 12-acylgroup of PhAR was pursued. Replacement of the vanillyl headgroup of PhAR with various aromatic or alkyl amino groups decreased activity at TRPV1 receptors, although the dopamine, cyclopropylamine, 1'-(R)- and 1'-(S)-methyl-ethanolamine, and ethanolamine derivatives retained significant potency (EC(50) 31-126 nM). Within these compounds, the 12-phenylacetylricinoleyl cyclopropylamide and ethanolamide were the strongest ligands at CB(2) receptors, with K(i) of 22 and 44 nM, and 14- and >20-fold selectivity over cannabinoid CB(1) receptors, respectively. The propyl- and allyl-derivatives also exhibited high affinity at CB(2) receptors (K(i)=40 and 22 nM, with 40 and >80-fold selectivity over CB(1) receptors, respectively), but no activity at TRPV1 receptors. The cyclopropyl- and allyl-derivatives behaved as CB(2) inverse agonists in the GTP-gamma-S binding assay. Addition of para-methoxy, -tert-butyl or -chlorine groups to the 12-phenylacetyl moiety of PhAR produced compounds that retained full potency at TRPV1 receptors, but with improved selectivity over CB(2) or CB(1) receptors. Thus, the manipulation of PhAR led to the development of the first CB(2)/TRPV1 dual ligands and of an entirely new class of inverse agonists at CB(2) receptors. Both types of compounds might find application in the treatment of inflammation, and represent new molecular probes to investigate the endocannabinoid-endovanilloid signalling system.

Subanalgesic doses of dexketoprofen and HCT-2037 (nitrodexketoprofen) enhance fentanyl antinociception in monoarthritic rats

Subanalgesic doses of the non-steroidal antiinflammatory drugs (NSAID) dexketoprofen trometamol and nitroparacetamol (NCX-701) enhance mu-opiate fentanyl effect in acute nociception. It is not known if a similar combination of drugs is effective in situations of spinal cord sensitization. The aim of this study was to assess if the enhancement of fentanyl antinociception can be observed in carrageenan-induced monoarthritis, when combined with dexketoprofen (DKT) or nitrodexketoprofen (HCT-2037). Withdrawal reflexes were recorded as single motor units in male Wistar rats anesthetized with alpha-chloralose. Fentanyl was studied alone and in the presence of 0.4, 0.8 micromol/kg of DKT or 0.3 micromol/kg of HCT-2037. In responses to noxious mechanical stimulation, the ID50 of fentanyl was enhanced twofold by 0.8 micromol/kg DKT and more than fourfold by HCT-2037 and no significant recovery was observed 45 min later. DKT 0.4 micromol/kg was, however, very little effective. The opioid antagonist naloxone did not reverse the effect. Enhancement of fentanyl effect on wind-up was only observed with HCT-2037 but not with DKT. We conclude that the combined administration of subanalgesic doses of dexketoprofen derivatives, specially its nitroderivative, and the mu-opiate fentanyl is an effective antinociceptive therapy in situations of articular inflammation involving a naloxone-independent mechanism of action.

Comparison of the antinociceptive activity of two new NO-releasing derivatives of the NSAID S-ketoprofen in rats

1 Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) enzymes inducing analgesic, anti-inflammatory and antipyretic actions. They are not devoid of severe side effects and so, the search for new compounds with similar or higher effectiveness and a lower incidence of undesired actions is important. Nitric oxide (NO)-releasing NSAIDs resulted from this search. 2 We have compared the antinociceptive effectiveness of cumulative doses of two new NO-releasing derivatives of S-ketoprofen, HCT-2037 and HCT-2040, using the recording of spinal cord nociceptive reflexes in anesthetized and awake rats and after intravenous and oral administration. 3 S-ketoprofen and HCT-2040 were equieffective in reducing responses to noxious mechanical stimulation after i.v. administration in anesthetized animals (ID50s: 1.3+/-0.1 and 1.6+/-0.2 micromol kg(-1) respectively), but did not modify wind-up. HCT-2037 was two-fold more potent (ID50 of 0.75+/-0.1 micromol kg(-1)) in responses to mechanical stimuli and very effective in reducing wind-up (63+/-17% of control; P<0.01; MED: 0.4 micromol kg(-1)), indicating a greater activity than the parent compound. 4 In awake animals with inflammation, HCT-2037 p.o. fully inhibited mechanical allodynia, 91+/-12% reduction, and hyperalgesia, 94+/-8% reduction. Equivalent doses of S-ketoprofen only partially reduced either allodynia (50+/-11%) or hyperalgesia (40+/-4%). The effect on responses to noxious thermal stimulation was similar for the two compounds. 5 We conclude that the molecular changes made in the structure of S-ketoprofen including an NO moiety in its structure, improve the antinociceptive profile of the compound opening new perspectives in a safer use of NSAIDs as analgesic drugs.

