Duration of effect and effect of multiple doses of topical ophthalmic 0.5% proparacaine hydrochloride in clinically normal dogs.
OBJECTIVE
To determine the duration of effect and the effect of multiple doses of topical ophthalmic application of 0.5% proparacaine hydrochloride on corneal sensitivity in clinically normal dogs.


METHODS
8 clinically normal dogs.


METHODS
Dogs were randomly allocated to treatment order in a 2 x 2 (period X treatment) crossover study. Treatments consisted of topical application of ophthalmic 0.5% proparacaine (1 drop or 2 drops at a 1-minute interval); treatments were applied to both eyes. A Cochet-Bonnet aesthesiometer was used to determine corneal touch threshold (CTT) before corneal application, 1 and 5 minutes after corneal application, and at 5-minute intervals thereafter for 90 minutes.


RESULTS
The CTT value before treatment differed significantly from CTT values after treatment until 45 minutes after application in the 1-drop group and until 55 minutes after application in the 2-drop group. As determined by use of the Cochet-Bonnet aesthesiometer, a significantly greater anesthetic effect was detected for the 2-drop treatment, compared with the effect for the 1-drop treatment, at 30, 35, 40, 45, 50, and 55 minutes after application. Maximal anesthetic effect lasted for 15 minutes for the 1-drop treatment and 25 minutes for the 2-drop treatment.


CONCLUSIONS
Duration of corneal anesthetic effect induced by topical ophthalmic application of 0.5% proparacaine in dogs of this study is considerably longer than that reported elsewhere. Serial application of doses of 0.5% proparacaine increases the duration and magnitude of corneal anesthetic effects.
Herring
Ian P
IP
Department of Small Animal Clinical Sciences Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061-0442, USA.
Bobofchak
Mark A
MA
Landry
Matthew P
MP
Ward
Daniel L
DL
D000287:Administration, Topical; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000494:pharmacology*; D000818:Animals; D003315:Cornea / Q000187:drug effects; D004285:Dogs; D009883:Ophthalmic Solutions; D011430:Propoxycaine / Q000008:administration & dosage* / Q000494:pharmacology*; D013997:Time Factors
D000779:Anesthetics, Local; D009883:Ophthalmic Solutions; C005717:proxymetacaine; D011430:Propoxycaine