What to Avoid After a Rituximab Infusion

Rituximab depletes a specific type of immune cell called B cells, and that depletion lasts for months after each infusion. The practical result is a window of increased vulnerability to infections, certain vaccines, viral reactivation, and complications from other medical procedures. What you need to avoid, and for how long, depends on the specific risk, but the common thread is straightforward: your immune system is operating with fewer resources than usual, and anything that challenges it or interferes with its recovery needs careful timing or outright avoidance.

Why Infections Become a Bigger Concern

Rituximab targets a protein found on the surface of B cells, wiping out most of them from your bloodstream. B cells are central to how your body produces antibodies, so once they are depleted, your ability to fight off new infections drops. B-cell levels typically stay low for several months after an infusion and can take six months or longer to recover. During that time, ordinary infections that your body would normally handle without much trouble can become more serious.

Research on long-term rituximab safety has found that infection rates vary across different patient populations, but certain patterns hold. People who have had a serious infection during a previous course of rituximab face higher risk with subsequent treatments. Smoking history and having switched from another therapy also raise the risk.¹ The practical upshot is that in the weeks and months after your infusion, you should take infection-avoidance seriously: stay away from people who are actively sick, be attentive to hand hygiene, and talk to your doctor about prophylactic antibiotics if your treatment involves other immunosuppressants at the same time.

Combining rituximab with corticosteroids deserves special attention. Steroids suppress the immune system through a different pathway, and together with rituximab, they can compound your vulnerability. Early data on COVID-19 suggested that rituximab, especially when paired with steroids, was associated with more severe disease and higher mortality.¹ If you are on both medications, talk with your doctor about whether your steroid dose can be reduced or about additional precautions like masking during respiratory virus season.

Live Vaccines and Immunization Timing

Live vaccines contain weakened but still active forms of a virus or bacterium. In someone with a healthy immune system, these weakened organisms trigger immunity without causing disease. But when your B cells are depleted, a live vaccine can potentially cause the very infection it was designed to prevent. That means vaccines like the live shingles vaccine, the MMR (measles, mumps, rubella) vaccine, the live nasal-spray flu vaccine, and yellow fever vaccine should all be avoided after rituximab. Non-live vaccines, like the flu shot or the COVID-19 mRNA vaccines, are safe to receive, but they work less well because your body cannot mount a full antibody response without B cells.

Most guidelines recommend completing any necessary live vaccinations at least four weeks before starting rituximab. If you have already had your infusion and need a vaccine, the general approach is to wait until B cells have recovered, which your doctor can check with a blood test. For non-live vaccines, the timing trade-off is different: you can get them at any point, but the response will be blunted if given while B cells are still depleted. Some clinicians recommend waiting at least five to six months after the last infusion before vaccinating, so the immune system has a better chance of producing a protective response.

Hepatitis B Reactivation

One of the more serious and underappreciated risks after rituximab is the reactivation of hepatitis B virus in people who were previously infected, even those who appeared to have cleared the virus long ago. The virus can linger in liver cells in a dormant state, kept in check by the immune system. When rituximab wipes out B cells, the immune surveillance weakens, and the virus can flare back up. These reactivation events can cause liver failure and, in rare cases, death.²

A large population-based cohort study spanning 17 years found that about 1% of rituximab treatment events resulted in hepatitis B reactivation.³ That number may sound small, but the consequences can be severe, and it is entirely preventable. The standard recommendation is that everyone should be screened for hepatitis B before starting rituximab. If you test positive for current or past infection, antiviral prophylaxis, typically a daily pill, can prevent reactivation. Despite clear guidelines, the same study identified gaps in screening practices, meaning some patients fall through the cracks. If you are about to start rituximab and have not been tested for hepatitis B, bring it up with your doctor.

