Penetration of atenolol in the rabbit eye

The ocular penetration of topically applied [14C]-atenolol in the rabbit was determined by means of liquid scintillation counting. Only one eye was treated, the fellow eye serving as a control. Blood plasma levels were measured as well. The absolute amount of atenolol which penetrated the eye was very low, but a relatively high concentration was achieved in the tissues of the nictitating membrane. We could only detect an increase in the amount of atenolol with time in the aqueous humor. In all other ocular tissues, including iris and ciliary body, the atenolol level remained constant with time. Hardly any atenolol could be detected in the untreated eye and none in the blood plasma. These findings suggest that the ocular penetration of atenolol administered as an eye drop is very poor. Ocular penetration, therefore, hardly seems to play a part in the antiglaucomatous effect of atenolol.