Differential effects of spinal (R)-ketoprofen and (S)-ketoprofen against signs of neuropathic pain and tonic nociception: evidence for a novel mechanism of action of (R)-ketoprofen against tactile allodynia

Strategies Tackling Viral Replication and Inflammatory Pathways as Early Pharmacological Treatment for SARS-CoV-2 Infection: Any Potential Role for Ketoprofen Lysine Salt?

COVID-19 is an infective disease resulting in widespread respiratory and non-respiratory symptoms prompted by SARS-CoV-2 infection. Interaction between SARS-CoV-2 and host cell receptors prompts activation of pro-inflammatory pathways which are involved in epithelial and endothelial damage mechanisms even after viral clearance. Since inflammation has been recognized as a critical step in COVID-19, anti-inflammatory therapies, including both steroids and non-steroids as well as cytokine inhibitors, have been proposed. Early treatment of COVID-19 has the potential to affect the clinical course of the disease regardless of underlying comorbid conditions. Non-steroidal anti-inflammatory drugs (NSAIDs), which are widely used for symptomatic relief of upper airway infections, became the mainstay of early phase treatment of COVID-19. In this review, we discuss the current evidence for using NSAIDs in early phases of SARS-CoV-2 infection with focus on ketoprofen lysine salt based on its pharmacodynamic and pharmacokinetic features.

Enantioselective chitosan-based racemic ketoprofen imprinted polymer: Chiral recognition and resolution study

This work presented a novel racemic imprinting process employing the chiral properties of chitosan monomer. The preparation of racemic ketoprofen (RS-KTP) imprinted polymer (RS-MIP) was conducted using glutaraldehyde as a crosslinker. The nature of elution solvent affected the % desorption ratio suggesting a heterogenous nature of the formed binding sites. Good imprinting was indicated by an imprinting factor of 3.50 for S-KTP. The enantioselectivity of the RS-MIP was indicated by enantioselectivity coefficient of 2.31 and % enantiomeric excess (%ee) of 28.55%. A SPE cartridge packed with RS-MIP enabled resolution of RS-KTP using gradient elution solvent system. Scatchard plot revealed two binding sites types of different affinity towards S-KTP and density observed for the RS-MIP. The binding capacity of RS-MIP showed observed dependence on the % ee of S-KTP indicating its enantioselectivity. The success of using racemic template for the preparation of enantioselective MIP brings a new possibility to achieve enantioseparation of racemic mixtures having very expensive or unavailable pure enantiomers.

L-cysteine capped silver nanoparticles as chiral recognition sensor for ketoprofen enantiomers

A simple, inexpensive but effective approach for visual chiral recognition of ketoprofen enantiomers was developed using L-cysteine capped silver nanoparticles (L-Cys-AgNPs) as a colorimetric sensor. Upon the addition of R-ketoprofen to L-Cys-AgNPs, rapid aggregation occurred, and the solution changed color from yellow to green. However, the presence of S-ketoprofen did not induce any color change. The results were characterized using UV-Vis, FESEM, FT-IR, SERS, and zeta potential measurements. The chiral assay described in this work is easily distinguished with the naked eyes or using a UV-Vis spectrometer. The sensor revealed a good linear response to ketoprofen enantiomers in the concentration range of 8.33-33.3 μM with a detection limit of 4.52 μM and relative standard deviation of 3.73%. The proposed method was utilized for the determination of ketoprofen racemic mixtures in water samples and commercial tablets. The method excels by its simplicity, low cost, and good availability of materials.

A randomized controlled trial on Aspirin and complex regional pain syndrome after radius fractures

Complex regional pain syndrome (CRPS) is often diagnosed in patients who are recovered with surgery or injury. CRPS is usually diagnosed in patients recovering from distal radius fractures. The aim of study was the effects of aspirin in prevention of the complex regional pain syndrome (CRPS) following a fracture of distal radius. In a double-blind, randomized controlled trial, 91 patients with unilateral extra-articular distal radius fractures were randomly allocated to receive either placebo (PLA) or 500 mg of aspirin (ASA) daily for 7 days. The effect of aspirin on the occurrence of CRPS was evaluated. The patients were assessed clinically and radiographically in the second, fourth and twelfth weeks by a physician who was unaware of the treatment allocation. Ninety-one patients (ASA, n=44; PLA, n=47) were enrolled in the study. The prevalence of CRPS in all patients was 16.5%. The prevalence of CRPS in the aspirin group was lower (13.6%) than the placebo group (19.1%), but this difference was not statistically significant. The only significant difference was the lower rate of regional osteoporosis seen in the radiographs of aspirin group. Mean age was significantly higher in the patients with CRPS. Also, comminuted distal radius fractures (A3-type) were significantly more common in the patients with CRPS. Administration of aspirin in patients with a distal radius fracture was associated with a lower incidence of CRPS, but, not statistically significant. Further investigations needs to be done with a larger sample size, longer follow-up period and multi-center design.

Towards an Effective and Safe Treatment of Inflammatory Pain: A Delphi-Guided Expert Consensus

OBJECTIVE

The clinical management of inflammatory pain requires an optimal balance between effective analgesia and associated safety risks. To date, mechanisms associated with inflammatory pain are not completely understood because of their complex nature and the involvement of both peripheral and central mechanisms. This Expert Consensus document is intended to update clinicians about evolving areas of clinical practice and/or available treatment options for the management of patients with inflammatory pain.

METHOD

An international group of experts in pain management covering the pharmacology, neurology and rheumatology fields carried out an independent qualitative systematic literature search using MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials.

RESULTS

Existing guidelines for pain management provide recommendations that do not satisfactorily address the complex nature of pain. To achieve optimal outcomes, drug choices should be individualized to guarantee the best match between the characteristics of the patient and the properties of the medication. NSAIDs represent an important prescribing choice in the management of inflammatory pain, and the recent results on paracetamol question its appropriate use in clinical practice, raising the need for re-evaluation of the recommendations in the clinical practice guidelines.

