Effect of ocular hypotensive agents on the intraocular metabolism of ranibizumab in rabbit

Objective  To compare the effects of brinzolamide-timolol (B&T) eye drops and dipivefrine hydrochloride (DH) eye drops on the intraocular metabolism of ranibizumab after intravitreal injection in rabbit.

Methods  Eighteen New Zealand white rabbits were randomly and equally divided into DH group, B&T group, and control group.The right eye was selected as the experimental eye.The B&T and DH groups received DH and B&T eye drops, respectively, twice daily, 30 μl each time.The control group did not receive any treatment.Intraocular pressure (IOP) was measured in both eyes before the first administration and 1 hour after the first administration on the second day.After IOP measurement, the experimental eye received an intravitreal injection of 0.25 mg ranibizumab (10 mg/ml).Aqueous humor samples were collected 1, 3, 7, 10, 14, 21 and 28 days after injection.Ranibizumab concentration in the aqueous humor was measured by ELISA kit.Pharmacokinetic parameters including time to peak concentration ( t _max), peak concentration ( C _max), elimination half-life ( t _1/2) and area under the concentration-time curve (AUC) of ranibizumab were calculated.This experiment was approved by the Ethics Committee of Henan Eye Hospital (No.HNEECA-2023-03).

Results  The t _max of ranibizumab in the aqueous humor was 1 day in all three groups.The C _max values in the control, B&T and DH groups were (8.122±2.445), (13.079±3.140) and (8.299±0.899)μg/ml, respectively.Except for day 3 in the control group, the ranibizumab concentrations in aqueous humor of the B&T group were higher than that of the DH group and the control group at all time points after injection, with statistically significant significances (all P<0.05).The t _1/2 of ranibizumab in aqueous humor in the control group, B&T group, and DH group were (2.90±0.29), (3.36±0.35) and (2.80±0.29) days, respectively, and the AUC _0-t values were (52.697±10.178), (80.244±11.249) and (51.985±8.734)μg/ml·d, respectively.The t _1/2 and AUC _0-t of ranibizumab in aqueous humor of the B&T group were significantly higher than those of the DH group and the control group, and the differences were statistically significant (all P<0.05).The mean bioavailability in the B&T group was increased by 52.3% compared to the control group.

Conclusions  B&T eye drops prolong the half-life and enhance the intraocular bioavailability of ranibizumab after intravitreal injection in rabbits, whereas DH has no significant effect on its intraocular metabolism.

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