Oseltamivir 45mg Capsules
It is used to treat or prevent the flu. It may be given to you for other reasons. Talk with the doctor.
Drug Class
Antiviral
Pharmacologic Class
Neuraminidase Inhibitor
Pregnancy Category
Category C
FDA Approved
Oct 1999
DEA Schedule
Not Controlled
Overview
What is this medicine?
Oseltamivir is an antiviral medicine used to treat or prevent the flu (influenza). It works by stopping the flu virus from spreading in your body. It's most effective when started within the first 1-2 days of flu symptoms.
How to Use This Medicine
Taking Your Medication
To get the most benefit from your medication, take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. You can take this medication with or without food. If it causes stomach upset, taking it with food may help.
Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start feeling well. If you have difficulty swallowing the medication, consult your doctor for guidance. In some cases, your doctor may recommend mixing the capsule contents with a sweet liquid, such as chocolate syrup, caramel topping, corn syrup, or light brown sugar dissolved in water, to make it easier to take.
If needed, a liquid suspension can be prepared from the capsules. Discuss this option with your doctor or pharmacist to determine the best approach for your situation.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature in a dry place, avoiding bathrooms. If a liquid suspension is prepared from the capsules, it should be stored in the refrigerator to prevent spoilage. Do not freeze the suspension. Any unused portion of the suspension should be discarded after 35 days if stored in the refrigerator, or after 5 days if stored at room temperature.
Keep all medications in a secure location, out of the reach of children and pets, to prevent accidental ingestion or exposure.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose (less than 2 hours away), skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To get the most benefit from your medication, take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. You can take this medication with or without food. If it causes stomach upset, taking it with food may help.
Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start feeling well. If you have difficulty swallowing the medication, consult your doctor for guidance. In some cases, your doctor may recommend mixing the capsule contents with a sweet liquid, such as chocolate syrup, caramel topping, corn syrup, or light brown sugar dissolved in water, to make it easier to take.
If needed, a liquid suspension can be prepared from the capsules. Discuss this option with your doctor or pharmacist to determine the best approach for your situation.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature in a dry place, avoiding bathrooms. If a liquid suspension is prepared from the capsules, it should be stored in the refrigerator to prevent spoilage. Do not freeze the suspension. Any unused portion of the suspension should be discarded after 35 days if stored in the refrigerator, or after 5 days if stored at room temperature.
Keep all medications in a secure location, out of the reach of children and pets, to prevent accidental ingestion or exposure.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose (less than 2 hours away), skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take with food to reduce stomach upset.
- Complete the full course of medication, even if you start feeling better.
- Practice good hygiene (hand washing, covering coughs/sneezes) to prevent spread of flu.
- Stay home when sick to avoid infecting others.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
Treatment: 75 mg orally twice daily for 5 days. Prophylaxis: 75 mg orally once daily for at least 10 days (up to 6 weeks during community outbreak).
Dose Range:
75 - 75 mg
Condition-Specific Dosing:
influenza_treatment:
75 mg BID for 5 days
influenza_prophylaxis:
75 mg QD for 10 days (or longer)
Pediatric Dosing
Neonatal:
Treatment (term infants <1 year): 3 mg/kg BID for 5 days. Prophylaxis: 3 mg/kg QD for 10 days. (Dosing for premature infants should be individualized based on postmenstrual age and postnatal age).
Infant:
Treatment (1-12 months): 3 mg/kg BID for 5 days. Prophylaxis: 3 mg/kg QD for 10 days.
Child:
Treatment (1-12 years, weight-based): <15 kg: 30 mg BID; 15-23 kg: 45 mg BID; 23-40 kg: 60 mg BID; >40 kg: 75 mg BID. All for 5 days. Prophylaxis: Half of treatment dose once daily for 10 days.
Adolescent:
Treatment (>13 years): 75 mg BID for 5 days. Prophylaxis: 75 mg QD for 10 days.
Dose Adjustments
Renal Impairment:
Mild:
No adjustment needed (CrCl >60 mL/min)
Moderate:
Treatment (CrCl 30-60 mL/min): 30 mg BID for 5 days. Prophylaxis: 30 mg QD for 10 days.
Severe:
Treatment (CrCl 10-30 mL/min): 30 mg once daily for 5 days. Prophylaxis: 30 mg every other day for 10 days.
Dialysis:
Hemodialysis: Treatment: 30 mg immediately, then 30 mg after every other hemodialysis cycle. Peritoneal Dialysis: Treatment: 30 mg immediately, then 30 mg once weekly. Prophylaxis: Not established, consider individual risk/benefit.