CONCLUSIONS

Increasing clinicians' knowledge of the available pharmacologic options to treat different pain mechanisms offers the potential for safe, individualized treatment decisions. We hope that it will help implement the needed changes in the management of inflammatory pain by providing the best strategies and new insights to achieve the ultimate goal of managing the disease and obtaining optimal benefits for patients.

FUNDING

Dompé Farmaceutici SPA and Paolo Procacci Foundation.

[Evaluation of the neurotoxic effects of intrathecal administration of (S)-(+)-Ketoprofen on rat spinal cords: randomized controlled experimental study]

BACKGROUND AND OBJECTIVES

Intrathecal administration of non-steroidal anti-inflammatory drugs is more efficacious for post-operative pain management. Cyclooxygenase inhibiting non-steroidal anti-inflammatory drugs like (S)-(+)-Ketoprofen, may be effective at lower intrathecal doses than parenteral ones. Preclinical safety regarding possible neurotoxicity associated with the intrathecal (S)-(+)-Ketoprofen was not evaluated. Here we analysed the neurotoxicity of intrathecally administered (S)-(+)-Ketoprofen in rats.

METHODS

A randomized placebo-controlled experimental study was conducted. Sprague-Dawley rats (250-300g) aged 12-16 weeks were randomly divided into 2 treatments [100 and 800μg (S)-(+)-Ketoprofen] and control (sterile water) groups. Intrathecal catheters were placed via the atlantoaxial space in anesthetized rats. Pinch-toe tests, motor function evaluations and histopathological examinations of the spinal cord and nerve roots were performed at days 3, 7 and 21. Spinal cord sections were evaluated by light microscopy for the dorsal axonal funiculus vacuolation, axonal myelin loss, neuronal chromatolysis, neuritis, meningeal inflammation, adhesions, and fibrosis.

RESULTS

Rats in all the groups exhibited normal pinch-toe testing response (score=0) and normal gait at each observed time (motor function evaluation score=1). Neurotoxicity was higher with treatments on days 3 and 7 than that on day 21 (2, 3, 0, p=0.044; 2, 5, 0, p=0.029, respectively). On day 7, the total scores reflecting neuronal damage were higher in the 800μg group than those in the 100μg and Control Groups (5, 3, 0, p=0.048, respectively).

CONCLUSION

Intrathecal (S)-(+)-Ketoprofen caused dose-dependent neurohistopathological changes in rats on days 3 and 7 after injection, suggesting that (S)-(+)-Ketoprofen should not be intrathecally administered.

Evaluation of the neurotoxic effects of intrathecal administration of (S)-(+)-Ketoprofen on rat spinal cords: randomized controlled experimental study

Background and objectives

Intrathecal administration of non-steroidal anti-inflammatory drugs is more efficacious for post-operative pain management. Cyclooxygenase inhibiting non-steroidal anti-inflammatory drugs like (S)-(+)-Ketoprofen, may be effective at lower intrathecal doses than parenteral ones. Preclinical safety regarding possible neurotoxicity associated with the intrathecal (S)-(+)-Ketoprofen was not evaluated. Here we analysed the neurotoxicity of intrathecally administered (S)-(+)-Ketoprofen in rats.

Methods

A randomized placebo-controlled experimental study was conducted. Sprague-Dawley rats (250–300 g) aged 12–16 weeks were randomly divided into 2 treatments [100 and 800 μg (S)-(+)-Ketoprofen] and control (sterile water) groups. Intrathecal catheters were placed via the atlantoaxial space in anesthetized rats. Pinch-toe tests, motor function evaluations and histopathological examinations of the spinal cord and nerve roots were performed at days 3, 7 and 21. Spinal cord sections were evaluated by light microscopy for the dorsal axonal funiculus vacuolation, axonal myelin loss, neuronal chromatolysis, neuritis, meningeal inflammation, adhesions, and fibrosis.

Results

Rats in all the groups exhibited normal pinch-toe testing response (score = 0) and normal gait at each observed time (motor function evaluation score = 1). Neurotoxicity was higher with treatments on days 3 and 7 than that on day 21 (2, 3, 0, p = 0.044; 2, 5, 0, p = 0.029, respectively). On day 7, the total scores reflecting neuronal damage were higher in the 800 μg group than those in the 100 μg and Control Groups (5, 3, 0, p = 0.048, respectively).

Conclusion

Intrathecal (S)-(+)-Ketoprofen caused dose-dependent neurohistopathological changes in rats on days 3 and 7 after injection, suggesting that (S)-(+)-Ketoprofen should not be intrathecally administered.

Pharmacological modulation of neuropathic pain-related depression of behavior: effects of morphine, ketoprofen, bupropion and [INCREMENT]9-tetrahydrocannabinol on formalin-induced depression of intracranial self-stimulation in rats

Neuropathic pain is often associated with behavioral depression. Intraplantar formalin produces sustained, neuropathy-associated depression of intracranial self-stimulation (ICSS) in rats. This study evaluated pharmacological modulation of formalin-induced ICSS depression. Rats with intracranial electrodes targeting the medial forebrain bundle responded for electrical brain stimulation in an ICSS procedure. Bilateral intraplantar formalin administration depressed ICSS for 14 days. Morphine (0.32-3.2 mg/kg), ketoprofen (0.1-10 mg/kg), bupropion (3.2-32 mg/kg), and [INCREMENT]9-tetrahydrocannabinol (THC; 0.32-3.2 mg/kg) were evaluated for their effectiveness to reverse formalin-induced depression of ICSS. Drug effects on formalin-induced mechanical allodynia were evaluated for comparison. Morphine and bupropion reversed both formalin-induced ICSS depression and mechanical allodynia, and effects on ICSS were sustained during repeated treatment. Ketoprofen failed to reverse either formalin effect. THC blocked mechanical allodynia, but decreased ICSS in control rats and exacerbated formalin-induced depression of ICSS. The failure of ketoprofen to alter formalin effects suggests that formalin effects result from neuropathy rather than inflammation. The effectiveness of morphine and bupropion to reverse formalin effects agrees with other evidence that these drugs block pain-depressed behavior in rats and relieve neuropathic pain in humans. The effects of THC suggest general behavioral suppression and do not support the use of THC to treat neuropathic pain.

