Objective: The article documents results of experiments focused to influence the physiological IOP values after application of the COSOPT eye drops (double combination of bbb-blocker and carbonic anhydrase inhibitor), aminoacid 10% L-arginin.HCl and their mixture in rabbits. Methods: COSOPT followed by 10% L-arginin.HCl and mixture of 10% L-arginin.HCl with COSOPT was instilled weekly into the left conjunctival sac of 5 adult rabbits (females of the New Zealand White species). The IOP and pupilar diameter were measured in 5, 15, 30, 60, 120, 180, 240 min. and 24 hours after instillation. The right eye was ušed as control. Results: The antiglaucomatic COSOPT no significantly decreased the rabbit IOP during 24 hours (mean value 1.85 %) in vivo. The aminoacid 10 % L-arginin.HCl achieved significant decrease of the IOP: the mean value was 16.03 % reaching maximum in 60th and 180th min. After instillation of the 10% L-arginin.HCl and COSOPT mixture in the IOP showed significant decrease with mean value of 9,64 % (except values in 5th min. and 24th hour). Compared with control eye, the major decrease of the IOP was measured in 240th min. (mean value 17.98 %). However even in 24 hours after instillation the IOP was not reaching the values of the control eye, shoving also the IOP decrease. Conclusion: We assume that in a double combination of antiglaucomatics in COSOPT a new substance was created. This substance interacted in vitro with the aminoacid 10% L-arginin.HCl resulting in a new "bio-antiglaucomatis" better penetrating into the target area. This new substance was responsible for more significant decrease after the mixture application compared with COSOPT alone. The presence of aminoacid can slow down the undesirable effect of the antiglaucomatics together with the possible neuroprotection.

        Key words: the IOP influence in experiment - the effect of COSOPT and mixture of L-arginin.HCl in COSOPT on physiologic IOP of the rabbits