Tamiflu75 mg

Tamiflu is indicated for the treatment and prevention of influenza in adults and children. Its use is classified below by strength of evidence:

• Established/FDA-approved: Treatment of acute, uncomplicated illness due to influenza A and B virus infection in patients who have been symptomatic for no more than 48 hours.
• Established/FDA-approved: Prophylaxis (prevention) of influenza A and B following close contact with an infected individual, or during a community influenza outbreak.
• Guideline-supported: Treatment of influenza in hospitalized patients, pregnant women, and patients at high risk of complications (e.g. chronic lung/heart/kidney disease, immunocompromised, elderly), even when started after 48 hours of symptom onset, per CDC and WHO guidance.
• Off-label (not FDA-approved but reported in the literature): Treatment of avian influenza (H5N1) and other novel influenza strains, and extended-duration treatment in severely ill hospitalized patients, under specialist guidance.

Tamiflu is not effective against the common cold or other respiratory illnesses not caused by influenza virus, and should not be used empirically without a reasonable suspicion of influenza.

Each capsule of Oseltamivir contains Oseltamivir phosphate equivalent to 30 mg, 45 mg, or 75 mg of oseltamivir base. A powder for oral suspension is also available, which when reconstituted provides Oseltamivir 6 mg/mL.

Tamiflu is an orally administered antiviral medicine belonging to the neuraminidase inhibitor class. It is a prodrug that is converted in the liver to its active form, Tamiflu carboxylate, which interferes with the release of new influenza virus particles from infected cells, thereby limiting the spread of infection within the respiratory tract. Tamiflu is used to treat and prevent influenza A and B and is most effective when started early in the course of illness, though it may still provide benefit later, especially in high-risk or hospitalized patients.

Tamiflu belongs to the antiviral drug class known as neuraminidase inhibitors, used specifically against influenza A and B viruses.

Mechanism of Action

Oseltamivir is a prodrug hydrolyzed primarily in the liver to oseltamivir carboxylate, a selective inhibitor of influenza virus neuraminidase. By blocking this enzyme, Oseltamivir prevents newly formed virus particles from being released from infected respiratory cells, reducing viral spread and shortening the duration of illness.

Pharmacokinetics

• Absorption: Well absorbed orally; food does not significantly reduce absorption but may reduce nausea.
• Metabolism: Extensively converted to the active metabolite by hepatic esterases.
• Elimination: Primarily excreted unchanged (as active metabolite) by the kidneys; dose adjustment is required in renal impairment (see Dosage and Use in Special Populations).
• Half-life: Approximately 6-10 hours for the active metabolite.

Tamiflu capsules should be swallowed whole with water and may be taken with or without food; taking it with a light meal can help reduce nausea. The oral suspension should be measured only with the dosing device provided by the pharmacy, not a household spoon. For best effect, the first dose of Tamiflu should be taken as soon as possible after influenza symptoms begin.

Tamiflu has relatively few clinically significant drug interactions:

• Probenecid: Reduces renal clearance of the active metabolite of Tamiflu by competing for tubular secretion, approximately doubling its plasma concentration; dose adjustment may be needed with concurrent use in renal impairment.
• Live attenuated influenza vaccine (LAIV, nasal spray): Tamiflu may inhibit replication of the live vaccine virus and reduce its effectiveness; avoid LAIV within 48 hours before to 2 weeks after a course of Tamiflu, unless medically indicated. Inactivated (injectable) influenza vaccines are not affected.

No clinically significant interactions have been established with warfarin or oral contraceptives.

Common side effects of Tamiflu include:

• Nausea and vomiting (most common; may be reduced by taking with food)
• Headache
• Diarrhea, abdominal pain
• Insomnia in some patients

Less common but serious effects include:

• Neuropsychiatric events - abnormal behavior, confusion, delirium, hallucinations, or self-injury, reported rarely, predominantly in pediatric and adolescent patients (see Precautions and Warnings)
• Severe skin reactions such as Stevens-Johnson syndrome, toxic epidermal necrolysis, or erythema multiforme (rare)
• Allergic reactions including anaphylaxis (rare)

Patients or caregivers should seek prompt medical attention for any unusual behavior, severe rash, or signs of an allergic reaction while taking Tamiflu.