Evaluation of Postoperative Anti-nociceptive Efficacy of Intrathecal Dexketoprofen in Rats

BACKGROUND

Some studies have suggested that the intrathecal use of cyclooxygenase enzyme inhibitors provides an anti-nociceptive effect. Therefore, the occurrence of side effects seen in systemic usage can be eliminated.

AIMS

The primary objective of this experimental, randomized, controlled trial was to test the hypothesis asserting that intrathecal dexketoprofen trometamol would demonstrate an analgesic effect during postoperative period.

STUDY DESIGN

Animal experimentation.

METHODS

Forty rats were randomized into 4 groups 7 days after intrathecal catheterization; the following drugs were given through catheter lumens: Group Lidocaine (Group L): Lidocaine 20 μg; Group Lidocaine-Morphine (Group LM): Lidocaine 20 μg and morphine 0.5 μgr; Group Lidocaine-Dexketoprofen (Group LD): Lidocaine 20 μg and dexketoprofen trometamol 100 μg; and Group Dexketoprofen (Group D): Dexketoprofen trometamol 100 μg. Paw incision was achieved under ether inhalation. To measure analgesic potential, hot plate and tail immersion tests were used as nociceptive tests during the postoperative period.

RESULTS

The mean reaction times detected in groups during hot plate and tail immersion tests were shortest in Group L at 15, 30, 45, 60, 75, 90, 105, and 120 minutes after start of surgery (p<0.01, all others). In the groups using dexketoprofen, as in the morphine group, longer reaction times were detected than in the lidocaine group at all measurement times except 120 minutes (p<0.01).

CONCLUSION

Intrathecal dexketoprofen in the optimal perioperative pain management is effective, and can be administered as an adjuvant in clinics after neurotoxicity studies in animals, and effective dose studies in volunteers.

Antinociceptive effects of imidazoline I2 receptor agonists in the formalin test in rats

The imidazoline I2 receptor is an emerging drug target for analgesics. This study extended previous studies by examining the antinociceptive effects of three I2 receptor agonists (2-BFI, BU224, and CR4056) in the formalin test. The receptor mechanisms and anatomical mediation of I2 receptor agonist-induced antinociception were also examined. Formalin-induced flinching responses (2%, 50 μl) were quantified after treatment with I2 receptor agonists alone or in combination with the I2 receptor antagonist idazoxan. Anatomical mediation was studied by locally administering 2-BFI into the plantar surface or into the right lateral ventricle through cannulae (intracerebroventricular). The locomotor activity was also examined after central (intracerebroventricular) administration of 2-BFI. 2-BFI (1-10 mg/kg, intraperitoneal) and BU224 (1-10 mg/kg, intraperitoneal) attenuated the spontaneous flinching response observed during 10 min (phase 1) and 20-60 min (phase 2) following formalin treatment, whereas CR4056 (1-32 mg/kg, intraperitoneal) decreased only phase 2 flinching response. The I2 receptor antagonist idazoxan attenuated the antinociceptive effects of 2-BFI and BU224 during phase 1, but not phase 2. Peripheral administration of 2-BFI (1-10 mg/kg, intraplantar) to the hind paw of rats had no antinociceptive effect. In contrast, centrally delivered 2-BFI (10-100 µg, intracerebroventricular) dose-dependently attenuated phase 1 and phase 2 flinching at doses that did not reduce the locomotor activity. Together, these data revealed the differential antinociceptive effects of I2 receptor agonists and the differential antagonism profiles by idazoxan, suggesting the involvement of different I2 receptor subtypes in reducing different phases of formalin-induced pain-like behaviors. In addition, the results also suggest the central mediation of I2 receptor agonist-induced antinociceptive actions.

Systemic LPS induces spinal inflammatory gene expression and impairs phrenic long-term facilitation following acute intermittent hypoxia

Although systemic inflammation occurs in most pathological conditions that challenge the neural control of breathing, little is known concerning the impact of inflammation on respiratory motor plasticity. Here, we tested the hypothesis that low-grade systemic inflammation induced by lipopolysaccharide (LPS, 100 μg/kg ip; 3 and 24 h postinjection) elicits spinal inflammatory gene expression and attenuates a form of spinal, respiratory motor plasticity: phrenic long-term facilitation (pLTF) induced by acute intermittent hypoxia (AIH; 3, 5 min hypoxic episodes, 5 min intervals). pLTF was abolished 3 h (vehicle control: 67.1 ± 27.9% baseline; LPS: 3.7 ± 4.2%) and 24 h post-LPS injection (vehicle: 58.3 ± 17.1% baseline; LPS: 3.5 ± 4.3%). Pretreatment with the nonsteroidal anti-inflammatory drug ketoprofen (12.5 mg/kg ip) restored pLTF 24 h post-LPS (55.1 ± 12.3%). LPS increased inflammatory gene expression in the spleen and cervical spinal cord (homogenates and isolated microglia) 3 h postinjection; however, all molecules assessed had returned to baseline by 24 h postinjection. At 3 h post-LPS, cervical spinal iNOS and COX-2 mRNA were differentially increased in microglia and homogenates, suggesting differential contributions from spinal cells. Thus LPS-induced systemic inflammation impairs AIH-induced pLTF, even after measured inflammatory genes returned to normal. Since ketoprofen restores pLTF even without detectable inflammatory gene expression, "downstream" inflammatory molecules most likely impair pLTF. These findings have important implications for many disease states where acute systemic inflammation may undermine the capacity for compensatory respiratory plasticity.

Enantiospecific ketoprofen concentrations in plasma after oral and intramuscular administration in growing pigs

Background

Ketoprofen is a non-steroidal anti-inflammatory drug which has been widely used for domestic animals. Orally administered racemic ketoprofen has been reported to be absorbed well in pigs, and bioavailability was almost complete. The objectives of this study were to analyze R- and S-ketoprofen concentrations in plasma after oral (PO) and intra muscular (IM) routes of administration, and to assess the relative bioavailability of racemic ketoprofen for both enantiomers between those routes of administration in growing pigs.

