Myofascial Pain Syndrome: An Update on Clinical Characteristics, Etiopathogenesis, Diagnosis, and Treatment

Myofascial pain syndrome (MPS) is a chronic regional pain condition characterized by trigger points-hyperirritable spots within taut bands of muscle fibers that cause both localized and referred pain. The pathogenesis, diagnostic criteria, and classification of MPS are still under investigation, which complicates the development of standardized treatment protocols. Although diagnostic tools have improved, MPS often remains underrecognized due to symptom overlap with other pain disorders, such as fibromyalgia, neuropathic pain, and joint disorders. Factors contributing to its onset and persistence include muscle overuse, postural imbalance, systemic conditions, and psychological and behavioral influences. This narrative review explores the primary risk factors, current hypotheses on pathogenesis, diagnosis and differential diagnosis, and both conventional and emerging treatments. Sufficient evidence supports the use of local anesthetic injections for MPS. Some evidence suggests that dry needling, acupuncture, magnetic stimulation, ultrasound therapy, laser therapy, extracorporeal shock wave therapy, and manual therapy may be effective, particularly compared to sham or placebo. However, non-steroidal anti-inflammatory drugs, diclofenac, botulinum toxin, and transcutaneous electrical nerve stimulation show insufficient evidence, while the effectiveness of muscle relaxants, antidepressants, gabapentin, opioids, topical lidocaine, capsaicin, EMLA cream, and kinesio taping remains inconclusive. Effective management of MPS requires a patient-centered approach that integrates empirically supported and evidence-based treatments tailored to individual needs. This review synthesizes the current understanding of MPS and highlights the need for high-quality research to improve clinical decision-making in managing this complex condition.

Efficacy of Phlai (Zingiber montanum) Spray Cool Formula in Managing Upper Trapezius Myofascial Pain Syndrome: A Randomized Controlled Trial

Phlai (Zingiber montanum) has long been valued for its anti-inflammatory and analgesic properties in traditional medicine. This study aimed to develop and assess the physical stability, chemical composition, and clinical efficacy of a novel Phlai spray cool formula (PSCF) compared to a diclofenac spray (DS) in patients with chronic myofascial pain syndrome. The chemical analysis revealed curcumin (28.73 ± 5.73 mg/100 g), β-sitosterol (50.92 ± 1.27 mg/100 g), and lauric acid (38.86 ± 1.72 g/100 g) as key active compounds. PSCF demonstrated stable physicochemical properties, including pH and peroxide value across storage conditions. In a randomized controlled trial involving 66 participants, PSCF and DS groups exhibited comparable reductions in pain intensity, as measured by the Visual Analog Scale (VAS), from baseline to week 2. Both groups also showed significant improvements in neck disability index (NDI), pressure pain threshold (PPT), and cervical range of motion (CROM). By week 2, the increase in CROM for flexion and extension reached 23.54 ± 4.09° and 19.43 ± 3.20°, respectively, with no significant intergroup differences. The SF-36 health survey indicated notable improvements in overall health status and quality of life, particularly in physical and emotional domains. The analgesic effects of PSCF are attributed to the combined action of menthol, β-sitosterol, and curcumin. The study demonstrated that PSCF offers a therapeutic effect comparable to diclofenac spray without adverse reactions, highlighting its potential as an alternative topical analgesic for chronic myofascial pain management.

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.

Comparative effectiveness of noninvasive therapeutic interventions for myofascial pain syndrome: a network meta-analysis of randomized controlled trials

BACKGROUND

Myofascial pain syndrome (MPS) has an impact on physical health and quality of life for patients, with various noninvasive methods used for relieving myofascial pain. The authors aimed to compare the effectiveness of different noninvasive therapeutic interventions for MPS.

MATERIALS AND METHODS

The authors searched PubMed, Embase, CINAHL Complete, Web of Science, Cochrane, and Scopus to identify randomized controlled trials describing the effects of any noninvasive treatments in patients with MPS. The primary outcome was pain intensity, while pressure pain threshold and pain-related disability were secondary outcomes.

