Diclofenac potassium liquid-filled soft gelatin capsules in the management of patients with postbunionectomy pain: a Phase III, multicenter, randomized, double-blind, placebo-controlled study conducted over 5 days

Pain Reduction With AbobotulinumtoxinA for the Treatment of Hallux Valgus in Adult Participants: Results of a Randomized and Placebo-Controlled Phase 2 Trial

AbobotulinumtoxinA (aboBoNT-A, Dysport® [Ipsen, Paris, France]) inhibits acetylcholine release at the neuromuscular junction and may modulate pain signaling in hallux valgus (HV). This randomized study (NCT03569098) included a double-blind phase (aboBoNT-A 300U, 500U or placebo injections into forefoot muscles) and an open-label aboBoNT-A treatment period in participants with an HV diagnosis and no HV surgery. The primary endpoint was change from baseline in numeric pain rating scale (NPRS) score at week 8. Secondary endpoints included change in NPRS (other time points) and proportion of participants with ≥20% reduction from baseline NPRS (responders). Post-hoc analyses assessed number of days in a 7-day evaluation period that participants spent in a lower pain state than at baseline. Participants received aboBoNT-A 300U (n = 63), 500U (n = 60) or placebo (n = 63). Superiority to placebo was not observed with either aboBoNT-A dose at week 8, thus the primary endpoint was unmet. At week 12, a trend toward efficacy was observed with aboBoNT-A 500U versus placebo and the proportion of participants with ≥20% reduction from baseline NPRS was greater with aboBoNT-A 500U versus placebo (p = .006). Participants in the aboBoNT-A 500U group spent more days with lower NPRS than their lowest baseline score, and with NPRS ≥2 points lower than their mean baseline NPRS at weeks 8 and 12 versus placebo (all p < .05; post-hoc). AboBoNT-A was well tolerated. Although the primary endpoint was unmet, other endpoints showed a nominal advantage for aboBoNT versus placebo for treatment of HV-related pain, particularly at week 12. Further clinical evaluation is needed to establish whether botulinum toxins represent a viable non-operative treatment option for HV-associated pain. PLAIN LANGUAGE SUMMARY: Hallux valgus is the medical name for a bunion, a foot deformity that can worsen over time. Patients with bunions experience pain and walking can become difficult, which can affect their quality of life. Foot support aids (e.g., braces, splints and inserts) are available, but surgery is the standard treatment. This study looked at how injections of a specific type of botulinum toxin, called abobotulinumtoxinA or "aboBoNT-A", into the foot may help to reduce pain in patients with bunions. The study included 186 patients aged 18 to 75 years who had not had surgery on their bunion. The researchers looked at how well the injections worked using scales that measure the pain levels the patient experienced. The main outcome was whether patients who had aboBoNT-A injections had less pain after 8 weeks than they did before treatment. The study included patients who were injected with saltwater (no treatment) to check that any treatment effect was real. Researchers also looked at the results after 12 weeks, as well as how many patients had less pain after treatment than before and how many days in a given week patients experienced less pain after treatment than they did before. There was no reduction in pain levels with aboBoNT-A injections after 8 weeks compared with no treatment. However, the other study outcomes suggested that aboBoNT-A resulted in a small benefit compared with no treatment, especially after 12 weeks. Further medical research is needed to establish whether botulinum toxins represent an alternative treatment to surgery for the pain associated with bunions.

Exploring the Relationship Between Clinical Presentation in Hallux Valgus and Response to AbobotulinumtoxinA Treatment

The relationship between pain/disability and angular deviation of the hallux valgus (HV), and the impact of orthotic use, laterality, and pain variability on treatment outcomes remain unclear. This was explored in post hoc analyses of a placebo-controlled trial of abobotulinumtoxinA (aboBoNT-A; Dysport®) for HV-associated pain (NCT03569098). The primary endpoint was not met in this study (change from baseline Numeric Pain Rating Scale [NPRS] score vs placebo at week 8); however, there was a greater reduction from baseline in mean NPRS score at week 12 with aboBoNT-A 500U versus placebo (p = .06). Adults with painful HV without surgery were randomized (1:1:1) to aboBoNT-A 300U, aboBoNT-A 500U, or placebo. NPRS was completed for 7 days before baseline and weeks 4, 8, and 12. Over-the-counter orthoses were permitted. Participants (N = 186) had a mean [standard deviation, SD] age of 48.2 [13.1] years, 18% (33/186) used orthotics, and 67% (124/186) had bilateral HV. No associations between baseline pain severity and angular deviation were identified. Participants with high pain variability at baseline (SD > 2) had a poorer response to aboBoNT-A treatment than those with less variability. In conclusion, no relationship between HV-related pain/disability and angular deviation was observed. PLAIN LANGUAGE SUMMARY: A bunion (medical term: hallux valgus) is a common adult foot problem in which the big toe points inward toward the other toes, and this can be painful. How much the big toe points inward (how deformed the foot is) has been linked to the amount of pain the patient experiences. A better understanding of this foot deformity and bunion pain will help doctors and patients to make the right treatment decisions. A study was completed looking at how injections of a type of botulinum toxin (abobotulinumtoxinA) into specific muscles in the foot may help to reduce bunion pain in patients without surgery. This subsequent analysis of the study data looked at the amount of foot deformity in patients, the bunion pain they experienced, and which factors affected how well abobotulinumtoxinA worked to reduce bunion pain. The results of this study showed that the amount of foot deformity was not linked to the level of bunion pain. When deciding the best treatment option to relieve bunion pain, it is important that doctors not only consider how deformed the foot is, but also other important factors such as foot pain levels.

