Figure 2 Changes of intraocular pressure (IOP) after a first administration of ocular hypotensive agents. The results showed that brimonidine, timolol, brinzolamide, and bimatoprost eye drops had an ocular hypotensive effect on rats with elevated IOP. IOP of brimonidine-treated and timolol-treated groups was reduced to a minimum level at 2 h after administration, and then slightly rebounding, but was still significantly lower than that of the model control group at 24 h after administration (P<0.05). The effect of bimatoprost was not obvious within 6 h after administration. The IOP was reduced at 8 h after administration and maintained at that level until 24 h. The IOP of the rats treated with brinzolamide was reduced to the lowest at 4 h after administration, and then gradually increased. The IOP at 6 h after administration was not significantly different from that of the control group (P>0.05). IOP returned to pre-dose levels at 8 h after administration. The ocular hypotensive effect of pilocarpine in this model was not obvious.