Abstract
Purpose: :
: Iintravitreal injection of Kenalog–40 (K40) has garnered wide–spread clinical use for numerous conditions resulting in macular edema including diabetic retinopathy, vascular occlusion, and age related macular degeneration even though it has not been formulated specifically for intraocular administration. Thus, there is potential concern for specific retinal cytotoxicity in addition to the appreciated complications of elevated intraocular pressure and cataract. We evaluated the effect K40 and its components on the viability of BREC and BRPC.
Methods: :
Commercially available K40 was prepared by centrifugation at 3000g x 10min. The vehicle was removed and saved and the triamcinolone (TA) pellet was resuspended and washed 3x with sterile normal saline (NS) and then resuspended to 40mg/ml. Concentration of TA in the vehicle and the resuspended pellet was determined by HPLC. BREC and BRPC were plated at 3x10(3) cells/well in 96 well plates. After 24 hours, TA, K40 or the vehicle was added in equal volumes and various doses studied. Control wells received NS. At 24 and 48 hours, cyctotoxicity was evaluated by assessing cell viability by adding 2mg/ml 1–(4,5–Dimethylthiazol–2–yl)–3,5–diphenylformazan (MTT), incubation for 2 hours, solubilization of the formazan product in DMSO and OD read at 540nM.
Results: :
Concentration by LC–SRM of TA in the vehicle was undetectable (<0.1 ug/ml) while resuspended TA was 39mg/ml. After 24 & 48 hours, respectively, 2mg/ml TA reduced BRPC viability to 60+8% (p=0.003) and 38+10% (p<0.001) of control. Equivalent amounts of vehicle after 24 & 48 hours did not significantly affect BRPC (103+22%, p=NS and 90+13%, p=NS) while 2mg/ml K40 reduced viability to an intermediate extent (72+24%, p=0.15 and 52+17%, p<0.01). In contrast, BREC were unaffected by TA alone (124+27%, p=NS; 119+38%, p=NS). However after 24 & 48 hours exposure to 2 mg/ml of K40, BREC viability was reduced vs. control by (73+24%, p=0.03 and 74+47%, p=0.15). Vehicle treatment of BREC for 24 & 48 hours induced a reduction in BREC viability to 62+8%, p<0.001 and 61+11%, p<0.001 of control, respectively.
Conclusions: :
These data suggest that effects on retinal cell viability in culture by K40 is both modest in extent and complex in mechanism. Potential adverse effects observed in BRPC appear related to the TA and are ameliorated by the vehicle while in BREC the vehicle exerts an adverse effect, which is ameliorated by TA. Although short–term use in patients appears nontoxic to date, these data suggest that chronic usage in patients still requires careful study.
Keywords: corticosteroids • drug toxicity/drug effects • diabetic retinopathy