Aqueous vascular endothelial growth factor and ranibizumab concentrations after monthly and bimonthly intravitreal injections of ranibizumab for age-related macular degeneration

To evaluate vascular endothelial growth factor (VEGF) and ranibizumab concentrations in eyes with age-related macular degeneration (AMD) after monthly and bimonthly intravitreal ranibizumab (IVR) injections. Aqueous humor samples were obtained from 26 eyes with AMD before and after IVR injections. Nine eyes received three monthly injections and 17 eyes received two bimonthly injections. The VEGF and ranibizumab concentrations were measured by enzyme-linked immunosorbent assay. The aqueous VEGF concentrations in the monthly injection group decreased below the lowest detectable limit in eight of nine eyes 1 month after the first injection and seven of nine eyes 1 month after the second injection (P < 0.001, mean baseline value, 94.7 pg/ml); the aqueous VEGF concentrations in the bimonthly injection group decreased below the lowest detectable limit in two of 17 eyes 2 months after the first injection (P < 0.001, mean baseline value, 152.4 pg/ml). The mean aqueous ranibizumab concentrations with monthly injections were 71.2 ng/ml 1 month after the first injection, and 96.3 ng/ml 1 month after the second injection. The mean aqueous ranibizumab concentrations in the bimonthly injection group were 2.5 ng/ml in 15 of 17 eyes, and below the lowest detectable limit in two of 17 eyes 2 months after the first injection. In this pilot study with limited follow-up, intravitreal injection of ranibizumab can suppress aqueous VEGF completely for 1 month in most cases. Its effect does not last for 2 months enough to suppress VEGF completely in most cases, although aqueous VEGF at 2 months after intravitreal injection of ranibizumab is less than that before injection in most cases.