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.

Abstract

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.

PROCEDURE:

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.

• Authors: Caryn E Plummer, Edward O MacKay, Kirk N Gelatt
• Journal: Veterinary ophthalmology (Vet Ophthalmol) 2006 Jul-Aug Vol. 9 Issue 4 Pg. 245-9 ISSN: 1463-5216 [Print] England
• PMID: 16771760 (Publication Type: Controlled Clinical Trial, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antihypertensive Agents
• Drug Combinations
• Ophthalmic Solutions
• Sulfonamides
• Thiophenes
• Timolol
• dorzolamide

Topics

• Administration, Topical
• Animals
• Antihypertensive Agents (administration & dosage, pharmacology, therapeutic use)
• Dog Diseases (drug therapy, physiopathology)
• Dogs
• Drug Administration Schedule
• Drug Combinations
• Female
• Glaucoma, Open-Angle (drug therapy, veterinary)
• Heart Rate (drug effects)
• Intraocular Pressure (drug effects)
• Male
• Ophthalmic Solutions
• Pupil (drug effects)
• Sulfonamides (administration & dosage, pharmacology, therapeutic use)
• Thiophenes (administration & dosage, pharmacology, therapeutic use)
• Timolol (administration & dosage, pharmacology, therapeutic use)
• Tonometry, Ocular (veterinary)
• Treatment Outcome