Precorneal residence time in humans of sodium hyaluronate as measured by gamma scintigraphy.

The aim of the present study was to quantify in man the distribution and clearance of two aqueous sodium hyaluronate (SH) solutions of 0.125% and 0.250% after the administration of 25 microliters onto the cornea. Isotonic phosphate buffer (PB) was used as a reference instillation. No systemic or local medication was given to the seven 18- to 30-year-old, healthy male volunteers. A detailed evaluation of the anterior segment of the eye, as well as a Schirmer test and a break-up time measurement, yielded results within the normal range. The clearance of 0.125% and 0.250% SH solutions radiolabelled with sodium pertechnetate Tc-99m was measured by gamma scintigraphy and compared with that of a PB solution tagged with the same radiolabel. There was no statistically significant difference between the quantities of 0.125% SH and PB solutions remaining in the precorneal space at 20 min (paired t-test, P = 0.78, n = 7). However, in comparing the 0.250% SH with the PB solution, we observed a statistically significant difference (P = 0.01, n = 7) in the amount remaining in the precorneal space after the same interval. Actually, 53% of the radiolabelled 0.250% SH solution remained on the cornea as compared with 30% for the 0.125% SH solution and 18.3% for the PB solution. These results suggest that an SH solution of 0.250% might have a prolonged residence time on the precorneal surface, and that SH could therefore be used as an additive in various drug-release systems for the eye.