Side Effects of Tamiflu (oseltamivir)

Tamiflu (oseltamivir) is an antiviral medication used to treat and prevent influenza (the "flu"). Tamiflu suppresses and decreases the spread of influenza A and B viruses, the viruses responsible for the flu. It blocks the action of neuraminidase, an enzyme produced by the viruses that enables the viruses to spread from infected cells to healthy cells.

By preventing the spread of virus from cell to cell, the symptoms and duration of influenza infection are reduced. On average, Tamiflu reduces the duration of symptoms by one and a half days if treatment is started within forty-eight hours of the beginning of symptoms. 

Common side effects of Tamiflu include

• nausea,
• vomiting,
• diarrhea,
• bronchitis,
• abdominal pain,
• headache, and
• dizziness.

Serious side effects of Tamiflu include

• allergic reactions,
• skin reactions,
• seizures,
• behavioral disturbances, and
• aggravation of diabetes.

Drug interactions of Tamiflu include the live attenuated flu vaccine that is given by injection because Tamiflu prevents viral replication. Live attenuated flu vaccine should not be administered within two weeks before or 48 hours after administration of Tamiflu.

The Centers for Disease Control (CDC) recommends use of Tamiflu for treating flu in pregnant women. The CDC recommends that women with flu who have recently given birth may be treated with Tamiflu. Tamiflu passes into breast milk. Consult your doctor before breastfeeding. 

The most frequent side effects of oseltamivir are:

• Nausea
• Vomiting
• Diarrhea
• Bronchitis
• Abdominal pain
• Headache
• Dizziness

Administering oseltamivir after meals helps reduce nausea.

Other reported adverse events include:

• Allergic reactions
• Skin reactions
• Seizures
• Behavioral disturbances
• Aggravation of diabetes

The following serious adverse reactions are discussed below and elsewhere in the labeling:

• Serious skin and hypersensitivity reactions
• Neuropsychiatric events

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Adverse Reactions From Treatment And Prophylaxis Trials In Adult And Adolescent Subjects (13 Years Of Age And Older)

The overall safety profile of Tamiflu is based on data from 2,646 adult and adolescent subjects that received the recommended dosage of 75 mg orally twice daily for 5 days for treatment of influenza and 1,943 adult and adolescent subjects that received the recommended dosage of 75 mg orally once daily for up to 6 weeks for prophylaxis of influenza in clinical trials.

The most common adverse reactions in the pooled treatment and pooled prophylaxis trials in adults and adolescents are displayed in Table 5. The majority of these adverse reactions were reported on a single occasion, occurred on either the first or second treatment day and resolved spontaneously within 1-2 days.

This summary includes otherwise healthy adults/adolescents and subjects “at risk” (subjects at higher risk of developing complications associated with influenza, e.g., elderly patients and patients with chronic cardiac or respiratory disease). In general, the safety profile in the subjects “at risk” was qualitatively similar to that in otherwise healthy adults/adolescents.

Table 5 : Adverse Reactions Occurring in ≥1% of Adults and Adolescents (13 years of age and older) in Treatment and Prophylaxis Trials*

Adverse Reactions From Treatment And Prophylaxis Trials In Pediatric Subjects (1 Year To 12 Years Of Age)

A total of 1,481 pediatric subjects (including otherwise healthy pediatric subjects aged 1 year to 12 years and asthmatic pediatric subjects aged 6 to 12 years) participated in clinical trials of Tamiflu for the treatment of influenza.

A total of 859 pediatric subjects received treatment with Tamiflu for oral suspension either at a 2 mg per kg twice daily for 5 days or weight-band dosing. Vomiting was the only adverse reaction reported at a frequency of ≥1% in subjects receiving Tamiflu (16%) compared to placebo (8%).

Amongst the 148 pediatric subjects aged 1 year to 12 years who received Tamiflu at doses of 30 to 60 mg once daily for 10 days in a post-exposure prophylaxis study in household contacts (n = 99), and in a separate 6-week seasonal influenza prophylaxis safety study (n = 49), vomiting was the most frequent adverse reaction (8% on Tamiflu versus 2% in the no prophylaxis group).

Adverse Reactions From Treatment Trials In Pediatric Subjects (2 Weeks To Less Than 1 Year Of Age)

Assessment of adverse reactions in pediatric subjects 2 weeks to less than 1 year of age was based on two open-label studies that included safety data on 135 influenza-infected subjects 2 weeks to less than 1 year of age (including premature infants at least 36 weeks post conceptional age) exposed to Tamiflu at doses ranging from 2 to 3.5 mg per kg of the formulation for oral suspension twice daily orally for 5 days.

The safety profile of Tamiflu was similar across the age range studied, with vomiting (9%), diarrhea (7%) and diaper rash (7%) being the most frequently reported adverse reactions, and was generally comparable to that observed in older pediatric and adult subjects.

Adverse Reactions From The Prophylaxis Trial In Immunocompromised Subjects

In a 12-week seasonal prophylaxis study in 475 immunocompromised subjects, including 18 pediatric subjects 1 year to 12 years of age, the safety profile in the 238 subjects receiving Tamiflu 75 mg once daily was consistent with that previously observed in other Tamiflu prophylaxis clinical trials.

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of Tamiflu. Because these reactions are reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency or establish a causal relationship to Tamiflu exposure.

• General disorders and administration site conditions: Swelling of the face or tongue, allergy, anaphylactic/anaphylactoid reactions, hypothermia
• Skin and subcutaneous tissue disorders: Rash, dermatitis, urticaria, eczema, toxic epidermal necrolysis, Stevens-Johnson Syndrome, erythema multiforme
• Gastrointestinal Disorders: Gastrointestinal bleeding, hemorrhagic colitis
• Cardiac Disorders: Arrhythmia
• Hepatobiliary Disorders: Hepatitis, abnormal liver function tests
• Nervous System Disorders: Seizure
• Metabolism and Nutrition Disorders: Aggravation of diabetes
• Psychiatric Disorders: Abnormal behavior, delirium, including symptoms such as hallucinations, agitation, anxiety, altered level of consciousness, confusion, nightmares, delusions

Influenza Vaccines

Live Attenuated Influenza Vaccine

The concurrent use of Tamiflu with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for Tamiflu to inhibit replication of live vaccine virus and possibly reduce the efficacy of LAIV, avoid administration of LAIV within 2 weeks before or 48 hours after Tamiflu administration, unless medically indicated.

Inactivated Influenza Vaccine

Inactivated influenza vaccine can be administered at any time relative to use of Tamiflu.

Drugs Without Clinically Significant Drug Interaction With Tamiflu

No dose adjustments are needed for either oseltamivir or the concomitant drug when coadministering oseltamivir with amoxicillin, acetaminophen, aspirin, cimetidine, antacids (magnesium and aluminum hydroxides and calcium carbonates), rimantadine, amantadine, or warfarin.