human varicella-zoster immunoglobulin: clinical use

Prescribing considerations

• Confirm significant exposure and assess susceptibility; detectable VZV antibodies generally make this product unnecessary.
• Use current UK post-exposure pathways because intramuscular VZIG has been withdrawn.
• Ensure adequate hydration and assess thrombotic risk factors.
• Never administer intravascularly. Consider the limited evidence for subcutaneous use when intramuscular injection is contraindicated.
• Record the product name and batch number for traceability.

Contraindications and cautions

• Hypersensitivity to the active substance or an excipient.
• Hypersensitivity to human immunoglobulins, particularly in patients with anti-IgA antibodies.
• Exercise particular caution with IgA deficiency, previous atypical blood-product reactions, bleeding disorders or increased thromboembolic risk.

Monitoring

• Watch for hypersensitivity, hypotension or shock during and after administration.
• Advise immediate assessment for symptoms of arterial or venous thrombosis.
• Interpret subsequent serology and direct antiglobulin tests in light of passively transferred antibodies.
• Continue surveillance for varicella because prophylaxis may not prevent every infection.

Clinical pharmacology

A plasma-derived preparation containing predominantly IgG and a high concentration of antibodies against varicella-zoster virus. After intramuscular administration, systemic availability is delayed and the antibodies persist for several weeks before breakdown by the reticuloendothelial system.

Formulation and product differences

• The product is a sterile, single-use solution for intramuscular injection derived from human donor plasma.
• It contains a small amount of IgA and includes sodium chloride, glycine and sodium acetate among its excipients.
• Potency varies between batches and is printed on the vial label.
• It must not be mixed with other medicines or frozen.