Those who took degarelix were also found to experience much greater falls in their prostate-specific antigen (PSA) levels at 14 and 28 days than men taking leuprolide.
For the study, the researchers from Canada, the USA, France, Denmark and the Netherlands studied 610 men as part of the Phase Three trial, randomly assigning them to one of three study groups.
"Androgen deprivation hormone therapy is an effective response to prostate cancer, but the drugs that are most widely used cause an initial rise in testosterone - the hormone we are trying to reduce - when the patient first takes them" explained lead author Dr Laurence Klotz from the Division of Urology at the University of Toronto, Canada.
He added: "We prefer to avoid this biochemical surge as it can stimulate the prostate cancer cells and exacerbate a number of clinical symptoms, such as spinal cord compression and bone pain. It could also result in more rapid growth of microscopic disease that is present in the patient but is too small to be detected.
"Degarelix is a new gonadotrophin-releasing hormone (GnRH) antagonist. It works by binding to, and blocking, the GnRH receptors in the pituitary gland, reducing the amount of LH and FSH hormones that are released. This leads directly to a rapid fall in testosterone."
Klotz said: "More than 2,000 patients have now taken part in clinical trials for degarelix and there have been no signs of immediate or late-onset systemic allergic reactions, in contrast to other reported trials of other GnRH antagonists.
"The aim of the study was to show that degarelix was not inferior to leuprolide when it came to maintaining low testosterone levels over a one-year treatment period. We have conclusively shown that this is the case.
"However, we have also demonstrated that degarelix - which is an antagonist - offers an advantage, in that it reduces testosterone and PSA levels very quickly. It doesn't cause the initial surge of testosterone seen with agonist drugs like leuprolide - the other drug featured in this study.
"This is relevant as biochemical surges in testosterone can stimulate the prostate cancer cells and cause unpleasant side effects for patients. They may also require further drug therapy to counteract the effects of agonist drugs like leuprolide."
The study was published in the December issue of BJU International.