Overview

The goal of this clinical trial is to learn if antibiotics (amoxicillin) work to treat chronic low back pain in adults. In some patients, this type of back pain may be caused by bacteria in the vertebrae, resulting in a condition known as "Modic type I change."

The main questions the trial aims to answer are:

• What is the efficacy (primary objective) of antibiotic treatment for patients with chronic low back pain and Modic type I changes?
• What is the cost-effectiveness (secondary objective) of antibiotic treatment for patients with chronic low back pain and Modic type I changes?

Researchers will compare amoxicillin to a placebo (a look-alike substance that contains no active drug) to see if amoxicillin works to treat chronic low back pain.

Participants in the trial will:

• Be invited for an MRI scan to determine if they have a Modic type I change; those who do will be included in the study.
• Take either amoxicillin or a placebo daily for 100 days.
• Take probiotics daily for 100 days to reduce the occurrence and impact of any side effects from the antibiotics.
• Attend clinic visits at baseline (the start), 4 weeks, 3 months, and 12 months for checkups and tests.
• Complete questionnaires at baseline, 3 months, 6 months, and 12 months.

Eligibility

Inclusion Criteria:

• Aged 18-65 years.
• Chronic low back pain (i.e. duration >6 months) after a previous (MRI confirmed) disc herniation within the past 6 months to 2 years.
• At least 2 of the following questions should be answered with "Yes":
  • Does training and/or exercise increase your pain?
  • Is your sleep during the night disturbed due to your back pain?
  • Is it painful to turn over in bed at night?
  • Do you suffer from morning pain?
• The mean pain intensity should be at least 5 points on a 0-10 NRS-scale, calculated

  as the mean pain intensity of 3 indices: current pain, worst pain within the preceding two weeks, and the usual mean pain within the preceding two weeks.

• Modic Type I changes visible on the MRI-scan in the vertebrae adjacent to the previous herniated disc.

Exclusion Criteria:

• Received antibiotic treatment in the past month.
• Current pregnancy, lactation or pregnancy-wish.
• Severe physical or psychiatric co-morbidities.
• LBP resulting from a specific cause such as a tumor or fracture.
• Surgery or epidural injection in the past 6 months.
• Previous antibiotic course of 100 days.
• Contra-indication for amoxicillin use: allergy to penicillins/amoxicillin, cephalosporin or carbapenem; mononucleosis; leukemia; phenylketonuria (PKU)
• Contra-indication for MRI.
• Current use of any of the following medications: allopurinol, methotrexate, phenylbutazone or probenecid.
• Hepatic or renal (eGFR≤30) impairment.
• Inability to swallow capsules.