APR 15, 2014
The long-term stability and the range of suppression times found in this prospective study suggest some patients could benefit from individualized injection intervals.
The authors do not state whether the eyes were phakic or pseudo-phakic, which may have significant impact on clearance of drugs from the eye. However, the study results correlate with clinical trials that injected drugs at monthly intervals.
The authors analyzed aqueous humor samples from 17 patients (17 eyes) given ranibizumab injections for DME. For each patient, they determined VEGF levels in relation to the time interval from the previous ranibizumab injection.
Vascular endothelial growth factor (VEGF) was completely suppressed in all patients for a mean of 33.7 days (range 27 to 42) after injection. VEGF suppression times were individually stable up to 16 months’ follow up. There was no statistically significant difference in VEGF levels at baseline and before the beginning of a new injection series (123.6 pg/mL vs. 125.1 pg/mL; P = 1.0).
They write that they do not know what factors determine suppression times, although to some degree absolute VEGF levels might influence them. They also note that they could not determine correlations between VEGF suppression and clinical course of DME.