Periocular accumulation of timolol and betaxolol in glaucoma patients under long-term therapy.
OBJECTIVE
To determine if betaxolol or timolol is present in measurable concentration in the Tenon capsule in patients under long-term topical therapy.


METHODS
Small (1-cc) specimens of Tenon capsule were removed at the time of filtering surgery from 15 glaucoma patients under long-term preoperative topical therapy, nine of whom had been treated with timolol and six of whom had been receiving betaxolol. Methanol extracts of these tissue samples were analyzed quantitatively for the presence of either beta-adrenergic antagonist by high-performance liquid chromatography.


RESULTS
Drug was detected in every specimen. A mean total of 2.6 (range, 0.1-30.0) microg of betaxolol was detected per 1-cc specimen.


CONCLUSIONS
Timolol and betaxolol penetrate the conjunctiva and accumulate in the Tenon capsule. In patients under long-term therapy, the periocular tissue can accumulate a greater quantity of beta-antagonist than is present in a daily dosage of applied eyedrops, manyfold higher than the maximal intraocular concentration.
Department of Ophthalmology, University of Texas Health Science Center, San Antonio 78284-6230, USA.
W E
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Sponsel
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Terry
H D
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Khuu
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KW
Lam
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Frenzel
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015784:Betaxolol / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D003228:Conjunctiva / Q000378:metabolism*; D003238:Connective Tissue / Q000378:metabolism*; D005260:Female; D018463:Filtering Surgery; D005901:Glaucoma / Q000188:drug therapy* / Q000378:metabolism / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D013997:Time Factors; D013999:Timolol / Q000008:administration & dosage / Q000493:pharmacokinetics*
D000319:Adrenergic beta-Antagonists; D009883:Ophthalmic Solutions; D013999:Timolol; D015784:Betaxolol