JAK inhibitors are a class of medications that influence the immune system’s activity. These drugs are prescribed to treat various autoimmune and inflammatory conditions. By modulating immune responses, JAK inhibitors aim to reduce inflammation and symptoms associated with these diseases.
Common Side Effects
Common side effects include respiratory infections (e.g., common cold, bronchitis, upper respiratory tract infections), often presenting with a runny nose, sore throat, or cough.
Nausea, headache, and diarrhea are common. Acne is another frequent skin side effect, especially in patients treated for eczema, often responding to standard dermatological treatments.
Elevated cholesterol may require monitoring. Blood tests can also indicate elevated liver enzymes, suggesting liver irritation. Discuss these common side effects with a healthcare provider.
Serious Side Effects
Less common, but serious, side effects include an increased risk of serious infections, such as pneumonia and shingles (herpes zoster).
Cardiovascular problems (heart attack, stroke) are another serious risk. A higher incidence of major adverse cardiovascular events has been observed in patients aged 50 or older with existing cardiovascular risk factors. Blood clots (DVT, PE) are also serious, rare, and can be life-threatening.
An increased risk of certain cancers (lung, lymphoma, non-melanoma skin cancer) has also been noted. The U.S. Food and Drug Administration (FDA) has issued warnings for specific JAK inhibitors (tofacitinib, baricitinib, and upadacitinib) regarding these risks. This underscores the need for careful patient selection and ongoing monitoring.
How JAK Inhibitors Cause Side Effects
JAK inhibitors block Janus kinase (JAK) enzymes within cells. These enzymes are part of the JAK-STAT signaling pathway, which transmits signals from outside the cell to the nucleus. This pathway is involved in immune and inflammatory responses.
JAK inhibitors disrupt inflammation-promoting signaling cascades, treating autoimmune conditions. However, because JAK enzymes are involved in many bodily functions, blocking them can inadvertently affect other systems. Suppressing the immune system, for instance, can diminish the body’s ability to fight infections, increasing the risk of common and serious infections.
Impact on other cellular pathways can influence metabolic processes, leading to elevated cholesterol. Effects on cell growth and differentiation, partly regulated by JAK pathways, might contribute to increased cancer risk or blood clot formation. The broad influence of JAK inhibition on cytokine signaling (cytokines are inflammatory proteins) explains the wide range of potential side effects.
Monitoring and Managing Side Effects
Regular medical check-ups and lab tests are important for patients on JAK inhibitors. Providers monitor blood counts, liver enzymes, and cholesterol through periodic blood tests to detect potential side effects early.
Patients should be vigilant for symptoms indicating a serious side effect. Report signs of infection (e.g., fever, persistent cough, unexplained weight loss) immediately. Symptoms like chest pain, shortness of breath, sudden limb swelling, or arm/leg weakness could signal a serious cardiovascular event or blood clot, requiring immediate medical attention.
Maintaining open communication with the healthcare team is important. Patients should discuss their medical history (including prior heart conditions, blood clots, or cancer) before starting JAK inhibitors. If side effects occur, providers may recommend symptomatic relief (e.g., for nausea or headaches), dose adjustments, or switching treatments.