Real-world safety analyses have flagged hepatitis B reactivation as a priority concern with rituximab, alongside other serious infections, reinforcing the need for clinicians to monitor for it actively.⁴

Neurological Symptoms That Warrant Immediate Attention

Progressive multifocal leukoencephalopathy, usually called PML, is a rare but very serious brain infection caused by a common virus that most people carry without problems. In immunocompromised patients, including those on rituximab, the virus can reactivate and attack the brain’s white matter. PML is often fatal and has no reliable treatment, so the best defense is early detection.

Rituximab leads to prolonged B-cell depletion, and the resulting immune gap can create conditions where the virus replicates unchecked.⁵ If you notice any new or unexplained neurological symptoms after a rituximab infusion, such as weakness on one side of the body, vision changes, confusion, difficulty speaking, or personality changes, report them to your doctor right away. Guidelines advise that any further rituximab dosing should be suspended until PML has been ruled out, and if PML is confirmed, rituximab must be permanently discontinued.⁶

PML remains rare in rituximab-treated patients, and this heading is not meant to alarm you. The point is that any new neurological change in this context is not something to shrug off or wait out. Quick evaluation, typically involving brain imaging and sometimes a spinal fluid test, is the appropriate response.

Planning Surgeries and Dental Procedures

If you need surgery, whether elective or semi-urgent, the timing relative to your rituximab infusion matters. Your depleted B cells leave you more susceptible to surgical-site infections and other postoperative complications. A study of 133 patients with rheumatoid arthritis who underwent surgery after rituximab treatment found that about 7% experienced complications, including surgical-site infections in roughly 6% of cases. Orthopedic surgeries accounted for the majority, and spine surgery was associated with a higher complication rate.⁷

There is no universally agreed-upon waiting period, but many clinicians prefer to schedule elective procedures when B cells have started to recover, or at least to time surgery so it does not fall in the first few weeks after an infusion, when immune suppression is at its deepest. Dental work involving extractions or gum surgery carries a similar concern: any procedure that breaks through mucosal barriers creates an entry point for bacteria, and your ability to contain that is reduced. A simple cleaning is generally fine, but anything more invasive should be discussed with both your dentist and your prescribing physician so they can coordinate timing and potentially prescribe prophylactic antibiotics.

Pregnancy, Contraception, and Breastfeeding

If you are of childbearing age, pregnancy should be avoided for at least 12 months after your last rituximab infusion. A review of pregnancy outcomes after maternal rituximab exposure found that while few congenital malformations or neonatal infections occurred, the recommendation to avoid pregnancy during that window remains standard practice.⁸ Rituximab can cross the placenta and deplete fetal B cells, which is the primary concern. If you discover you are pregnant while on rituximab, do not panic, but contact your doctor promptly to discuss monitoring and next steps.

Breastfeeding is a separate question, and the evidence here is more reassuring than many people expect. Studies have measured the amount of rituximab that passes into breast milk and found it to be very low. One study found that the relative infant dose was less than 0.4%, well below the threshold generally considered acceptable.⁹ Another study in women with multiple sclerosis found a median relative infant dose of just 0.07%, and all infant blood levels of rituximab were undetectable. The infants’ own B-cell counts stayed within normal ranges.¹⁰ Rituximab also has low oral bioavailability, meaning even the small amount in breast milk would be largely broken down in the infant’s gut. For women with serious autoimmune conditions, continuing rituximab while breastfeeding may be a reasonable option after discussing the risks and benefits with their neurologist or rheumatologist.

Delayed Reactions to Watch For

Most infusion-related reactions happen during or shortly after the rituximab drip itself: flushing, chills, throat tightness, or drops in blood pressure. These are managed in the infusion center with pre-medications and by slowing the rate. But there is a less well-known delayed reaction called serum sickness that can appear days or even a couple of weeks later, after you have gone home and may not connect new symptoms to the infusion.