Methods

Eleven pigs received racemic ketoprofen at dose rates of 4 mg/kg PO and 3 mg/kg IM in a randomized, crossover design with a 6-day washout period. Enantiomers were separated on a chiral column and their concentrations were determined by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated and relative bioavailability (F_rel) was determined for S and R –ketoprofen.

Results

S-ketoprofen was the predominant enantiomer in pig plasma after administration of the racemic mixture via both routes. The mean (± SD) maximum S-ketoprofen concentration in plasma (7.42 mg/L ± 2.35 in PO and 7.32 mg/L ± 0.75 in IM) was more than twice as high as that of R-ketoprofen (2.55 mg/L ± 0.99 in PO and 3.23 mg/L ± 0.70 in IM), and the terminal half-life was three times longer for S-ketoprofen (3.40 h ± 0.91 in PO and 2.89 h ± 0.85 in IM) than R-ketoprofen (1.1 h ± 0.90 in PO and 0.75 h ± 0.48 in IM). The mean (± SD) relative bioavailability (PO compared to IM) was 83 ± 20% and 63 ± 23% for S-ketoprofen and R-ketoprofen, respectively.

Conclusions

Although some minor differences were detected in the ketoprofen enantiomer concentrations in plasma after PO and IM administration, they are probably not relevant in clinical use. Thus, the pharmacological effects of racemic ketoprofen should be comparable after intramuscular and oral routes of administration in growing pigs.

Substrate-Selective Inhibition of Cyclooxygenase-2: Development and Evaluation of Achiral Profen Probes

Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid and the endocannabinoids 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA). We recently reported that (R)-profens selectively inhibit endocannabinoid oxygenation but not arachidonic acid oxygenation. In this work, we synthesized achiral derivatives of five profen scaffolds and evaluated them for substrate-selective inhibition using in vitro and cellular assays. The size of the substituents dictated the inhibitory strength of the analogs, with smaller substituents enabling greater potency but less selectivity. Inhibitors based on the flurbiprofen scaffold possessed the greatest potency and selectivity, with desmethylflurbiprofen (3a) exhibiting an IC(50) of 0.11 μM for inhibition of 2-AG oxygenation. The crystal structure of desmethylflurbiprofen complexed to mCOX-2 demonstrated a similar binding mode to other profens. Desmethylflurbiprofen exhibited a half-life in mice comparable to that of ibuprofen. The data presented suggest that achiral profens can act as lead molecules toward in vivo probes of substrate-selective COX-2 inhibition.

Ketoprofen in piglets: enantioselective pharmacokinetics, pharmacodynamics and PK/PD modelling

The chiral pharmacokinetics and pharmacodynamics of ketoprofen were investigated in a placebo-controlled study in piglets after intramuscular administration of 6 mg/kg racemic ketoprofen. The absorption half-lives of both enantiomers were short, and S-ketoprofen predominated over R-ketoprofen in plasma. A kaolin-induced inflammation model was used to evaluate the anti-inflammatory, antipyretic and analgesic effects of ketoprofen. Skin temperatures increased after the kaolin injection, but the effect of ketoprofen was small. No significant antipyretic effects could be detected, but body temperatures tended to be lower in the ketoprofen-treated piglets. Mechanical nociceptive threshold testing was used to evaluate the analgesic effects. The piglets in the ketoprofen-treated group had significantly higher mechanical nociceptive thresholds compared to the piglets in the placebo group for 12-24 h following the treatment. Pharmacokinetic/pharmacodynamic modelling of the results from the mechanical nociceptive threshold testing gave a median IC(50) for S-ketoprofen of 26.7 μg/mL and an IC(50) for R-ketoprofen of 1.6 μg/mL. This indicates that R-ketoprofen is a more potent analgesic than S-ketoprofen in piglets. Estimated ED(50) for racemic ketoprofen was 2.5 mg/kg.

Neuropathic pain management in chronic laminitis

Managing pain in horses afflicted by chronic laminitis is one of the greatest challenges in equine clinical practice because it is the dreadful suffering of the animals that most often forces the veterinarian to end the battle with this disease. The purpose of this review is to summarize our current understanding of the complex mechanisms involved in generating and amplifying pain in animals with laminitis and, based on this information, to propose a modified approach to pain therapy. Furthermore, a recently developed pain scoring technique is presented that may help better quantify pain and the monitoring of responses to analgesic treatment in horses with laminitis.

Expression genetics identifies spinal mechanisms supporting formalin late phase behaviors

Background

Formalin injection into rodent hind paws is one of the most commonly employed pain assays. The resulting nocifensive behaviors can be divided into two phases differing in timing, duration and underlying mechanisms. Spinal sensitization has long been felt to participate in the second phase of this response, although this sensitization is incompletely understood. By using correlative analysis between spinal gene expression and mouse strain-dependent intensity of late phase behavior, we hypothesized genes participating in variability of the response could be identified.

Results

Late phase formalin behavior scores among 10 inbred mouse strains were correlated with a spinal cord gene expression database constructed using expression arrays. Messenger RNA levels for several genes were highly correlated with the late phase behavioral responses. Most of these genes had already been implicated in mechanisms regulating pain and analgesia. One of the most strongly correlated genes, Mapk8 coding for c-Jun N-terminal kinase 1 (JNK1), was chosen for further analysis. Studies using additional strains of mice confirmed that spinal cord mRNA expression levels of Mapk8 followed the pattern predicted by strain-specific levels of formalin behavior. Interestingly, spinal cord JNK1 protein levels displayed an inverse relationship with mRNA measurements. Finally, intrathecal injections of the selective JNK inhibitor, SP600125, selectively reduced late phase licking behavior.

Conclusions

Wide differences in pain behaviors, including those resulting from the injection of formalin, can be observed in inbred strains of mice suggesting strong genetic influences. Correlating levels of gene expression in tissues established to be mechanistically implicated in the expression of specific behaviors can identify genes involved in the behaviors of interest. Comparing formalin late phase behavior levels with spinal cord gene expression yielded several plausible gene candidates, including the Mapk8 gene. Additional molecular and pharmacologic evidence confirmed a functional role for this gene in supporting formalin late phase responses.

