Propionibacterium acnes injection
Propionibacterium acnes (non-viable) / Corynebacterium parvum
Also known as: Immunoregulin · Eqstim · Arthrokehlan A · Coparvax · Corymunun · Imunoparvum · Corynebacterium parvum · NSC-220537
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunct to antibiotic therapy in the treatment of chronic recurring canine pyoderma | 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 | IV | 4 times at 3-4 day intervals, then once weekly until symptoms abate or stabilize. Maintenance doses once per month are recommended. | — | 🌎 NA |
| Adjunctive therapy of chronic recurrent canine pyoderma | 0.03-0.07 mL/kg | IV | twice weekly | 10 weeks | 🌎 NA |
- Adjunct to antibiotic therapy in the treatment of chronic recurring canine pyoderma: Shake well before use.
- Adjunctive therapy of chronic recurrent canine pyoderma: Combined with antibiotic therapy.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive therapy of feline retrovirus infections | 0.5 mL | IV | twice weekly for 2 weeks, then one injection weekly | 20 weeks or until cat is seronegative | 🌎 NA |
| Adjunctive therapy of feline retrovirus infections | 0.25-0.5 mL | IV | twice weekly then every other week | 16 weeks | 🌎 NA |
| Antiviral immunostimulant to increase hematopoiesis in FeLV-positive cats | 5 lb cats: 0.25 mL; 10 lb cats: 0.5 mL | IV, IP | 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) | Variable | 🌎 NA |
- Antiviral immunostimulant to increase hematopoiesis in FeLV-positive cats: Some protocols suggest follow-up with injections once weekly for 20 weeks or longer as needed.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Immunostimulant for adjunctive therapy of primary or secondary viral or bacterial respiratory tract infections | 1 mL per 114kg (250 lb) body weight | IV | q48-72h | — | 🌎 NA |
| Immunostimulant for adjunctive therapy of primary or secondary viral or bacterial respiratory tract infections | 1 mL per 114kg (250 lb) body weight | IV | Repeat dosage on day 3 (or day 4), at day 7, and weekly as needed | — | 🌎 NA |
| Adjunctive treatment to improve fertility in mares with endometritis | 1 mL per 114 kg (250 lb) body weight | IV | Given days 0, 2, and 6 | — | 🌎 NA |
- Immunostimulant for adjunctive therapy of primary or secondary viral or bacterial respiratory tract infections: Using EqStim
- Immunostimulant for adjunctive therapy of primary or secondary viral or bacterial respiratory tract infections: Using EqStim
- Adjunctive treatment to improve fertility in mares with endometritis: Using EqStim. Best results in mares bred 2 days before to 8 days after initial administration.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
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 of action
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-α, IFN-γ) → 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.
Safety & warnings
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)
Precautions
Use with caution in patients with cardiac dysfunction. Safe use during pregnancy has not been established. Ensure strict intravenous administration, as extravasation may cause severe local tissue inflammation.
Drug interactions
May compromise immunostimulant effects; manufacturer recommends discontinuing steroids at least 7 days prior to initiating therapy.
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.
Available products
Formulations
- Injection: 0.4 mg/mL in 5 mL and 50 mL vials
Veterinary
- Immunoregulin® (Neogen): 0.4 mg/mL in 5 mL and 50 mL vials (Labeled for dogs)
- Eqstim® (Neogen): 0.4 mg/mL in 5 mL and 50 mL vials (Labeled for horses)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store refrigerated; do not freeze. Shake well before using.
Client information
What is this medication?
Your pet is receiving an injection of a biologic response modifier (often called an immunostimulant). It contains killed bacteria that act as a "wake-up call" to your pet's immune system, helping their body fight off chronic bacterial or viral infections.
What to Expect
- Flu-like symptoms: Because the immune system is being activated, it is common for pets to experience mild, temporary side effects within hours of the injection. These may include tiredness (lethargy), a mild fever, chills, or a temporary loss of appetite.
- Treatment timeline: This medication is usually given as a series of injections over several weeks or months, often alongside traditional antibiotics or antiviral medications.
When to Contact Your Veterinarian
Emergency Warning: Rarely, pets can have a severe allergic reaction (anaphylaxis) to the injection. Seek immediate veterinary care if your pet develops facial swelling, hives, severe vomiting/diarrhea, difficulty breathing, or sudden collapse shortly after the injection.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.