Hypothalamo-pituitary-adrenal axis dysfunction as a contributory factor to chronic pain and depression

Chronic pain and depressive illness are variably resistant to treatment with current pharmacologic therapies. Pain as a reflex sensory response is accompanied by a fast autonomic and delayed neuroendocrine response mediated by the sympathoadrenal and hypothalamo-pituitary-adrenal (HPA) axis, respectively. The emotional aspect of the pain response is encoded by corticolimbic systems (including the HPA axis) to encapsulate the relationship between pain, memory, and mood. These same systems contribute to the symptomatology of depression, a common symptom of which is pain. Conversely, many chronic pain patients may suffer from depressive illness, which appears to develop as a consequence of chronic pain. A comparison of key changes in HPA function after chronic stress in animals with clinical depression in humans, reveals some striking similarities. In this article, the role of the HPA axis in the etiology of chronic pain and depression is discussed.

A nitric oxide (NO)-releasing derivative of gabapentin, NCX 8001, alleviates neuropathic pain-like behavior after spinal cord and peripheral nerve injury

1. Nitric oxide (NO) participates, at least in part, to the establishment and maintenance of pain after nerve injury. Therefore, drugs that target the NO/cGMP signaling pathway are of interest for the treatment of human neuropathic pain. Various compounds endowed with NO-releasing properties modulate the expression and function of inducible nitric oxide synthase (iNOS), the key enzyme responsible for sustained NO production under pathological conditions including neuropathic pain. 2. With this background, we synthesized a new chemical entity, [1-(aminomethyl)cyclohexane acetic acid 3-(nitroxymethyl)phenyl ester] NCX8001, which has a NO-releasing moiety bound to gabapentin, a drug currently used for the clinical management of neuropathic pain. We examined the pharmacological profile of this drug with respect to its NO-releasing properties in vitro as well as to its efficacy in treating neuropathic pain conditions (allodynia) consequent to experimental sciatic nerve or spinal cord injuries. 3. NCX8001 (1-30 microm) released physiologically relevant concentrations of NO as it induced a concentration-dependent activation of soluble guanylyl cyclase (EC(50)=5.6 microm) and produced consistent vasorelaxant effects in noradrenaline-precontracted rabbit aortic rings (IC(50)=1.4 microm). 4. NCX8001, but not gabapentin, counteracted in a concentration-dependent fashion lipopolysaccharide-induced overexpression and function of iNOS in RAW264.7 macrophages cell line. Furthermore, NCX8001 also inhibited the release of tumor necrosis factor alpha (TNFalpha) from stimulated RAW264.7 cells. 5. NCX8001 (28-280 micromol x kg(-1), i.p.) reduced the allodynic responses of spinal cord injured rats in a dose-dependent fashion while lacking sedative or motor effects. In contrast, gabapentin (170-580 micromol x kg(-1), i.p.) resulted less effective and elicited marked side effects. 6. NCX8001 alleviated the allodynia-like responses of rats to innocuous mechanical or cold stimulation following lesion of the sciatic nerve. This effect was not shared by equimolar doses of gabapentin. 7. Potentially due to the slow releasing kinetics of NO, NCX8001 alleviated pain-like behaviors in two rat models of neuropathic pain in a fashion that is superior to its parent counterpart gabapentin. This new gabapentin derivative, whose mechanism deserves to be explored further, offers new hopes to the treatment of human neuropathic pain.