Zilpaterol
Zilpaterol is a potent beta-2 adrenergic agonist used as a cattle feed additive (zilpaterol hydrochloride, Zilmax) to increase muscle growth and leanness. It is not a human medicine and has essentially no human data. It has faced marketing suspension and welfare scrutiny in cattle, and its residues are banned in the EU and many other regions. It is included as a beta-agonist repartitioning agent, not for any human use.
01 Overview
Zilpaterol is a beta-agonist growth promoter fed to cattle in the weeks before slaughter to increase lean muscle mass and dressing percentage. Marketed as Zilmax, it is more potent than ractopamine on a per-milligram basis. Like other beta-agonist repartitioning agents it raises cyclic AMP in muscle and fat to shift nutrient use toward protein accretion.
It is not approved or studied for human use, and the human evidence base is effectively absent — its profile is inferred from its beta-agonist pharmacology and livestock toxicology. Zilmax was subject to a voluntary market suspension after reports of lameness and welfare problems in feedlot cattle. Residues are prohibited in the EU and numerous other jurisdictions. It is catalogued here as a member of the beta-agonist family, with no human dosing context.
02 Mechanism
Potent beta-adrenergic (predominantly beta-2) agonist and nutrient-repartitioning agent. Raises cyclic AMP in skeletal muscle and adipose tissue, increasing protein deposition and lipolysis to produce leaner, more muscular carcasses in cattle.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Cattle feed additive | 60–90 mg/day | Oral | Formulated in cattle feed (about 60-90 mg per head per day in finishing regimens); there is no human dose and no human use case. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Increased muscle mass (cattle)Increases lean muscle and carcass yield in finishing cattle; livestock effect only. | greater lean yield | Preclinical | |
| Reduced fat (cattle)Shifts deposition away from fat toward muscle in treated cattle. | leaner carcass | Preclinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Beta-agonist cardiovascular stimulationOn pharmacological grounds a potent beta-agonist would raise heart rate and cause palpitations; direct human data are absent. | Moderate | No human data | Preclinical | |
| Animal welfare effects (lameness)Reports of lameness and mobility problems in feedlot cattle contributed to a voluntary marketing suspension of Zilmax. | Moderate | In treated cattle | Observational |