Polyprenyl Immunostimulant™ product information

Polyprenyl Immunostimulant™
Helping the body fight diseases®

Available worldwide*

Polyprenyl Immunostimulant™ (PI) is the only USDA-approved therapeutic for the treatment of Feline Viral Rhinotracheitis (FVR).

What is Polyprenyl Immunostimulant™?

Polyprenyl Immunostimulant™ is manufactured by Sass & Sass, Inc. and is the only therapeutic approved by the USDA for the treatment of feline rhinotracheitis. It is a very safe, well-tolerated oral liquid designed with cats in mind. Polyprenyl Immunostimulant™ is formulated as a 2 mg/mL solution of phosphorylated polyprenols and is offered in 10 mL vials or packs of 6 x 10 mL vials. 

Polyprenyl Immunostimulant™ works by upregulating innate immunity and directing cellular immune response. It is a very safe product which aids in the reduction of clinical signs resulting from rhinotracheitis infection in cats 8 weeks of age or older. Polyprenyl Immunostimulant™ is often referred to as PI or PPI.

Polyprenyl Immunostimulant™ quick facts

Polyprenyl Immunostimulant™ reprograms the cat's innate immunity, restores quality of life, returning your cat to a healthy and happy self.

Polyprenyl Immunostimulant™ reduces the severity of clinical signs resulting from feline herpesvirus infection (URI, FHV-1, FVR, FRV) in cats eight weeks of age or older.​

Polyprenyl Immunostimulant™ is administered orally; a single dose equals 0.25 ml/kg. The recommended dosage is two oral doses of Polyprenyl Immunostimulant™ daily for 15 days.​​

Safety studies in 390 cats showed that oral administration of 0.5 mg/kg of Polyprenyl Immunostimulant™ twice daily for 15 days is safe for cats eight weeks of age or older. No signs of illness were note in toxicity tests conducted at 5 mg/kg dose of Polyprenyl Immunostimulant™.​

Polyprenyl Immunostimulant™ is the only USDA-approved oral treatment for feline rhinotracheitis. No analogs or similars exist.
• 100% sourced and manufactured in the USA.
• Exceptional safety record: no adverse events reported during studies or seven years post-market introduction.
• Small volume of liquid is easy to administer to cats.​

Benefits of Polyprenyl Immunostimulant™

Polyprenyl Immunostimulant™ is a unique veterinary treatment of feline viral rhinotracheitis (FVR, FRV, FHV-1), a common and ubiquitous upper respiratory infection (URI). Polyprenyl Immunostimulant™, also referred to as PI or PPI, was designed and developed specifically for cats.

Polyprenyl Immunostimulant™ reduces the severity of the disease in cats by doing what antivirals cannot accomplish: it restores the cat’s innate immunity to fight the viral infection effectively. It is a very safe, well-tolerated, easily administered small dose  oral liquid designed with cats and their guardians in mind. Because the dose needed to treat a cat is low, and the course of treatment short, this is also an affordable treatment for any cat suffering for FVR.

Is your cat sneezing a lot? Are you tired of fighting chronic URI (Upper Respiratory Infections)? It's time to try something different. Polyprenyl Immunostimulant™ is a proven product for the treatment of Feline Rhinotracheitis, designed with cats and their guardians in mind.

Why choose Polyprenyl Immunostimulant™?

A common option for attempting to treat Feline Viral Rhinotracheitis (FVR) is with off-label, generic human antiviral drugs that are not tailored to cats. These human drugs have known side effects on a cat’s organism; they often need to be compounded, which is costly, or come in large size pills that are definitely not cat-friendly.

Cat guardians should ask themselves this question: would you use a horse-specific medicine on yourself? If your answer is “probably not”, then why would you use a human-specific medicine on a cat when the option exists to treat the cat with feline-specific medicine? Why treat one species with medicine developed for another, completely different species?

For cat’s DVMs and VMDs, the question is similar: would MDs prescribe or even recommend a veterinary medicine to their human patients? The answer is easy: “definitely NOT,” just like dedicated veterinarians would NOT consider prescribing or use human-specific medicine for cats unless proper veterinary studies of safety and efficacy have also been conducted with that human medicine.

Human generic direct antivirals (like, for example, Famciclovir) only able to lessen the viral load during flare-ups, but they do not completely eliminate the virus. As cats and cat guardians do not read the viral titer reports, if the viral infection has destroyed the cat’s immunity, all the cat’s guardian can do is witness their cats feel equally bad regardless of the viral load.

Using human-specific medicine to treat felines is like using veterinary drugs to treat human patients: it is not recommended. Unlike antivirals prescribed for FVR, Polyprenyl Immunostimulant™ is cat-specific.

How does Polyprenyl Immunostimulant™ work?

Polyprenyl Immunostimulant™ works by upregulating innate immunity and directing the cellular immune response. It is a very safe and effective product which has proven efficacy for the treatment of cats eight weeks of age or older against rhinotracheitis (FVR). PI also alleviates the feeling of sickness in cats by restoring the proper immune response.

If your cat (or your patient) keeps experiencing rhinotracheitis episodes, and you keep treating with antivirals, but the cat relapses time and again, it is time to address the root of the cause instead of the effect: the cat’s immune system is so compromised that it cannot mount the proper response against the virus’ attacks. Polyprenyl Immunostimulant™ treats the root of the problem, resulting in the reduction or elimination of its effects.

How much Polyprenyl Immunostimulant™ do you need to treat your cat? Use our calculator to find out dosage and number of vials based on your cat's weight.

* Polyprenyl Immunostimulant™ is not or may not be available in a small number of countries due to country-specific regulations or contractual limitations.

Cat Guardians

Order information for cat guardians


Register or log in page for veterinarians

PI Current Serial

Now distributing Polyprenyl Immunostimulant™ serial with expiration date
August 2022.