Systemic absorption of topically applied ocular timolol.

Symptoms and findings arising from the systemic beta blockade caused by topical ocularly applied timolol appear shortly after drug application. We studied the systemic absorption of 20 microliters of 0.5% timolol instilled unilaterally in the lower conjunctival cul-de-sac in 6 volunteers. At 3 min one subject, at 5 min three and at 8 min all but one showed measurable (greater than or equal to 215 pg/ml) timolol concentrations in the plasma. The rapid systemic absorption of topically applied ocular timolol observed in our study is consistent with the rapid appearance of the cardiovascular and pulmonary side effects reported in connection with timolol eye drop therapy.