Efficacy and Safety of Intravenously Administered Tramadol in Patients with Moderate to Severe Pain Following Bunionectomy: A Randomized, Double-Blind, Placebo-Controlled, Dose-Finding Study

INTRODUCTION

This study is part of the registrational program for intravenously administered (IV) tramadol in the USA and compared the analgesic benefit and tolerability of two doses of IV tramadol (50 mg and 25 mg) to placebo in adult patients undergoing bunionectomy, an orthopedic surgical model.

METHODS

This was a phase 3, multicenter, double-blind, three-arm, randomized, placebo-controlled, multiple-dose, parallel-group trial to evaluate IV tramadol in the management of postoperative pain following bunionectomy. Eligible patients were randomized (1:1:1 ratio) to IV tramadol 50 mg, 25 mg, or placebo. Primary endpoint was summary of pain intensity differences over 48 h (SPID48). Key secondary endpoints included SPID24, total consumption of rescue analgesia, and patient global assessment of efficacy (PGA). Safety assessments included treatment emergent adverse events (TEAEs), clinical laboratory tests, vital signs, and electrocardiograms (ECGs). Assessment of the dose-response was an important objective of the study.

RESULTS

The study established a dose response, with IV tramadol 50 mg demonstrating statistically significant benefit (p < 0.05) over placebo for primary and all key secondary efficacy endpoints, whereas tramadol 25 mg demonstrated intermediate results between the 50 mg and placebo arms. IV tramadol 50 mg was well tolerated; most common TEAEs were nausea and vomiting; and there were no meaningful differences among treatments for vital signs, ECG, and laboratory assessments. The largest proportion of patients completed tramadol 50 mg (98.6%) compared to tramadol 25 mg (91.8%) and placebo (88.2%).

CONCLUSION

IV tramadol 50 mg was effective and well tolerated as treatment for postoperative pain following bunionectomy surgery, while IV tramadol 25 mg, although well tolerated, was judged an ineffective dose for the treatment of pain in this setting. IV tramadol 50 mg was further developed in the registrational program for the USA.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT03290378.

PROSPECT guideline for hallux valgus repair surgery: a systematic review and procedure-specific postoperative pain management recommendations

Hallux valgus repair is associated with moderate-to-severe postoperative pain. The aim of this systematic review was to assess the available literature and develop recommendations for optimal pain management after hallux valgus repair. A systematic review using PROcedure SPECific Postoperative Pain ManagemenT (PROSPECT) methodology was undertaken. Randomized controlled trials (RCTs) published in the English language from inception of database to December 2019 assessing postoperative pain using analgesic, anesthetic, and surgical interventions were identified from MEDLINE, EMBASE, and Cochrane Database, among others. Of the 836 RCTs identified, 55 RCTs and 1 systematic review met our inclusion criteria. Interventions that improved postoperative pain relief included paracetamol and non-steroidal anti-inflammatory drugs or cyclo-oxygenase-2 selective inhibitors, systemic steroids, ankle block, and local anesthetic wound infiltration. Insufficient evidence was found for the use of gabapentinoids or wound infiltration with extended release bupivacaine or dexamethasone. Conflicting evidence was found for percutaneous chevron osteotomy. No evidence was found for homeopathic preparation, continuous local anesthetic wound infusion, clonidine and fentanyl as sciatic perineural adjuncts, bioabsorbable magnesium screws, and plaster slippers. No studies of sciatic nerve block met the inclusion criteria for PROSPECT methodology due to a wider scope of included surgical procedures or the lack of a control (no block) group. The analgesic regimen for hallux valgus repair should include, in the absence of contraindication, paracetamol and a non-steroidal anti-inflammatory drug or cyclo-oxygenase-2 selective inhibitor administered preoperatively or intraoperatively and continued postoperatively, along with systemic steroids, and postoperative opioids for rescue analgesia.

Multimodal Analgesia in Foot and Ankle Surgery

Progress in surgical acute pain management has allowed most foot and ankle surgery to be performed in ambulatory outpatient surgical centers. Multimodal analgesia focuses on improving postoperative pain by combining pharmacologic and other modalities, addressing multiple pain mechanisms and receptor pathways while reducing adverse effects through lower doses of oral medications. Local anesthesia techniques provide excellent pain relief with few adverse events. Multimodal analgesia in foot and ankle surgery provides superior pain relief, and reduced opioid dependence and opioid-related side effects, improving patient satisfaction, safety, and timely return to function.

