Drug reference

Zanamivir

Antiviral · Influenza

AntiviralInfluenzaATC J05AH01

CDSCO approvedATC J05AH01

EXCRETION

—

not curated

INTERACTIONS

—

none in our sources

PREGNANCY

—

not curated

Mechanism

Zanamivir is an inhaled neuraminidase inhibitor that competitively blocks the active site of influenza A and B neuraminidase, preventing the enzymatic cleavage of sialic acid residues necessary for virion release from infected cells. Administered by oral inhalation, it achieves high concentrations in the respiratory tract mucosa — the primary site of influenza infection. Unlike oseltamivir (oral), zanamivir's very low oral bioavailability (<5%) necessitates inhalation delivery, but this route provides direct drug delivery to the infection site.

Indications

Treatment of influenza (most effective if started within a few hours of onset, licensed for use within 48 hours of the first symptoms)Post-exposure prophylaxis of influenza (given within 36 hours of exposure to influenza when influenza is circulating in the community)Treatment in patients with severe influenza or in those who are immunocompromised, if viral shedding continues (off-label)Use in exceptional circumstances (e.g., when vaccination does not provide protection)prevention of influenza A virus infectionsprevention of influenza B virus infectionstreatment of influenza A virus infectionstreatment of influenza B virus infectionsalternative to oseltamivir for influenza A (including amantadine-resistant, nH1N1, H5N1 strains) and influenza Bprophylactic use in household contactsexhibits effectiveness like that of oseltamiviractive against some influenza virus strains that are resistant to oseltamivirTreatment of influenza A and B viruses (most effective if given within 48 hours of infection)Prophylaxis against influenzaComplicated influenza infections in hospitalized patientsTreatment for high-risk groups (children <2 years, adults >65 years, patients with chronic conditions, immunosuppressed individuals, pregnant women, women who have delivered infants ≤2 weeks previously, patients <19 years old receiving long-term aspirin treatment, Native Americans/Alaska Natives, morbidly obese individuals, and residents of nursing homes or chronic-care facilities)

Dosing

Adult: 10 mg (two inhalations) twice daily for 5 days (treatment); once-daily inhaled (prophylaxis)
Pediatric: 10 mg (two inhalations) twice daily for 5 days (children 5 years or older)
Geriatric: Can reduce the risk of complications from influenza in the elderly.

Pharmacokinetics

Half-life

2.5–5 h; ~1.7 h (IV)

Bioavailability

<5% (oral); 4% to 17% (systemic absorption after inhalation)

Protein binding

<10%

Excretion

100% renal excretion

Contraindications

patients with underlying airway disease (due to risk of serious adverse events)
asthma (due to risk of severe bronchospasm)
Inhalation of zanamivir powder may cause bronchospasm in patients with COPD or asthma
Asthma (relative contraindication for intranasal)
COPD (relative contraindication for intranasal)

Side effects

Common

wheezingbronchospasmheadachedizzinessnausearashes (mild and infrequent)

Serious

acute deteriorations in lung function (including fatal outcomes in those with underlying asthma or chronic obstructive airway disease)
bronchospasm (can be severe in asthmatics)