RESULTS

The analysis included 40 studies. Manual therapy [mean difference (MD) of pain: -1.60, 95% CI: -2.17 to -1.03; MD of pressure pain threshold: 0.52, 95% CI: 0.19 to 0.86; MD of pain-related disability: -5.34, 95% CI: -8.09 to -2.58], laser therapy (MD of pain: -1.15, 95% CI: -1.83 to -0.46; MD of pressure pain threshold: 1.00, 95% CI: 0.46 to 1.54; MD of pain-related disability: -4.58, 95% CI: -7.80 to -1.36), extracorporeal shock wave therapy (MD of pain: -1.61, 95% CI: -2.43 to -0.78; MD of pressure pain threshold: 0.84, 95% CI: 0.33 to 1.35; MD of pain-related disability: -5.78, 95% CI: -9.45 to -2.12), and ultrasound therapy (MD of pain: -1.54, 95% CI: -2.24 to -0.84; MD of pressure pain threshold: 0.77, 95% CI: 0.31 to 1.22) were more effective than no treatment.

CONCLUSION

Our findings support that manual therapy, laser therapy, and extracorporeal shock wave therapy could effectively reduce pain intensity, pressure pain threshold, and pain-related disability with statistical significance when compared with placebo. This finding may provide clinicians with appropriate therapeutic modalities for patients with MPS among different scenarios.

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).

Characterising the Features of 381 Clinical Studies Evaluating Transcutaneous Electrical Nerve Stimulation (TENS) for Pain Relief: A Secondary Analysis of the Meta-TENS Study to Improve Future Research

Background and Objectives: Characterising the features of methodologies, clinical attributes and intervention protocols, of studies is valuable to advise directions for research and practice. This article reports the findings of a secondary analysis of the features from studies screened as part of a large systematic review of TENS (the meta-TENS study). Materials and Methods: A descriptive analysis was performed on information associated with methodology, sample populations and intervention protocols from 381 randomised controlled trials (24,532 participants) evaluating TENS delivered at a strong comfortable intensity at the painful site in adults with pain, irrespective of diagnosis. Results: Studies were conducted in 43 countries commonly using parallel group design (n = 334) and one comparator group (n = 231). Mean ± standard deviation (SD) study sample size (64.05 ± 58.29 participants) and TENS group size (27.67 ± 21.90 participants) were small, with only 13 of 381 studies having 100 participants or more in the TENS group. Most TENS interventions were ‘high frequency’ (>10 pps, n = 276) and using 100 Hz (109/353 reports that stated a pulse frequency value). Of 476 comparator groups, 54.2% were active treatments (i.e., analgesic medication(s), exercise, manual therapies and electrophysical agents). Of 202 placebo comparator groups, 155 used a TENS device that did not deliver currents. At least 216 of 383 study groups were able to access other treatments whilst receiving TENS. Only 136 out of 381 reports included a statement about adverse events. Conclusions: Clinical studies on TENS are dominated by small parallel group evaluations of high frequency TENS that are often contaminated by concurrent treatment(s). Study reports tended focus on physiological and clinical implications rather than the veracity of methodology and findings. Previously published criteria for designing and reporting TENS studies were neglected and this should be corrected in future research using insights gleaned from this analysis.

Evaluation of Sustained Acoustic Medicine for Treating Musculoskeletal Injuries in Military and Sports Medicine

Background

Musculoskeletal injuries are common in collegiate, professional, and military personnel and require expedited recovery to reduce lost work time. Sustained acoustic medicine (SAM) provides continuous long-duration ultrasound at 3MHz and 132mW/cm². The treatment is frequently prescribed to treat acute and chronic soft tissue injuries and reduce pain. The objective of this study was to evaluate the efficacy of SAM treatment for musculoskeletal injuries and accelerated recovery.

Methods

An 18-question electronic survey and panel discussion were conducted on Athletic Trainers (ATs) using SAM treatment in professional, collegiate, and military sports medicine. The survey included both qualitative and quantitative questions. In addition, a panel discussion discussed SAM effectiveness with expert ATs. Power calculation of sampling and statistical evaluation of data was utilized to generalize the results.

Results

Survey respondents (n=97) and panelists (n=142) included ATs from all National Athletic Trainers Association districts. SAM was primarily used for musculoskeletal injuries (83.9%, p<0.001) with a focus on healing tendons and ligaments (87.3%, p<0.001). SAM treatment was also used on joints (44.8%), large muscle groups (43.7%), and bone (41.4%). SAM provided clinical improvement in under 2 weeks (68.9%, p<0.001) and a 50% reduction in pain medication (63%, p<0.001). In addition, patients were highly receptive to treatment (87.3%, p<0.001), and ATs had a high level of confidence for improved function and returned to work after 30-days of SAM use (81.2%, p<0.001).

