Testosterone Therapy in a Patient With Fluoroquinolone-Associated Tendinopathy: A Case Report of Rapid-Onset Achilles Injury Following Ciprofloxacin.

Testosterone replacement therapy (TRT) is increasingly used in men with testosterone deficiency, and emerging observational data have suggested an association between therapeutic testosterone exposure and tendon injury. Fluoroquinolones are independently associated with tendinopathy and tendon rupture, particularly involving the Achilles tendon. We report a man in his 30s receiving physiologic TRT who developed severe, rapidly progressive bilateral Achilles tendon symptoms shortly after starting ciprofloxacin 500 mg twice daily for a urinary tract infection with suspected prostatic and upper urinary tract involvement. Testosterone therapy had been initiated approximately two months earlier and was continued unchanged throughout the event and recovery. Ciprofloxacin was discontinued after the onset of tendon symptoms, followed by gradual clinical improvement over several weeks. The close temporal relationship with ciprofloxacin exposure and subsequent improvement after withdrawal supports ciprofloxacin as the likely acute precipitating factor. Concurrent physiologic TRT may have represented an additional susceptibility factor; however, a causal interaction between testosterone therapy and fluoroquinolones has not been established. This case highlights an unusually rapid and severe presentation of fluoroquinolone-associated Achilles tendinopathy and supports further investigation into whether therapeutic androgen exposure may modify tendon vulnerability in patients receiving fluoroquinolones.