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. 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™ 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.​