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Ocular pharmacokinetics of dorzolamide and brinzolamide after single and multiple topical dosing: implications for effects on ocular blood flow.

ABSTRACT: Ophthalmic carbonic anhydrase inhibitors have been shown to improve retinal and optic nerve blood flow. However, the relative tissue distributions of commercially available carbonic anhydrase inhibitors to the optic nerve are not known. The objective of this study was to compare the ocular pharmacokinetics and tissue distribution profiles of dorzolamide and brinzolamide after single and multiple topical applications. Pigmented rabbits were treated with single or multiple topical administrations of 30 ?l of Trusopt (dorzolamide hydrochloride ophthalmic solution, 2%) to one eye and 30 ?l of Azopt (brinzolamide ophthalmic suspension, 1%) to the other eye. Rabbits were euthanized at 10 predetermined time intervals over a period of 24 h, and ocular tissues and plasma samples were collected. For multiple dosing, rabbits were dosed twice per day with an 8-h interval between two doses, groups of rabbits were euthanized at 7, 14, and 21 days at 1 h after the last dose, and ocular tissues and plasma samples were collected. Drug levels in tissue samples were measured using liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameters (C(max), T(max), and AUC(0-24)) were estimated by noncompartmental analysis. After a single dose, dorzolamide delivery (AUC(0-24)) to the aqueous humor, anterior sclera, posterior sclera, anterior retina, posterior retina, anterior vitreous, and optic nerve was 2-, 7-, 2.6-, 1.4-, 1.9-, 1.2-, and 9-fold higher than those of brinzolamide. C(max) was 2- to 5-fold higher for dorzolamide than that of brinzolamide in all of the ocular tissue. After multiple dosing, dorzolamide levels in the aqueous humor, sclera, retina, vitreous humor, and optic nerve were higher than those of brinzolamide, but statistical significance was achieved only with aqueous humor, vitreous humor, and optic nerve. Dorzolamide levels in the aqueous humor, anterior vitreous, posterior vitreous, and optic nerve were 1.4- to 3.2-, 2.4- to 2.7-, 2.2- to 4.5-, and 2.4- to 5.2-fold higher than those of brinzolamide. Upon multiple dosing, both drugs accumulated in all of the tissues except the conjunctiva, where the drug levels were lower than those observed with single dosing. No significant differences were found in the AUC values of these two drugs in the cornea and conjunctiva after single and multiple dosing. Drug levels were significantly higher in anterior regions than posterior regions in the sclera, retina, and vitreous for both drugs.

SUBMITTER: Kadam RS

PROVIDER: S-EPMC3164276 | biostudies-other | 2011 Sep

REPOSITORIES: biostudies-other

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Ocular pharmacokinetics of dorzolamide and brinzolamide after single and multiple topical dosing: implications for effects on ocular blood flow.

Kadam Rajendra S RS Jadhav Gajanan G Ogidigben Miller M Kompella Uday B UB

Drug metabolism and disposition: the biological fate of chemicals 20110614 9

Ophthalmic carbonic anhydrase inhibitors have been shown to improve retinal and optic nerve blood flow. However, the relative tissue distributions of commercially available carbonic anhydrase inhibitors to the optic nerve are not known. The objective of this study was to compare the ocular pharmacokinetics and tissue distribution profiles of dorzolamide and brinzolamide after single and multiple topical applications. Pigmented rabbits were treated with single or multiple topical administrations ...[more]

