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Absorption of ocular timolol: drug concentrations and ß‐receptor binding activity in the aqueous humour of the treated and contralateral eye
Author(s) -
Saari K. Matti,
AliMelkkilä Timo,
Vuori MarjaLiisa,
Kaila Timo,
Lisalo Esko
Publication year - 1993
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.1993.tb04659.x
Subject(s) - timolol , aqueous humour , chemistry , medicine , absorption (acoustics) , pharmacology , drug , ophthalmology , aqueous humor , intraocular pressure , materials science , composite material
. We studied the ocular and systemic absorption of 40 μl of topical 0.5% timolol in 57 patients using radioligand binding techniques. The mean concentration of timolol in aqueous humour of the treated eye was 1.9 ± 0.8 μg/ml 74 minutes after instillation of the drug. About 18 h after drug instillation the aqueous humour concentration of timolol was 105.5 ± 60.9 ng/ml. Timolol was found in 15 (42%) contralateral eyes. Concentration of timolol in the contralateral eye increased from 0.04 ± 0.08 ng/ml at 50 min to 0.3 ± 0.2 ng/ml at 134 min and was 0.2 ± 0.4 ng/ml at 18 h after instillation. Timolol concentrations in the aqueous humour of the treated eye appeared to be high enough to occupy ß 1 ‐ and ß 2 ‐receptors completely (100%) at 74 min and at 18 h after drug instillation. Timolol concentrations in the contralateral eye were high enough to occupy up to 33.0 ± 24.7% of the ß 2 ‐receptors and up to 51.7 ± 35.1% of ß 2 ‐receptors. High drug concentrations and complete ß‐receptor occupancy in the aqueous humour of the treated eye after topical timolol are in agreement with the long‐lasting ocular hypotensive effects. The low drug concentrations and partial receptor occupancy in the contralateral eye may also be of some clinical significance.