Exploring the Interplay between Rescue Drugs, Data Imputation, and Study Outcomes: Conceptual Review and Qualitative Analysis of an Acute Pain Data Set

In placebo-controlled acute surgical pain studies, provisions must be made for study subjects to receive adequate analgesic therapy. As such, most protocols allow study subjects to receive a pre-specified regimen of open-label analgesic drugs (rescue drugs) as needed. The selection of an appropriate rescue regimen is a critical experimental design choice. We hypothesized that a rescue regimen that is too liberal could lead to all study arms receiving similar levels of pain relief (thereby confounding experimental results), while a regimen that is too stringent could lead to a high subject dropout rate (giving rise to a preponderance of missing data). Despite the importance of rescue regimen as a study design feature, there exist no published review articles or meta-analysis focusing on the impact of rescue therapy on experimental outcomes. Therefore, when selecting a rescue regimen, researchers must rely on clinical factors (what analgesics do patients usually receive in similar surgical scenarios) and/or anecdotal evidence. In the following article, we attempt to bridge this gap by reviewing and discussing the experimental impacts of rescue therapy on a common acute surgical pain population: first metatarsal bunionectomy. The function of this analysis is to (1) create a framework for discussion and future exploration of rescue as a methodological study design feature, (2) discuss the interplay between data imputation techniques and rescue drugs, and (3) inform the readership regarding the impact of data imputation techniques on the validity of study conclusions. Our findings indicate that liberal rescue may degrade assay sensitivity, while stringent rescue may lead to unacceptably high dropout rates.

Evolving therapeutic strategies to improve nonsteroidal anti-inflammatory drug safety

Nonsteroidal anti-inflammatory drugs (NSAIDs) possess potent anti-inflammatory and analgesic properties through inhibition of cyclooxygenase enzymes (COX-1 and COX-2), which are responsible for synthesis of proinflammatory mediators. NSAIDs are frequently used for treatment of acute and chronic pain conditions. However, their use is associated with serious dose-dependent gastrointestinal (GI), cardiovascular, renal, and hepatic adverse effects, which pose a serious clinical concern for both patients and physicians. During the past 2 decades, approaches to improving the tolerability of NSAIDs were mainly directed toward discovery of COX-2 selective NSAIDs (coxibs), which were expected to minimize the risk of GI injury. Unfortunately, the results from multiple clinical studies have shown that treatment with coxibs may increase the risk for cardiovascular complications. This review summarizes current strategies used to reduce the toxicity of NSAIDs and outlines novel therapeutic approaches still in preclinical development. To minimize the risk of GI ulcerations and bleeding, combination therapies with gastroprotective agents are currently recommended. The new therapeutic agents anticipated to have similar effects include nitric oxide- and hydrogen sulfide-releasing NSAIDs. Novel manufacturing technologies enhance dissolution and absorption of NSAID products, allowing for their administration at low doses, which could lead to improved drug tolerability without diminishing the analgesic and anti-inflammatory efficacy of NSAIDs. This principle is in line with the current recommendation by the US Food and Drug Administration that NSAIDs should be used at the lowest effective dosage. Finally, NSAID formulations targeted directly to the site of inflammation are expected to reduce systemic drug exposure and thus decrease the risk of systemic adverse effects.

SoluMatrix® Diclofenac: Sustained Opioid-Sparing Effects in a Phase 3 Study in Patients with Postoperative Pain

OBJECTIVES

To evaluate opioid rescue medication usage and the opioid-sparing effect of low-dose SoluMatrix^® diclofenac developed using SoluMatrix Fine Particle Technology™ in a phase 3 study in patients experiencing pain following bunionectomy surgery.

DESIGN

Multicenter, randomized, double-blind, parallel-group study (NCT01462435).

SETTING

Four clinical research centers in the United States.

SUBJECTS

Four hundred twenty-eight patients aged 18 to 65 years who experienced moderate-to-severe pain following bunionectomy surgery.

METHODS

Patients were randomized to receive low-dose SoluMatrix diclofenac 35 mg or 18 mg capsules three times daily (35-mg group or 18-mg group), celecoxib 400 mg loading dose followed by 200-mg capsules twice daily (celecoxib 200-mg group), or placebo capsules postsurgery. Patients were permitted to receive opioid-containing rescue medication as needed.

