K.A. Bichenova, I.V. Sakaeva, E.I. Sakanyan, E.B. Nechaeva, L.L. Kojemyakina

Nowadays viscous eye drops and eye gels cover about 15 % of total amount of ophthalmic preparations on the domestic pharmaceutical market. In eye drops formulations more often used polymers are hypromellose and methylcellulose. Viscosity is important quality characteristic of polymer solutions. The determination of viscosity of eye preparations is necessary for optimal eye functioning and for guarantee of prolonged action of drug. National quality regulatory documentation has no recommendations to carrying out of test viscosity determination in eye drops. According to quantitative content of polymer eye drops may be distinguished like Newtonian or non Newtonian liquids. The determination of kinematic viscosity is carried out for Newtonian liquids. Non Newtonian liquids are characterized by dynamic viscosity. If polymer content in preparation is lower than 10 mg/ml, this preparation can be considered like Newtonian liquid. The viscosity of Newtonian liquids usually determine with a capillary viscometer. It is known that viscosity changes with temperature. Leading foreign pharmacopoeias (European, USA, Japanese) have harmonized monographs on hypromellose and methylcellulose. According to these monographs procedure of viscosity determination should be carried out at a temperature (20±0,1) °С with a capillary viscometer. Experimental studies were carried out in order to optimize a procedure of viscosity testing. The kinematic viscosity of four testing preparations containing polymers was determined at a temperature of 15 °С, 18 °С, 20 °С, 23 °С and 25 °С. In the result of this experiment capillary viscometer method for eye drops is offered, recommendations for the establishment of normative values of viscosity are given.