Comparison of the effects of topical administration of a fixed combination of dorzolamide-timolol to monotherapy with timolol or dorzolamide on IOP, pupil size, and heart rate in glaucomatous dogs.
OBJECTIVE
To determine whether the combination multiple-dose dorzolamide-timolol administered topically has any greater effects on the reduction of intraocular pressure, pupil size, and heart rate in dogs with glaucoma than do either timolol or dorzolamide alone.


METHODS
Applanation tonometry, pupil size, and heart rate measurements were made at 7 a.m., 1 p.m., and 7 p.m. daily of 12 laboratory Beagles with inherited primary open-angle glaucoma during each active phase of this study. Timolol 0.5% was administered first twice daily for 4 consecutive days. Dorzolamide 2.0% was administered next three times daily for 4 consecutive days. The fixed combination of the two (timolol 0.5% and dorzolamide 2.0%) was administered twice daily for 4 consecutive days during the final week of the study. Between administration of each drug, a withdrawal period of at least 10 days was instituted. Statistical comparisons between the effects of the three drugs were performed.


RESULTS
Intraocular pressure (IOP) was decreased with the administration of all three drugs: timolol alone, dorzolamide alone, and the combination of the two decreased IOP after 1 day of treatment 2.83 +/- 0.70 mmHg, 6.47 +/- 0.32 mmHg, and 6.56 +/- 0.37 mmHg, respectively. After 4 days of treatment, the IOP decreased even further: timolol alone, dorzolamide alone, and the combination of the two decreased IOP 3.75 +/- 0.88 mmHg, 7.50 +/- 0.29 mmHg, and 8.42 +/- 0.58 mmHg, respectively. Heart rate was significantly decreased with timolol (-11.9 +/- 2.0 bpm) and the combination preparation (-8.6 + 2.4 bpm), but not with dorzolamide (-3.7 +/- 1.8 bpm) alone. Pupil size was significantly decreased with timolol (-1.42 + 0.40 mm) and the combination preparation (-1.3 + 0.33 mm), but not with dorzolamide (0.97 +/- 0.36 mm) alone.


CONCLUSIONS
The combination dorzolamide-timolol appears to be more effective at reducing intraocular pressure in glaucomatous dogs than is either timolol or dorzolamide alone.
Plummer
Caryn E
CE
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0126, USA.
MacKay
Edward O
EO
Gelatt
Kirk N
KN
D000287:Administration, Topical; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D004283:Dog Diseases / Q000188:drug therapy* / Q000503:physiopathology; D004285:Dogs; D004334:Drug Administration Schedule; D004338:Drug Combinations; D005260:Female; D005902:Glaucoma, Open-Angle / Q000188:drug therapy / Q000662:veterinary*; D006339:Heart Rate / Q000187:drug effects; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D009883:Ophthalmic Solutions; D011680:Pupil / Q000187:drug effects; D013449:Sulfonamides / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D013876:Thiophenes / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D013999:Timolol / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D014065:Tonometry, Ocular / Q000662:veterinary; D016896:Treatment Outcome
D000959:Antihypertensive Agents; D004338:Drug Combinations; D009883:Ophthalmic Solutions; D013449:Sulfonamides; D013876:Thiophenes; D013999:Timolol; C062765:dorzolamide