Propionibacterium acnes injection
**Propionibacterium acnes injection** is a non-specific immunostimulant and biologic response modifier (BRM) formulated from a killed (non-viable) suspension of the bacterium *Propionibacterium acnes* (formerly known as *Corynebacterium parvum*). ### Clinical Applications * **Dogs:** Primarily used as an adjunct to antibiotic therapy for **chronic recurring pyoderma** to reduce lesion severity and frequency. * **Horses:** Utilized as an adjunctive treatment for primary or secondary **viral or bacterial respiratory tract infections**, and off-label to improve fertility in mares with **persistent endometritis**. * **Cats:** Used off-label for the management of **feline retrovirus infections** (FeLV, FIV) and feline rhinotracheitis, though efficacy data is mixed. > **Clinical Pearl:** Because it relies on an intact immune system to mount a response, its efficacy can be highly variable. It is almost exclusively used as an *adjunctive* therapy rather than a standalone treatment.
Mechanism: As a non-specific immunostimulant, *P. acnes* acts by stimulating the reticuloendothelial system and cell-mediated immunity. * **PAMP Recognition:** The killed bacteria contain Pathogen-Associated Molecular Patterns (PAMPs) that are recognized by **Toll-Like Receptors (TLRs)** (likely TLR9) on antigen-presenting cells. * **Macrophage Activation:** Induces robust activation of macrophages and dendritic cells. * **Cytokine Cascade:** Stimulates the production of lymphokines and pro-inflammatory cytokines (e.g., IL-12, TNF-ฮฑ, IFN-ฮณ) โ promotes a **Th1-type immune response**. * **Effector Cell Enhancement:** Increases **Natural Killer (NK) cell** activity and enhances overall cell-mediated immunity to help clear chronic bacterial or viral infections.
Dosing by species
- Adjunctive therapy of feline retrovirus infections ยท 0.5 mL ยท IV ยท twice weekly for 2 weeks, then one injection weekly ยท 20 weeks or until cat is seronegative
- Adjunctive therapy of feline retrovirus infections ยท 0.25-0.5 mL ยท IV ยท twice weekly then every other week ยท 16 weeks
- Antiviral immunostimulant to increase hematopoiesis in FeLV-positive cats ยท 5 lb cats: 0.25 mL; 10 lb cats: 0.5 mL ยท IV, IP ยท twice weekly for 2 weeks, then once weekly until remission and once monthly after that to maintain clinical improvement. (For 10 lb cats: once weekly for 3 weeks and once monthly for 2 months for a total of nine injections) ยท Variable ยท Some protocols suggest follow-up with injections once weekly for 20 weeks or longer as needed.
- Immunostimulant for adjunctive therapy of primary or secondary viral or bacterial respiratory tract infections ยท 1 mL per 114kg (250 lb) body weight ยท IV ยท q48-72h ยท Using EqStim
- Immunostimulant for adjunctive therapy of primary or secondary viral or bacterial respiratory tract infections ยท 1 mL per 114kg (250 lb) body weight ยท IV ยท Repeat dosage on day 3 (or day 4), at day 7, and weekly as needed ยท Using EqStim
- Adjunctive treatment to improve fertility in mares with endometritis ยท 1 mL per 114 kg (250 lb) body weight ยท IV ยท Given days 0, 2, and 6 ยท Using EqStim. Best results in mares bred 2 days before to 8 days after initial administration.
- Adjunct to antibiotic therapy in the treatment of chronic recurring canine pyoderma ยท For animals weighing up to 15 lbs = 0.25-0.5 mL; 15-45 lbs = 0.25-1 mL; 45-75 lbs = 1-1.5 mL; >75 lbs = 1.5-2 mL ยท IV ยท 4 times at 3-4 day intervals, then once weekly until symptoms abate or stabilize. Maintenance doses once per month are recommended. ยท Shake well before use.
Routes of administration
Contraindications
- Hypersensitivity to the compound
- Canine lymphoma
- Leukemias with CNS involvement
- FIV or FIP in cats (according to some sources)
Adverse effects
- Lethargy
- Hyperthermia (fever)
- Chills
- Anorexia
- Anaphylactic reactions
- Local tissue inflammation (if extravasated)
- Vomiting (long-term use)
- Malaise (long-term use)
- Acidosis (long-term use)
- Increased water consumption (long-term use)
- Hepatitis (long-term use)
Drug interactions
- Glucocorticoids ยท May compromise immunostimulant effects; manufacturer recommends discontinuing steroids at least 7 days prior to initiating therapy.
- Immunosuppressive drugs ยท May compromise immunostimulant effects.
Monitoring
- Clinical efficacy (resolution of pyoderma lesions, improvement in respiratory signs, or viral remission)
- Adverse effects (lethargy, fever, chills)
- Signs of anaphylaxis immediately following injection
Overdose
Specific overdosage information is not available. The primary concern with acute administration is the potential for **anaphylactic (severe allergic) reactions**. The manufacturer states that the antidote for such reactions is **epinephrine**.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.