PMID: 21673129

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Project description:Fixed-combination medications can benefit patients requiring multiple agents to lower their intraocular pressure (IOP), but combining agents with complementary mechanisms of action is challenging if their dosing frequency differs. This study compares in vivo pharmacokinetic and ocular tolerability of bimatoprost 0.01% ophthalmic solutions dosed once or twice daily. Reports of twice-daily dosing in glaucoma patients are also reviewed.New Zealand White rabbits were administered bimatoprost 0.01% monotherapy or fixed-combination bimatoprost 0.01%/brimonidine 0.1%, once or twice daily in both eyes for 4 days. Ocular tissues were harvested and analyzed by liquid chromatography-tandem mass spectrometry. The pharmacokinetic parameters calculated included maximum observed concentration, time to maximum concentration, and area under the concentration-time curve.Due to extensive metabolism, bimatoprost concentration was below the quantitation limit by 1 hour post-dose in all samples. Bimatoprost acid exposure, however, could be measured up to 6-8 hours post-dose and was similar in the aqueous humor and iris-ciliary body (pharmacological site of action) of animals treated once or twice daily with either bimatoprost 0.01% or fixed-combination bimatoprost 0.01%/brimonidine 0.1%. Increasing dosage frequency in rabbits did not raise the incidence of drug-related conjunctival hyperemia (most common adverse event associated with bimatoprost use in humans), suggesting comparable ocular tolerability of the once- and twice-daily regimens for each formulation.Bimatoprost 0.01% administered once or twice daily as monotherapy and in fixed-combination with brimonidine 0.1% in rabbits show similar pharmacokinetic profiles of bimatoprost acid, especially in the iris-ciliary body. Key findings from previous clinical studies suggest that by varying the concentration of benzalkonium chloride (a preservative with corneal penetration-enhancing properties), formulations of bimatoprost 0.01% can be administered once or twice daily. These findings support development of bimatoprost 0.01%-based fixed-dose combination therapies administered twice daily for patients who require multiple adjunctive medications to control their IOP.

Project description:IntroductionFixed-combination intraocular pressure (IOP)-lowering medications simplify treatment regimens for patients requiring 2 ocular hypotensive agents to maintain sufficiently low IOP. The aim of this study was to evaluate the safety and efficacy of fixed-combination brinzolamide 1%/brimonidine 0.2% (BBFC) versus concomitant administration of brinzolamide 1% plus brimonidine 0.2% (BRINZ + BRIM) in patients with open-angle glaucoma or ocular hypertension.MethodsThis was a prospective, phase 3, multicenter, double-masked, 6-month trial. Patients who had insufficient IOP control with monotherapy or who were receiving 2 IOP-lowering medications were randomized 1:1 to receive twice-daily BBFC or BRINZ + BRIM. IOP was assessed at 9 a.m. and 11 a.m. during week 2, week 6, month 3, and month 6 visits. The primary efficacy endpoint was mean diurnal IOP change from baseline to month 3; noninferiority was concluded if the upper limit of the 95% CI of the between-group difference was <1.5 mmHg. Supportive endpoints included mean IOP, IOP change from baseline, and percentage of patients with IOP <18 mmHg. Adverse events were recorded.ResultsThe mean diurnal IOP change from baseline with BBFC (least squares mean ± standard error -8.5 ± 0.16 mmHg) was noninferior to that with BRINZ + BRIM (-8.3 ± 0.16 mmHg; mean difference -0.1 mmHg; 95% CI -0.5 to 0.2 mmHg). The upper limits of the 95% CIs were <1.5 mmHg at all time points. Decreases from baseline >8 mmHg were observed for least squares mean diurnal IOP in both groups as early as week 2 and continued to the end of the study. The results of all other supportive endpoints were similar to the primary efficacy endpoint. The most common ocular adverse drug reactions were hyperemia of the eye (reported as ocular or conjunctival hyperemia), visual disturbances, ocular allergic reactions, and ocular discomfort. Common systemic adverse drug reactions included dysgeusia, oral dryness, and fatigue/drowsiness.ConclusionBrinzolamide 1%/brimonidine 0.2% fixed combination was as well tolerated and effective as concomitant therapy with its components. BBFC reduces treatment burden in patients who require multiple IOP-lowering medications.

Dataset Information

Ocular pharmacokinetics of dorzolamide and brinzolamide after single and multiple topical dosing: implications for effects on ocular blood flow.

Publications

Ocular pharmacokinetics of dorzolamide and brinzolamide after single and multiple topical dosing: implications for effects on ocular blood flow.

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