RESULTS

Significantly fewer patients who received SoluMatrix diclofenac 35 mg or 18 mg or celecoxib required rescue medication during 0-24 h and >24-48 h postsurgery compared with placebo. Patients in the SoluMatrix diclofenac 35 mg or 18 mg groups or in the celecoxib group used fewer mean rescue medication tablets over 0-24 h and >24-48 h compared with placebo-treated patients. Patients in the SoluMatrix diclofenac 35 mg and 18 mg groups and in the celecoxib group also required rescue medication at later times and at slower rates compared with placebo-treated patients. No serious adverse effects occurred in patients receiving SoluMatrix diclofenac.

CONCLUSIONS

SoluMatrix diclofenac at two dosage strengths demonstrated an opioid-sparing effect postoperatively in this phase 3 study.

SUMMARY

The opioid-sparing effect following low-dose SoluMatrix diclofenac (35 mg or 18 mg three times daily) administration was evaluated in patients experiencing pain following bunionectomy. Significantly fewer patients receiving SoluMatrix diclofenac or celecoxib (400 mg loading, 200 mg twice daily) required rescue medication during 0-24 h and >24-48 h following bunionectomy compared with placebo. No serious adverse events were reported among patients who received SoluMatrix diclofenac. SoluMatrix diclofenac may reduce opioid usage in the postoperative setting in patients with acute pain.

Single dose oral diclofenac for acute postoperative pain in adults

BACKGROUND

Diclofenac is a nonsteroidal anti-inflammatory drug, available as a potassium salt (immediate release) or sodium salt (enteric coated to suppress dissolution in the stomach). This review updates an earlier review published in the Cochrane Database of Systematic Reviews (Issue 2, 2009) entitled 'Single dose oral diclofenac for acute postoperative pain in adults'.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of a single oral dose of diclofenac for moderate to severe postoperative pain, using methods that permit comparison with other analgesics evaluated in standardised trials using almost identical methods and outcomes.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the Oxford Pain Relief Database, two clinical trial registries, and the reference lists of articles. The date of the most recent search was 9 March 2015.

SELECTION CRITERIA

Randomised, double-blind, placebo-controlled clinical trials of single dose, oral diclofenac (sodium or potassium) for acute postoperative pain in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently considered studies for inclusion in the review, assessed risk of bias, and extracted data. We used the area under the pain relief versus time curve to derive the proportion of participants with at least 50% pain relief over six hours prescribed either diclofenac or placebo. We calculated the risk ratio (RR) and number needed to treat to benefit (NNT). We used information on the use of rescue medication to calculate the proportion of participants requiring rescue medication and the weighted mean of the median time to use. We also collected information on adverse effects.

MAIN RESULTS

This update included three new studies, providing a 26% increase in participants in comparisons between diclofenac and placebo. We included 18 studies involving 3714 participants, 1902 treated with diclofenac and 1007 with placebo. This update has also changed the focus of the review, examining the effects of formulation in more detail than previously. This is a result of increased understanding of the importance of speed of onset in determining analgesic efficacy in acute pain.The largest body of information, for diclofenac potassium 50 mg, in seven studies, produced an NNT for at least 50% of maximum pain relief compared with placebo of 2.1 (95% confidence interval (CI) 1.9 to 2.5) (high quality evidence). There was a graded improvement in efficacy as doses rose from 25 mg to 100 mg, both for participants achieving at least 50% maximum pain relief, and for remedication within 6 to 8 hours. Fast-acting formulations (dispersible products, solutions, and softgel formulations) had a similar efficacy for a 50 mg dose, with an NNT of 2.4 (2.0 to 3.0). Diclofenac sodium in a small number of studies produced a lesser effect, with an NNT of 6.6 (4.1 to 17) for the 50 mg dose.Adverse event rates were low in these single dose studies, with no difference between diclofenac and placebo (moderate quality evidence).

AUTHORS' CONCLUSIONS

Diclofenac potassium provides good pain relief at 25 mg, 50 mg, and 100 mg doses. Diclofenac sodium has limited efficacy and should probably not be used in acute pain.

Low-dose SoluMatrix diclofenac : a review of safety across two Phase III studies in patients with acute and osteoarthritis pain

INTRODUCTION

Similar to other NSAIDs, diclofenac is associated with serious dose-related cardiovascular, gastrointestinal, and renal adverse events. Low-dose SoluMatrix diclofenac , containing submicron particles of diclofenac, was developed to provide effective analgesia at lower drug doses compared with currently available NSAIDs.

AREAS COVERED

The efficacy and safety of low-dose SoluMatrix diclofenac was evaluated in two randomized, placebo-controlled Phase III studies: a study in patients with acute pain following bunionectomy surgery and a study in patients with osteoarthritis pain of the hip or knee. In this review article, we summarize safety data from these studies.

EXPERT OPINION

The safety results from the Phase III studies indicate that all dosing regimens of low-dose SoluMatrix diclofenac up to 12 weeks are generally well tolerated. Few serious gastrointestinal, cardiovascular, renal, or hepatic adverse events commonly associated with NSAID use were reported in these studies. Although not directly compared, the safety of SoluMatrix diclofenac was similar to findings for other diclofenac drug products. The potential for safe and effective management of acute and chronic pain at reduced NSAID doses is attractive; definitive characterization of SoluMatrix diclofenac safety requires confirmation by long-term studies.

