Interferon Omega
Interferon-omega is a recombinant **type I interferon** of feline origin. It acts as a potent immunomodulator and antiviral agent. * **Veterinary Use**: It is primarily utilized in veterinary medicine for the treatment of severe viral infections, notably **canine parvovirus** and feline retroviruses (**FeLV and FIV**). * **Cross-Species Efficacy**: **Clinical Pearl:** Although it is a feline-origin protein, it is highly effective in dogs because type I interferons share cross-species receptor affinity. However, prolonged use in dogs may lead to the formation of neutralizing antibodies. * **Emerging Uses**: It has shown potential benefits in treating canine atopic dermatitis, feline infectious peritonitis (FIP), feline calicivirus (FCV), and feline herpesvirus (FHV-1) dermatitis or keratitis. * **Availability**: It is commercially available in the EU and other regions but is not commercially available in the USA (requires legal importation for compassionate use).
Mechanism: Interferon-omega does not act as a direct virucidal agent. Instead, it induces an antiviral state in host cells: 1. **Receptor Binding**: Binds to specific type I interferon receptors on the surface of target cells. 2. **Signal Transduction**: Activates the **JAK-STAT signaling pathway**. 3. **Gene Transcription**: Induces the transcription of interferon-stimulated genes (ISGs). 4. **Antiviral Proteins**: Leads to the production of key enzymes such as **2'-5' oligoadenylate synthetase (OAS)** and **protein kinase R (PKR)**. 5. **Viral Inhibition**: These enzymes inhibit viral mRNA translation and degrade viral RNA → effectively halting viral replication. Additionally, it nonspecifically enhances host immune defense mechanisms by stimulating natural killer (NK) cells and macrophages.
Dosing by species
- Treatment of FeLV and/or FIV (non-terminal clinical stages) · 1 million Units/kg SC once daily · SC · q24h · 5 days (Three separate 5-day treatments performed at day 0, day 14, and day 60)
- FHV-1 facial dermatitis · Day 0: 1.5 million Units/kg (half peri-lesionally/intradermally, half SC). Day 2 and 9: 1.5 million Units/kg SC. Days 19, 21, and 23: 0.75 million Units/kg peri-lesionally/intradermally + 0.75 million Units/kg SC. · SC / Intradermal / Peri-lesional · Specific days · 23 days · Cat was sedated with propofol for peri-lesional and intradermal injections.
- Treatment of parvovirus (enteric form) · 2.5 million Units/kg IV once daily · IV · q24h · 3 days · The earlier the dog is treated, the more likely of success.
- Treatment of atopic dermatitis · Dogs 8-15 kg = 1 million Units; 15-29 kg = 2 million Units; 29-40 kg = 3 million Units; >40 kg = 4 million Units · SC · Specific days · Days 0, 3, 7, 14, 21, 35, 56, 90, 120, & 150 · Further larger-scale studies needed to confirm cost-effectiveness and safety for long-term treatment.
- Parvovirus · 2.5 million units/kg · IV · q24h · 3 days
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Concurrent vaccination in dogs (wait until fully recovered)
- Vaccination in cats during and after treatment (due to the immunosuppressive nature of FeLV/FIV)
- Substitution with human interferons (alpha, beta, or gamma)
- No specific contraindications available in the monograph
Adverse effects
- Hyperthermia (typically 3-6 hours post-dose)
- Vomiting
- Soft feces or mild diarrhea (cats)
- Transient fatigue or lethargy (cats)
- Slight decreases in RBCs, WBCs, and platelets (usually resolves within a week)
- Increased ALT (usually resolves within a week)
- Antibody formation in dogs (with prolonged or repeated treatment)
- Transient fatigue
- Hyperthermia
- Mild diarrhoea
- Decreased WBCs (leukopenia)
- Decreased platelets (thrombocytopenia)
- Decreased RBCs (anaemia)
- Increased liver enzyme activities
- Ocular irritation (with topical use in cats)
Drug interactions
- Hepatotoxic drugs · May increase the risk of liver toxicity; use with caution.
- Myelosuppressive drugs · May increase the risk of bone marrow suppression; use with caution.
- Vaccines · Should not be administered concurrently until the animal has clinically recovered. · major
- Antibiotics · Improves prognosis; no negative interactions observed. · null
- NSAIDs · Improves prognosis; no negative interactions observed. · null
Monitoring
- Clinical efficacy (resolution of viral infection signs)
- Complete Blood Count (CBC) to monitor for myelosuppression
- Hepatic function tests (ALT)
- Complete Blood Count (WBCs, RBCs, platelets)
- Liver enzyme activities
- Body temperature
- Clinical signs of gastrointestinal upset or fatigue
Overdose
In safety studies, 10X overdoses in dogs and cats caused mild lethargy/somnolence, slight hyperthermia, and slight increases in respiratory and heart rates. In all animals tested, clinical signs resolved within 7 days and no specific treatment was required.
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.