An ethical requirement of clinical trials, equipoise means that the researchers are not certain which arm will receive the best treatment.
Equipoise® is the popularly referenced brand name for the veterinary injectable steroid boldenone undecylenate. Specifically it is a derivative of testosterone, which exhibits strong anabolic and moderately androgenic properties. The undecylenate ester greatly extends the activity of the drug (the undecylenate ester is only one carbon atom longer than decanoate), so that clinically injections would need to be repeated every three or four weeks.
A state in which an investigator is uncertain about which arm of a clinical trial would be therapeutically superior for a patient. An investigator who has a treatment preference or finds out that one arm of a comparative trial offers a clinically therapeutic advantage should disclose this information to subjects participating in the trial.