Effects of eyelid closure and nasolacrimal duct occlusion on the systemic absorption of ocular timolol in human subjects.

Eyelid closure and nasolacrimal occlusion may decrease the systemic absorption of topically applied drugs. We studied the absorption kinetics of 20 microliter 0.5% timolol eyedrops in eight healthy volunteers. Each subject was supine for 30 minutes after the drug application. In randomized order, the volunteers kept their eyelids closed (ELC), or applied nasolacrimal occlusion (NLO) or blinked normally. Blood samples were drawn up to 90 minutes and analyzed for timolol with a radioreceptor assay. There was great interindividual variation in the timolol absorption. NLO reduced the total timolol absorption, but in some subjects the initial absorption was also enhanced by this procedure.