Human Health Issues related to Avian Influenza in Canada

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Appendix J: Sample Oseltamivir Information Sheet

OSELTAMIVIR PHOSPHATE (Tamiflu®):

Oseltamivir is a drug which prevents the spread of the influenza virus in an infected person. It is a neuraminidase inhibitor which inhibits the enzyme responsible for cleaving the viral load from the host cell thus preventing it from further dissemination. It is active against both influenza A and B viruses.

Oseltamivir is indicated both as a chemoprophylactic and treatment agent. It is most effective in uncomplicated influenza cases.

Indications:

Oseltamivir is indicated for the treatment of influenza in patients 1 year of age and older within 2 days (48 hours) of onset of symptoms. The efficacy for oseltamivir has not been established for those patients beginning treatment after this 2 day period. It can be also used as a chemoprophylactic agent in persons 13 years of age and older. Oseltamivir is prescribed as an adjunct to influenza vaccination but is not a substitute for the vaccine. Oseltamivir is not indicated in children < 1 year of age.

Contraindications:

Hypersensitivity to the drug or any of its excipients. The drug formulation contains pregelatinized starch, talc, povidone K 30, croscarmellose sodium, and sodium stearyl fumarate. The capsule shell contains gelatin, titanium dioxide, yellow iron oxide, black iron oxide, red iron oxide, and FD&C Blue No. 2 colourant.

Pharmacokinetics:

Oseltamivir is administered orally. Oseltamivir is a prodrug that is hepatically metabolized extensively to oseltamivir carboxylate by hepatic esterases. Oseltamivir and oseltamivir carboxylate have low protein binding. Neither oseltamivir nor oseltamivir carboxylate are substrates, nor inhibitors of the cytochrome P450 isoenzymes.

Oseltamivir carboxylate is eliminated renally by excretion into the urine. Dosage adjustments are recommended in patients with renal impairment and with serum creatinine clearance < 30 mL/min.

Precautions:

Safety in hepatic impairment has not been established. Adjust dosing if serum creatinine < 30 mL/min. Pregnancy category C: crosses the placenta and secreted into breast milk but no human data on safety; use in pregnancy and lactation only if potential benefits outweigh the risks.

Drug Interactions:

No significant drug interactions. Co-administration with probenecid may result in a 2-fold increase in exposure to oseltamivir carboxylate, however this does not compromise the safety margin of the oseltamivir carboxylate.

Adverse Effects:

Nausea and vomiting are reported most commonly and are generally mild to moderate, occurring during the first 2 days of therapy.

Other less common effects include diarrhea, abdominal pain, otitis media/ear disorder, asthma, epistaxis, pneumonia, sinusitis, bronchitis, conjunctivitis, dermatitis, lymphadenopathy, and tympanic membrane disorder.

Observed effects (post-marketing): rash, swelling of the face or tongue, toxic epidermal necrolysis, dermatitis, rash, eczema, urticaria, erythema multiforme, Stevens-Johnson-Syndrome, hepatitis, abnormal liver function tests, arrhythmia, seizure, confusion, anaphylactic reactions, and aggravation of diabetes. The causal relationship of these adverse effects to the drug has not been established.

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