Plasma timolol in glaucoma patients.

Plasma timolol levels were measured in our timolol-treated glaucoma patients employing three protocols: (1) measurements in ten patients over age 60 on chronic timolol therapy before, one hour, and three hours after receiving one drop of 0.5% timolol, (2) measurements in nine adult patients, with and without punctal occlusion, and (3) random measurement of plasma timolol in children on chronic timolol therapy while under general anesthesia. In the ten patients over age 60 years, baseline mean plasma timolol was 0.34 ng/ml, increasing to a mean of 1.34 ng/ml one hour after receiving drops. When punctal occlusion was applied, the mean one-hour plasma timolol diminished to 0.9 ng/ml, approximately 40% less than that observed without punctal occlusion. The plasma timolol levels examined in nine determinations in five children ranged from a low 3.5 ng/ml in a five-year-old child to 34 ng/ml in a three-week-old infant.