Morphological investigation of cavity formation in articular cartilage induced by ofloxacin in rats.

Ofloxacin, a quinolone antibacterial agent, induced blisters and/or erosions in the articular cartilage of the humeral trochlea, femoral condyle, and femoral head of immature rats. Histologically, cavity formation was seen in the middle zone of the articular cartilage. Changes were detected as early as 5 hr after a single oral administration of 1000 or 3000 mg/kg. These changes were characterized by condensation, atrophy, and deformation of the nuclei of chondrocytes distributed in the middle zone. In such nuclei, aggregation of heterochromatin was observed. Degenerated cells with vacuolated and partially disintegrated cytoplasms were also seen in this zone. These lesions were followed by edema of the matrix accompanied with markedly decreased stainability with safranin-O, and a cavity was formed later by liquefaction of the cartilage. The changes were reversible, with rebounding occurring even with continued treatment with ofloxacin. The proliferation of chondrocytes around the lesion chiefly contributed to the repair. Ofloxacin had no adverse effects on the articular cartilage in rats when treatment was initiated at 8 weeks of age or later.