The goal of this clinical trial is to assess the clinical efficacy and safety of sodium aescinate in treating low back pain (LBP) in adult participants.

The goal of this clinical trial is to evaluate the efficacy and safety of oral sodium aescinate in improving symptoms and function in adult participants aged 18-65 years with low back pain (LBP) lasting at least 12 weeks and a Visual Analog Scale (VAS) score > 4 points. The main questions it aims to answer are:

1. Does oral sodium aescinate tablets reduce pain intensity (measured by VAS score) in adult LBP patients at 1, 3, and 6 weeks after treatment?
2. Is oral sodium aescinate tablets safe for adult LBP patients, with an acceptable adverse event profile during the 6-week treatment period?

Researchers will compare participants receiving sodium aescinate (experimental group) to those receiving a placebo (control group) to see if the experimental intervention results in significant improvements in pain, disability, functional status, and lumbar paraspinal muscle conditions (cross-sectional area and fat infiltration rate) compared to the placebo.

Participants will:

1. Undergo screening (medical history review, physical examination, and relevant tests) to confirm eligibility and sign an informed consent form.
2. Be randomly assigned to either the experimental or control group in a 1:1 ratio.
3. Take 2 tablets of the assigned study medication (sodium aescinate tablets or placebo) twice daily for 6 consecutive weeks.
4. Complete follow-up visits at baseline (week 0), week 1, week 3, and week 6 for efficacy assessments (VAS, Oswestry Disability Index [ODI], Japanese Orthopaedic Association [JOA] score, 36-Item Short Form Health Survey [SF-36] score).
5. Undergo lumbar MRI scans at baseline and week 6 to measure paraspinal muscle cross-sectional area and fat infiltration rate.
6. Report any adverse events experienced during the 6-week treatment period.

Inclusion Criteria:

1. Meets the diagnostic criteria for chronic low back pain (cLBP) recommended by the Clinical Practice Guidelines for Chronic Low Back Pain in China (2024 Edition): the course of disease lasts at least 12 weeks, with pain occurring in the region below the lower costal margin, above the gluteal crease (horizontal gluteal fold), and between the midaxillary lines on both sides, which may be accompanied by pain in one or both lower extremities.
2. Has moderate to severe pain, with a Visual Analog Scale (VAS) score > 4 points.
3. Aged between 18 and 65 years old.
4. Has a clear understanding of the study content, good compliance, and high willingness to cooperate.
5. Has signed a written informed consent form voluntarily.

Exclusion Criteria:

1. Is in the acute pain phase or acute exacerbation of chronic pain.
2. Has low back pain caused by other reasons such as infectious diseases or tumors, including but not limited to spinal tumors, spinal tuberculosis, spinal cord infections, etc.
3. Has a history of allergy to sodium aescinate.
4. Suffers from systemic diseases or organ dysfunction.
5. Has participated in other clinical trials within 1 month before enrollment.
6. Has severe mental illness or other conditions that prevent cooperation with the study.
7. Is a pregnant or lactating woman, or a woman planning to become pregnant.
8. Has metal implants or other conditions that are not suitable for MRI examination.
9. Is considered by the researcher to have conditions that are unfavorable for completing the study course.

A dedicated researcher (not involved in data collection, analysis, or follow-up) prepares and distributes the study medications (sodium aescinate tablets and matching placebo), which are identical in appearance, dosage form, and administration route to ensure masking. Emergency unblinding is permitted for safety reasons, with documentation of the date and reason required within 48 hours.