Nefopam and ketoprofen synergy in rodent models of antinociception

Combinations of analgesics with different mechanisms of action offer the possibility of efficient analgesia with a decrease in side effects as a result of reduced dosages of one or both compounds. Based on a clinical observation of synergism between nefopam, a centrally acting non-opioid that inhibits monoamines reuptake, and ketoprofen, a non-steroidal anti-inflammatory drug, the objective of this study was to further explore this antinociceptive synergy in four distinct animal models of pain (both drugs were administered subcutaneously). Strong antinociceptive properties were observed in the mouse writhing abdominal test with ED50 values of 2.56+/-0.38 and 1.41+/-0.41 mg/kg for nefopam and ketoprofen, respectively. In the inflammatory phase of the mouse formalin test, both compounds significantly inhibited the licking time of the injected hind-paw with ED50 of 4.32+/-0.17 mg/kg for nefopam and 49.56+/-15.81 mg/kg for ketoprofen. Isobolographic analysis revealed that this drug combination is synergistic in the formalin test and additive in the writhing test. In rat carrageenan-induced tactile allodynia, single administration of nefopam or ketoprofen only partially reduced allodynia. Combination of low analgesic doses of nefopam (10 or 30 mg/kg) with low analgesic doses of ketoprofen (30 or 100 mg/kg) significantly reduced or reversed allodynia, with a more pronounced anti-allodynic effect and a longer duration efficacy. In a rat model of postoperative thermal hyperalgesia induced by incision, co-administration of nefopam at a low analgesic dose (10 mg/kg) with ketoprofen at non-analgesic doses (30 or 100 mg/kg) showed the appearance of a strong anti-hyperalgesic effect, maintained during at least 3 h. In conclusion, co-administration of nefopam with ketoprofen is synergistic, and should allow either to increase their analgesic efficacy and/or to reduce their side effects.

Cyclooxygenase-independent inhibition of H2O2-induced cell death by S-ketoprofen in renal cells

The stress response of the distal tubule to oxidative attack may be relevant to recovery from acute renal failure. In distal tubular Madin-Darby cells (MDCK), H(2)O(2) induced up-regulation of cyclooxygenases (COX-1 and COX-2), prostaglandin-E(2) production and caspase-independent cell death. Cell death was inhibited by S-ketoprofen, but not by the much weaker COX inhibitor R-ketoprofen. Interestingly, we identified 15-deoxy-Delta(12,14)-prostaglandin-J(2) (15d-PGJ(2)), a peroxisome-proliferator activated receptor-gamma agonist, as a lethal prostaglandin whose effect was reproduced by the PPAR-gamma agonist ciglitazone. Nevertheless, H(2)O(2)-induced cell death was unaffected by other non-steroidal anti-inflammatory drugs (NSAIDs) or all-trans-retinoic acid. Moreover, c-Jun-N-terminal kinase inhibitor SP600125 prevented 15-deoxy-Delta(12,14)-PGJ(2)-induced cell death, but not H(2)O(2)-induced cell death. PPAR-gamma antagonist GW9662 showed no affect on the cell death. These results indicated that protection by S-ketoprofen was COX-independent and PPARgamma independent. Moreover, the IC(50) value of the action of S-ketoprofen for the inhibition of H(2)O(2)-induced MDCK cell death ( approximately equal 140microM) was much higher than the IC(50) value for the inhibition of COX-1 and COX-2 activities ( approximately equal 1microM). Further design of S-ketoprofen derivatives devoid of COX inhibitory activity will give opportunity to protect the kidney against oxidative attack while avoiding unwanted effects of NSAID.

Plasma and cerebrospinal fluid concentrations of indomethacin in children after intravenous administration

The objective of this study was to evaluate the cerebrospinal fluid (CSF) permeation of indomethacin in healthy children. The participants (n = 31, aged 4-144 months) received indomethacin (0.35 mg/kg) as a 10-minute intravenous infusion prior to surgery under spinal anaesthesia. A single CSF and plasma sample from each individual was collected 14 to 225 minutes after the infusion. Indomethacin concentrations were determined from the CSF, plasma, and protein-free plasma. Total plasma, protein-free plasma, and CSF concentrations of indomethacin ranged between 90 and 2200 ng/mL (median, 780 ng/mL), 0.3 and 0.8 ng/mL (median, 0.5 ng/mL), and 0.2 and 5.0 ng/mL (median, 1.4 ng/mL), respectively. The CSF to plasma concentration ratio remained less than 0.01. There was no correlation between the administration time and CSF concentrations. Eleven children developed 12 nonserious adverse effects, from which 5 were central nervous system (CNS) effects (agitation). In conclusion, indomethacin permeated into the CSF of children, which enables both desired and adverse CNS effects of indomethacin.

Pharmacologic therapies for complex regional pain syndrome

Complex regional pain syndrome (CRPS) remains a challenging condition to diagnose and treat. There are few large-scale, randomized trials of pharmacologic agents, and most published studies are small, uncontrolled, or presented only in abstract form at meetings. The most commonly used agents, such as anticonvulsants, antidepressants, and opiates, have been found to be useful for other neuropathic pain conditions in large-scale trials but have not been adequately studied in CRPS. Systemic steroids delivered by multiple routes continue to be used, with some good evidence for short-term administration. N-methyl-D-aspartate antagonists have recently gained in popularity, without evidence from well-controlled trials. Bisphosphonates have been well studied and offer promise. In addition, there has been interest in thalidomide; however, we are still awaiting well-controlled trials. This article presents an overview of the available data regarding pharmacologic therapies for CRPS. These agents should be used in conjunction with a comprehensive interdisciplinary approach aimed at functional restoration and improved quality of life.

