To investigate intraocular concentrations and pharmacokinetics of ranibizumab after a single intravitreal injection in humans.

Prospective, noncomparative, interventional case series.

We included 18 nonvitrectomized eyes of 18 patients (age range, 61–85 years) that were diagnosed with both clinically significant cataract and macular edema secondary to either exudative age-related macular degeneration, diabetic maculopathy, or retinal vein occlusion. Each eye received a single intravitreal injection of 0.5 mg ranibizumab. An aqueous humor sample was obtained during cataract surgery between 1 and 37 days after injection. Concentrations of unbound ranibizumab in these samples were quantified by enzyme-linked immunosorbent assay.

Ranibizumab concentration in aqueous humor peaked the first day after injection (range, 36.9–66.1 μg/mL) and subsequently declined in a mono-exponential fashion. Nonlinear regression analysis determined an initial peak concentration (c_max) of 56.1 μg/mL and an elimination half-life (t_1/2) of 7.19 days with a coefficient of determination (R²) of 0.90. Correction of ranibizumab concentrations for ocular volume as calculated from axial length measurements did not alter regression analysis results significantly (t_1/2, 7.15 days; R², 0.89).

In human nonvitrectomized eyes, the aqueous half-life of 0.5 mg intravitreally injected ranibizumab is 7.19 days, slightly shorter than the half-life of 9.82 days previously determined for bevacizumab by comparable methods.