title: Efficacy of tropicamide, homatropine, cyclopentolate, atropine and hyoscine as mydriatics in Angora goats.
abstract: OBJECTIVE
  To document the efficacy of five commercially available mydriatics for their potential for diagnostic and therapeutic use in Angora goats.
  
  
  METHODS
  Over 8 weeks, the mydriatic effects of 1% tropicamide, 2% homatropine, 1% cyclopentolate, 1% atropine and 0.25% hyoscine were evaluated. Given as block treatments, drugs were applied randomly to one eye of 10 Angora goats, and the contralateral eye served as a control. Vertical and horizontal pupil diameters were measured to document onset of effect, time to reach a difference of 5 mm in the vertical/horizontal pupil diameter between eyes, time to maximum pupillary dilation, and duration of mydriatic action.
  
  
  RESULTS
  Onset of mydriasis for all drugs occurred within 15 minutes. Time to reach a difference of 5 mm in the vertical pupil diameter between eyes was shortest for 1% tropicamide and 0.25% hyoscine (0.5 h), then 2% homatropine and 1% atropine (0.75 h), and longest for 1% cyclopentolate (1.5 h). The maximum vertical pupillary dilation occurred earliest with 1% tropicamide and 1% atropine (2 h), followed by 0.25% hyoscine (3 h), 2% homatropine (4 h), and latest with 1% cyclopentolate (8 h). The duration of vertical dilation of the pupil was shortest with 1% tropicamide (6 h), then 2% homatropine (12 h), 1% cyclopentolate (12 h), 1% atropine (24 h), and longest for 0.25% hyoscine (96 h). The time to reach maximum horizontal dilation of the pupil in treated eyes was shortest with 1% cyclopentolate (1 h), followed by 1% tropicamide (1.5 h), 0.25% hyoscine (3 h), 2% homatropine (3.5 h), and 1% atropine (4 h). The duration of horizontal pupil dilation was shortest with 1% tropicamide (4.5 h), and longest with 0.25% hyoscine (48 h).
  
  
  CONCLUSIONS
  All five mydriatics induced clinical dilation. Tropicamide (1%) had the shortest duration of effect, but gave incomplete dilation. Good dilation was achieved with 1% cyclopentolate and 2% homatropine, but took too long to reach maximum dilation for routine mydriasis. The largest vertical dilation of the pupil was achieved with 1% atropine and 0.25% hyoscine, but pupils remained dilated for more than 24 h.
  
  
  CONCLUSIONS
  For routine mydriasis in goats, it is recommended that 1% tropicamide be used, though there may be incomplete dilation. For a longer duration of mydriasis, such as in the treatment of anterior uveitis, 1% atropine or 0.25% hyoscine would be the drugs of choice.
authors: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North 4442 , New Zealand. whelann@uoguelph.ca
authors: N C
authors: NC
authors: Whelan
authors: F
authors: F
authors: Castillo-Alcala
authors: I
authors: I
authors: Lizarraga
mesh_terms: D000287:Administration, Topical; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003519:Cyclopentolate / Q000494:pharmacology; D006041:Goats; D009184:Mydriatics / Q000494:pharmacology*; D009883:Ophthalmic Solutions; D012601:Scopolamine / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D014331:Tropicamide / Q000494:pharmacology
chemical_list: D009184:Mydriatics; D009883:Ophthalmic Solutions; D014326:Tropanes; D001285:Atropine; C100236:homatropine; D012601:Scopolamine; D003519:Cyclopentolate; D014331:Tropicamide