Nonsteroidal anti-inflammatory drugs and acetaminophen ameliorate muscular mechanical hyperalgesia developed after lengthening contractions via cyclooxygenase-2 independent mechanisms in rats

Efficacy and Safety of Ultrasound-Guided Acupotomy Versus Celecoxib in Patients with Thoracodorsal Myofascial Pain Syndrome: A Randomized Controlled Trial

Objective: To evaluate the efficacy and safety of ultrasound-guided acupotomy (UgA) for the treatment of thoracodorsal myofascial pain syndrome (TDMPS) and monitor its mid-term efficacy at 3 months after treatment. Methods: A 3-week, evaluator-blinded randomized clinical trial was conducted among 100 patients with TDMPS (visual analogue scale [VAS] score > 3) in the outpatient clinic of the Department of Orthopaedics of the Second Affiliated Hospital of Anhui University of Traditional Chinese Medicine, with a 3-month follow-up starting after completion of treatment. These patients were randomly assigned to receive UgA (n = 50) or oral celecoxib (n = 50). Recruitment was conducted between January 2021 and July 2022. The primary outcome was the VAS score, and the secondary outcomes included the Oswestry Disability Index (ODI), Pain Anxiety Symptoms Scale (PASS), and TNF-α and IL-1β levels. Outcome data were collected at baseline, week 3 (post-treatment) and week 15 (follow-up). Results: Compared with that in the celecoxib group, the pain in the UgA group was alleviated more strongly, with an adjusted mean group difference of -0.69 (95% CI,-1.07 to -0.31 after multiple imputation) at week 3 and -1.96 (95% CI,-2.33 to -1.59 after multiple imputation) at week 15 (p < 0.001 for overall group × time interaction). Both groups exhibited improvements in the ODI and PASS scores at weeks 3 and 15, but these improvements were significantly greater in the UgA group (p < 0.05). At week 3, the TNF-α and IL-1 levels were significantly lower in both groups, but celecoxib was more effective (p < 0.05). Results from analyses with multilevel multiple imputation for missingness were similar. Conclusion: UgA led to greater and safer alleviation of pain, dysfunction, and pain anxiety in patients treated with TDMPS than did celecoxib and had a durable 3-month efficacy but was inferior to celecoxib in reducing the level of inflammatory factors. These findings may prompt clinicians to recommend UgA as an alternative and supplementary therapy for pain management in patients with TDMPS.

Acetaminophen influences musculoskeletal signaling but not adaptations to endurance exercise training

Acetaminophen (ACE) is a widely used analgesic and antipyretic drug with various applications, from pain relief to fever reduction. Recent studies have reported equivocal effects of habitual ACE intake on exercise performance, muscle growth, and risks to bone health. Thus, this study aimed to assess the impact of a 6-week, low-dose ACE regimen on muscle and bone adaptations in exercising and non-exercising rats. Nine-week-old Wistar rats (n = 40) were randomized to an exercise or control (no exercise) condition with ACE or without (placebo). For the exercise condition, rats ran 5 days per week for 6 weeks at a 5% incline for 2 min at 15 cm/s, 2 min at 20 cm/s, and 26 min at 25 cm/s. A human equivalent dose of ACE was administered (379 mg/kg body weight) in drinking water and adjusted each week based on body weight. Food, water intake, and body weight were measured daily. At the beginning of week 6, animals in the exercise group completed a maximal treadmill test. At the end of week 6, rats were euthanized, and muscle cross-sectional area (CSA), fiber type, and signaling pathways were measured. Additionally, three-point bending and microcomputer tomography were measured in the femur. Follow-up experiments in human primary muscle cells were used to explore supra-physiological effects of ACE. Data were analyzed using a two-way ANOVA for treatment (ACE or placebo) and condition (exercise or non-exercise) for all animal outcomes. Data for cell culture experiments were analyzed via ANOVA. If omnibus significance was found in either ANOVA, a post hoc analysis was completed, and a Tukey's adjustment was used. ACE did not alter body weight, water intake, food intake, or treadmill performance (p > .05). There was a treatment-by-condition effect for Young's Modulus where placebo exercise was significantly lower than placebo control (p < .05). There was no treatment by condition effects for microCT measures, muscle CSA, fiber type, or mRNA expression. Phosphorylated-AMPK was significantly increased with exercise (p < .05) and this was attenuated with ACE treatment. Furthermore, phospho-4EBP1 was depressed in the exercise group compared to the control (p < .05) and increased in the ACE control and ACE exercise group compared to placebo exercise (p < .05). A low dose of ACE did not influence chronic musculoskeletal adaptations in exercising rodents but acutely attenuated AMPK phosphorylation and 4EBP1 dephosphorylation post-exercise.