Dexketoprofen-induced antinociception in animal models of acute pain: Synergy with morphine and paracetamol

The antinociceptive activity of dexketoprofen was studied in mice using the acetic acid writhing test (acute tonic pain), the tail flick test (acute phasic pain) and the formalin assay (inflammatory pain). Isobolographic analysis was used to study the antinociceptive interactions between morphine and paracetamol co-administered with dexketoprofen. In the writhing test, the intraperitoneal administration of dexketoprofen or ketoprofen resulted in parallel dose-response curves with equal efficacy, but higher relative potency for dexketoprofen. In the tail flick test, the curves were parallel with similar efficacy and potency. The administration of morphine or paracetamol in both tests resulted in dose-response curves not parallel with that of dexketoprofen, which showed a potency between morphine and paracetamol. In the formalin assay, the antinociceptive activity of morphine during phase I was 122, 295 and 1695 times higher than dexketoprofen, ketoprofen and paracetamol, respectively. Isobolographic analysis demonstrated that the combination of sub-analgesic doses of dexketoprofen with morphine or with paracetamol was strongly synergic in all three tests. Synergistic drug combinations should improve effective pharmacological treatment of pain, minimizing drug specific adverse effects. These findings are undoubtedly worthy of additional controlled clinical trials in severe pain syndromes.

Pharmacological correlation between the formalin test and the neuropathic pain behavior in different species with chronic constriction injury

Research on mechanisms of drug action, and preclinical screening of molecules with a potential activity on neuropathic pain requires extensive animal work. The chronic constriction injury model is one of the best-characterized models of neuropathic pain behavior in rats, but requires extensive time consuming operations and animal handling. The formalin test is easier to perform, and a well validated model. The latter may serve as an effective prescreening test of molecules and may facilitate drug targeting. In the present study the activity of different pharmacological reference compounds was tested in rats and gerbils on the cold plate for animals that had undergone chronic constriction injury and in the second phase of the formalin test. In rats, a comparable outcome in both test conditions was observed for morphine, fentanyl, MK-801 and flunarizine. Clonidine had more activity in the second phase of the formalin test, whereas baclofen, tramadol, amitryptiline, ketamine and topiramate showed more activity in the cold plate. In gerbils, both test conditions yielded comparable results for fentanyl and ketoprofen. Tramadol and CP-96345 tended to have more activity in the second phase of the formalin test, whereas morphine, SR-48968, SR-142801 and R116301 demonstrated more activity in the cold plate test. This study demonstrates a good correlation between the second phase of the formalin test and the cold allodynia in the CCI model for, both for rats and gerbils. Drugs with a proven activity in humans, used as reference compounds, also showed good pharmacological activity in this animal study.

Chiral separation of ketoprofen on an achiral C8 column by HPLC using norvancomycin as chiral mobile phase additives

A high-performance liquid chromatographic method for chiral separation of ketoprofen racemate was developed. (R)- and (S)-ketoprofen enantiomers were separated on a Hypersil BDS C8 column (150 mm x 4.6 mm i.d., 5 microm) at 25 degrees C, using acetonitrile-triethylamine acetate (TEAA) buffer (pH 5.2, 20 mM) (35:65, v/v) containing 2.0 mM norvancomycin as the mobile phase. Effects of norvancomycin concentration, content of acetonitrile and TEAA buffer pH on the enantioseparation were investigated. The method was validated for linearity, repeatability, limits of detection (LOD) and limits of quantification (LOQ). Calibration curves (r2 = 0.999) were constructed in the range of 2.01-200.8 microg ml(-1) for (S)-ketoprofen and 2.04-152.4 microg ml(-1) for (R)-ketoprofen, respectively. Repeatability (n = 5) showed less than 2% relative standard deviation (R.S.D.). LOD and LOQ for the two enantiomers were found to be 0.20 and 0.78 ng for (S)-ketoprofen, 0.20 and 0.86 ng for (R)-ketoprofen, respectively. Norvancomycin and vancomycin as chiral mobile phase additives (CMPAs) in the chiral separation showed similar abilities of enantioseparation. However, to obtain the optimum enantioseparation, a lower concentration of norvancomycin than that of vancomycin is required.

Cerebrospinal Fluid Distribution of Ketoprofen after Intravenous Administration in Young Children

OBJECTIVE

The purpose of this study was to evaluate the cerebrospinal fluid (CSF) distribution of an NSAID, ketoprofen, in children. Ketoprofen concentrations were determined from the CSF, plasma and protein-free plasma samples.

METHODS

Children (n = 21), aged 13-94 months, were given intravenous ketoprofen (1 mg/kg) prior to surgery under spinal anaesthesia. Single venous blood and CSF samples from each patient were collected simultaneously 7-67 minutes after the drug administration. Ketoprofen concentrations in the samples were determined using gas chromatography-mass spectrometry.

RESULTS

Ketoprofen entered the CSF and was detectable in all samples. However, CSF delivery was limited; the ratio of ketoprofen concentration in CSF to plasma remained below 0.006 at all times. Ketoprofen was highly bound (> 98%) to plasma proteins. The free ketoprofen fraction was not in equilibrium with the CSF, and no clear peak drug concentration in the CSF was observed.

CONCLUSION

This study shows that ketoprofen is able to enter the CSF of children, which enables central analgesic effects of ketoprofen. However, the slow distribution of ketoprofen into the CSF and the apparently low absolute concentrations has to be taken into account when central analgesic effects are desired.

Pharmacokinetic-pharmacodynamic correlations and biomarkers in the development of COX-2 inhibitors

The mechanism by which COX inhibitors exert their analgesic effect is well established. However, data show no direct correlation between drug concentrations in plasma and the analgesic or adverse effects in chronic inflammatory conditions. This represents a major problem in the development of COX inhibitors, since it is difficult to predict the appropriate dosing regimen for the treatment of chronic inflammatory pain, based upon information from pre-clinical studies and eventually early clinical studies. The factors that determine response in inflammatory pain must be understood in order to make predictions about the time course of the analgesic effect. In this review the determinants of drug response and their variability will be discussed: physicochemical properties, pharmacokinetics (PK), pathophysiology and disease progression. From a mechanistic point of view, endogenous mediators of inflammation might be used as a biomarker for the analgesic effect and safety assessment. Such a biomarker can be an intermediate step between drug exposure and response. In addition, its concentration-effect relationship could be characterized by pharmacokinetic-pharmacodynamic (PK/PD) modelling. Indeed, recent investigations have shown that COX-2 inhibition, as determined by modelling of prostaglandin E2 (PGE2) levels in the whole blood assay in vitro can be used as a marker to predict drug effects (analgesia) in humans. A model-derived parameter, IC80, (total and unbound) was found to correlate directly with the analgesic plasma concentration of different COX inhibitors varying in enzyme selectivity. These findings indicate that PGE2 and thromboxane B2 inhibition can be used to predict and select efficacious doses in humans.