Advances in NSAID development: evolution of diclofenac products using pharmaceutical technology

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) of the phenylacetic acid class with anti-inflammatory, analgesic, and antipyretic properties. Contrary to the action of many traditional NSAIDs, diclofenac inhibits cyclooxygenase (COX)-2 enzyme with greater potency than it does COX-1. Similar to other NSAIDs, diclofenac is associated with serious dose-dependent gastrointestinal, cardiovascular, and renal adverse effects. Since its introduction in 1973, a number of different diclofenac-containing drug products have been developed with the goal of improving efficacy, tolerability, and patient convenience. Delayed- and extended-release forms of diclofenac sodium were initially developed with the goal of improving the safety profile of diclofenac and providing convenient, once-daily dosing for the treatment of patients with chronic pain. New drug products consisting of diclofenac potassium salt were associated with faster absorption and rapid onset of pain relief. These include diclofenac potassium immediate-release tablets, diclofenac potassium liquid-filled soft gel capsules, and diclofenac potassium powder for oral solution. The advent of topical formulations of diclofenac enabled local treatment of pain and inflammation while minimizing systemic absorption of diclofenac. SoluMatrix diclofenac, consisting of submicron particles of diclofenac free acid and a proprietary combination of excipients, was developed to provide analgesic efficacy at reduced doses associated with lower systemic absorption. This review illustrates how pharmaceutical technology has been used to modify the pharmacokinetic properties of diclofenac, leading to the creation of novel drug products with improved clinical utility.

Assay sensitivity of pain intensity versus pain relief in acute pain clinical trials: ACTTION systematic review and meta-analysis

The magnitude of the effect size of an analgesic intervention can be influenced by several factors, including research design. A key design component is the choice of the primary endpoint. The purpose of this meta-analysis was to compare the assay sensitivity of 2 efficacy paradigms: pain intensity (calculated using summed pain intensity difference [SPID]) and pain relief (calculated using total pain relief [TOTPAR]). A systematic review of the literature was performed to identify acute pain studies that calculated both SPIDs and TOTPARs within the same study. Studies were included in this review if they were randomized, double-blind, placebo-controlled investigations involving medications for postsurgical acute pain and if enough data were provided to calculate TOTPAR and SPID standardized effect sizes. Based on a meta-analysis of 45 studies, the mean standardized effect size for TOTPAR (1.13) was .11 higher than that for SPID (1.02; P = .01). Mixed-effects meta-regression analyses found no significant associations between the TOTPAR - SPID difference in standardized effect size and trial design characteristics. Results from this review suggest that for acute pain studies, utilizing TOTPAR to assess pain relief may be more sensitive to treatment effects than utilizing SPID to assess pain intensity.

PERSPECTIVE

The results of this meta-analysis suggest that TOTPAR may be more sensitive to treatment effects than SPIDs are in analgesic trials examining acute pain. We found that standardized effect sizes were higher for TOTPAR compared to SPIDs.

Assessment of rescue opioid use in patients with post-bunionectomy pain treated with diclofenac potassium liquid-filled capsules

When used in multimodal analgesia for acute pain, nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce the requirement for opioids during the perioperative period. To provide more insight into pain treatment during the outpatient period, we examined the use of opioid rescue medication (RM) and described the relationship between pain intensity and RM use in patients with acute pain after bunionectomy. Patients received placebo or 25 mg of a liquid-filled capsule version of the NSAID diclofenac potassium (DPLFC; n=188 patients/group) every 6 hours during the 48-hour inpatient period through the end of outpatient dosing on day 4. Opioid RM (hydrocodone/acetaminophen tablets, 5 mg/500 mg) was available as needed, but taken at least 1 hour post-study medication. Fewer patients taking DPLFC versus placebo requested opioid RM during the inpatient period (4.8%-44.7% versus 25.0%-90.4%) and also during the outpatient period (3.7%-16.0% versus 13.1%-46.4%). Moderate or severe pain after surgery (P=0.0307 and P=0.0002, respectively) or at second dose (P=0.0006 and P=0.0002, respectively) was predictive of RM use. Patients taking RM (placebo/DPLFC) reported more adverse events (RM 55.7%/40.6%; no RM 29.4%/26.0%). Most adverse events in the RM group were opioid-related. In summary, this study shows that DPLFC lowers the requirement for opioids, which is associated with a reduction in the occurrence of treatment side effects, while maintaining adequate analgesia for patients with moderate acute pain in both the outpatient and outpatient periods. Patients with more severe pain are more likely to use RM, but they still use fewer opioids when treated with DPLFC. This suggests that multimodal treatment using DPLFC and an opioid may offer an important clinical benefit in the treatment of acute pain, including in the home environment.

