Side Effects of Infliximab

Introduction

Infliximab is a biologic medication used to manage several chronic inflammatory and autoimmune conditions, including rheumatoid arthritis, Crohn’s disease, ulcerative colitis, ankylosing spondylitis, and psoriasis. It works by targeting a specific protein in the body known as tumor necrosis factor-alpha (TNF-α), which plays a key role in inflammation. By blocking TNF-α, infliximab helps reduce inflammation and alleviate symptoms such as pain, swelling, and tissue damage.

While infliximab has proven highly effective for many patients, its use is associated with a range of potential side effects, varying from mild to severe. Understanding these possible reactions enables patients and caregivers to recognize changes early and communicate effectively with healthcare providers. Because infliximab influences the immune system, careful monitoring is essential throughout treatment.

How Infliximab Works and Why Side Effects Occur

Infliximab belongs to a class of medications called monoclonal antibodies. These are laboratory-engineered proteins designed to target specific molecules in the body. Infliximab binds to TNF-α, neutralizing its activity and preventing it from triggering inflammation.

However, because TNF-α is also important in regulating the body’s immune defense, blocking it can alter immune function. This suppression is central to how infliximab treats inflammatory conditions, but it also explains many of its side effects. Reduced immune activity can make the body more susceptible to infections and affect how it responds to environmental or internal stressors.

In addition, as a biologic medication, infliximab is administered intravenously. This method introduces a large protein molecule directly into the bloodstream, which can sometimes provoke immune reactions or infusion-related responses. Understanding these mechanisms helps explain why side effects range from temporary fatigue to more serious infections or allergic reactions.

Common Side Effects of Infliximab

The most frequent side effects of infliximab tend to be mild to moderate and often appear within the first few days or weeks of treatment. Many patients tolerate the medication well, especially after their body adjusts to repeated infusions. However, it is important to be aware of potential reactions that may require medical attention.

Infusion-related reactions are among the most common. These typically occur during or within a few hours after an infusion session. Symptoms can include headache, dizziness, flushing, shortness of breath, itching, or mild chest discomfort. Such reactions are often caused by the body’s temporary immune response to the introduction of the medication. Healthcare professionals typically monitor patients closely during and after infusions and may slow the infusion rate or administer medications such as antihistamines or corticosteroids to manage these symptoms.

Fatigue and weakness are also commonly reported. These symptoms may arise as the immune system adjusts or due to the underlying inflammatory condition being treated.

Mild infections such as colds, sore throat, or sinus infections are another frequent side effect. Because infliximab suppresses immune function, the body may take slightly longer to recover from minor infections.

Abdominal pain, nausea, and diarrhea can occur in some individuals, particularly those using infliximab for gastrointestinal conditions. These side effects are generally mild and temporary but should be discussed with a healthcare provider if they persist.

Skin reactions, including rashes, itching, or redness, may also appear. Some individuals experience localized irritation near the infusion site or develop dry skin between treatments.

While these side effects are usually manageable, persistent or worsening symptoms should always be reported to a healthcare provider for evaluation.

Serious Side Effects and Risks

Although less common, infliximab can cause serious side effects that require immediate medical attention. These reactions are often linked to the medication’s immune-suppressing effects or the body’s immune response to the drug itself.

One of the most significant risks associated with infliximab is serious infection. Because TNF-α helps defend against bacteria, viruses, and fungi, its suppression can make individuals more vulnerable to infections such as pneumonia, bronchitis, or urinary tract infections. In rare cases, infliximab can reactivate latent infections—dormant infections that exist in the body without causing symptoms. The most notable example is tuberculosis (TB), which can become active again in patients previously exposed to the bacteria. For this reason, doctors routinely test for TB and hepatitis B before starting infliximab therapy.

Another possible but rare complication is severe allergic or hypersensitivity reactions. These can occur shortly after infusion or even days later. Symptoms may include swelling of the face or throat, difficulty breathing, rapid heartbeat, or hives. Severe allergic reactions require urgent medical care and may lead to discontinuation of the medication.

