Intravenous injections of 500 mg dorzolamide increased
ONP
o 2 from 16.4 ± 6.1 mm Hg to
26.9 ± 12.2 mm Hg, or 52.5% ± 21.2% (
n = 5;
P = 0.017;
Fig. 2 A
). As shown in
Table 2 , dorzolamide significantly lowered
arterial pH, and also increased arterial
P
co 2, but had no significant
effect on arterial P
o 2. The
effect of dorzolamide on ONP
o 2 was dependent on the dose injected and was seen with dosages of 1000,
500, 250, 125, 63, 27, 15, and 6 mg
(Fig. 3) . Most of the effect of dorzolamide was reached at 500 to 1000 mg total
dosage, and additional injections of the drug had only a small effect
on ONP
o 2. Control intravenous
injections of 20 ml of the vehicle sodium citrate buffer solution alone
had no effect on ONP
o 2 in three
experiments.
Intravenous injections of 500 mg acetazolamide increased
ONP
o 2 from 23.6 ± 9.5 mm Hg to
30.9 ± 10.0 mm Hg (
n = 6
; P = 0.0008).
Figure 2B shows a typical response to intravenous injection of
acetazolamide. This effect on
ONP
o 2 was also seen after
injections of 250, 125, 31, and 15 mg acetazolamide and with 1000-mg
dosages administered in two equal doses
(Fig. 3) . Control intravenous
injections of 20 ml saline had no effect on
ONP
o 2. As indicated in
Table 2 , 500 mg acetazolamide significantly lowered arterial pH and also
increased arterial P
co 2, but had
no significant effect on arterial
P
o 2. Additional injections of
500 and 1000 mg acetazolamide had little further effect on
ONP
o 2 after initial
administration of 1000 mg acetazolamide, indicating that a maximum
effect had been reached by the injections first administered. The
effects of acetazolamide and dorzolamide on
ONP
o 2 were dose dependent, and
dorzolamide was more potent, as illustrated in
Figure 3 . The effect of
dorzolamide injections on ONP
o 2 was also present when the intraocular pressure was fixed at 15 mm Hg.