Intrathecal Catheterization and Solvents Interfere with Cortical Somatosensory Evoked Potentials Used in Assessing Nociception in Awake Rats

We assessed the objective measurement of central sensitization processes in the awake rat after subcutaneous formalin with cortical somatosensory evoked potentials (CSEPs). Cranial extradural electrodes and intrathecal catheters were implanted in adult male Wistar rats. After 7 days of recovery, CSEPs were induced by electrical stimuli at the tail and recorded before/after the injection of 50 microL of 2% formalin into the hindpaw of rats for 1 h. The drug and tested vehicles were delivered intrathecally 5 min before the injection of formalin. The peak-to-peak amplitude of the P1-N1 (the early positive-negative sequence pair of CSEPs) and the baseline-to-peak amplitude of the N2 (the late negative component of CSEPs) were analyzed. We found that the amplitudes of both signals increased (154.3% +/- 10.9% and 168.7% +/- 9.8%, respectively) from 10 min after formalin injection to the end of the 60-min test period. Pretreatment with intrathecal ketorolac dose-dependently prevented the increases induced by formalin in both measured variables. Moreover, the increases in P1-N1 and N2 were markedly attenuated either by intrathecal polyethylene-10 tubing or by the solvents used for injection, thus indicating the need for distinguishing an impaired nociceptive signal from antinociception when the effects of drugs are evaluated.

Is the Second Phase of the Formalin Test Useful to Predict Activity in Chronic Constriction Injury Models? A Pharmacological Comparison in Different Species

This study presents data of several reference drugs in rats and gerbils for both the second phase of the formalin test and the cold allodynia in animals with a constriction injury of the sciatic nerve. A pharmacological validation of the formalin test and the CCI model in gerbils was performed. It was evaluated whether the second phase of the formalin test could be used as a pharmacological screening to predict outcome in the cold plate test in CCI animals. Male Sprague Dawley and Wistar rats and male gerbils were used for both tests. For the formalin test, animals were injected in the right hind paw (5% formalin rat: 0.05 microl; gerbil: 0.01 microl) and flinching and licking or biting were recorded. For CCI testing, a Bennett operation was performed on the left hind paw 7 days before testing. Cold plate allodynia was evaluated before and after drug treatment. In rats, a good correlation between both test conditions for morphine, fentanyl, MK-801 and flunarizine was found. Clonidine tends to have more activity in the second phase of the formalin test, whereas baclofen, tramadol, amitryptiline, ketamine and topiramate demonstrate to be more active in the cold plate. In gerbils, a good correlation between both test conditions for fentanyl and ketoprofen was found. Tramadol and CP-96345 tend to have more activity in the second phase of the formalin test, whereas morphine, SR-48968, SR-142801 and R116301 demonstrates to be more active in the cold plate test. In the present acute test conditions, there is a correlation in the pharmacological activity in rats and gerbils for the tested compounds a correlation between the second phase of the formalin test and the cold allodynia in CCI animals is found. Comparing to human data the screening drugs tested in this study show a correlation between animal and human studies in these specific circumstances. Further validation studies are needed to make these correlations clinical applicable.

Nonsteroidal anti-inflammatory drugs for postoperative pain: a focus on children

Pain is a common symptom after surgery in children, and the need for effective pain management is obvious. For example, after myringotomy, despite the brief nature of the procedure, at least one-half of children have significant pain. After more extended surgery, such as tonsillectomy, almost all children have considerable pain longer than 7 days. Nonsteroidal anti-inflammatory drugs (NSAIDs) are useful for postoperative pain management because surgery causes both pain and inflammation. Several pediatric studies indicate NSAIDs are effective analgesics in the management of mild and moderate pain. In the treatment of severe pain, NSAIDs should be given with acetaminophen (paracetamol) or opioids, and the use of an appropriate regional analgesic technique should be considered. NSAIDs are more effective in preventing pain than in the relief of established pain. Pain following surgery is best managed by providing medication on a regular basis, preventing the pain from recurring. This proactive approach should be implemented for any procedure where postoperative pain is the likely outcome. In children, the choice of formulation can be more important than the choice of drug. Intravenous administration is preferred for children with an intravenous line in place; thereafter mixtures and small tablets are feasible options. Children dislike suppositories, and intramuscular administration should not be used in nonsedated children. Ibuprofen, diclofenac, ketoprofen and ketorolac are the most extensively evaluated NSAIDs in children. Only a few trials have compared different NSAIDs, but no major differences in the analgesic action are expected when appropriate doses of each drug are used. Whether NSAIDs differ in the incidence and severity of adverse effects is open to discussion. Because NSAIDs prevent platelet aggregation they may increase bleeding. A few studies indicate that ketorolac may increase bleeding more so than other NSAIDs, but the evidence is conflicting. Severe adverse effects of NSAIDs in children are very rare, but it is important to know about adverse effects in order to recognize and treat them when they do occur. NSAIDs are contraindicated in patients in whom sensitivity reactions are precipitated by aspirin (acetylsalicylic acid) or other NSAIDs. They should be used with caution in children with liver dysfunction, impaired renal function, hypovolemia or hypotension, coagulation disorders, thrombocytopenia, or active bleeding from any cause. In contrast, it seems that most children with mild asthma may use NSAIDs.

Comparison of epidural pain treatment with sufentanil-ropivacaine infusion with and without epinephrine in children

BACKGROUND

Epidural analgesia provides outstanding pain relief after surgery, but it is also associated with numerous adverse effects. In order to improve postoperative pain management in children we determined whether the use of epinephrine added to epidural sufentanil-ropivacaine infusion reduced drug requirements, the intensity and duration of postoperative pain and the incidence and severity of adverse effects.