Hepatic Impairment:
Mild:
No adjustment
Moderate:
No adjustment
Severe:
No adjustment (limited data, but not extensively metabolized by liver)
Pharmacology
Mechanism of Action
Oseltamivir is a prodrug that is hydrolyzed by hepatic esterases to its active metabolite, oseltamivir carboxylate (OC). OC is a potent and selective inhibitor of influenza A and B virus neuraminidase, an enzyme that is essential for viral replication and release from infected cells. By inhibiting neuraminidase, OC prevents the release of new virions from infected cells and inhibits further spread of the virus within the respiratory tract.
Pharmacokinetics
Absorption:
Bioavailability:
75% (of oseltamivir carboxylate)
Tmax:
0.5-1 hour (oseltamivir), 2-3 hours (oseltamivir carboxylate)
FoodEffect:
Food does not significantly affect the peak plasma concentration or AUC of oseltamivir carboxylate, but may reduce the incidence of gastrointestinal side effects.
Distribution:
Vd:
23-26 L (oseltamivir carboxylate)
ProteinBinding:
3% (oseltamivir carboxylate)
CnssPenetration:
Limited (low concentrations in CSF, but sufficient to inhibit viral replication in CNS in animal models)
Elimination:
HalfLife:
6-10 hours (oseltamivir carboxylate)
Clearance:
Not available (primarily renal excretion)
ExcretionRoute:
Renal (glomerular filtration and tubular secretion)
Unchanged:
Not available (oseltamivir carboxylate is not further metabolized and is excreted unchanged)
Pharmacodynamics
OnsetOfAction:
Rapid (within hours of first dose)
PeakEffect:
Within 24-72 hours of symptom onset (when treatment is most effective)
DurationOfAction:
Approximately 12 hours (based on BID dosing)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Immediately
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Neurological problems, particularly in people with the flu, which can lead to death, especially in children. Seek help immediately if you experience:
+ Confusion
+ Changes in behavior
+ Speech problems
+ Shakiness
+ Seizures
+ Hallucinations
A severe skin reaction, known as Stevens-Johnson syndrome or toxic epidermal necrolysis, which can cause serious health problems and even death. Get medical help right away if you notice:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in your mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects, although many people may not experience any or may only have mild symptoms. If you are bothered by any of the following side effects or if they do not go away, contact your doctor or seek medical attention:
Diarrhea
Upset stomach
Vomiting
* Headache
Reporting Side Effects
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Neurological problems, particularly in people with the flu, which can lead to death, especially in children. Seek help immediately if you experience:
+ Confusion
+ Changes in behavior
+ Speech problems
+ Shakiness
+ Seizures
+ Hallucinations
A severe skin reaction, known as Stevens-Johnson syndrome or toxic epidermal necrolysis, which can cause serious health problems and even death. Get medical help right away if you notice:
+ Red, swollen, blistered, or peeling skin (with or without fever)
+ Red or irritated eyes
+ Sores in your mouth, throat, nose, or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects, although many people may not experience any or may only have mild symptoms. If you are bothered by any of the following side effects or if they do not go away, contact your doctor or seek medical attention:
Diarrhea
Upset stomach
Vomiting
* Headache
Reporting Side Effects
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe allergic reactions (rash, itching, swelling, severe dizziness, trouble breathing)
- Sudden confusion, delirium, hallucinations, or unusual behavior (especially in children and adolescents)
- Seizures
- Worsening flu symptoms or development of new symptoms (e.g., difficulty breathing, chest pain)
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
If you have kidney disease, as this may affect your ability to take this medication.
This is not an exhaustive list of potential interactions. To ensure your safety, it is crucial to discuss all of your:
Prescription and over-the-counter (OTC) medications
Natural products
Vitamins
Health problems
with your doctor and pharmacist. They will help determine whether it is safe for you to take this medication in conjunction with your other medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
If you have kidney disease, as this may affect your ability to take this medication.
This is not an exhaustive list of potential interactions. To ensure your safety, it is crucial to discuss all of your:
Prescription and over-the-counter (OTC) medications
Natural products
Vitamins
Health problems
with your doctor and pharmacist. They will help determine whether it is safe for you to take this medication in conjunction with your other medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
This medication is not a substitute for a flu shot. If your doctor has recommended that you receive a flu vaccine, it is crucial that you follow their advice. This medication will not treat the common cold, and it does not prevent the spread of the flu to others.
