1. Clinical Overview
Pegylated Interferon Alpha 2B (120mcg) is a long-acting, covalent conjugate of recombinant human interferon alpha-2b with a single, linear 12 kDa polyethylene glycol (PEG) chain. This pegylation significantly prolongs its half-life, reduces immunogenicity, and allows for once-weekly subcutaneous administration. It is a potent immunomodulator and antiviral agent, primarily used in the treatment of chronic hepatitis B and C infections in the Indian context. It exerts its effects by binding to specific cell surface receptors, activating the JAK-STAT signaling pathway, leading to the transcription of interferon-stimulated genes (ISGs) that inhibit viral replication and modulate immune responses.
| Onset | Duration | Bioavailability |
|---|---|---|
| Antiviral and immunomodulatory effects begin within hours of administration, but measurable clinical and virological responses (e.g., reduction in viral load) are typically observed within 4 to 12 weeks of initiating therapy. | The pharmacological effect persists for approximately 7 days, permitting once-weekly dosing. The immunomodulatory effects may last beyond the dosing interval. | Approximately 80-90% following subcutaneous injection. |
2. Mechanism of Action
Peginterferon alfa-2b binds to specific, high-affinity cell surface receptors (IFNAR1 and IFNAR2) present on most human cells. This binding activates the intracellular JAK-STAT (Janus kinase-signal transducer and activator of transcription) signaling pathway. Activation leads to the transcription and translation of over 300 interferon-stimulated genes (ISGs). The resulting proteins create an antiviral state within cells by inhibiting various stages of viral replication (entry, uncoating, synthesis of mRNA, protein synthesis, assembly, and release). It also exerts potent immunomodulatory effects by enhancing the activity of natural killer (NK) cells, cytotoxic T lymphocytes, and macrophage phagocytosis, and by modulating the expression of major histocompatibility complex (MHC) antigens.
3. Indications & Uses
- Chronic Hepatitis C (HCV) infection in adults
- Chronic Hepatitis B (HBV) infection in adults with compensated liver disease and evidence of viral replication
4. Dosage & Administration
Adult Dosage: Chronic Hepatitis C: 1.5 mcg/kg body weight subcutaneously once weekly. Often used in combination with ribavirin. Duration: 24 weeks for genotypes 2 & 3, 48 weeks for genotypes 1 & 4. Chronic Hepatitis B: 180 mcg fixed dose (or 1.5 mcg/kg) subcutaneously once weekly for 48 weeks.
Administration: For subcutaneous injection only. Administer in the abdomen or thigh. Rotate injection sites. Allow the pre-filled pen/syringe to reach room temperature (approx. 30 minutes) before injection to reduce discomfort. Do not shake. Inspect for particulate matter or discoloration before use.
5. Side Effects
Common side effects may include:
- Flu-like symptoms (fever, chills, headache, myalgia, arthralgia - often managed with pre-dose paracetamol)
- Fatigue, asthenia
- Injection site reactions (erythema, pain, swelling)
- Alopecia (reversible)
- Anorexia, nausea
- Insomnia
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Ribavirin | Additive hemolytic anemia; synergistic antiviral effect against HCV. | Major |
| Telbivudine | Increased risk of severe peripheral neuropathy. | Major |
| Theophylline | Peginterferon reduces theophylline clearance, increasing theophylline levels and risk of toxicity. | Moderate |
| Methadone | May increase methadone AUC, potentially requiring dose adjustment. | Moderate |
| Zidovudine (AZT) | Additive myelosuppression (neutropenia, anemia). | Major |
| NRTIs (e.g., Stavudine, Didanosine) | Increased risk of lactic acidosis and hepatic steatosis. | Major |
| Warfarin | May alter INR; increased monitoring required. | Moderate |
7. Patient Counselling
- DO administer the injection on the same day each week.
- DO rotate injection sites to prevent lipoatrophy.
- DO use proper subcutaneous injection technique as demonstrated by your healthcare provider.
- DO keep a symptom diary to track side effects.
- DO NOT skip doses without consulting your doctor.
- DO NOT share pens or syringes.
- DO NOT use if the solution is cloudy or discolored.
- DO NOT stop other prescribed medications (e.g., ribavirin) unless advised.
8. Toxicology & Storage
Overdose: Exacerbation of common side effects: severe fatigue, high fever, chills, profound myelosuppression (pancytopenia), severe nausea/vomiting, acute psychiatric symptoms (agitation, confusion), hepatic enzyme elevations, and cardiovascular collapse.
Storage: Store under refrigeration at 2°C to 8°C in the original carton to protect from light. Do not freeze. Do not shake. If needed, the pre-filled pen can be kept at room temperature (not above 30°C) for up to 24 hours prior to use. Discard any unused product after the single use. Keep out of reach of children.