Relenza Side Effects

Generic name: zanamivir

Medically reviewed by Drugs.com. Last updated on Dec 7, 2024.

Note: This document provides detailed information about Relenza Side Effects associated with zanamivir. Some dosage forms listed on this page may not apply specifically to the brand name Relenza.

Applies to zanamivir: inhalation disk.

Precautions

It is very important that your doctor check your or your child's progress after treatment. This is to make sure that the infection is cleared up completely, and to allow your doctor to check for any unwanted effects.

This medicine is not a substitute for an annual flu shot. It also will not keep you or your child from getting a bacterial infection that starts with flu-like symptoms.

Zanamivir may cause people with lung disease (e.g., chronic obstructive lung disease or asthma) to have shortness of breath, trouble breathing, or wheezing. If you have these symptoms after using this medicine, stop using this medicine and call your doctor right away.

Bronchospasm (wheezing) is a risk for patients with asthma or chronic respiratory disease. Always have a fast-acting inhaled bronchodilator available for your use.

This medicine may cause serious allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Stop using this medicine and call your doctor right away if you or your child have itching, hives, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you are using this medicine.

Zanamivir may cause some people, especially children and teenagers, to be agitated, irritable, or display other abnormal behaviors, which may result in injury. If you, your child, or your caregiver notice any of these side effects, tell your doctor or your child's doctor right away.

Make sure your doctor knows if you or your child plan to get the live nasal flu vaccine (FluMist®) before you start using this medicine. You should not receive the vaccine within two weeks before or 48 hours after using this medicine.

If your or your child's symptoms do not improve after you or your child finish taking the medicine, or if they become worse, check with your doctor.

Common side effects of Relenza

Some side effects of zanamivir may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Serious side effects of Relenza

Along with its needed effects, zanamivir (the active ingredient contained in Relenza) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking zanamivir:

For healthcare professionals

Applies to zanamivir: inhalation powder.

General adverse events

In clinical trials, the incidence of adverse events in patients treated with the inhalation powder was similar to that in the placebo (lactose vehicle) group.

The side effects reported most commonly with the IV formulation were elevated ALT, elevated AST, hepatocellular injury, diarrhea, and rash.^[Ref]

Respiratory

Inhalation powder:

• Very common (10% or more): Throat/tonsil discomfort/pain (up to 19%), cough (up to 17%), viral respiratory infections (up to 13%), nasal signs/symptoms (up to 12%)
• Common (1% to 10%): Sinusitis, bronchitis, ear/nose/throat infections, nasal inflammation, decline in forced expiratory volume in 1 second (FEV1)
• Frequency not reported: Bronchospasm-like events, congestion, rhinitis, dry throat, ear/nose/throat hemorrhage, asthma, exacerbation of asthma, respiratory arrest, lung tightness, decline in lung function, throat tightness/constriction
• Postmarketing reports: Bronchospasm, dyspnea^[Ref]

In a Phase 1 study, bronchospasm was reported in 1 of 13 patients with mild or moderate asthma (but without acute influenza-like illness) after administration of this drug. In a Phase 3 study of patients with acute influenza-like illness and underlying asthma or chronic obstructive pulmonary disease, 24 of 244 patients on this drug (compared to 22 of 237 patients on placebo) experienced greater than 20% decline in FEV1 after 5 days of treatment.

Serious cases of bronchospasm (including fatalities) have been reported during therapy in patients with and without underlying airways disease. Most of these cases were reported during postmarketing experience; causality was difficult to evaluate.^[Ref]

Nervous system

Inhalation powder:

• Very common (10% or more): Headaches (up to 24%)
• Common (1% to 10%): Dizziness
• Postmarketing reports: Seizures, syncope, vasovagal-like episodes shortly after inhalation

IV formulation:

• Frequency not reported: Convulsions, depressed level of consciousness^[Ref]

Other

Inhalation powder:

• Common (1% to 10%): Malaise/fatigue, temperature regulation disturbances (fever/chills)
• Frequency not reported: Malaise, fatigue, fever
• Postmarketing reports: Facial edema

IV formulation:

• Uncommon (0.1% to 1%): Elevated alkaline phosphatase
• Frequency not reported: Oropharyngeal edema, facial edema^[Ref]

Musculoskeletal

Inhalation powder:

• Common (1% to 10%): Muscle pain, musculoskeletal pain, arthralgia/articular rheumatism
• Frequency not reported: Myalgia, arthralgia, elevated creatine phosphokinase^[Ref]

Dermatologic

Inhalation powder:

• Frequency not reported: Urticaria
• Postmarketing reports: Rash, serious cutaneous reactions (e.g., erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), urticaria

IV formulation:

• Common (1% to 10%): Rash
• Uncommon (0.1% to 1%): Urticaria
• Frequency not reported: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis^[Ref]

Hypersensitivity

Inhalation powder:

• Postmarketing reports: Allergic/allergic-like reactions (including oropharyngeal edema, serious skin rashes, anaphylaxis, anaphylactic/anaphylactoid reactions, facial edema)

IV formulation:

• Frequency not reported: Anaphylactic/anaphylactoid reactions^[Ref]

Psychiatric

Inhalation powder:

• Postmarketing reports: Delirium, altered level of consciousness, confusion, abnormal behavior, delusions, hallucinations, agitation, anxiety, nightmares

IV formulation:

• Frequency not reported: Abnormal behavior, hallucinations, delirium

Abnormal behavior and delirium leading to injury, with fatal outcomes in some cases, with the use of this drug in influenza patients have been reported. Although frequency was unknown, based on usage of this drug, these events appeared 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), contribution of this drug to these events was not established.

Gastrointestinal

Inhalation powder:

• Common (1% to 10%): Diarrhea, nausea, vomiting, nausea/vomiting
• Frequency not reported: Abdominal pain

IV formulation:

• Common (1% to 10%): Diarrhea^[Ref]

Metabolic

Inhalation powder:

• Common (1% to 10%): Feeding problems (decreased/increased appetite, anorexia)
• Frequency not reported: Hyperkalemia^[Ref]

Hepatic

Inhalation powder:

• Frequency not reported: Elevated liver enzymes

IV formulation:

• Common (1% to 10%): Elevated ALT, elevated AST, hepatocellular injury^[Ref]

Hematologic

Inhalation powder:

• Frequency not reported: Lymphopenia, neutropenia^[Ref]

Cardiovascular

Inhalation powder:

• Frequency not reported: Hypotension
• Postmarketing reports: Arrhythmias^[Ref]

Renal

Inhalation powder:

• Frequency not reported: Acute renal failure, increased serum creatinine^[Ref]

In 1 case report, acute renal failure, increased serum creatinine, hyperkalemia, and hypotension developed in a patient with multiple medical problems and multiple other medications.^[Ref]

See also:

Further information

Relenza side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer