Effect of long-term oral administration of a low dosage of clenbuterol on body fat percentage in working and nonworking adult horses

Am J Vet Res. 2015 May;76(5):460-6. doi: 10.2460/ajvr.76.5.460.


Objective: To determine the anabolic and lipolytic effects of a low dosage of clenbuterol administered orally in working and nonworking equids.

Animals: 8 nonworking horses and 47 polo ponies in active training.

Procedures: Each polo pony continued training and received either clenbuterol (0.8 μg/kg) or an equal volume of corn syrup (placebo) orally twice daily for 21 days, and then was evaluated for another 21-day period. Nonworking horses received clenbuterol or placebo at the same dosage for 21 days in a crossover trial (2 treatments/horse). For working and nonworking horses, percentage body fat (PBF) was estimated before treatment and then 2 and 3 times/wk, respectively. Body weight was measured at intervals.

Results: Full data sets were not available for 8 working horses. For working horses, a significant treatment effect of clenbuterol was detected by day 3 and continued through the last day of treatment; at day 21, the mean change in PBF from baseline following clenbuterol or placebo treatment was -0.80% (representing a 12% decrease in PBF) and -0.32%, respectively. By day 32 through 42 (without treatment), PBF change did not differ between groups. When treated with clenbuterol, the nonworking horses had a similar mean change in PBF from baseline from day 6 onward, which peaked at -0.75% on day 18 (an 8% decrease in PBF). Time and treatment had no significant effect on body weight in either experiment.

Conclusions and clinical relevance: Among the study equids, long-term low-dose clenbuterol administration resulted in significant decreases in body fat with no loss in body weight.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / drug effects*
  • Adipose Tissue / metabolism
  • Administration, Oral
  • Animals
  • Clenbuterol / administration & dosage
  • Clenbuterol / metabolism*
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Female
  • Horses / metabolism*
  • Male
  • Time Factors


  • Clenbuterol