METHODS

A prospective, randomized, double blind, parallel group study design was used in 61 children. The children were given continuous epidural sufentanil-ropivacaine infusion either with (n=32) or without (n=29) epinephrine for postoperative analgesia. Intravenous ketoprofen, a non-steroid anti-inflammatory drug, was used for all children, and epidural ropivacaine was used for rescue analgesia. The drug consumption, intensity of pain at rest and during activity, and all adverse effects were recorded.

RESULTS

: The need for sufentanil (P=0.001) and ropivacaine (P=0.006) was significantly lower in the with-epinephrine group than in the without-epinephrine group. The mean duration of epidural infusion (62 h) was similar in both groups. Four children in the without-epinephrine group were noticed to have a low oxygen saturation (SpO2<90%), and in one child a low respiratory rate (8 breaths min-1). The incidence of pruritus was higher in the without-epinephrine group (P=0.026).

CONCLUSION

Both infusions provided effective pain relief, and epinephrine as an adjuvant to continuous epidural sufentanil-ropivacaine infusion seems to be useful in children.

Diffusion of ketoprofen into the cerebrospinal fluid of young children

BACKGROUND

The objective was to examine whether or not ketoprofen enters the cerebrospinal fluid after a single oral dose of 1 mg.kg-1 syrup, and to find out what is the lowest plasma concentration that will achieve a measurable level in the cerebrospinal fluid.

METHODS

We measured ketoprofen concentrations both in plasma and cerebrospinal fluid of 10 young and healthy children (aged 9-86 months) after surgery with spinal anaesthesia. Samples of cerebrospinal fluid were collected 30 min after drug administration, at the same time as venous blood samples. A validated high-performance liquid chromatography method with a lower limit of 0.02 microg x ml(-1) was used to detect ketoprofen concentrations in cerebrospinal fluid and plasma.

RESULTS

Ketoprofen was detectable in the cerebrospinal fluid only in the child who had the highest plasma concentration, 7.4 microg x ml(-1), while at plasma concentrations 6.5 microg x ml(-1) or less, cerebrospinal fluid (CSF) concentrations remained unmeasurable. The detected CSF/plasma ratio was 0.008.

CONCLUSIONS

These results indicate that ketoprofen at a dose of 1 mg x kg(-1) is too low to produce measurable CSF levels within 30 min of oral administration.

Pharmacokinetics of a 24-hour intravenous ketoprofen infusion in children

BACKGROUND

No pharmacokinetic data are available with respect to the plasma concentration of ketoprofen during intravenous infusion in children.

METHODS

We present here the pharmacokinetics of ketoprofen after a 10-min intravenous infusion of 1 mg/kg followed by a 24-h infusion of 4 mg/kg in 18 children aged 7 months to 16 years. Venous blood samples were collected at 5 min, 1, 2, 4, 24 h following the loading dose, and then 1, 2 and 4 h after the end of the infusion. A validated HPLC method was used to measure plasma levels of ketoprofen.

RESULTS

The steady state plasma concentration of ketoprofen was 2.0 microg/mL (range 1.3-2.7 microg/mL). The clearance of ketoprofen was 0.09 L x h(-1) x kg(-1) (range 0.06-0.13 L x h(-1) x kg(-1)). The distribution volume was 0.16 L/kg (range 0.12-0.21 L/kg). The terminal half-life was 1.3 h (range 0.8-1.7 h).

CONCLUSION

The pharmacokinetics of ketopofen in children is similar to that reported in adults. Our results indicate that ketoprofen is a feasible drug for continuous intravenous infusion in acute pain treatment in children.

Pathobiology of neuropathic pain

This review deals with physiological and biological mechanisms of neuropathic pain, that is, pain induced by injury or disease of the nervous system. Animal models of neuropathic pain mostly use injury to a peripheral nerve, therefore, our focus is on results from nerve injury models. To make sure that the nerve injury models are related to pain, the behavior was assessed of animals following nerve injury, i.e. partial/total nerve transection/ligation or chronic nerve constriction. The following behaviors observed in such animals are considered to indicate pain: (a) autotomy, i.e. self-attack, assessed by counting the number of wounds implied, (b) hyperalgesia, i.e. strong withdrawal responses to a moderate heat stimulus, (c) allodynia, i.e. withdrawal in response to non-noxious tactile or cold stimuli. These behavioral parameters have been exploited to study the pharmacology and modulation of neuropathic pain. Nerve fibers develop abnormal ectopic excitability at or near the site of nerve injury. The mechanisms include unusual distributions of Na(+) channels, as well as abnormal responses to endogenous pain producing substances and cytokines such as tumor necrosis factor alpha (TNF-alpha). Persistent abnormal excitability of sensory nerve endings in a neuroma is considered a mechanism of stump pain after amputation. Any local nerve injury tends to spread to distant parts of the peripheral and central nervous system. This includes erratic mechano-sensitivity along the injured nerve including the cell bodies in the dorsal root ganglion (DRG) as well as ongoing activity in the dorsal horn. The spread of pathophysiology includes upregulation of nitric oxide synthase (NOS) in axotomized neurons, deafferentation hypersensitivity of spinal neurons following afferent cell death, long-term potentiation (LTP) of spinal synaptic transmission and attenuation of central pain inhibitory mechanisms. In particular, the efficacy of opioids at the spinal level is much decreased following nerve injury. Repeated or prolonged noxious stimulation and the persistent abnormal input following nerve injury activate a number of intracellular second messenger systems, implying phosphorylation by protein kinases, particularly protein kinase C (PKC). Intracellular signal cascades result in immediate early gene (IEG) induction which is considered as the overture of a widespread change in protein synthesis, a general basis for nervous system plasticity. Although these processes of increasing nervous system excitability may be considered as a strategy to compensate functional deficits following nerve injury, its by-product is widespread nervous system sensitization resulting in pain and hyperalgesia. An important sequela of nerve injury and other nervous system diseases such as virus attack is apoptosis of neurons in the peripheral and central nervous system. Apoptosis seems to induce neuronal sensitization and loss of inhibitory systems, and these irreversible processes might be in common to nervous system damage by brain trauma or ischemia as well as neuropathic pain. The cellular pathobiology including apoptosis suggests future strategies against neuropathic pain that emphasize preventive aspects.