Does a Negative Antibiotic Trial Disprove the Infection Hypothesis in Acute Disc Herniation?

A recent study by Cicuttini et al., (2026) published in JAMA Network Open, (doi:10.1001/jamanetworkopen.2026.12848) reported that oral amoxicillin (500 mg twice daily) provided no clinical benefit in patients with acute lumbar disc herniation and concluded that antibiotics are ineffective in this setting.

However, before accepting that conclusion, an important pharmacological question must be addressed: was the antibiotic dose sufficient to test the hypothesis?

Czaplewski et al., (2023) investigated intradiscal exposure of amoxicillIn after oral administration concluding that 0.5g amoxicillin twice a day was unlikely to be effective, but did not estimate the proportion of treated patients that might be adequately treated (https://doi.org/10.1038/s44259-023-00002-7).

Antimicrobial therapy, efficacy depends on achieving adequate drug exposure at the site of infection. Modern antibiotic development relies on pharmacokinetic/pharmacodynamic (PK/PD) modelling and Probability of Target Attainment (PTA) analyses to determine whether a dosing regimen is likely to deliver therapeutic concentrations. Typically, a PTA of at least 90% is sought.

Our recent modelling suggests that the amoxicillin regimen used in the study would achieve an intradiscal PTA of only 0.67% (https://doi.org/10.21203/rs.3.rs-10748663/v1). If correct, this means that among the 85 patients randomised to active treatment, virtually none would be expected to attain effective antibacterial concentrations within disc tissue.

This has important implications for interpreting the study. The trial demonstrated that very low-dose amoxicillin did not improve outcomes, but it may not have adequately tested whether bacterial infection contributes to disease. An antibiotic cannot eliminate bacteria if it fails to reach therapeutic concentrations at the site where those bacteria are presumed to reside.

Negative clinical trials are essential to scientific progress. However, when investigating a potential infectious mechanism, it is critical to distinguish between a treatment that truly lacks efficacy and a regimen that never achieved adequate target exposure.

The key question is therefore not simply, "Did antibiotics work?" Rather, it is: "Did the antibiotic reach effective concentrations within the disc to give the hypothesis a fair test?"

Until that question is answered, it may be premature to conclude that the study disproves a role for bacterial infection in a subset of patients with acute disc herniation.

Keywords: acute disc herniation, amoxicillin, low back pain, bacterial infection, PK/PD, probability of target attainment, disc infection, antibiotic therapy, clinical pharmacology, lumbar disc herniation.

Cicuttini FM, Wluka AE, Pan F, et al. Efficacy of Antibiotics for Chronic Low Back Pain With Disc Herniation: A Randomized Clinical Trial. JAMA Netw Open 2026; 9: e2612848.

Czaplewski LG, Zeitlinger M, Standing JF. Intradiscal pharmacokinetics of oral antibiotics to treat Chronic Lower Back Pain. npj Antimicrob Resist 2023; 1: 1–9.

Czaplewski L, Gilligan C, McHale D. Higher exposure to antibiotics is associated with greater clinical improvement of chronic low back pain with Modic changes. 2026; published online Sept 1. DOI:https://doi.org/10.21203/rs.3.rs-10748663/v1.