Purpose: To assess the efficiency of the antiglaucomatic 0.5 % Timolol mixture with two amino acids: (1) 10 % L-taurine and (2) 10 % L-arginine on the physiological IOP in rabbits. Methods: Into the left conjunctival sac of 5 adult female rabbits of the New Zealand White species was instilled (a) 0.5 % Timolol alone; (b) the mixture of 10 % L-arginine and 10 % L-taurine in aqua pro injectione; (c) the mixture of 10 % Larginine and 10 % L-taurine in 0.5 % Timolol. The IOP was measured before and 5, 15, 30, 60, 120, 180, 240 min., and 24 hours after the instillation. The right eye was used as control. Results: (a) The mixture of the amino acids arginine and taurine in Timolol achieved significant IOP decrease in rabbits (except results at 5 min. and 24 hours after instillation) in all measured times with the maximum in 120 and 180 min. showing the biphasic character of the IOP decrease; (b) the mixture of amino acid taurine and arginine reached the border of significance (p < 0.05). The IOP decrease showed biphasic character, with the maximum in 60 min. (decrease of 3.8 mm Hg) and in 120 min. (decrease of 3.3 mm Hg); (c) the antiglaucomatic drops 0.5 % Timolol alone decreased the IOP values without significance comparing with the control eye. The maximum decrease was measured in 120 min. (2.9 mm Hg). Conclusions: The mixture of amino acids taurine and arginine in 0.5 % Timolol proved significant decrease of the IOP physiological values in rabbits. The maximum decrease was achieved 120, 180 min., and 24 hours after the instillation. The average value of the decrease 24 hours after instillation, compared with the control eye, was 3.2 mm Hg.

        Key words: amino acids taurine and arginine, Timolol, IOP in rabbits