Effects of oral administration of methazolamide on intraocular pressure and aqueous humor flow rate in clinically normal dogs
Skorobohach, B.J.; Ward, D.A.; Hendrix, D.V.H.
American Journal of Veterinary Research 64(2): 183-187
ISSN/ISBN: 0002-9645 PMID: 12602587 DOI: 10.2460/ajvr.2003.64.183
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 humour flow rate (AHFR) by use of anterior segment fluorophotometry before and during treatment. Animals: 25 healthy adult Beagles. Procedure: 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 700 h 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 700 and at 1500 and 2300 h 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 h 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 1000 and 1300 h but not at 1800 and 2100 h, 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 and Clinical Relevance: oral administration of methazolamide decreases IOPs and AHFRs in clinically normal dogs, with effectiveness diminishing in the evening.