Quinolone Ear Drops and Achilles Tendon Rupture.

BACKGROUND: Delayed eardrum healing has been observed in the ear opposite to the ear treated with otic quinolones (OQ) in rats. Case reports describe tendinopathies after OQ treatment, suggesting adverse systemic effects.

METHODS: We studied patients 19-64 years with diagnosis of otitis externa or media in private insurance between 2005-2015. We compared OQ treatment against otic neomycin, oral amoxicillin or azithromycin. Outcomes included Achilles tendon rupture (ATR), Achilles tendinitis (AT) and all-type tendon rupture (ATTR). We applied an active comparator, new user design with 1-year look-back and ceased follow-up at initiation of systemic steroids or oral quinolones, external injury, hospitalization and after 35 days. We used trimmed stabilized inverse probability of treatment weights to balance comparison groups in a survival framework. Negative outcomes (clavicle fractures or sports injuries) were examined to rule out differences due to varied physical activity (unmeasured confounding).

RESULTS: We examined 1,501,009 treated otitis episodes. Hazard ratios (HR) for OQ exposure associated with ATR were 4.49 (95%CI 1.83-11.02), AT 1.04 (95%CI 0.73-1.50), ATTR 1.71 (95%CI 1.21-2.41). Weighted risk differences (RD) per 100,000 episodes for OQ exposure were ATR 7.80 (95%CI 0.72-14.89), AT 1.01 (95%CI -12.80-14.81), ATTR 18.57 (95%CI 3.60-33.53). Corresponding HRs and RDs for clavicle fractures and sports injuries were HR = 1.71 (95%CI 0.55-5.27) and HR = 1.45 (95%CI 0.64-3.30), suggesting limited residual confounding.

CONCLUSIONS: OQ exposure may lead to systemic consequences. Clinicians should consider this potential risk and counsel patients accordingly. Risk factors and mechanisms for this rare, adverse effect deserve further evaluation. Mechanistic and other clinical studies are warranted to corroborate this finding. Presented at the American Otological Society 154th Annual Virtual Meeting; April 11, 2021.