Zanamivir Side Effects
Some side effects of zanamivir may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
For the Consumer
Applies to zanamivir: inhalation powder
Get emergency medical help if you have any of these signs of an allergic reaction while taking zanamivir: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Some people using zanamivir have had rare side effects of confusion, delirium and self-injury. These symptoms have occurred most often in children. It is not known whether zanamivir was the exact cause of these symptoms. However, anyone using zanamivir should be watched closely for signs of confusion or unusual behavior. Call a doctor at once if you or the child using zanamivir has any of these symptoms.
Stop using zanamivir and call your doctor at once if you have wheezing or severe breathing problems, or if you feel like you might pass out.
Less serious side effects of zanamivir may include:
nausea, vomiting, diarrhea;
fever, chills, joint pain;
ear pain; or
cold symptoms such as stuffy nose, sneezing, sore throat;
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.
For Healthcare Professionals
Applies to zanamivir: inhalation powder
Zanamivir is generally well-tolerated. In clinical trials, the incidence of adverse events in patients treated with zanamivir was similar to that in the placebo (lactose vehicle) group.
In a Phase I study, bronchospasm was reported in 1 of 13 patients with mild or moderate asthma following the administration of zanamivir. In a Phase III study of patients with acute influenza-like illness and underlying asthma or chronic obstructive pulmonary disease, more patients on zanamivir (10%) than on placebo (9%) experienced greater than 20% decline in FEV1 after 5 days of treatment.
Respiratory side effects have included cough (up to 17%), viral respiratory infections (up to 13%), nasal signs and symptoms (up to 12%), sinusitis (up to 3%), bronchitis (2%), ear, nose and throat infections (up to 2%), nasal inflammation (1%), decline in FEV1, congestion, rhinitis, and dry throat. Asthma, exacerbation of asthma, bronchospasm, respiratory arrest, dyspnea, lung tightness, and/or decline in lung function may occur in patients with underlying respiratory disease treated with zanamivir. Bronchospasm and dyspnea have been reported during postmarketing experience.
Nervous system side effects have included headache (up to 24%) and dizziness (up to 2%). Seizures, syncope, and vasovagal-like episodes shortly after inhalation have been reported during postmarketing experience.
Other side effects have included throat and tonsil discomfort and pain (up to 19%), malaise (up to 8%), fatigue (up to 8%), temperature regulation disturbances (fever and/or chills; up to 9%), and abdominal pain in less than 1.5% of patients. Facial edema has been reported during postmarketing experience.
Musculoskeletal side effects have included muscle pain (up to 8%), musculoskeletal pain (6%), arthralgia and articular rheumatism (up to 2%), and myalgia (less than 1.5%).
Dermatologic side effects have included urticaria in less than 1.5% of patients. Rash, including serious cutaneous reactions (e.g., erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), and urticaria have been reported during postmarketing experience.
Hypersensitivity side effects have included allergic or allergic-like reactions, including oropharyngeal edema, serious skin rashes, and anaphylaxis during postmarketing experience.
Psychiatric side effects have included delirium, including symptoms such as altered level of consciousness, confusion, abnormal behavior, delusions, hallucinations, agitation, anxiety, nightmares, during postmarketing experience.
Abnormal behavior and delirium leading to injury, with fatal outcomes in some cases, with the use of zanamivir in influenza patients have been reported. Although frequency is unknown, based on zanamivir usage, these events appear to be uncommon. These events were primarily reported in pediatric patients and often had an abrupt onset and rapid resolution. Since influenza may be associated with neurologic and behavioral symptoms (including hallucinations, delirium, and abnormal behavior, with fatal outcomes in some cases), zanamivir's contribution to these events has not been established.
Gastrointestinal side effects have included diarrhea (up to 3%), nausea (up to 3%), and vomiting (up to 2%).
Metabolic side effects have included feeding problems (decreased or increased appetite and anorexia; up to 4%) and elevated creatine phosphokinase.
Hepatic side effects have included elevated liver enzymes.
Hematologic side effects have included lymphopenia and neutropenia.
Cardiovascular side effects have included arrhythmias during postmarketing experience.
Renal side effects have included one case report acute renal failure, increased serum creatinine, hyperkalemia, and hypotension in a patient with multiple medical problems and multiple other medications.
More zanamivir resources
- zanamivir MedFacts Consumer Leaflet (Wolters Kluwer)
- zanamivir Inhalation, oral/nebulization Advanced Consumer (Micromedex) - Includes Dosage Information
- Zanamivir Professional Patient Advice (Wolters Kluwer)
- Zanamivir Monograph (AHFS DI)
- Relenza Prescribing Information (FDA)
- Relenza Consumer Overview
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