Ocular timolol levels after drug withdrawal: an experimental model.
Carbon 14-labelled timolol maleate was instilled into both eyes of 12 pigmented rabbits daily for 42 days. Drug levels in the aqueous humour and ocular tissues were measured up to 42 days after drug withdrawal. The results indicate that timolol concentrates mainly in melanotic tissues, with slow release. Even 42 days after withdrawal the drug was still present in pigmented ocular tissues. Timolol was detected in the aqueous up to 5 days after withdrawal. These findings explain the long-term depressant effect of topically administered timolol on aqueous production. We conclude that lower or less frequent doses of timolol should be considered in patients with glaucoma.
Department of Ophthalmology, University of Toronto, Ont.
G E
GE
Trope
I A
IA
Menon
G S
GS
Liu
J R
JR
Thibodeau
M A
MA
Becker
S D
SD
Persad
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D005123:Eye / Q000378:metabolism*; D008543:Melanins / Q000378:metabolism; D008954:Models, Biological; D009883:Ophthalmic Solutions; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D011817:Rabbits; D013999:Timolol / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014602:Uvea / Q000378:metabolism
D008543:Melanins; D009883:Ophthalmic Solutions; D013999:Timolol