Effects of oral administration of methazolamide on intraocular pressure and aqueous humor flow rate in clinically normal dogs.
OBJECTIVE
To determine magnitude and duration of the effect of oral administration of methazolamide at 2 dosages on intraocular pressure (IOP) in dogs in single-dose and multiple-dose trials and to determine aqueous humor flow rate (AHFR) by use of anterior segment fluorophotometry before and during treatment.


METHODS
25 healthy adult Beagles.


METHODS
Baseline IOPs and AHFRs were determined on days 0 and 1, respectively. On day 2, the single-dose trial was initiated with oral administration of 25 or 50 mg of methazolamide at 7 AM to 2 groups of 10 dogs each. Five dogs served as controls. In the multiple-dose trial, the same dogs received 25 or 50 mg of methazolamide at 7 AM and at 3 and 11 PM on days 3 through 9.


RESULTS
Intraocular pressures varied diurnally with highest IOPs in the morning. In the single-dose trial, IOP decreased significantly at 3 to 6 hours after treatment and then increased significantly at later time points, compared with baseline values. In the multiple-dose trial, dogs in both treatment groups had significantly lower IOPs during the treatment period at 10 AM and 1 PM but not at 6 and 9 PM, compared with baseline values. In both treatment groups morning IOPs had returned to baseline values by the first day after treatment. Evening IOPs were significantly increased by 2 to 3 days after treatment, compared with baseline values. The AHFRs in both treatment groups were significantly lower than pretreatment AHFRs.


CONCLUSIONS
Oral administration of methazolamide decreases IOPs and AHFRs in clinically normal dogs, with effectiveness diminishing in the evening.
Skorobohach
Brian J
BJ
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN 37996, USA.
Ward
Dan A
DA
Hendrix
Diane V H
DV
D000284:Administration, Oral; D000818:Animals; D001082:Aqueous Humor / Q000187:drug effects*; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage* / Q000494:pharmacology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008704:Methazolamide / Q000008:administration & dosage* / Q000494:pharmacology*
D002257:Carbonic Anhydrase Inhibitors; D008704:Methazolamide