Relenza Side Effects
Generic name: zanamivir
Medically reviewed by Drugs.com. Last updated on Nov 27, 2022.
Note: This document contains side effect information about zanamivir. Some dosage forms listed on this page may not apply to the brand name Relenza.
Applies to zanamivir: inhalation disk.
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:
- dizziness and fainting
- fast, slow, or irregular heartbeat
- flushing or reddening of the skin
- increased sensitivity to sunlight
- itching, pain, redness, swelling, or watering of the eye or eyelid
- joint pain
- severe skin rash or hives
- shortness of breath or troubled breathing
- swelling or puffiness of the face
- swollen glands or tightness in the throat
- tightness in the chest or wheezing
Other 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:
- Change in hearing
- cough producing mucus
- ear drainage
- ear, nose, and throat infections
- fever or chills
- nasal signs and symptoms
- pain and pressure over cheeks
- pain in the ear
- shortness of breath
For Healthcare Professionals
Applies to zanamivir: inhalation powder.
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]
-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]
-Very common (10% or more): Headaches (up to 24%)
-Common (1% to 10%): Dizziness
-Postmarketing reports: Seizures, syncope, vasovagal-like episodes shortly after inhalation
-Frequency not reported: Convulsions, depressed level of consciousness[Ref]
-Common (1% to 10%): Malaise/fatigue, temperature regulation disturbances (fever/chills)
-Frequency not reported: Malaise, fatigue, fever
-Postmarketing reports: Facial edema
-Uncommon (0.1% to 1%): Elevated alkaline phosphatase
-Frequency not reported: Oropharyngeal edema, facial edema[Ref]
-Common (1% to 10%): Muscle pain, musculoskeletal pain, arthralgia/articular rheumatism
-Frequency not reported: Urticaria
-Common (1% to 10%): Rash
-Uncommon (0.1% to 1%): Urticaria
-Frequency not reported: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis[Ref]
-Postmarketing reports: Allergic/allergic-like reactions (including oropharyngeal edema, serious skin rashes, anaphylaxis, anaphylactic/anaphylactoid reactions, facial edema)
-Frequency not reported: Anaphylactic/anaphylactoid reactions[Ref]
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.
-Postmarketing reports: Delirium, altered level of consciousness, confusion, abnormal behavior, delusions, hallucinations, agitation, anxiety, nightmares
-Frequency not reported: Abnormal behavior, hallucinations, delirium
-Common (1% to 10%): Diarrhea, nausea, vomiting, nausea/vomiting
-Frequency not reported: Abdominal pain
-Common (1% to 10%): Diarrhea[Ref]
-Common (1% to 10%): Feeding problems (decreased/increased appetite, anorexia)
-Frequency not reported: Elevated liver enzymes
-Common (1% to 10%): Elevated ALT, elevated AST, hepatocellular injury[Ref]
-Frequency not reported: Hypotension
-Postmarketing reports: Arrhythmias[Ref]
-Frequency not reported: Acute renal failure, increased serum creatinine[Ref]
More about Relenza (zanamivir)
- Check interactions
- Compare alternatives
- Pricing & coupons
- Reviews (5)
- Dosage information
- During pregnancy
- Drug class: inhaled anti-infectives
- En español
Related treatment guides
1. Product Information. Relenza (zanamivir). Glaxo Wellcome. 2001.
2. Cerner Multum, Inc. UK Summary of Product Characteristics.
3. Cerner Multum, Inc. Australian Product Information.
4. Williamson JC, Pegram PS. Respiratory distress associated with zanamivir. N Engl J Med. 2000;342:661-2.
5. Macdonald L. New influenza drugs zanamivir (Relenza (TM)) and oseltamivir (Tamiflu (TM)): unexpected serious reactions. Can Med Assn J. 2000;163:879-81.
6. Montalto NJ, Gum KD, Ashley JV. Updated treatment for influenza A and B. Am Fam Physician. 2000;62:2467-76.
7. Dreitlein WB, Maratos J, Brocavich J. Zanamivir and oseltamivir: Two new options for the treatment and prevention of influenza. Clin Ther. 2001;23:327-55.
8. Cheer SM, Wagstaff AJ. Zanamivir: an update of its use in influenza. Drugs. 2002;62:71-106.
9. Moscona A. Neuraminidase inhibitors for influenza. N Engl J Med. 2005;353:1363-73.
10. Jefferson T, Demicheli V, Rivetti D, Jones M, Di Pietrantonj C, Rivetti A. Antivirals for influenza in healthy adults: systematic review. Lancet. 2006;367:303-13.
11. Laforce C, Man CY, Henderson FW, et al. Efficacy and safety of inhaled zanamivir in the prevention of influenza in community-dwelling, high-risk adult and adolescent subjects: a 28-day, multicenter, randomized, double-blind, placebo-controlled trial. Clin Ther. 2007;29:1579-1590.
12. McNicholl IR, McNicholl JJ. Neuraminidase inhibitors: zanamivir and oseltamivir. Ann Pharmacother. 2001;35:57-70.
13. Anekthananon T, Pukritayakamee S, Ratanasuwan W, et al. Oseltamivir and inhaled zanamivir as influenza prophylaxis in Thai health workers: a randomized, double-blind, placebo-controlled safety trial over 16 weeks. J Antimicrob Chemother. 2013;68:697-707.
14. Monto AS, Fleming DM, Henry D, et al. Efficacy and safety of the neuraminidase inhibitor zanamivir in the treatment of influenza A and B virus infections. J Infect Dis. 1999;180:254-61.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Some side effects may not be reported. You may report them to the FDA.