Serum sickness presents as a combination of fever, rash, and joint or muscle pain.¹¹ A retrospective analysis of 39 reported cases found that more than half developed symptoms within the first week, while nearly half appeared between days 8 and 14.¹² Some patients also develop swollen lymph nodes.¹³ Serum sickness is rare overall, but it is treatable with corticosteroids and antihistamines once recognized. The risk is not avoiding the reaction itself, which is not preventable, but failing to recognize it and delaying treatment because it appears well after the infusion day. If you develop unexplained fever, a new rash, or aching joints in the two weeks following your infusion, contact your care team rather than assuming it is unrelated.

Pneumocystis Prevention

Pneumocystis jirovecii is a fungal organism that causes a type of pneumonia in people with weakened immune systems. This infection was once mainly associated with HIV, but it is now recognized as a risk in patients on B-cell-depleting therapies like rituximab, particularly when combined with other immunosuppressants. Prevention is straightforward: a low-dose prophylactic antibiotic, most commonly trimethoprim-sulfamethoxazole, taken regularly.

Whether every rituximab patient needs this prophylaxis or only certain higher-risk groups is still debated. A study of patients with a type of blood-vessel inflammation treated with rituximab found that about 44% received prophylaxis while the rest did not, and no cases of Pneumocystis pneumonia occurred in either group.¹⁴ That reassuring finding suggests prophylaxis works when used, and that the baseline risk in some populations may be lower than feared. Separately, research in patients receiving intensive combination chemotherapy with rituximab found that adequate prophylaxis kept Pneumocystis pneumonia rates no higher than expected.¹⁵ Ask your prescribing physician whether prophylaxis makes sense for your specific situation, especially if you are on concurrent immunosuppressive medications.

Exercise and Physical Activity After Infusion

Many patients wonder whether they should rest or stay active after their infusion. There are no blanket restrictions on physical activity, but how you feel matters. The infusion itself, along with the pre-medications (which often include antihistamines and sometimes acetaminophen or steroids), can leave you fatigued, lightheaded, or achy for a day or two. Listening to your body and taking things easy on infusion day and the day after is reasonable. Once those immediate effects pass, returning to your usual routine, including exercise, is generally fine.

Interestingly, a pilot study in patients with chronic lymphocytic leukemia tested whether a single session of vigorous cycling affected rituximab’s ability to destroy cancer cells in laboratory conditions. The exercise session increased the number of natural killer cells in the bloodstream and boosted rituximab-driven cell killing by roughly 130%.¹⁶ This was an early-stage, lab-based finding and not something to change treatment plans over, but it does push back against the instinct to simply rest and avoid exertion. The immune system is not a battery that drains faster when you move. For most patients, maintaining regular moderate exercise during rituximab treatment may support overall health without adding meaningful risk. The exception would be exercising in crowded indoor spaces like gyms during respiratory virus season, where the infection exposure, rather than the exercise itself, is the concern.

Herbal Supplements and Medication Interactions

Rituximab itself is a large protein molecule cleared by the body through pathways different from most conventional drugs, so it has fewer direct drug-drug interactions than many medications. That said, people on rituximab are often taking other drugs at the same time, including chemotherapy agents, disease-modifying antirheumatic drugs, or corticosteroids. Herbal supplements can interfere with those companion medications in ways that matter. St. John’s wort, for example, is a well-known enzyme inducer that accelerates the breakdown of many drugs, including certain chemotherapy agents. One study found that St. John’s wort reduced the blood levels of the chemotherapy drug docetaxel by about 12% in cancer patients.¹⁷ If you are receiving rituximab as part of a combination chemotherapy regimen, even a modest reduction in the effectiveness of a partner drug could affect treatment outcomes.

Beyond St. John’s wort, supplements like echinacea and high-dose green tea extract have theoretical immune-modulating effects that could be unpredictable in someone whose B cells are depleted. The honest answer is that these interactions are poorly studied in the rituximab population specifically, and “poorly studied” is not the same as “safe.” The safest approach is to bring a full list of everything you take, including vitamins, herbal teas, and over-the-counter products, to your oncologist or rheumatologist before each treatment cycle. They can flag anything that might interfere with your treatment or add unnecessary immune stress during the recovery window.