Inhibition of cAMP-activated intestinal chloride secretion by diclofenac: cellular mechanism and potential application in cholera

Cyclic AMP-activated intestinal Cl⁻ secretion plays an important role in pathogenesis of cholera. This study aimed to investigate the effect of diclofenac on cAMP-activated Cl⁻ secretion, its underlying mechanisms, and possible application in the treatment of cholera. Diclofenac inhibited cAMP-activated Cl⁻ secretion in human intestinal epithelial (T84) cells with IC₅₀ of ∼20 µM. The effect required no cytochrome P450 enzyme-mediated metabolic activation. Interestingly, exposures of T84 cell monolayers to diclofenac, either in apical or basolateral solutions, produced similar degree of inhibitions. Analyses of the apical Cl⁻ current showed that diclofenac reversibly inhibited CFTR Cl⁻ channel activity (IC₅₀∼10 µM) via mechanisms not involving either changes in intracellular cAMP levels or CFTR channel inactivation by AMP-activated protein kinase and protein phosphatase. Of interest, diclofenac had no effect on Na⁺-K⁺ ATPases and Na⁺-K⁺-Cl⁻ cotransporters, but inhibited cAMP-activated basolateral K⁺ channels with IC₅₀ of ∼3 µM. In addition, diclofenac suppressed Ca²⁺-activated Cl⁻ channels, inwardly rectifying Cl⁻ channels, and Ca²⁺-activated basolateral K⁺ channels. Furthermore, diclofenac (up to 200 µM; 24 h of treatment) had no effect on cell viability and barrier function in T84 cells. Importantly, cholera toxin (CT)-induced Cl⁻ secretion across T84 cell monolayers was effectively suppressed by diclofenac. Intraperitoneal administration of diclofenac (30 mg/kg) reduced both CT and Vibrio cholerae-induced intestinal fluid secretion by ∼70% without affecting intestinal fluid absorption in mice. Collectively, our results indicate that diclofenac inhibits both cAMP-activated and Ca²⁺-activated Cl⁻ secretion by inhibiting both apical Cl⁻ channels and basolateral K⁺ channels in intestinal epithelial cells. Diclofenac may be useful in the treatment of cholera and other types of secretory diarrheas resulting from intestinal hypersecretion of Cl⁻.

Diarrhea in cholera results from stimulation of cAMP-mediated intestinal Cl⁻ secretion by cholera toxin (CT). This study demonstrates that diclofenac, a widely used non-steroidal anti-inflammatory drug (NSAID), inhibited cAMP-activated Cl⁻ secretion in human intestinal epithelial (T84) cells by inhibiting both apical Cl⁻ channels (i.e. CFTR) and cAMP-activated basolateral K⁺ channels (i.e. KCNQ1/KCNE3). The mechanism by which CFTR was inhibited did not involve changes in intracellular cAMP levels and activation of negative regulators of CFTR activity including AMP-activated protein kinase (AMPK) and protein phosphatase. In addition, diclofenac suppressed two other types of apical Cl⁻ channels, namely, Ca²⁺-activated Cl⁻ channels and inwardly rectifying Cl⁻ channels, and Ca²⁺-activated basolateral K⁺ channels (i.e. K_Ca3.1) without affecting Na⁺-K⁺ ATPase and Na⁺-K⁺-Cl⁻ cotransporter activities. Of particular importance, diclofenac at 30 mg/kg, which is the human equivalent dose for treatment of pain and inflammation (∼2 mg/kg in human), exhibited anti-secretory efficacy in mouse closed-loop models of cholera induced by either CT or V. cholerae. This study provides a rational basis for further development of diclofenac and related compounds as anti-diarrheal therapy for cholera and other types of diarrheas resulting from Cl⁻ transport-driven intestinal fluid secretion.

Pain Management for Elective Foot and Ankle Surgery: A Systematic Review of Randomized Controlled Trials

Pain after foot and ankle surgery can significantly affect the postoperative outcomes. We performed a systematic review of randomized controlled trials assessing postoperative pain after foot and ankle surgery, because the surgery will lead to moderate-to-severe postoperative pain, but the optimal pain therapy has been controversial. A systematic review of randomized controlled trials in English reporting on pain after foot and ankle surgery in adults published from January 1946 to February 2013 was performed. The primary outcome measure was the postoperative pain scores. The secondary outcome measures included supplemental analgesic requirements and other recovery outcomes. With 953 studies identified, 45 met the inclusion criteria. The approaches improving pain relief (reduced pain scores or opioid requirements) included peripheral nerve blocks, wound infiltration, intravenous dexamethasone, acetaminophen, nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 selective inhibitors, and opioids. Wound instillation, intra-articular injection, and intravenous regional analgesia had variable analgesia. The lack of homogeneous study design precluded quantitative analyses. Optimal pain management strategies included locoregional analgesic techniques plus acetaminophen and nonsteroidal anti-inflammatory drugs or cyclooxygenase-2 selective inhibitors, with opioids used for "rescue," and 1 intraoperative dose of parenteral dexamethasone. Popliteal sciatic nerve blocks would be appropriate when expecting severe postoperative pain (extensive surgical procedure), and ankle blocks and surgical incision infiltration would be appropriate when expecting moderate postoperative pain (less extensive and minimally invasive surgical procedures). Additional studies are needed to assess multimodal analgesia techniques.