Conclusion

SAM is an effective, safe, easy-to-use, noninvasive, comfortable, and versatile therapeutic for healing musculoskeletal injuries.

Transcutaneous electrical stimulation in neck pain: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The objective of this systematic review was to investigate the effectiveness of electrical stimulation (ES) for neck pain (NP).

DATABASES AND DATA TREATMENT

The databases CINAHL, Embase, MEDLINE (via OVID), PEDro and Web of Science were searched, with no date restrictions. Two independent reviewers selected randomized controlled trials (RCTs) reporting pain, range of motion or psychosocial factors in people with NP, in which ES was applied. Methodological quality was assessed using the PEDro scale. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) was used to evaluate the quality of evidence. Thirty studies met eligibility criteria.

RESULTS

Main results showed evidence of moderate quality that ES combined with other intervention significantly decreases the pain intensity compared to other intervention immediately post-treatment and at short-term follow-up; evidence of low quality showed significant effects of ES combined with other intervention in decreasing neck disability compared to other intervention immediately post-treatment; evidence of very-low quality that ES increased the pressure pain threshold compared to placebo immediately post-treatment and that ES + other intervention also increased the pressure pain threshold compared to other intervention at short-term follow-up.

CONCLUSIONS

ES combined with other intervention seems to be useful to relieve pain and to improve disability in people with NP, however, more studies are needed.

SIGNIFICANCE

Electrical stimulation seems to be effective for improving pain intensity, immediately post-treatment in people with neck pain, mainly as an adjunct therapeutic modality. Nevertheless, high-quality RCTs are still needed to investigate the efficacy of electrical stimulation in neck pain.

Low-Intensity Continuous Ultrasound for the Symptomatic Treatment of Upper Shoulder and Neck Pain: A Randomized, Double-Blind Placebo-Controlled Clinical Trial

Purpose

Low-intensity continuous ultrasound (LICUS) is an emerging high-dosimetry ultrasound-based therapy for accelerated tissue healing and the treatment of myofascial pain. In this study, LICUS treatment is clinically evaluated for chronic upper neck and shoulder pain in a randomized, multi-site, double-blind, placebo-controlled study.

Patients and Methods

CONSORT guidelines were followed in conducting and reporting the clinical trial. Thirty-three participants with upper trapezius myofascial pain were randomized for treatment with active (n=25) or placebo (n=8) devices. Investigators and subjects were blinded to treatment groups. Participants self-reported pain daily, rating from 0–10 on the numeric rating scale. If pain rating was more significant than or equal to 3, the LICUS (3MHz, 0.132W/cm², 1.3W, 4 hours) was self-applied for total energy dosimetry of 18,720 Joules per treatment. During the 4-week study, daily pain rating was recorded. If LICUS treatment was delivered, pain before, during, and after treatment were recorded as well as the global rate of change (GROC). Independent t-tests were used to assess change from baseline and differences between treatment groups. ClinicalTrials.gov: NCT02135094.

Results

There was a 100% completion rate for participants enrolled in the study and no significant differences between the groups regarding demographic variables or baseline outcome measures. Participants treated with active therapy observed a significant mean pain reduction from baseline of 2.61 points for active (p<0.001), compared to 1.58 points decrease from baseline for placebo (p=0.087), resulting in a 1.03 points significant decrease in the active group over placebo (p=0.003). The total GROC was significantly higher in the active group at 2.84 points compared to the placebo group at 0.46 points (p<0.001).

Conclusion

Low-intensity continuous ultrasound treatment significantly reduced pain in patients with upper trapezius myofascial pain of the neck and shoulder. LICUS treatment showed a clinically meaningful improvement in the GROC scores for patients. The results from this clinical trial indicate that the LICUS treatment of 18,720 Joules can effectively be used to treat clinical pain related to upper trapezius myofascial pain. Further research could investigate varying dosimetry to improve efficacy and/or reduce the dose.

