Trimetoquinol: bronchodilator effects in horses with heaves following aerosolised and oral administration.
BACKGROUND
The bronchodilator effects of trimetoquinol (TMQ) have been studied when administered i.v. or intratracheally, but not in an aerosolised form.


OBJECTIVE
To define the relationship between the therapeutic and adverse responses (therapeutic index) of TMQ when administered as an aerosol or by the oral route.


METHODS
Increasing doses of TMQ were administered to horses with heaves as an aerosol and by the oral route. Dose ranged 100-1000 microg/horse for aerosolised TMQ and from 6-60 microg/kg bwt for the oral route. Airway and cardiac effects were assessed by measurement of maximal change in pleural pressure (deltaPplmax) and heart rate (HR), respectively. Side effects of sweating, agitation and muscle trembling were scored subjectively. Duration of action of aerosolised (1000 pg/horse) and oral (6-60 microg/kg bwt) TMQ was evaluated over 6 h.


RESULTS
Aerosol administration of TMQ caused dose-dependent bronchodilation but did not change HR or cause other observable side effects. When 1000 microg/horse was administered via aerosol, TMQ produced a 2-phase bronchodilation; an immediate effect lasting up to 30 min and a second phase between 2 and 4 h. Oral TMQ was therapeutically ineffective.


CONCLUSIONS
Aerosol administration of TMQ is a safe and effective method of producing bronchodilation in horses.
Camargo
F C
FC
Maxwell H. Gluck Equine Research Center and the Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA.
Robinson
N E
NE
Berney
C
C
Eberhart
S
S
Baker
S
S
Detolve
P
P
Derksen
F J
FJ
Lehner
A F
AF
Hughes
C
C
Tobin
T
T
D000280:Administration, Inhalation; D000284:Administration, Oral; D000402:Airway Obstruction / Q000188:drug therapy / Q000662:veterinary*; D000818:Animals; D001993:Bronchodilator Agents / Q000009:adverse effects / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D008297:Male; D012008:Recurrence; D016896:Treatment Outcome; D014213:Tretoquinol / Q000009:adverse effects / Q000627:therapeutic use*
D001993:Bronchodilator Agents; D014213:Tretoquinol