Indomethacin submicron particle capsules provide effective pain relief in patients with acute pain: a phase 3 study

Although frequently prescribed to relieve acute pain in patients, non-steroidal anti-inflammatory drugs (NSAIDs) are associated with dose-related gastrointestinal, cardiovascular, and renal complications. Investigational, submicron particle NSAIDs are being developed that could provide effective pain relief at lower doses than currently available oral NSAIDs. This is the first phase 3 study evaluating the analgesic efficacy and safety of lower-dose indomethacin submicron particle capsules in patients following elective surgery. This multicenter, double-blind study enrolled patients aged 18 to 68 years who underwent bunionectomy under regional anesthesia. Patients with a pain intensity rating of ≥40 mm on a 100-mm Visual Analog Scale were randomized to receive indomethacin submicron particle capsules (40 mg 3 times daily [TID], 40 mg twice daily [BID], or 20 mg TID), celecoxib (400 mg loading dose, then 200 mg BID), or placebo. The primary efficacy parameter was the overall (summed) pain intensity difference measured by a Visual Analog Scale during a period of 48 hours. Scheduled assessments measured secondary efficacy parameters such as patient pain intensity differences. Indomethacin submicron particle capsules 40 mg 3 times daily (509.6 ± 91.9 overall [summed] pain intensity difference), 40 mg twice daily (328.0 ± 92.9 overall [summed] pain intensity difference), and 20 mg 3 times daily (380.5 ± 92.9 overall [summed] pain intensity difference) reduced pain intensity from 0 to 48 hours (P ≤ 0.046 for all 3 groups) compared with placebo (67.8 ± 91.4 overall [summed] pain intensity difference). There was some evidence of patient analgesia for celecoxib (279.4 ± 91.9 overall [summed] pain intensity difference; P = 0.103). Some evidence of pain control was observed in patients as early as 2 hours following administration of indomethacin submicron particle capsules and was sustained throughout the treatment period. Indomethacin submicron particle capsules were generally well tolerated by patients. These results suggest that lower-dose indomethacin submicron particle capsules are a potentially promising treatment option for patients with acute pain.

An assessment of the efficacy and safety of diclofenac potassium liquid-filled capsules in patients with various levels of baseline pain intensity

CONTEXT

Diclofenac potassium liquid-filled soft gelatin capsule (DPSGC; Zipsor*) is a novel formulation of diclofenac potassium used to treat mild to moderate acute pain.

OBJECTIVE

To investigate whether DPSGC 25 mg provided significant reduction in pain intensity compared with placebo, regardless of baseline pain intensity, a post hoc analysis was performed of pooled data from two replicate randomized controlled trials (NCT00366444 and NCT00375934) that evaluated the safety and efficacy of DPSGC in postbunionectomy treatment.

METHODS

Patients from the two randomized trials were assigned to one of two subgroups: patients with baseline numerical pain rating scale (NPRS) scores of 4 or greater to less than 7 and those with baseline NPRS scores of 7 or greater. Within each subgroup, efficacy and safety of DPSGC was compared with placebo.

RESULTS

Across the two studies, 73 DPSGC- and 59 placebo-treated patients had baseline pain intensity scores ranging from 4 or greater to less than 7, while 128 DPSGC- and 141 placebo-treated patients had baseline pain intensity scores of 7 or greater. Significantly lower mean 48-hour NPRS scores were observed in the DPSGC group, regardless of baseline pain intensity (P < 0.0001). In both subgroups, at least twice as many patients treated with DPSGC rated the study drug as very good or excellent compared with patients taking placebo. Potential limitations for this post hoc analysis include study design and patient population. As with all studies investigating treatment for pain, the use of rescue medication may also be a potential limitation.

CONCLUSIONS

DPSGC provided significantly greater improvements in pain compared with placebo following bunionectomy, regardless of patients' baseline pain level.

A phase 3, randomized, placebo-controlled trial of DepoFoam® bupivacaine (extended-release bupivacaine local analgesic) in bunionectomy

BACKGROUND

DepoFoam® bupivacaine (Pacira Pharmaceuticals, Inc., San Diego, CA, USA), an extended-release liposomal bupivacaine-based analgesic, was compared with placebo for the prevention of pain after bunionectomy in a randomized, multicenter, double-blind phase 3 clinical study.

