Natalizumab is a monoclonal antibody drug used in the treatment of relapsing forms of multiple sclerosis (MS). It exerts its effect by inhibiting α4-integrin-mediated migration of immune cells. Despite its relatively good efficacy, potential side effects and specific risks must be watched out for during the medication period.

What are the side effects of Natalizumab?

Systemic reactions

Headache (35%).

Fatigue (24%).

Arthralgia (15%).

Allergic reactions (7%).

Infections

Urinary tract infections (18%).

Lower respiratory tract infections (15%).

Gastroenteritis (9%).

Vaginitis (8%, in female patients).

Others

Rash (9%).

Menstrual disorders (7%, in females).

Depression (17%).

Abnormal liver function (5%).

Severe side effects of Natalizumab that require vigilance

Allergic reactions (including anaphylactic shock)

Manifestations: Urticaria, hypotension, dyspnea, chest pain, etc., which mostly occur within 2 hours after infusion.

Management: Immediately discontinue the drug, administer anti-allergic treatment, and the drug must not be used again.

Progressive multifocal leukoencephalopathy (PML)

Risk factors: Long-term medication (> 2 years), previous immunosuppressive therapy, and positive JC virus antibody.

Monitoring: If new-onset neurological symptoms (such as cognitive impairment, muscle weakness) occur, emergency MRI and cerebrospinal fluid testing are required.

Immunogenic reactions

Approximately 6% of patients develop persistent anti-drug antibodies, which lead to decreased efficacy and increased risk of infusion reactions.

Precautions for Natalizumab use

Contraindications and special populations

Contraindications: Contraindicated in patients allergic to natalizumab or its components.

Pregnant women (Category C): Animal experiments have shown that fetal thrombocytopenia may occur; human data are limited, and the pros and cons must be weighed.

Lactating women: Whether the drug is excreted in breast milk is unknown; it is recommended to discontinue the drug or stop breastfeeding.

Key points for medication management

Dosing regimen: 300mg administered by intravenous infusion once every 4 weeks, with the infusion time being ≥ 1 hour.

Monitoring requirements: Observe for 1 hour after infusion to be alert for allergic reactions.

Regular testing: Conduct regular testing of JC virus antibodies and neurological function.

Drug interactions

Avoid combined use: Other immunosuppressants (such as azathioprine) may increase the risk of PML.

Interferon beta-1a: May reduce the clearance rate of natalizumab, but no dose adjustment is needed.

Storage and preparation

The stock solution should be refrigerated (2-8℃), and the diluted solution should be used within 8 hours. Freezing or shaking is prohibited.