Safety information on oseltamivir (Tamiflu) and zanamivir (Relenza) for pandemic swine influenza A/H1N1

Latest Safety Information from the MHRA

Tamiflu and Relenza are both neuraminidase enzyme inhibitors. They act by inhibiting entry of influenza virus into uninfected cells and preventing the release of recently formed virus particles from infected cells. Tamiflu is given orally (capsules and solution) and Relenza is given by inhalation (Diskhaler system).

Both have substantial experience of use and favourable benefit-risk profiles.

Tamiflu Side effect profile

The most common side effects of Tamiflu are nausea, vomiting, diarrhoea, abdominal pain, and headache. These may usually occur after the first dose and will usually stop as treatment continues. The frequency of these effects is reduced if Tamiflu is taken with food. More-serious side effects are very rare (see Summary of Product Characteristics for further information).

The product information for Tamiflu lists neuropsychiatric disorders (reports of convulsions and delirium) in the side-effects section. These events were added to the product information as a precautionary measure—a causal association between Tamiflu and the reported events is uncertain.

Drug interactions

Clinically important drug interactions with Tamiflu are unlikely, including those involving competition for renal tubular secretion. However, care should be taken when prescribing Tamiflu for patients who are taking co-excreted medicines with a narrow therapeutic margin (eg, chlorpropamide or methotrexate).

No dose adjustment is required when coadministering with probenecid in patients with normal renal function. Coadministration of probenecid, a potent inhibitor of the anionic pathway of renal tubular secretion, results in an approximate two-fold increase in exposure to the active metabolite of oseltamivir.

Renal impairment

Dose adjustment is recommended for adults with severe renal insufficiency (ie, ≤30 mL/min). Tamiflu is not recommended for patients with a creatinine clearance of ≤10 mL/min or in those undergoing dialysis.

Full Update

Press reports and comment regarding Tamiflu and Relenza:

Swine flu: more than 400 cases of Tamiflu side effects

Flu drug 'nearly killed daughter of TV presenter'

Leading article: This abuse of Tamiflu is dangerous for all of us

Government virus expert paid £116k by swine flu vaccine manufacturers GlaxoSmithKline

GlaxoSmithSwine



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