Transcutaneous electrical nerve stimulation (TENS) for chronic neck pain

BACKGROUND

Chronic neck pain is a highly prevalent condition, affecting 10% to 24% of the general population. Transcutaneous electrical nerve stimulation (TENS) is the noninvasive, transcutaneous use of electrical stimulation to produce analgesia. It is a simple, low-cost and safe intervention used in clinical practice as an adjunct treatment for painful musculoskeletal conditions that have a considerable impact on daily activities, such as chronic neck pain. This review is a split from a Cochrane Review on electrotherapy for neck pain, published in 2013, and focuses specifically on TENS for chronic neck pain.

OBJECTIVES

To evaluate the effectiveness of transcutaneous electrical nerve stimulation (TENS) (alone or in association with other interventions) compared with sham and other clinical interventions for the treatment of chronic neck pain.

SEARCH METHODS

We searched Cochrane Back and Neck Trials Register, CENTRAL, MEDLINE, Embase, five other databases and two trials registers to 9 November 2018. We also screened the reference lists of relevant studies to identify additional trials. There were no language, source, or publication date restrictions.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) involving adults (≥ 18 years of age) with chronic neck pain (lasting > 12 weeks) that compared TENS alone or in combination with other treatments versus active or inactive treatments. The primary outcomes were pain, disability and adverse events.

DATA COLLECTION AND ANALYSIS

Two independent review authors selected the trials, extracted data and assessed the risk of bias of included studies. A third review author was consulted in case of disagreements. We used the Cochrane 'Risk of bias' tool (adapted by Cochrane Back and Neck), to assess the risk of bias of individual trials and GRADE to assess the certainty of evidence. We used risk ratios (RRs) to measure treatment effects for dichotomous outcomes, and mean differences (MDs) for continuous outcomes, with their respective 95% confidence intervals (CIs).

MAIN RESULTS

We included seven RCTs with a total of 651 participants, mean age 31.7 to 55.5 years, conducted in three different countries (Turkey, Jordan and China). The length of follow-up ranged from one week to six months. Most RCTs used continuous TENS, with a frequency of 60 Hz to 100 Hz, pulse width of 40 μs to 250 μs and tolerable intensity, described as a tingling sensation without contraction, in daily sessions lasting 20 to 60 minutes. Due to heterogeneity in interventions and outcomes, we did not pool individual study data into meta-analyses. Overall, we judged most studies as being at low risk for selection bias and high risk for performance and detection bias. Based on the GRADE approach, there was very low-certainty evidence from two trials about the effects of conventional TENS when compared to sham TENS at short-term (up to 3 months after treatment) follow-up, on pain (assessed by the Visual Analogue Scale (VAS)) (MD -0.10, 95% CI -0.97 to 0.77) and the percentage of participants presenting improvement of pain (RR 1.57, 95% CI 0.84 to 2.92). None of the included studies reported on disability or adverse events.

AUTHORS' CONCLUSIONS

This review found very low-certainty evidence of a difference between TENS compared to sham TENS on reducing neck pain; therefore, we are unsure about the effect estimate. At present, there is insufficient evidence regarding the use of TENS in patients with chronic neck pain. Additional well-designed, -conducted and -reported RCTs are needed to reach robust conclusions.

Use of low level of continuous heat and Ibuprofen as an adjunct to physical therapy improves pain relief, range of motion and the compliance for home exercise in patients with nonspecific neck pain: A randomized controlled trial

BACKGROUND

It has been well documented at heat reduces pain and increases healing by increasing blood flow in tissue.

OBJECTIVE

The purpose of this study was to see if the use of low level continuous heat (LLCH) and Ibuprofen used as a home therapy between physical therapy sessions at a clinic resulted in better therapy outcomes in people with chronic neck pain.

METHODS

Ninety-two patients with chronic nonspecific neck pain were randomly divided into 4 groups; LLCH group, LLCH with Ibuprofen (IP) group, sham LLCH with sham IP group, and controls. All subjects underwent 45 minutes of conventional physical therapy twice a week for 2 weeks. the neck disability index (NDI), subjective pain, range of motion (ROM), strength of the neck, and home exercise compliance were measured.

RESULTS

Both LLCH and IP significantly reduced pain and NDI score, and increased ROM (p< 0.01). Home exercise compliance in LLCH and LLCH with IP group was significantly higher than the placebo and control groups (p < 0.05).