Autoimmune responses can occasionally develop during long-term use of infliximab. The immune system may begin producing antibodies against the medication, reducing its effectiveness and potentially triggering lupus-like symptoms such as joint pain, rash, or fatigue.

Liver effects have been reported in a small number of patients. These can include elevated liver enzyme levels or, rarely, more serious liver injury. Signs of liver issues include yellowing of the skin or eyes, dark urine, or persistent nausea. Regular monitoring through blood tests helps detect any early changes in liver function.

In rare cases, infliximab use has been associated with nervous system disorders, including demyelinating diseases such as multiple sclerosis-like symptoms or seizures. Although these events are uncommon, they underscore the importance of reporting any new neurological symptoms.

Some studies have also noted a potential connection between long-term TNF-α inhibitor use and a slightly increased risk of certain cancers, such as lymphoma or skin cancer. However, these risks appear to be very low and may relate more to the underlying immune dysfunction of the treated diseases than to the medication itself. Ongoing research continues to monitor this relationship.

Monitoring and Precautions During Treatment

Because infliximab can influence multiple systems in the body, consistent medical monitoring is an essential part of therapy. Before starting treatment, healthcare providers typically perform comprehensive evaluations, including screening for tuberculosis, hepatitis, and other chronic infections. Blood tests help assess liver and kidney function, and a review of current medications identifies potential interactions.

During treatment, regular follow-up appointments allow doctors to track progress, monitor for side effects, and adjust doses if necessary. Patients are encouraged to promptly report symptoms such as fever, persistent cough, unexplained weight loss, or skin changes.

Vaccination status is also important. Live vaccines are generally avoided during infliximab treatment because the suppressed immune system may not respond appropriately. Non-live vaccines, such as flu or pneumonia shots, may still be recommended to help reduce infection risk.

Pregnancy and breastfeeding considerations should be discussed with a healthcare professional. While infliximab has been used safely in many pregnancies, decisions about its use depend on balancing the benefits for the parent’s condition with potential risks to the developing baby.

Patients should also avoid starting or stopping infliximab without medical advice, as abrupt changes can worsen underlying disease symptoms or trigger immune reactions.

Managing Side Effects

Most side effects of infliximab can be managed with medical supervision and supportive care. For mild infusion reactions, healthcare teams may adjust infusion speed or pre-medicate with antihistamines or acetaminophen. Maintaining adequate hydration and rest after treatment helps minimize fatigue and discomfort.

If infections occur, early treatment with appropriate antibiotics or antivirals is essential. Patients should be aware of early signs of infection, such as fever, cough, or unusual tiredness, and seek prompt evaluation.

Lifestyle choices also play a role in managing side effects and maintaining overall health. A balanced diet, regular moderate exercise, and avoiding tobacco and excessive alcohol can help support immune function and liver health.

Ongoing communication between patients and healthcare providers ensures that potential side effects are identified early and addressed effectively. In some cases, if side effects become severe or unmanageable, doctors may switch to an alternative medication.

Conclusion

Infliximab is an important treatment option for managing autoimmune and inflammatory diseases, offering relief to individuals whose symptoms may not respond to conventional therapies. By targeting TNF-α, it reduces inflammation and helps improve quality of life for many patients.

However, as with all biologic medications, infliximab can cause side effects ranging from mild infusion reactions to more serious immune-related complications. The key to safe and effective use lies in vigilant monitoring, early recognition of symptoms, and regular communication with healthcare professionals.

With proper oversight, many individuals tolerate infliximab well and achieve significant improvements in their underlying condition. Awareness, adherence to medical guidance, and proactive management remain central to minimizing risks and ensuring positive treatment outcomes.

Disclaimer

This article is for informational purposes only and does not provide medical advice, diagnosis, or treatment. It summarizes general information about infliximab and its potential side effects. Individuals considering or currently receiving infliximab should consult a qualified healthcare professional for personalized guidance. Responses to treatment, side effects, and outcomes vary based on individual health conditions, dosage, and concurrent medications.