White Paper: Low-Dose Naltrexone (LDN) as an Adjunct in FIP Recovery

Key Points

- Research suggests LDN may help with FIP recovery, but it's not a standard treatment yet.

- LDN could reduce inflammation and support immune normalization in cats post-FIP treatment.

- More studies are needed to confirm its effectiveness and safety for FIP.

Overview

Low-Dose Naltrexone (LDN) has been proposed as a potential adjunctive therapy for cats recovering from Feline Infectious Peritonitis (FIP), especially to address lingering symptoms like anemia and inflammation after antiviral treatments like GS-441524 or GC376. While it shows promise, it's not yet a widely recognized treatment for FIP.

Proposed Benefits

LDN may act as a TLR4/NF-κB antagonist, lowering levels of inflammatory cytokines like IL-6, TNF-α, and IL-1β. This mechanism may help normalize immune responses without causing immunosuppression. It is proposed at 0.1 mg/day (~0.03 mg/kg), compounded as an oral suspension or transdermal gel.

Current Status

There are no established clinical trials or guidelines recommending LDN for FIP. However, its use is being explored due to its known anti-inflammatory and immune-modulating effects in other conditions.

Detailed Analysis of LDN for FIP Recovery

LDN is presented as a low-risk, immunologically rational adjunct for cats recovering from FIP. Persistent symptoms such as non-regenerative anemia, cachexia, and inflammation may benefit from immune modulation targeting IL-6 and TNF-α. LDN is unlikely to interact negatively with GS-441524 or common adjuncts like B12 and Denamarin.

Formulation and Dosing

The proposed feline dose is 0.1 mg/day (~0.03 mg/kg), delivered via ethanol-free compounded oral liquid or transdermal gel. There is no known contraindication with FIP antivirals or standard nutritional supports.

Potential Clinical Effects

- Increased reticulocyte counts within 10–14 days - Weight and albumin improvement within 21–28 days - Reduction in transfusion need - Decrease in cytokine-mediated relapse risk

Current Veterinary Use

LDN is used off-label for autoimmune conditions, arthritis, and certain cancers in veterinary practice. Its use in FIP remains speculative but feasible.

Trade and Research Implications

LDN is patentable in formulation and method-of-use. It has no abuse potential and is unscheduled in microdoses. It is being offered to the public domain; the Berkeley Open Source License may be used if institutional licensing is required.

Conclusion

LDN offers a plausible adjunct to support post-FIP recovery. Though unproven, its mechanism and safety profile justify controlled study. It is now offered to veterinary and academic teams for open development.

Citations

- Current pharmacotherapeutic properties of low-dose naltrexone therapy in humans and possible therapeutic and prophylactic indications in cats and dogs: https://www.researchgate.net/publication/378857015

- FIP Treatment Guide for Veterinarians: https://www.fipvetguide.com

- VCA Hospitals: Feline Infectious Peritonitis: https://vcahospitals.com/know-your-pet/feline-infectious-peritonitis

- LDN Science: LDN in Animal Health: https://www.ldnscience.org/lp/ldn-animals