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

What Are the Side Effects of Natalizumab?

Systemic Reactions

Headache (35%).

Fatigue (24%).

Arthralgia (joint pain) (15%).

Allergic reactions (7%).

Infections

Urinary tract infection (18%).

Lower respiratory tract infection (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., most commonly occurring within 2 hours after infusion.

Management: Discontinue the medication immediately, administer anti-allergic treatment, and prohibit subsequent use of the drug.

Progressive Multifocal Leukoencephalopathy (PML)

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

Monitoring: If new neurological symptoms appear (e.g., cognitive impairment, muscle weakness), emergency MRI and cerebrospinal fluid testing are required.

Immunogenic Reactions

Approximately 6% of patients develop persistent anti-drug antibodies, leading to reduced efficacy and an increased risk of infusion reactions.

Precautions for Taking Natalizumab

Contraindications and Special Populations

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

Pregnant women (Pregnancy Category C): Animal studies have shown fetal thrombocytopenia; human data are limited, so the risks and benefits must be weighed.

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

Key Medication Management Points

Dosage regimen: 300mg administered via intravenous infusion once every 4 weeks, with an infusion time of ≥ 1 hour.

Monitoring requirements: Observe the patient for 1 hour after infusion to watch for allergic reactions.

Regular testing: Conduct periodic testing for JC virus antibodies and neurological function assessments.

Drug Interactions

Avoid concurrent use: Other immunosuppressants (e.g., azathioprine) may increase the risk of PML.

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

Storage and Preparation

The stock solution must be refrigerated (2–8°C).

The diluted solution should be used within 8 hours.

Freezing or shaking is prohibited.