Considering thymalfasin therapy
Safety desk
The short answer: reported reactions, missing information about the medicine and your own health history all matter. Words on a seller’s bottle or website cannot tell you whether that medicine is safe for you.
Soreness, redness and irritation where the shot was given were the most common reactions described in the studies reviewed in 2024 by the Food and Drug Administration (FDA), the agency for US drugs.
Those studies used material made to standards for medicines, with health professionals supervising its use. Their results cannot show that an unapproved product from another source is safe.
Quality concern
In its 2024 review, the FDA said it lacked key information about unwanted substances, clumps of peptide and germs in the raw ingredient.
Clumps or unwanted substances may cause the body’s defences, called the immune system, to treat the injected substance as an invader. That reaction is called immunogenicity.
Read the FDA quality assessmentThe FDA’s 2024 review described rises in readings from blood tests used to check the liver in people with hepatitis B, a liver infection. It also described abnormal readings from a thyroid blood test, a test of part of the body’s hormone system, in people with hepatitis C, another liver infection. These were changes in test results.
Other reports concerned people receiving a stem-cell transplant, a treatment that gives them cells to rebuild the system that makes blood cells. Reports included a blood disorder in which the body destroyed its own red blood cells and a patient died. They also included failure of the transplanted cells to start making new blood cells.
These reports do not prove the peptide caused the problems. They also cannot tell us how often these problems happen.
In 2024, the FDA described the Italian medicine instructions for thymalfasin (Zadaxin). Those instructions said it must not be used in children, during pregnancy or while breastfeeding. They also called for caution with allergies, autoimmune disease and other medicines that act on the body’s defences.
Autoimmune disease means the body’s defences attack its own tissues. These are warnings from Italy, reported by the FDA. They are not a set of US instructions for your care.
Tongue swelling or difficulty breathing are examples of severe symptoms that need emergency care. A severe allergic reaction can put someone’s life at risk.
MedlinePlus provides health information through the US National Library of Medicine and explains this emergency warning.
Patients and consumers can use the FDA reporting service, MedWatch, to report problems with medicines.