Effectiveness of Mitragynine Topical Patch for Pain Reduction in Myofascial Pain Syndrome

• Study Design Double-blinded, placebo-controlled randomized controlled trial
• Study Setting Rehabilitation Clinic, hospital
• Target Population Individuals with pain in the shoulder and neck region.
• Study Population Patients with subacute myofascial pain syndrome involving the upper trapezius muscle.
• Inclusion Criteria - Patients aged 18-50 years.

• Experiencing neck or shoulder pain for more than 3 months.
• Diagnosed with myofascial pain syndrome, with the most tender trigger point located in the upper trapezius muscle and a pain score between 30-60 mm measured using the Visual Analogue Scale (VAS).
• Exclusion Criteria - History of other neck-related conditions (e.g., whiplash injury, cervical radiculopathy, fibromyalgia syndrome, cervical spine surgery and/or fracture).

• History of systemic diseases (e.g., rheumatism, multiple sclerosis, cervical myelopathy), hepatitis, liver failure, or kidney disease (serum creatinine > 2.0 mg/dL).

• Symptoms or conditions contraindicating the use of patches, such as wounds or infections at the painful site.

• History of allergy to paracetamol or kratom.
• History of allergy to adhesive patches/plasters.
• Pregnant or breastfeeding women.
• Receipt of treatment with analgesics other than paracetamol, physical therapy, dry needling/acupuncture, massage, or topical medications within the previous week.
• Individuals who are unable to read or write.
• Participant Withdrawal Criteria - Participants experiencing severe allergic reactions (e.g., anaphylaxis, severe rash, or intolerable itching).

• Receipt of treatments other than paracetamol or any interventions outside those specified in the study during the follow-up period.
• Participants who wish to withdraw from the study.
• Study Termination Criteria The study will be terminated if participants experience significant adverse events, including severe allergic reactions (anaphylaxis) or systemic side effects such as nausea and vomiting, in at least 7 participants, representing 10% of the sample size.
• Sample Size 1. Irritation testing group: 10 healthy volunteers aged 18-50 years. 2. Efficacy testing group: 64 participants, calculated using the following formula: Sample size calculation for a randomized controlled trial with a continuous outcome μ_trt = mean VAS change in the treatment group μ_con = mean VAS change in the control group σ_trt = SD in the treatment group σ_con = SD in the control group λ = 1; α = 0.05; β = 0.2 The calculation was based on the study by Hsieh (2009) on the use of a diclofenac patch for reducing pain in the upper trapezius muscle.

Estimated values:

μ_trt = 2.57; μ_con = 3.92 σ_trt = 1.75; σ_con = 1.80 n_trt = 28; n_con = 28

Assuming a 10% dropout rate:

28 / 0.9 ≈ 32 participants per group Therefore, the total sample size ≈ 64 participants. 10 Variables and Operational Definitions Independent Variable

• Pain intensity: Used to indicate the level of pain on a scale ranging from 0-100 mm.

Dependent Variable

• Satisfaction score: Measured using a 5-point Likert scale with five levels of rating.

Confounding Variables

• Paracetamol consumption: Date and number of tablets taken will be recorded.
• Neck muscle stretching exercises: Date and frequency of stretching exercises will be recorded.

Inclusion criteria

• - Patients aged 18-50 years.
• Experiencing neck or shoulder pain for more than 3 months.
• Diagnosed with myofascial pain syndrome, with the most tender trigger point located in the upper trapezius muscle and a pain score between 30-60 mm measured using the Visual Analogue Scale (VAS).

Exclusion criteria

• - History of other neck-related conditions (e.g., whiplash injury, cervical radiculopathy, fibromyalgia syndrome, cervical spine surgery and/or fracture).
• History of systemic diseases (e.g., rheumatism, multiple sclerosis, cervical myelopathy), hepatitis, liver failure, or kidney disease (serum creatinine > 2.0 mg/dL).
• Symptoms or conditions contraindicating the use of patches, such as wounds or infections at the painful site.
• History of allergy to paracetamol or kratom.
• History of allergy to adhesive patches/plasters.
• Pregnant or breastfeeding women.
• Receipt of treatment with analgesics other than paracetamol, physical therapy, dry needling/acupuncture, massage, or topical medications within the previous week.
• Individuals who are unable to read or write.