Q1. In which specific clinical scenarios do you see Suprelorin used most successfully?
Suprelorin is most successful as an alternative to surgery for fertility and testosterone management in healthy, intact, sexually mature male dogs. It is ideal for owners who do not want to surgically castrate or for dogs where anaesthesia/surgery is high-risk (e.g., pulmonary stenosis). It is also highly effective for 'trialling' the effects of castration on behaviour before permanent surgery. For 'trialling' behaviour or for reversible fertility, we recommend using the 4.7mg implant. For the prescribing guide, please refer to the Suprelorin vet resources webpage and the APVMA label.
Other Successful Clinical Scenarios
- Disease Control: Aids in controlling androgen-induced diseases such as benign prostatic hyperplasia in male dogs.
- Female Dog Infertility (4.7mg only): Induces temporary infertility in prepubertal female dogs (12–16 weeks old) to delay the first oestrus and prevent pregnancy.
- Male Cat Management (4.7mg only): Induces temporary infertility and suppresses urine odour and sexual behaviors in intact male cats from 3 months of age.
- Ferrets (9.4mg only): for the temporary suppression of fertility in normal, entire male ferrets and as an aid in the management of hyperadrenocorticism in neutered ferrets.
Q2. What behavioural issues respond best - and which ones tend to show little or no improvement?
Behavioural Responses
- Best Responding Behaviours:
- Little to No Improvement:
Q3. How significant and clinically relevant is the testosterone flare phase, and how should I counsel owners about it?
Testosterone Flare Phase
- Significance: Occurs in the first 1–2 weeks (usually 9–20 days) post-implantation due to the initial pituitary stimulation, but is not clinically evident in most dogs.
- Behavioural Impact: This surge can manifest as a "flare-up" effect, where testosterone-driven behaviours (libido, aggression, roaming, urine marking) may temporarily worsen.
- Fertility: During this phase, animals remain fertile; sperm production does not cease for approximately 6 weeks in dogs and cats. Males and females on heat must be separated during this period.
- Medical Implications: In cases of Benign Prostatic Hyperplasia (BPH), the theoretical potential for a flare means that clinical signs may transiently worsen during the first 2 weeks; however, anecdotally, this phenomenon seems to occur infrequently.
Owner Counselling Guidelines
Counselling is essential to manage owner expectations and ensure safety:
- Transient Behavioural Changes: Advise owners of a possible transient increase in testosterone-related behaviours (libido, aggression, marking).
- Fertility Precautions:
- Monitoring: Suggest monitoring for a reduction in testicle size (approx. 1/3 reduction) as a physical indicator that the flare has passed and the implant is working.
Q4. What is the realistic onset time for behavioural change and prostate size reduction? How predictable is the duration of effect across different sizes and breeds?
Behavioural Change
- Male dogs: Behavioural changes typically begin once testosterone levels have declined, which generally occurs 2–3 weeks post-implantation.
- Male cats: Sexual behaviours begin to decrease within 1 week, with significant reductions in libido and urine marking from 4-6 weeks post-implantation.
Prostate Size Reduction
- Early Improvement: Clinical signs of Benign Prostatic Hyperplasia (BPH) can begin to improve within 1–2 weeks as testosterone levels decline.
- Significant Regression: A notable reduction in prostatic size (up to 60%) is expected by 6 weeks.
- Maximum Involution: Studies indicate the prostate can decrease by up to 70% over 9 weeks following castration effects.
Predictability Across Breeds/Sizes
- Duration: can vary between individuals regardless of breed and size.
- Size Factors: smaller dogs (<10 kg) may experience longer suppression than larger breeds. However, it is recommended to discuss the overall variable length of suppression with the owners of all sizes intended for breeding, as set out in the Prescribing guide (available on the Vet Resources webpage). Note that only the 4.7mg implant should be used in dogs intended for breeding, and while the duration of effect can be a minimum of 6 months, it can last up to 18 months or more in some cases.
Q5. Is fertility fully reversible in all cases, and how long does return to fertility typically take?
Reversibility and Return to Fertility
- Reversibility: Fertility is reversible once the implant wears off. In sexually mature males intended for breeding, it is recommended to confirm that the dog is fertile prior to implantation.
- Timeline: Return to normal testosterone levels in the majority of dogs averages 8–18 months (4.7mg) or 2–2.5 years (9.4mg). Viable sperm production typically follows 8–9 weeks after testosterone returns to normal. Refer to the prescribing guide on the Vet Resources webpage for more information.
Q6. Are there any long-term safety concerns with repeated implants (bone density, metabolism, endocrine effects)?
Long-Term Safety and Contraindications
- Safety: There are no reported systemic adverse reactions at recommended dosages. There is no evidence of significant negative impact on bone density (osteocyte function) in male dogs. Efficacy and safety studies indicate that repeated implants do not significantly affect general condition, clinical chemistry, hematology, renal and hepatic function. Long-term safety data beyond 4 years of repeated implants is currently limited.
- Bone Density and Growth: Prepubertal hormonal suppression may delay physeal (growth plate) closure in long bones, potentially resulting in taller individuals, though this typically occurs without clinical or pathological consequences. Efficacy and safety studies indicate that repeated implants do not significantly affect bone density.
