1. Clinical Overview
Human Normal Immunoglobulin (16.5% w/v) is a sterile, highly purified, concentrated solution of immunoglobulin G (IgG) antibodies derived from pooled human plasma of thousands of donors. It contains a broad spectrum of IgG antibodies reflective of the donor population's immunity, providing passive immunity against a wide range of pathogens. The 16.5% concentration (165 mg/mL) is a high-strength formulation designed for subcutaneous administration (SCIg), offering a convenient option for home-based therapy, particularly for chronic conditions like Primary Immunodeficiency Diseases (PIDD).
| Onset | Duration | Bioavailability |
|---|---|---|
| Rapid, with antibody levels rising immediately post-infusion. Clinical effects (e.g., reduced infection frequency) are observed over weeks to months of regular therapy. | Approximately 3 to 4 weeks, correlating with the average biological half-life of IgG. Regular infusions are required to maintain therapeutic serum levels. | For subcutaneous administration (SCIg), bioavailability is nearly 100% relative to intravenous administration (IVIg) when the same weekly dose is given, as it bypasses first-pass metabolism and is absorbed directly into the lymphatic system. |
2. Mechanism of Action
Provides passive immunity by supplementing functional IgG antibodies. Mechanisms include: 1) **Neutralization** of pathogens (bacteria, viruses, toxins) by direct binding, preventing cellular attachment and invasion. 2) **Opsonization** of microbes, enhancing phagocytosis by neutrophils and macrophages via Fc receptor binding. 3) **Modulation of Immune Response** through Fc receptor blockade on dendritic cells and macrophages, suppression of inflammatory cytokines, and provision of anti-idiotypic antibodies that regulate autoreactive B-cells.
3. Indications & Uses
- Replacement therapy in Primary Immunodeficiency Diseases (PIDD) e.g., X-linked agammaglobulinemia, Common Variable Immunodeficiency (CVID), Severe Combined Immunodeficiency (SCID)
- Maintenance therapy in Multifocal Motor Neuropathy (MMN) to improve muscle strength and disability
4. Dosage & Administration
Adult Dosage: **PIDD:** Initial dose typically 0.4-0.6 g/kg body weight IVIg monthly, converted to SCIg. **SCIg (16.5%):** Weekly dose is the previous monthly IV dose divided by the number of weeks (usually 4). Example: If monthly IV dose is 30g, weekly SCIg dose is ~7.5g. Infusion rate: Start at 10-20 mL/hr per site, can be increased gradually. **MMN/CIDP:** 0.4-0.6 g/kg IVIg monthly, with SCIg used for maintenance.
Administration: For **SUBCUTANEOUS USE ONLY.** Administer using an infusion pump. Multiple infusion sites (typically 2-4, e.g., abdomen, thighs) can be used simultaneously to accommodate larger volumes. Pre-treatment with analgesics/antipyretics/antihistamines may be considered. Do not mix with other medications. Patient must be trained for self-administration at home.
5. Side Effects
Common side effects may include:
- Local reactions at infusion site: pain, erythema, swelling, itching, induration (occur in >5% of patients)
- Mild systemic reactions: headache, fatigue, fever, chills, nausea, myalgia, arthralgia
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Live Attenuated Vaccines (e.g., MMR, Varicella, Yellow Fever) | Immunoglobulin may interfere with the immune response to live vaccines. Vaccination should be deferred for at least 3 months (up to 12 months for measles) after last Ig dose. | Major |
| Other Immunosuppressants (e.g., high-dose corticosteroids, cyclophosphamide) | May have additive immunosuppressive effect, increasing infection risk. Conversely, may enhance immunomodulatory effects in autoimmune conditions. | Moderate |
| Loop Diuretics (e.g., Furosemide) | Concurrent use in patients with renal impairment may increase risk of renal dysfunction. | Moderate |
| ACE Inhibitors | May increase risk of anaphylactoid reactions in patients receiving Ig, especially those with IgA deficiency. | Moderate |
7. Patient Counselling
- DO keep all scheduled infusion appointments to maintain protective antibody levels.
- DO learn proper aseptic technique for self-administration if on home therapy.
- DO rotate infusion sites to prevent tissue damage.
- DO report any signs of infection (fever, cough) to your doctor.
- DONT administer live vaccines without consulting your doctor.
- DONT skip pre-infusion hydration if advised.
8. Toxicology & Storage
Overdose: Symptoms of overdose are an extension of adverse effects: severe headache, aseptic meningitis, hyperviscosity syndrome (leading to thromboembolism), volume overload (hypertension, heart failure), acute renal failure.
Storage: Store at +2°C to +8°C (in a refrigerator). Do not freeze. Protect from light. Keep in outer carton. The product may be removed from refrigeration and stored at room temperature (not above 25°C) for a single period of up to 3 months. Do not return to refrigeration after this. Do not use after the expiry date. Do not shake vigorously.