By Dr. Hannah Weitzenfeld
For decades, ovariohysterectomy and castration have been the standard methods for controlling fertility in North American dogs and cats. While effective and permanent, these procedures are resource-intensive, requiring anesthesia, surgical equipment, a licensed veterinarian, and trained support staff.
The Rise of Non-Surgical Contraception
Recently, non-surgical contraception has gained traction as an efficient alternative to traditional methods. These contraceptives include immunocontraceptives, GnRH agonists and antagonists, sex steroids, gene therapy, and gonad cytotoxic drugs. Although some of these drugs have international approval, limitations such as efficacy, cost, duration, administration method, and safety have restricted their widespread use.
Suprelorin: A Noteworthy Option
One effective non-surgical option currently available to veterinarians is Suprelorin, a deslorelin-releasing implant. Deslorelin, a GnRH antagonist, inhibits testosterone production by downregulating GnRH receptors. Suprelorin has been approved in several countries and is now commercially available in Canada only in the 4.7 mg strength.
Although labeled only for male dogs in Canada, Suprelorin has been effective for both male and female dogs, as well as cats. The larger 9.4 mg implants, which last one to three years, can be obtained under an Emergency Drug Release (EDR). The duration of sterility for the different sizes of implants for male and female dogs is shown in Table 2 below.
Table 2. Suprelorin Implant Duration of Sterility after implantation in dogs.
Practical Application – Case Example: The Winnipeg Humane Society’s One Health Team provides surgical and non-surgical sterilization, vaccination, and parasite control in remote Manitoba communities. Dr. Gina Bowen, Director of Veterinary Services at WHS has been using Suprelorin in remote Manitoba communities through an Emergency Drug Release for several years. She notes that non-surgical implants can often be more practical than surgery in these areas due to weather conditions and limited resources.
In a recent clinic in God’s Lake, Dr. Bowen’s team performed surgeries on dogs previously implanted with Suprelorin, finding significantly smaller reproductive structures, which made subsequent surgeries easier and quicker.
Deslorelin implants – Pros and Cons: These implants have proven invaluable for controlling dog populations in remote communities, offering a safe and non-invasive sterilization method. This approach also helps build trust with clients who may have limited experience with veterinary care. Some drawbacks to note are that the sterility provided is temporary, as well as potential adverse effects. Table 3. Below compares the benefits and challenges with using deslorelin implants for sterilizing dogs.
Table 3. Benefits and challenges of using deslorelin implants for sterilizing dogs
| Benefits | Challenges |
| Minimal equipment required | |
| Fewer staff and less training needed | |
| Can be administered in extreme temperatures | Product requires refrigeration but cannot be frozen (freezing inactivates the drug). |
| Minimal time needed to administer, allowing sterilization of more animals in same time period | Delayed onset by several weeks. Initially induces a heat in sexually mature females (does not generally result in live births) |
| No sedation needed – injectable implant similar to microchip | |
| Can be administered by less experienced vets | Must be administered by a veterinarian |
| Better acceptance by owners | May need repeat administration or surgery after duration |
| Eliminates male libido | May increase risk of uterine disease in sexually mature females. |
Suprelorin 9.4 mg and the EDR Process: For veterinarians in Canada seeking to use the 9.4 mg Suprelorin implant, an Emergency Drug Release (EDR) is required. The EDR process involves completing an Emergency Drug Release form, obtaining signed consent from community leadership and each pet owner, providing discharge instructions to owners, and conducting follow-ups at 24 hours and 6 months. Sample forms, questions and instructions can be found here:
- Example of an EDR
- Example of template letter to be signed by community Chief and Council
- Some questions previously asked by EDR and with answers
- Vaccine and implant consent form for owners
- Owner discharge instructions
Off-label use for both female and male dogs over 4 months and over 10 kg can be requested. This larger implant, typically available directly from Virbac in Australia, is shipped via courier under cold storage conditions. Canadian customs fees and potential delays should be anticipated.
Conclusion
Combining deslorelin implants with traditional surgical methods can enhance population control programs in remote communities. Non-surgical sterilization is also a valuable tool for veterinarians working with animals with high anesthetic or surgical risk, for clients uncomfortable with surgery or anesthesia, or for temporary fertility control in breeding animals. By adopting innovative approaches, veterinarians can provide better care, manage animal populations effectively, and promote animal welfare.
As awareness and education about these options grow, they can help address the challenges faced by veterinarians, pet owners, and animal shelters.