Zanamivir should be used during pregnancy only if potential benefits justifies potential risks to the fetus. Zanamivir has been shown to be excreted in milk from rats. Because many drugs are excreted in human milk, caution should be exercised when zanamivir is administered to a nursing mother. Safety and efficacy has not been studied in children less than 12 years of age. No overall differences were observed in patients greater than 65 years of age when compared to younger patients.
Systemic exposure is limited following inhaled zanamivir administration.
IV zanamivir doses of 2 mg or 4 mg in patients with mild or moderate renal impairment resulted in decreased renal clearance and significantly increased half-life. Safety and efficacy have not been documented in the presence of severe renal insufficiency. The drug is excreted unchanged in the urine with excretion of a single dose completed within 24 hours, however no dosage adjustments are recommended in patients with impaired renal function. Clinically significant drug interactions cannot be predicted based on current data from in vitro studies. In clinical studies, zanamivir was tolerated similarly to placebo.