Objective To evaluate and compare the effects of oral isosorbide and glycerol on intraocular pressure (IOP), serum osmolality (SOSM), and blood glucose (BG) in normal dogs.
Methods Ten normal dogs were administered an oral dose of either isosorbide (1.5 g/kg), glycerol (1.5 g/kg) or control (water, 2 mL/kg) in a double blind protocol.
Prior to dosing, baseline IOP, SOSM, and BG were measured in all dogs. IOP was subsequently evaluated every 30 min for 6 h post-dosing. BG and SOSM were reassessed at times 1, 2, 4, and 6 h post-dosing. After 1-week washout periods, every dog was subject to each of the three treatments. The dogs were held NPO for 4 h after dosing.
Results The maximal decrease in IOP was 17% by 1 h and 13.5% by 30 min after glycerol and isosorbide administration, respectively. However, the overall changes in IOP were not significant when compared to the controls. SOSM increased above baseline after dosing with glycerol but decreased after isosorbide, which difference was significant at 1, 2, and 4 h post-administration. BG significantly increased after administration of glycerol relative to the control but was not significantly affected by isosorbide.
Conclusions Neither glycerol nor isosorbide significantly affected IOP when compared to the control. However, glycerol induced significant elevations in both BG relative to the control and SOSM relative to isosorbide.