- Local Reactions: Localised effects like hair coat modifications (thinning or changes in texture) or transient swelling at the injection site may occur.
- Advise Against Use: Avoid use in prepubertal males whose testicles have not descended (risk of cryptorchidism) and in mature females where it may induce unwanted oestrus or uterine pathology. It is not recommended for managing aggression toward humans.
Q7. In which patients would you advise against using Suprelorin?
Patients to Avoid
- Breeding: Use with caution in breeding animals due to potential delays in the return of fertility.
- Sexually Mature Female Dogs: Use is strictly not recommended for suppressing reproductive function or oestrus cycling. Implantation risks inducing an oestrus, which can lead to unwanted pregnancy and severe uterine or ovarian pathology, such as metropathy or cysts.
- Prepubertal Male Dogs: Usage has not been investigated in this group.
- Cryptorchid Dogs: Suprelorin should not be used in dogs with undescended testicles.
- Patients with Epilepsy: Due to a lack of data and evidence that sexual hormones modulate seizure susceptibility, use in dogs suffering from epilepsy is not recommended.
- Known Hypersensitivity: Patients with a known hypersensitivity to deslorelin or any of the implant's ingredients should not receive the product.
Q8. Can it be effectively used as a trial before surgical castration — and how reliable is that as a predictor of behavioural outcome?
Trial Before Surgery
- Effectiveness: Highly reliable for "road-testing" how a dog will respond to a low-testosterone state. If behaviours do not resolve during the implant's active phase, surgical castration is unlikely to help.
- Trial Reliability: Studies show that the effects of the implant reliably predict the outcomes of surgical castration in 81.7% of cases. It is a highly effective diagnostic tool for determining if a behaviour is testosterone-linked.
Suprelorin may be used as a good first step, as it provides the benefits of low testosterone without the risks of anaesthesia or permanent surgery, aligned with WSAVA guidelines for responsible pet owners.
Predictor of Behavioural Outcomes
- Positive Response: If a behaviour (e.g., roaming, urine marking, or inter-male tension) improves during the implant's active phase, it is highly likely to respond similarly to surgical castration.
- Lack of Response: If undesirable behaviours do not resolve while testosterone is at basal levels, surgical castration is unlikely to be an effective solution.
- Informed Decision-Making: In a large survey, 37% of owners opted to keep their dogs intact after a Suprelorin trial, likely because the implant showed surgery would not resolve the owner's primary concern or was not justified.
Q9. How do you position Suprelorin versus surgical castration when discussing options with owners?
When discussing castration options with owners, the conversation should focus on determining the best fit for both the owner and the dog by highlighting the differences between surgical and medical (Suprelorin) methods.
The following points can be used to position these two options:
- Reversibility vs. Permanence: Explain that surgical castration is a permanent, non-reversible method. In contrast, medical castration is reversible, as the implant's effects eventually wear off and testosterone levels return to normal. Especially important in behavioural cases where you may be concerned about the impact of lowering testosterone.
- Procedure Type: Describe surgery as a day procedure requiring general anaesthesia to remove both testicles, necessitating pre-surgery blood tests and post-operative wound care. Position medical castration as a procedure similar to microchipping that can be performed during a routine consultation without the need for anesthesia or hospital stay.
- Maintenance and Duration: Note that surgical castration is a one-time event. For medical castration, the implant must be replaced every 6 to 12 months (depending on size of implant chosen) to maintain its effect, providing an opportunity for regular health checks.
- Outcomes and Benefits: Clarify that medical castration provides the benefits of surgical castration (such as preventing pregnancy and reducing unwanted behaviours) without requiring surgery.
- Future Flexibility: Emphasise that choosing medical castration allows the owner to later decide whether to repeat the implant, let the effects wear off, or proceed with permanent surgery.
- Health Considerations: Mention that while both methods reduce certain health risks like testicular cancer, surgical castration in some breeds may have emerging links to long-term risks such as joint disorders or specific cancers.
Options for Positioning Suprelorin
1. The "Responsible First Step"
- The Trial Concept: Position it as a "road test" to see how a dog responds to lower testosterone before committing to a permanent, irreversible surgery.
- Risk Mitigation: It avoids the dilemma of "no way back" if castration adversely affects the dog's behavior, such as increasing fear or anxiety.
2. Prioritising Long-Term Health
- Hormonal Balance: Unlike surgery, which removes the testes and permanently disrupts the hormonal feedback loop (leading to high LH levels), Suprelorin keeps the entire reproductive hormone cascade under control.
- Reduced Disease Risk: Maintaining this balance may help reduce long-term risks associated with gonad removal, such as certain joint disorders (e.g., hip dysplasia) and cancers (e.g., osteosarcoma).
- WSAVA Support: Emphasise that the WSAVA guidelines recommend Suprelorin over orchidectomy for responsible pet owners.
3. Safety and Convenience
No Surgery/Anesthesia: Position it as a stress-free option for both the owner and the dog, as it can be administered during a standard consultation without the risks and recovery time associated with general anesthesia.
Simplicity: It is as simple and quick as microchipping, with no hospital stays or post-surgical care required.
