Department of Animal Science Florida Agricultural
Research Report AL-1983-3 Experiment Station
5-3 Gainesville, Florida
PALATABILITY OF CLENBUTEROL IN A SYRUP FORMULATION1
WHEN APPLIED TO THE GRAIN RATION OF HORSES
R.L. Asquith2 and A. Schwink i
Clenbuterol (NAB-365) is a halogen-substituted phenyletanolamine with a
beta-2-receptor-stimulating effect. VThe action of this drug on bronchial
musculature (bronchospasmolysis) has been shown in several.studies on various
animals and in humans (Nolte and Laumen, 1972;'Schuman, 1972; Curti, 1974;
Nolte et al, 1974; Kreuter, 1974; Renovanz et al, 1974; Uhl, 1974; Engelhardt,
1976). Many clinical trials have been conducted utilizing clenbuterol par-
enterally and by oral administration of granules. Sasse and Hajer (1977)
reported on their clinical experiences with clenbuterol in horses for treat-
ment of chronic obstructive pulmonary disease (COPD) and bronchopneumonia.
The purpose of this study was to determine the palatability of clenbuterol
when incorporated into a syrup formulation and applied to the grain ration of
horses, and observation of the animals for possible adverse reactions.
Whereas the taste preference for a given species represents the average
preferences in a large number of animals, there are also individual variations
within each species. (Houpt, 1983)
In research situations involving two separate studies, one trial demonstrated
that 5 out of 6 yearling horses preferred sucrose to water (Randall et al, 1978),
and 4 out of 5 ponies in the second trial preferred sweetened oats to plain oats
(Hintz, 1980). Although, one horse in the first study overtly discriminated
against sucrose when given a choice between sucrose and water, and in the second
study one pony exhibited a preference of plain oats to oats that had been sweetened.
These individual animal preferences in both flavor and perhaps odor tend to con-
found experiments using simple combinations of tastants.
Thirty-two clinically normal horses, varying in age from 1 to 20 years of age
were selected at random and placed on trial after a 5 day acclimation period to
evaluate their normal acceptance to the grain ration being fed. Each horse was
offered its usual amount and type of grain ration twice daily throughout the trial.
Water and Coastal Bermuda grass hay were fed ad libitum. All animals were weighed
prior to the start of the trial.
Treatment A syrup containing 24.9 pg of clenbuterol/ml was pumped onto the grain
ration by a dispenser designed to deliver a volume of syrup to treat 250 Ibs body
wt per stroke (15.2 ml of syrup per 1000 lb horse). This amount approximates 0.8 pg
clenbuterol/kg/body wt. Each animal was treated twice daily for a total of 21 days.
Ventipulmin syrup, Philips Roxane, Inc., St.Joseph, MO (Parent Co., Boehringer
2Asquith, DVM, Assoc. Professor of Equine Health, Department of Animal Science
3Schwink, DVM, MS, Philips Roxane, Inc., St.Joseph, MO
Palatability Observation Observations were made twice daily after each horse
had been allowed sufficient time to consume their ration. These observations
were recorded twice daily according to the following scoring method.
1. (CA) Complete acceptability (usual rate of grain consumption).
2. (DA) Delayed acceptability (reduced rate of grain consumption,
with or without adverse animal response.
3. (RF) Refused grain (did not eat).
4. (RD) Refused drug (selectively ate around the drug).
Clinical Observations All test animals were observed for any deviation of health
status and potential adverse signs that may have been associated with or drug re-
lated following treatment.
All animals remained clinically normal throughout the trial with no adverse
reaction to the ingested drug. None of the 32 horses were scored RF or RD, as
refusing grain or drug, at any time during the trial. Only 7 of the 32 horses on
the trial were scored as DA, delayed acceptance, at any point in the trial. Three
of the horses so classified showed delayed acceptance of grain in the pre-dosing
period before any drug was introduced. Using all the data, there was a 2.5%
delayed acceptance in the pre-dosing trials and a 6.2% delayed acceptance in the
dosing trials. This difference is very small and does not approach statistical
significance. Two of the seven horses scored for at least one delayed acceptance
were responsible for sixty percent of the delayed acceptance recorded and had
showed this characteristic in the predosing period. If the two horses showing
most of the delayed acceptance are removed, the figures become 1% and 2.5%,
Horses sometimes delay in the acceptance of grain. This study shows the
incidence of such cases is not significantly changed when clenbuterol (24.9 jg/ml)
is incorporated in a syrup formulation and applied as a top dressing to the grain
ration of horses. Thus, such a method provides a practical and acceptable means
of medication. The important result here was that none of 32 horses refused the
grain or selectively ate around the treated grain even after three weeks of dosing.
There was no evidence of a taste aversion being formed by the initial taste of the
drug-syrup combination as a learned response. The advantages of this modality of
treatment becomes apparent when this drug is indicated in a chronic respiratory
condition requiring an extended period of medication.
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spezifischen adrenergen B2-Bronchodilatators. Int. J. Clin. Pharmacol.
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einem neven Broncholytifum mit einer selektiven Wirkung auf die adrenergen
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