Before receiving a flu vaccine, discuss the timing with your doctor, especially if you have recently taken this medication. Similarly, if you have recently received a flu vaccine, consult with your doctor before starting this medication.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is vital to discuss the potential benefits and risks of this medication with your doctor, as this will help you make an informed decision about its use and its potential impact on you and your baby.
This medication is not a substitute for a flu shot. If your doctor has recommended that you receive a flu vaccine, it is crucial that you follow their advice. This medication will not treat the common cold, and it does not prevent the spread of the flu to others.
Before receiving a flu vaccine, discuss the timing with your doctor, especially if you have recently taken this medication. Similarly, if you have recently received a flu vaccine, consult with your doctor before starting this medication.
If you are pregnant, planning to become pregnant, or are breastfeeding, it is vital to discuss the potential benefits and risks of this medication with your doctor, as this will help you make an informed decision about its use and its potential impact on you and your baby.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Abdominal pain
- Headache
- Tremor
- Dizziness
- In rare cases, seizures or altered mental status
What to Do:
Call 1-800-222-1222 (Poison Control Center) immediately or seek emergency medical attention.
Drug Interactions
Major Interactions
- Live attenuated influenza vaccine (LAIV)
Moderate Interactions
- Probenecid
Monitoring
Baseline Monitoring
Renal function (CrCl)
Rationale: To determine appropriate dosing adjustments in patients with impaired renal function.
Timing: Prior to initiation of therapy
Routine Monitoring
Symptoms of influenza (e.g., fever, cough, sore throat, body aches)
Frequency: Daily during treatment
Target: Resolution or improvement of symptoms
Action Threshold: Lack of improvement or worsening symptoms may indicate treatment failure or alternative diagnosis.
Neuropsychiatric symptoms (e.g., delirium, hallucinations, abnormal behavior)
Frequency: Daily, especially in pediatric patients
Target: Absence of symptoms
Action Threshold: Emergence of new or worsening neuropsychiatric symptoms warrants immediate medical evaluation and consideration of treatment discontinuation.
Symptom Monitoring
- Nausea
- Vomiting
- Headache
- Abdominal pain
- Diarrhea
- Bronchitis
- Insomnia
- Vertigo
- Neuropsychiatric events (e.g., delirium, hallucinations, confusion, abnormal behavior, seizures, self-injury)
Special Patient Groups
Pregnancy
Oseltamivir is generally considered safe and effective for use during pregnancy when indicated for treatment or prophylaxis of influenza. The benefits of treating influenza in pregnant women (who are at higher risk for complications) generally outweigh the potential risks. Consult with a healthcare provider.
Trimester-Specific Risks:
First Trimester:
Limited data, but no increased risk of major birth defects observed in human studies.
Second Trimester:
No increased risk of adverse outcomes observed.
Third Trimester:
No increased risk of adverse outcomes observed.
Lactation
Oseltamivir and its active metabolite are excreted into breast milk in low concentrations. The amount ingested by a breastfed infant is very low and unlikely to cause adverse effects. It is generally considered compatible with breastfeeding, especially given the potential benefits of preventing influenza in the mother and infant.
Infant Risk:
Low risk of adverse effects to the breastfed infant.
Pediatric Use
Approved for treatment of influenza in patients 2 weeks of age and older, and for prophylaxis in patients 1 year of age and older. Dosing is weight-based for younger children. Close monitoring for neuropsychiatric events is recommended, especially in pediatric patients.
Geriatric Use
No dosage adjustment is typically needed based on age alone. However, elderly patients are more likely to have age-related decreases in renal function, which may necessitate dose adjustment based on creatinine clearance.
Clinical Information
Clinical Pearls
- Oseltamivir is most effective when initiated within 48 hours of influenza symptom onset for treatment.
- For prophylaxis, it should be started as soon as possible after exposure.
- Capsules can be opened and mixed with sweetened liquids (e.g., chocolate syrup, corn syrup, sugar water) for patients who cannot swallow pills, especially children.
- Resistance to oseltamivir can occur, but remains relatively uncommon in circulating seasonal influenza strains.
- It is not a substitute for annual influenza vaccination.
Alternative Therapies
- Zanamivir (Relenza) - inhaled neuraminidase inhibitor
- Peramivir (Rapivab) - IV neuraminidase inhibitor
- Baloxavir marboxil (Xofluza) - cap-dependent endonuclease inhibitor
Cost & Coverage
Average Cost:
$100 - $150 per 10 capsules (75mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (generic), Tier 3 (brand)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.