Johnny is a four year old male German Shepherd that was presented to the Yokine practice. His owner was concerned about his unpredictable behaviour towards men as he would lunge at any male passing by while he was out on his walks. He had also bitten his vet once before after an ear swab and had shown aggressive tendencies towards other boisterous dogs. Johnny’s owner was also pregnant and was worried about what his behavior would be like towards the new addition to the family.

Johnny’s diagnosis

Johnny was given a thorough physical examination to rule out any medical conditions that may result in aggressive type behaviours such as pain caused by osteo-arthritis. He was given a clean bill of health. It was discussed that castration may improve his behaviours that are testosterone driven. For personal reasons surgical castration was declined and so an alterative was required.


Suprelorin is an implant that lasts between six and twelve months. It contains a substance called deslorelin, which acts like the natural hormone gonadotropin releasing hormone (GnRH) which controls the secretion of other hormones involved in fertility. It is given as an implant that slowly releases a low dose of deslorin which blocks the production of follicle stimulating hormone and luteinizing hormone in male dogs. As a result, less testosterone circulates in the blood which means the dog stops producing sperm and its libido is reduced. There is a complete return to normal fertility approximately one year after the last treatment. Side effects include the occasional mild swelling at the implant site which resolves naturally, and it is not recommended for dogs that have not yet reached puberty.


Johnny had the implant administered, which is similar to a microchip, approximately four months ago. He has shown little to none of his previous aggressive tendencies towards other dogs and men. In addition, there have been no observable changes to his personality and he is much happier when visitors come to the house. Johnny now attends obedience training, is more tolerant of other dogs, and is more amenable to training.

Suprelorin is available as either a six or twelve month implant. It can be repeated as often as necessary. It is completely reversible and may give you an alternative if surgical castration is not an option.

Suprelorin can also be used in male ferrets for the same purpose.

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