CONCUSION

The use of LLCH alone and LLCH with IP as an adjunct to conventional physical therapy for chronic neck pain significantly improved pain attenuation and it causes greater compliance for home.

Effects of Myofascial Release on Pressure Pain Thresholds in Patients With Neck Pain: A Single-Blind Randomized Controlled Trial

OBJECTIVE

This study aimed to investigate the efficacy of myofascial release therapy (MRT) for improving pressure pain thresholds (PPTs) and pain in patients with mechanical neck pain.

DESIGN

Forty-one participants with neck pain were randomly allocated to either a MRT group (five sessions) or a physical therapy (PT) group (ten sessions) for 2 wks. The multimodal PT program included ultrasound therapy (US), transcutaneous electric nerve stimulation, and massage. Visual analog scale (VAS) and PPTs in suboccipital and upper trapezius muscles were measured at baseline, at the end of treatment, and at 1 month follow-up.

RESULTS

At the end of treatment, significant mean differences in VAS (-0.99, 95% confidence interval [CI] = -1.82 to -0.16), in both left (0.28, 95% CI = 0.06 to 0.50) and right (0.40, 95% CI = 0.16 to 0.63) suboccipital PPTs and in the right trapezius PPT (0.38, 95% CI = 0.07 to 0.69) were observed. At 1-month follow-up, significant mean differences were found for VAS (-1.85, 95% CI = -2.76 to -0.94) and both left (0.46, 95% CI = 0.12 to 0.80) and right (0.38, 95% CI = 0.06 to 0.69) suboccipital PPTs.

CONCLUSIONS

This study provides evidence that MRT could be better than a multimodal PT program for short-term improvement of pain and PPTs in patients with neck pain.

Alternatives to Opioids in the Pharmacologic Management of Chronic Pain Syndromes: A Narrative Review of Randomized, Controlled, and Blinded Clinical Trials

Chronic pain exerts a tremendous burden on individuals and societies. If one views chronic pain as a single disease entity, then it is the most common and costly medical condition. At present, medical professionals who treat patients in chronic pain are recommended to provide comprehensive and multidisciplinary treatments, which may include pharmacotherapy. Many providers use nonopioid medications to treat chronic pain; however, for some patients, opioid analgesics are the exclusive treatment of chronic pain. However, there is currently an epidemic of opioid use in the United States, and recent guidelines from the Centers for Disease Control (CDC) have recommended that the use of opioids for nonmalignant chronic pain be used only in certain circumstances. The goal of this review was to report the current body of evidence-based medicine gained from prospective, randomized-controlled, blinded studies on the use of nonopioid analgesics for the most common noncancer chronic pain conditions. A total of 9566 studies were obtained during literature searches, and 271 of these met inclusion for this review. Overall, while many nonopioid analgesics have been found to be effective in reducing pain for many chronic pain conditions, it is evident that the number of high-quality studies is lacking, and the effect sizes noted in many studies are not considered to be clinically significant despite statistical significance. More research is needed to determine effective and mechanism-based treatments for the chronic pain syndromes discussed in this review. Utilization of rigorous and homogeneous research methodology would likely allow for better consistency and reproducibility, which is of utmost importance in guiding evidence-based care.

Transdermal Adhesive Patches Loaded with Ketoprofen Evaluated by Dynamic Detection of Percutaneous Absorption

Topical delivery has many benefits toward NSAIDs administration, and the best-selling transdermal preparation in 2015 was the NSAID patch MOHRUS®. Herein, we report a ketoprofen adhesive patch (KAP) and evaluate the penetration and absorption compared to MOHRUS®. Microdialysis sampling technique was applied to determine drug penetration in the dermis and subcutaneous tissue. Simultaneously, blood samples were withdrawn over time to obtain the drug absorption in plasma. The ketoprofen concentrations in the dermis, subcutaneous tissue, and plasma were compared with the commercially available patch (MOHRUS®). Based on the detection, pharmacokinetic parameters including C_max, T_max, and AUC_0-8h were determined for both the formulations. No significant differences were found in the dermis, subcutaneous tissue, and plasma in rats according to the bioequivalence assessment. The KAP demonstrated multiple therapeutic advantages including the controlled drug release and the sustained drug concentration in the skin as well as in plasma. The pharmacokinetic study coupled with microdialysis sampling provided an effective strategy to evaluate transdermal delivery.