METHODS

Patients received placebo (n = 96) or DepoFoam bupivacaine 120 mg (n = 97) via wound infiltration prior to closure. Pain intensity was assessed using a numeric rating scale (NRS) from time 0 through to 72 hours postsurgically. The primary efficacy measure was area under the curve (AUC) of NRS scores through 24 hours. Other efficacy measures included AUC of NRS at other time points, proportion of patients who were pain-free, time to first opioid use, and total postsurgical consumption of supplemental opioid medication. Adverse events were also assessed.

RESULTS

The AUC for NRS scores was significantly less in patients treated with DepoFoam bupivacaine versus patients receiving placebo at 24 hours (P = 0.0005) and 36 hours (P < 0.0229). More patients treated with DepoFoam bupivacaine avoided use of opioid rescue medication during the first 24 hours (7.2% vs. 1%; P < 0.0404) and were pain-free (NRS ≤ 1) at 2, 4, 8, and 48 hours. Median time-to-first-opioid use was delayed in favor of DepoFoam bupivacaine (4.3 vs. 7.2 hours; P < 0.0001). Fewer adverse events were reported by patients treated with DepoFoam bupivacaine (59.8%) versus placebo (67.7%).

CONCLUSIONS

DepoFoam bupivacaine, a long-acting local analgesic, provided extended pain relief and decreased opioid use after bunionectomy, compared with placebo.

Diclofenac: an update on its mechanism of action and safety profile

BACKGROUND

Diclofenac is a proven, commonly prescribed nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-inflammatory, and antipyretic properties, and has been shown to be effective in treating a variety of acute and chronic pain and inflammatory conditions. As with all NSAIDs, diclofenac exerts its action via inhibition of prostaglandin synthesis by inhibiting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) with relative equipotency. However, extensive research shows the pharmacologic activity of diclofenac goes beyond COX inhibition, and includes multimodal and, in some instances, novel mechanisms of action (MOA).

DATA SOURCES

Literature retrieval was performed through PubMed/MEDLINE (through May 2009) using combinations of the terms diclofenac, NSAID, mechanism of action, COX-1, COX-2, and pharmacology. Reference citations resulting from publications identified in the literature search were reviewed when appropriate.

METHODS

This article reviews the established, putative, and emerging MOAs of diclofenac; compares the drug's pharmacologic and pharmacodynamic properties with other NSAIDs to delineate its potentially unique qualities; hypothesizes why it has been chosen for further recent formulation enhancement; and evaluates the potential effect of its MOA characteristics on safety.

DISCUSSION

Research suggests diclofenac can inhibit the thromboxane-prostanoid receptor, affect arachidonic acid release and uptake, inhibit lipoxygenase enzymes, and activate the nitric oxide-cGMP antinociceptive pathway. Other novel MOAs may include the inhibition of substrate P, inhibition of peroxisome proliferator activated receptor gamma (PPARgamma), blockage of acid-sensing ion channels, alteration of interleukin-6 production, and inhibition of N-methyl-D-aspartate (NMDA) receptor hyperalgesia. The review was not designed to compare MOAs of diclofenac with other NSAIDs. Additionally, as the highlighted putative and emerging MOAs do not have clinical data to demonstrate that these models are correct, further research is necessary to ascertain if the proposed pathways will translate into clinical benefits. The diversity in diclofenac's MOA may suggest the potential for a relatively more favorable profile compared with other NSAIDs.

Pharmacokinetic comparison of an oral diclofenac potassium liquid-filled soft gelatin capsule with a diclofenac potassium tablet

OBJECTIVE

To compare the pharmacokinetic profiles of diclofenac potassium liquid-filled soft gelatin capsules (DPSGC) using patented ProSorb dispersion technology with an immediate-release, diclofenac potassium 50-mg comparator tablet in two open-label, single-dose, randomized, crossover relative bioavailability studies in healthy volunteers.

METHODS

In Study 1, volunteers (n = 21) received DPSGC 50 mg or a diclofenac potassium 50-mg comparator tablet in two inpatient study periods. In Study 2 (n = 54), volunteers received DPSGC 25 mg, DPSGC 50 mg, or a diclofenac potassium 50-mg comparator immediate-release tablet in three inpatient study periods.

RESULTS

In both studies, DPSGC 50 mg displayed a significantly shorter T(max) and higher C(max) than the 50-mg diclofenac potassium comparator tablet. DPSGC 25 mg (Study 2) produced a shorter T(max) (0.45 h) and an equivalent C(max) (1125 ng/ml) to the 50-mg comparator drug. Plasma diclofenac concentration-time courses for the diclofenac potassium 50-mg comparator tablet showed many low, delayed, or multiple peaks compared with DPSGC treatments.

CONCLUSIONS

DPSGC 25 mg and 50 mg were more rapidly and consistently absorbed than diclofenac potassium 50-mg comparator tablets. The C(max) of DPSGC 25 mg was equivalent to the 50-mg diclofenac potassium comparator tablet. These characteristics may be beneficial when fast, consistent drug absorption is needed.