Pregnancy: Data on the use of Tamiflu in pregnancy have not shown a clear increase in adverse fetal outcomes, but studies remain limited. Tamiflu should be used during pregnancy only if clearly needed and if the potential benefit (particularly given the risk of severe influenza complications in pregnancy) justifies the potential risk to the fetus; use should be under the direct advice of a physician.

Lactation: Tamiflu and its active metabolite are excreted into breast milk in small amounts. It may be used during breastfeeding when clinically indicated, but a physician should be consulted, and the infant should be monitored for any unusual symptoms.

• Neuropsychiatric events: Rare cases of abnormal behavior, delirium, or self-injury have been reported, mainly in children and adolescents, both with influenza illness itself and during treatment with Tamiflu. Patients, especially children, should be monitored closely for unusual behavior throughout treatment.
• Not a substitute for vaccination: Tamiflu does not replace annual influenza vaccination, which remains the primary means of preventing influenza.
• Not for non-influenza illness: Tamiflu has not been shown to be effective for any illness caused by agents other than influenza viruses A and B; empiric use without reasonable clinical suspicion of influenza is discouraged.
• Bacterial superinfection: Influenza can be complicated by concurrent or secondary bacterial infection. If symptoms persist or worsen during or after treatment with Tamiflu, the possibility of a bacterial infection should be evaluated by a physician.
• Renal impairment: Dose adjustment is required; see Use in Special Populations.
• Complete the full prescribed course of Tamiflu as directed; do not stop early, skip doses, or share this medicine with others without medical advice.

Reported overdose symptoms with Tamiflu are generally similar to its common side effects, primarily nausea and vomiting; more serious effects have rarely been reported. There is no specific antidote for Tamiflu overdose. If an overdose is suspected, seek immediate medical attention or contact a poison control center right away; treatment is supportive and based on symptoms.

Store Tamiflu capsules at room temperature (below 30°C), away from light and moisture. Keep out of reach of children. If dispensed as a reconstituted oral suspension, follow the pharmacist's specific storage instructions and discard any unused suspension after the labeled period.

Renal Impairment

Hepatic Impairment

No dose adjustment is needed for mild to moderate hepatic impairment; data in severe hepatic impairment are limited.

Elderly

No dose adjustment is required based on age alone, though renal function should be assessed.

Pregnancy and Lactation

See Pregnancy and Lactation section.

Pediatric Use

See Pediatric Uses section.

The standard treatment course of Tamiflu is 5 days. For post-exposure prophylaxis, the usual course is at least 10 days; during a community influenza outbreak, prophylaxis may be extended up to 6 weeks under medical supervision. In severely ill, hospitalized, or immunocompromised patients, a physician may extend treatment duration based on clinical response.

The powder for oral suspension form of Tamiflu must be reconstituted by the pharmacist prior to dispensing. Water is added to the powder in the bottle and shaken well to produce a suspension containing Tamiflu 6 mg/mL. Only the oral dosing dispenser provided with the product should be used to measure and administer doses; household spoons should not be used, as they may result in inaccurate dosing.

Antiviral agent; Neuraminidase inhibitor

Oseltamivir's active metabolite, oseltamivir carboxylate, is a transition-state analog inhibitor of influenza virus neuraminidase, an enzyme on the surface of the virus required for the release of newly formed viral particles from infected host cells. By inhibiting neuraminidase, Oseltamivir prevents the spread of the virus to new, uninfected cells within the respiratory tract, reducing the duration and severity of infection.

C

Tamiflu is approved for the treatment of influenza in patients as young as 2 weeks of age, using weight-based dosing appropriate for infants and children. For prophylaxis, Tamiflu is approved for use in children 1 year of age and older. Safety and efficacy of Tamiflu for prophylaxis in infants below 1 year of age have not been established. As with adult patients, children and adolescents should be closely monitored for unusual behavior while taking Tamiflu, given rare reports of neuropsychiatric events in this age group (see Precautions and Warnings).