Neurochemical mechanism of muscular pain: Insight from the study on delayed onset muscle soreness

We reviewed fundamental studies on muscular pain, encompassing the characteristics of primary afferent fibers and neurons, spinal and thalamic projections, several muscular pain models, and possible neurochemical mechanisms of muscle pain. Most parts of this review were based on data obtained from animal experiments, and some researches on humans were also introduced. We focused on delayed-onset muscle soreness (DOMS) induced by lengthening contractions (LC), suitable for studying myofascial pain syndromes. The muscular mechanical withdrawal threshold (MMWT) decreased 1-3 days after LC in rats. Changing the speed and range of stretching showed that muscle injury seldom occurred, except in extreme conditions, and that DOMS occurred in parameters without muscle damage. The B2 bradykinin receptor-nerve growth factor (NGF) route and COX-2-glial cell line-derived neurotrophic factor (GDNF) route were involved in the development of DOMS. The interactions between these routes occurred at two levels. A repeated-bout effect was observed in MMWT and NGF upregulation, and this study showed that adaptation possibly occurred before B2 bradykinin receptor activation. We have also briefly discussed the prevention and treatment of DOMS.

Oral versus intravenous acetaminophen for perioperative pain management in adult patients undergoing non-cardiac surgery: A quantile segmented regression analysis

STUDY OBJECTIVE

Determine whether preferential use of perioperative enteral acetaminophen is associated with changes in perioperative pain, narcotic administration, or time to meeting criteria for post anesthesia care unit (PACU) discharge, compared to preferential parenteral administration.

DESIGN

Retrospective Cohort with quantile segmented regression analysis. Groups determined by date of surgery, one year pre-initiative and one year post-initiative.

SETTING

Operating room and PACU of a tertiary academic medical center.

PATIENTS

Adult (age > 18 years), ASA status 1-5, non-pregnant patients undergoing non-cardiac surgery of less than six hours duration admitted to the PACU postoperatively.

INTERVENTIONS

A multidisciplinary initiative to preferentially utilize enteral over parenteral acetaminophen.

MEASUREMENTS

The primary outcome was narcotic consumption in the PACU. Secondary outcomes were intraoperative narcotic administration, pain score on PACU admission and discharge, and time to meeting criteria for PACU discharge.

RESULTS

24,701 patients were included in the analysis; 12,379 had surgery prior to the initiative and 12,322 after. Enteral acetaminophen administration increased preoperatively from 13.49% to 26.84%, and postoperatively from 43.16% to 51.45%, while intraoperative parenteral APAP use dropped from 43.23% to 6.81%. Quantile Segmented regression analysis after adjusting for period (pre versus postintervention), day, age, gender, inpatient status, and ASA class demonstrated a decrease in adjusted median perioperative acetaminophen dose (-175 mg P < 0.001), with no significant difference in level change of intraoperative or PACU narcotic administration. There was no significant difference in median time to meet criteria for PACU discharge, though there was a significant change in the slope, (-0.36, p = 0.007.) Median pain scores measured on a standard 0-10 numeric rating scale at PACU admission did not change, while median pain scores at PACU discharge decreased slightly (-0.24 p < 0.001). There was no change in the probability of PONV.

CONCLUSION

In adult patients undergoing non-cardiac surgery of <6 h duration, preferential use of enteral rather than parenteral acetaminophen is associated with non-inferior outcomes in narcotic requirements, pain scores, time to PACU discharge, and probability of PONV when compared with routine parenteral administration. Further studies are needed to validate these findings.

