Purpose: To create a time- and dose-dependent mathematical model that compares the intravitreal vascular endothelial growth factor (VEGF) binding activity of bevacizumab with that of ranibizumab.
Methods: Intravitreal half-lives and relative equimolar VEGF binding activities of bevacizumab and ranibizumab were incorporated into a first-order decay model. Time-dependent bevacizumab activities (relative to ranibizumab) for different initial doses (1.25 and 2.5 mg) and reinjection intervals (single, weekly, and every 3 days) were calculated and graphed.
Results: Twenty-seven days to 38 days after a single bevacizumab (1.25 mg) injection, the intravitreal VEGF binding activity would be comparable with that of ranibizumab at 30 days. Bevacizumab (2.5 mg) injections would need to be performed every 3 days for 1 month to equal the peak activity after a ranibizumab injection.
Discussion: On the basis of this mathematical model, intravitreal bevacizumab maintains significant VEGF binding activity for 4 weeks to 5 weeks. More frequent bevacizumab injections increase the average binding activity but not to that seen with a single ranibizumab injection.