Common side effects of sodium hyaluronate, the active ingredient in Euflexxa, include diarrhea, headache, loss of appetite and stomach pain, as listed by Drugs.com. Users may also experience large purple patches on the skin, knee swelling, nausea, vomiting or itching of the skin.
Common side effects normally go away on their own as the patient's body gets used to the medication, and the patient's doctor may have advice about how to prevent or minimize these side effects, according to Drugs.com. Patients should contact their doctor if these side effects persist or become bothersome. Less common but serious side effects include cough, difficulty swallowing, fever and stuffiness as well as flushing, redness or blueness of the face. Other serious side effects include dizziness, severe faintness, facial swelling, chest tightness and difficulty breathing as well as redness or swelling at the point of injection. If these side effects occur, patients should contact a doctor immediately as they may require immediate medical attention, notes Drugs.com.
Retreatment with sodium hyaluronate does not seem to correlate with increased frequency, severity or risk of side effects. Several cases of allergic reactions or hypersensitivity to the substance have been reported, but localized reactions around the injection site and affected joint are the most common.