Brief research report: Repurposing pentoxifylline to treat intense acute swimming-Induced delayed-onset muscle soreness in mice: Targeting peripheral and spinal cord nociceptive mechanisms

In this study, we pursue determining the effect of pentoxifylline (Ptx) in delayed-onset muscle soreness (DOMS) triggered by exposing untrained mice to intense acute swimming exercise (120 min), which, to our knowledge, has not been investigated. Ptx treatment (1.5, 4.5, and 13.5 mg/kg; i.p., 30 min before and 12 h after the session) reduced intense acute swimming-induced mechanical hyperalgesia in a dose-dependent manner. The selected dose of Ptx (4.5 mg/kg) inhibited recruitment of neutrophils to the muscle tissue, oxidative stress, and both pro- and anti-inflammatory cytokine production in the soleus muscle and spinal cord. Furthermore, Ptx treatment also reduced spinal cord glial cell activation. In conclusion, Ptx reduces pain by targeting peripheral and spinal cord mechanisms of DOMS.

Preliminary evidence of safety and effectiveness of Loxoprofen Sodium Cataplasm combined with physiotherapy for myofascial pain syndrome treatment: A randomized controlled pilot clinical trial

BACKGROUND

Myofascial pain syndrome (MPS) is one of the most common causes of chronic skeletal muscle pain, which is closely related to skeletal muscle myofascial trigger point (MTRP). Since there is no first-line treatment for MPS, we investigated Loxoprofen Sodium Cataplasm combined with physiotherapy as a non-invasive therapy in patients at different levels to a protocol with superior efficacy that is safe and easy to promote. Moreover, this treatment could represent an alternative therapeutic strategy for low-income patients to a safer, more convenient, and more economical treatment scheme.

METHODS

A randomized clinical study was aimed at evaluating the safety and efficacy of Loxoprofen Sodium Cataplasm combined with physiotherapy in patients diagnosed with MPS in the pain clinic. We screened 100 patients with MPS, and using a computer-generated random allocation sequence, we stratified patients in a ratio of 2:1:1:1 (A: B: C: D) to one of the four treatment groups. Group A received Loxoprofen Sodium Cataplasm combined with extracorporeal shock wave therapy (ESWT) and transcutaneous electrical nerve stimulation (TENS). Group B received Loxoprofen Sodium Cataplasm alone. Group C received physiotherapy alone. Group D received Flurbiprofen Cataplasm combined with physiotherapy. After 2 weeks of treatment, the overall efficiency and secondary assessment indicators, including visual analog scale (VAS) scores, chronic soft tissue injury (CSTI) scores, Oswestry Disability Index (ODI) scores, or Northwick Park Neck Pain Questionnaire (NPQ) scores, were evaluated before and after treatment to analyze the difference in efficacy of each group.

RESULTS

All groups were well tolerated with no reported adverse events. Significant treatment differences in the change from baseline in overall efficiency (primary efficacy endpoint) (P = 0.0078) were observed in subjects of groups A and C.

CONCLUSION

Showing valuable data of efficacy in primary and secondary endpoints, Loxoprofen Sodium Cataplasm combined with physiotherapy is superior in the treatment of MPS.

TRIAL REGISTRATION NUMBER

https://www.chictr.org.cn/ (ChiCTR2100054756).

Plantar incision with severe muscle injury can be a cause of long-lasting postsurgical pain in the skin

AIMS

Although chronic local inflammation in deeper tissues after skin wound healing might produce chronification of acute postsurgical pain, its mechanisms have not been fully elucidated. We hypothesized that muscle injury and severe inflammation would prolong acute postsurgical pain by its central nervous system mechanisms.

MAIN METHODS

After approval of the Animal Care Committee, experiments were performed in Male Sprague-Dawley rats weighing 250-300 g. Plantar incision and plantar incision combined with cryoinjury of the plantar flexor digitorum brevis muscle were made in the plantar incision group and muscle injury group, respectively. Pain-related behaviors were assessed, and inflammatory cells were isolated from injured muscle and analyzed by flow cytometry. Spinal microglial activation was assessed with Iba-1 staining.

KEY FINDINGS

Mechanical hyperalgesia from day 5 to day 8 and spontaneous pain-related behavior from day 3 to day 7 were significantly greater in the muscle injury group than in the plantar incision group (P < 0.05), whereas there was no significant difference between the two groups in thermal hyperalgesia. In the muscle injury group, the number of inflammatory cells on day 4 was significantly larger and spinal Iba-1 expression levels on days 4 and 7 were significantly higher than those in the plantar incision group (P < 0.05).

SIGNIFICANCE

Surgical injury in deep tissues accompanying severe muscle inflammation induced prolonged postsurgical pain in the healing wound of the skin not by the persistence of muscle inflammation but by a central mechanism involving microglial activation at the level of the spinal cord.