Dimethyl Fumarate (Tecfidera) is an oral medication used to treat relapsing forms of multiple sclerosis (MS), including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease.
What Are the Side Effects of Dimethyl Fumarate (Tecfidera)?
Skin Reactions
Approximately 40% of patients experience flushing (symptoms including fever, redness, itching, and/or a burning sensation). This typically occurs in the early stage of treatment and improves or resolves over time.
Gastrointestinal Reactions
Abdominal pain (18%).
Diarrhea (14%).
Nausea (12%).
Laboratory Abnormalities
Lymphopenia (2%).
Elevated liver enzymes (ALT elevation in 4%, AST elevation in 4%).
Positive urine protein (6%).
Serious Side Effects of Dimethyl Fumarate (Tecfidera) to Be Alert For
Allergic Reactions and Angioedema
Dimethyl Fumarate may cause allergic reactions and angioedema, with symptoms including difficulty breathing, hives, and swelling of the throat and tongue.
These reactions may occur after the first dose or at any time during treatment.
If such symptoms appear, discontinue the medication immediately and seek emergency medical assistance.
Progressive Multifocal Leukoencephalopathy (PML)
PML is a rare but serious opportunistic brain infection caused by the JC virus, which usually leads to death or severe disability.
PML cases mainly occur in patients with a lymphocyte count of <0.8×10⁹/L that persists for more than 6 months.
If any suspicious symptoms of PML appear, discontinue the medication immediately and conduct a diagnostic evaluation.
Risk of Severe Infections
Herpes zoster: Including disseminated herpes zoster, herpes zoster ophthalmicus, herpes zoster meningoencephalitis, etc.
Other opportunistic infections: Viral infections such as herpes simplex virus, West Nile virus, and cytomegalovirus; fungal infections such as Candida and Aspergillus; bacterial infections such as Nocardia, Listeria monocytogenes, and Mycobacterium tuberculosis.
Severe infections may occur in patients with normal or decreased lymphocyte counts. When infection symptoms appear, consider suspending treatment until the infection resolves.
Lymphopenia
Dimethyl Fumarate may cause a decrease in lymphocyte count, with approximately 6% of patients experiencing a lymphocyte count of <0.5×10⁹/L.
2% of patients experience persistent severe lymphopenia (lymphocyte count of <0.5×10⁹/L lasting for at least 6 months).
Lymphocyte counts should be monitored before treatment, 6 months after the start of treatment, and every 6–12 months thereafter.
Precautions for Dimethyl Fumarate (Tecfidera) Administration
Administration in Special Populations
Pregnancy: Animal studies have shown adverse effects on offspring survival, growth, sexual maturation, and neurobehavioral function. The use during pregnancy requires weighing the pros and cons.
Lactation: There is no data on whether the drug is excreted into human milk. A cautious decision should be made on whether to discontinue the medication or stop breastfeeding.
Children: The efficacy in pediatric patients has not been established.
Elderly: Clinical studies did not include a sufficient number of patients aged 65 years and above.
Monitoring Requirements
Before treatment: Complete blood count (including lymphocyte count), liver function tests (ALT, AST, ALP, and total bilirubin).
During treatment: Monitor lymphocyte count every 6 months.
Monitor liver function as clinically needed.
Monitor for signs and symptoms of infection.
Drug Interactions
Strong/moderate CYP1A2 inhibitors may increase the blood concentration of Tecfidera.
Moderate CYP1A2 inducers and smoking may reduce the efficacy of Tecfidera.
Concomitant use with non-enteric-coated aspirin can alleviate flushing symptoms.
