Abstract
Purpose: :
To evaluate the in vitro toxicity of preservative-free lidocaine hydrochloride (LH) on human retinal pigment epithelial cells (ARPE-19) and rat neurosensory retinal cells (R28).
Methods: :
ARPE-19 and R28 cells were treated with 4% LH at 0.25 mg/ml (1X clinical dose), 0.5 mg/ml (2X), 1mg/ml (4X), 2 mg/ml (8X), 3 mg/ml (12X) or 4 mg/ml (16X). After 24 hours, cell viability (CV) was measured using the trypan blue dye exclusion assay. Mitochondrial dehydrogenase activity (MDA) was determined with the WST-1 assay.
Results: :
ARPE-19 cells treated with 16X, 12X, 8X LH showed decreased mean CV of 21.37±5.23% (p<0.001), 53.00±6.51% (p<0.001), 70.00±2.65% (p<0.01) respectively, compared to untreated ARPE19 controls (94.33±2.60%). Mean CV of ARPE-19 cells treated with 4X, 2X or 1X LH was not significantly reduced: 81.67±4.63% (p>0.05), 86.33±3.22% (p>0.05) and 91.67±3.48% (p>0.05). R28 cells treated with 16X, 12X, 8X LH had decreased mean CV of 11.33±1.86% (p<0.001), 23.00±3.61% (p<0.001), 53.33±4.41% (p<0.001) compared to untreated R28 controls (91.00±2.08%). R28 cells treated with 4X, 2X or 1X LH showed no significant reduction in mean CV: 79.67±2.60%(p>0.05), 83.33±4.41% (p>0.05) and 88.00±4.04% (p>0.05). MDA reduction (suggestive of impaired mitochondrial function) was observed in ARPE-19 cells treated with 16X, 12X, 8X: 80.00% (0.28±0.06, p<0.01), 74.12% (0.37±0.07, p<0.01), 64.94% (0.50±0.08, p<0.01). No significant MDA reductions were observed at lower LH doses 4X, 2X,1X: 24.71% (1.07±0.11, p>0.05), 9.18% (1.29±0.19, p>0.05) and 2.35% (1.38±0.23, p>0.05) compared to controls (1.42±0.18). MDA reduction was observed in R28 cells treated with 16X, 12X, 8X LH: 85.54% (0.05±0.01, p<0.001), 77.86% (0.08±0.012, p<0.001), 70.18% (0.11±0.02, p<0.001). No significant MDA reductions were observed at lower LH doses 4X, 2X,1X: 30.0% (0.26±0.04, p>0.05), 2.68% (0.36±0.05, p>0.05), 1.79% (0.37±0.04, p>0.05) compared to controls (0.37±0.05).
Conclusions: :
Preservative free lidocaine hydrochloride at concentrations 8X clinical dose or higher alters retinal cell function in vitro. However at doses 4X clinical dose or lower, no abnormalities were observed.