Polish Pharmaceutical Society

Water solutions of eye drops belong to the most often used ophthalmic drugs. Such solutions are applied to the cornea or into the conjunctiva sack in the amount of 1ñ2 drops, twice to four times a day. Because of the lacrimal system dynamics, eye drops are easily washed away with lacrimal fluid and removed from the eye. Therefore, the time of the direct contact of the fluid with the eye surface is short, and the amount of the drug absorbed constitu-tes only a part of the recommended dose. Hence, preparations of this form require often reapplication if the therapy is to be successful. Prolongation of the time when the therapeutic substance remains in the application spot can be achieved by applying higher viscosity systems, which enable longer contact with the eye surface and thus increased bioavailability of the drug. The most often used substances improving viscosity of eye drops preparations are: methylcellulose 500 ñ 4000 mPs, hydroxypropylmethylcellulose, hydroxy-ethylcellulose (1a), sodium carboxymethylcellulose, polyvinyl alcohol (1b) and polyacrylic acids (Carbo