Why modern medicine is retreating from the once-miraculous fluoroquinolone class of antibiotics

Health · Published 3 October 2026 Swipe more like this →

In short: Fluoroquinolones were once hailed as broad-spectrum powerhouses, but they now carry warnings for severe, disabling, and potentially permanent side effects. From tendon ruptures to psychiatric crises, regulators are increasingly restricting their use to cases where no other options exist, marking a significant shift in how we approach bacterial infections.

Quinolones represent a major class of broad-spectrum bactericidal antibiotics, with fluoroquinolones—defined by the addition of a fluorine atom—forming the most widely used group. These drugs are prized for their ability to penetrate tissues, including bone, and their high oral bioavailability, which often allows a 500mg oral dose to match the blood concentration of a 400mg intravenous dose. Because of these properties, they have historically been first-line treatments for serious infections like pyelonephritis and bacterial prostatitis.

However, the clinical profile of these drugs has darkened as reports of severe adverse events have accumulated. Patients may experience tendon damage, including rupture, which can occur shortly after starting treatment or months later. Other risks include aortic aneurysm, heart valve regurgitation, and central nervous system effects like convulsions. More recently, regulators have highlighted psychiatric risks, including depression and suicidal behavior, even in patients without prior mental health histories. These collective, often disabling side effects are sometimes referred to as 'floxing'.

In response, health authorities have significantly tightened prescribing guidelines. The UK and US regulators now advise that fluoroquinolones should only be used when other antibiotics are inappropriate or ineffective. This shift is particularly pronounced in pediatric care, where use is restricted to narrow, life-threatening scenarios like inhalation anthrax. Despite these risks, research continues into how to preserve their utility; for instance, new molecules like OXF-077 are being studied for their ability to inhibit the bacterial SOS response, potentially slowing the emergence of resistance to drugs like ciprofloxacin.

The reliance on these antibiotics remains high in resource-constrained settings, as seen in a 2021 study of COVID-19 patients in Mongolia, where fluoroquinolones were used in over a third of hospitalizations. This highlights the tension between the clinical need for potent, empirical treatments and the growing imperative for antimicrobial stewardship to mitigate the long-term risks of these powerful, yet problematic, therapeutic tools.

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