The most common side effect of Remicade (infliximab) is upper respiratory tract infection, affecting about 32% of patients in clinical trials. Other frequent side effects include nausea (21%), headache (18%), and sinus infections (14%). Most of these are mild and manageable, but Remicade also carries serious risks that are important to understand before and during treatment.
The Most Frequent Side Effects
In clinical trials involving over 1,100 patients with rheumatoid arthritis who received at least four infusions, the following side effects occurred in 5% or more of patients:
- Upper respiratory tract infection: 32%
- Nausea: 21%
- Headache: 18%
- Sinusitis: 14%
- Diarrhea: 12%
- Abdominal pain: 12%
- Sore throat: 12%
- Coughing: 12%
- Bronchitis: 10%
- Rash: 10%
Many of these overlap with what you’d experience during a typical cold or stomach bug, which can make it hard to tell whether Remicade is the cause. The pattern to watch for is whether these symptoms recur after each infusion or become persistent between treatments. Digestive symptoms like nausea, diarrhea, and stomach pain tend to be most noticeable in the first day or two after an infusion and often ease as your body adjusts over several treatment cycles.
Infusion Reactions
Because Remicade is given intravenously over a period of about two hours, reactions can happen during or shortly after the infusion itself. The most common infusion reactions are itching (about 20% of patients), flushing (10%), and shortness of breath (6%). These are typically mild and resolve on their own or with a brief pause in the infusion.
More severe reactions, including chest tightness, significant drops in blood pressure, or difficulty breathing, are less common but require immediate attention from the infusion team. Many clinics give antihistamines or acetaminophen before infusions to try to prevent reactions, though real-world registry data has not shown clear benefit from this approach. One large community study actually found that antihistamine premedication was associated with a higher incidence of infusion reactions, though the reasons for that link aren’t fully understood.
Delayed Reactions
Some reactions don’t show up until days later. Delayed hypersensitivity reactions can occur anywhere from 1 to 14 days after an infusion. Symptoms typically include muscle aches, joint pain, headache, fever, rash, and fatigue. These can be easy to mistake for a flu or a flare of the condition being treated. If you notice a consistent pattern of these symptoms appearing several days after each infusion, that’s worth reporting to your doctor.
Increased Risk of Infections
Remicade works by blocking a protein called TNF-alpha, which plays a central role in your immune system’s ability to fight infections. That’s the same mechanism that makes it effective against inflammatory diseases, but it also means your body is less equipped to fend off bacteria, viruses, and fungi while you’re on treatment.
The infections that concern doctors most are tuberculosis, invasive fungal infections (including histoplasmosis and other types that can spread throughout the body), and opportunistic bacterial infections. TB is a particular focus because Remicade can reactivate latent tuberculosis, a dormant infection that many people carry without knowing it. Most cases of TB reactivation in clinical data occurred within the first two months of starting treatment. For this reason, you’ll be tested for latent TB before your first infusion, and your doctor may repeat testing periodically.
Everyday infections like colds, sinus infections, and bronchitis are also more common, as reflected in the clinical trial numbers above. If you develop a fever, persistent cough, or symptoms of infection that don’t improve, your doctor may pause Remicade treatment until the infection clears.
Side Effects in Children
Children on Remicade experience many of the same side effects as adults, but certain problems show up more often. In a clinical trial of 103 pediatric Crohn’s disease patients, the following occurred at higher rates than in adults: anemia (11%), blood in stool (10%), low white blood cell counts (9%), flushing (9%), viral infections (8%), low neutrophil counts (7%), bone fractures (7%), and bacterial infections (6%).
The higher rates of low blood cell counts in children are worth noting because these can increase vulnerability to infections or slow healing. Pediatric patients also face a specific cancer risk discussed below.
Serious Warnings: Cancer and Liver Problems
Remicade carries FDA boxed warnings for both serious infections and malignancy. Lymphoma and other cancers, some fatal, have been reported in children and young adults treated with TNF blockers. A rare and aggressive form called hepatosplenic T-cell lymphoma has been reported in post-marketing surveillance, almost exclusively in adolescent and young adult males with Crohn’s disease or ulcerative colitis who were also taking other immune-suppressing drugs like azathioprine or 6-mercaptopurine.
Liver damage is another serious concern. While routine liver function testing isn’t mandated at specific intervals, your doctor will be watching for signs of liver problems. If you develop yellowing of the skin or eyes, dark urine, or unusual fatigue, these could signal liver injury that requires stopping the medication. Patients who carry hepatitis B need particularly close monitoring, as Remicade can cause the virus to reactivate.
Autoimmune Reactions
Paradoxically, a drug used to treat autoimmune conditions can sometimes trigger new autoimmune responses. Remicade can cause the body to produce certain antibodies that mimic lupus. In clinical safety data, roughly 64% of rheumatoid arthritis patients and 49% of Crohn’s disease patients developed new antinuclear antibodies during treatment, and 13% to 22% developed antibodies against their own DNA.
The antibodies alone usually don’t cause symptoms. Actual drug-induced lupus, with symptoms like rash, fever, joint pain, and in rare cases kidney involvement, is uncommon. When it does occur, it typically resolves after stopping the medication. Among all reported cases of lupus-like syndrome caused by TNF blockers, infliximab accounted for the majority of cases compared to similar drugs in the same class.