HomeHealth articlesantiviral drugsHow Does Oseltamivir Work to Treat Influenza?

Oseltamivir - Usage, Mechanism of Action, Precautions, and Side Effects

Verified dataVerified data
0

19 min read

Share

Oseltamivir is an antiviral medication used to treat and prevent influenza virus type A and type B in the body. Read this article to learn more about the drug.

Medically reviewed by

Dr. Rajesh Gulati

Published At November 10, 2022
Reviewed AtNovember 10, 2022

Introduction:

Oseltamivir is an antiviral drug with strong activity against the flu virus. The drug directly attacks the flu or influenza virus and prevents it from multiplying within the body. Hence, Oseltamivir's main mechanism of action is to reduce flu symptoms. The biggest advantage of the drug is that it helps the patient stay away from the flu if he consumes it before he gets sick. An important point to be noted is that Oseltamivir does not treat the common cold and its symptoms but helps manage influenza in people who have been exposed but have not developed the symptoms till now. Meta-analyses conclude that the administration of Oseltamivir is based on the clinician’s discretion. The doctor must carefully determine the risk-benefit ratio before administering the drug.

Drug Development and Approval History:

  • Oseltamivir was discovered by Gilead Sciences in 1995, co-developed with and marketed by F.Hoffmann-La Roche Ltd. Finally, the drug was approved for medical use in the United States and made commercially available in 1999.

  • Oseltamivir marked a revolution in the management of influenza because it was the first neuraminidase inhibitor that could be taken orally. The drug is also on the World Health Organization’s (WHO) list of essential medications.

  • Studies report that shikimic acid was used as a starting point in the synthesis of Oseltamivir.

  • Oseltamivir was approved by the United States Food and Drug Administration (FDA) in 1999 for the management of influenza in adults.

  • Finally, the US FDA approved the first generic version of the drug Oseltamivir on 3rd August 2016 for patients two weeks of age and above who have had the symptoms of flu for not more than 48 hours.

Information About Oseltamivir:

How Does Oseltamivir Work to Treat Influenza?

Oseltamivir is a neuraminidase inhibitor used in the prophylaxis and treatment of infection due to influenza viruses A and B. The drug exerts its antiviral effect by prohibiting the activity of the viral neuraminidase enzyme found on the surface of the virus. As a result, budding, viral replication, and infectivity get stopped after the drug shows its action. Once Oseltamivir enters the patient’s body, it gets converted into its active form, named Oseltamivir carboxylate. This active form of the drug gets attached to the influenza virus and prevents its multiplication or replication within the body. This strengthens the immune system of the body to fight infections and diseases. In addition to stimulating the immune system, Oseltamivir does not allow the virus to release its viral particles as they can spread anywhere and infect the person. However, nothing has been known about the onset of action of Oseltamivir. This is because the time of action of the drug depends on the patient’s age, overall health, and whether he is using the drug to prevent or treat influenza.

Information Regarding the Safety and Effectiveness of Oseltamivir:

The clinical studies report that Oseltamivir is effective in treating and preventing influenza. During the trial, it was discovered that adults who took Oseltamivir for influenza demonstrated improvements in the symptoms in a shorter period compared to the ones who took the placebo. Oseltamivir was also studied in children one to 12 years old and suffering from flu. They were given either a placebo or the drug itself. The results of this study were miraculous, as children with flu took fewer days to overcome their symptoms than the ones who took a placebo. The safety and effectiveness of Oseltamivir were also evaluated during the influenza season. The trial participants were divided into two groups, those who took Oseltamivir and those who did not receive their annual influenza vaccine. The trial results showed that 1% of the patients who received Oseltamivir developed influenza. On the contrary, out of the ones who took the placebo, 4 to 12% of the patients developed influenza.

Will the Patient Remain Contagious Even After Taking Oseltamivir for Influenza?

The patient might remain contagious or transmit infections to others. This is because the influenza virus is highly communicable and spreads through the droplets of saliva during coughing or sneezing. So, the patient taking Oseltamivir must remember that the drug only stimulates the immune system to help the body fight infections and does not completely cure the condition. Therefore, there are high chances of spreading the infection to others. In addition, people suffering from influenza remain contagious for five to seven days after the symptoms of influenza initiate. Hence, Oseltamivir is an antiviral drug that targets the virus and prevents it from making further copies (replication). So, the patient will remain contagious even after taking the drug and must take all the precautions to prevent influenza.

What Are the Uses of Oseltamivir?

Oseltamivir is mainly used to treat patients presenting with the symptoms of influenza (influenza virus type A and B). It is also used for influenza prophylaxis in people one year of age and above. However, Oseltamivir is not a substitute for the influenza vaccine because one of the best ways to protect against acquiring flu and controlling its spread is by getting vaccinated.

Dosage and Administration:

Oseltamivir must be administered for the treatment of influenza in patients two weeks of age or above or for influenza prophylaxis in patients one year of age or above, using the following:

  • Oseltamivir capsules.

  • Oseltamivir oral suspension (supplied as a powder). It is a preferred formulation of 6 mg per mL for patients unable to swallow capsules. However, the pharmacist must constitute the Oseltamivir powder with water to produce the oral suspension.

The capsules and oral suspension can be taken with or without food. However, the tolerability of Oseltamivir gets enhanced when it is taken with food. Oseltamivir dosage can be adjusted in patients with moderate to severe kidney impairment. Oseltamivir oral suspension is the best solution for patients encountering difficulty in swallowing tablets. However, suppose Oseltamivir oral suspension is unavailable to the pharmacist, Oseltamivir capsules can be opened and mixed with sweet liquids like sugar-free chocolate syrup, caramel topping, corn syrup, or light brown syrup dissolved in water. The pharmacist can also prepare an emergency supply of the Oseltamivir 75 mg capsule if there is an emergency situation, and neither the sweetened liquids nor the oral suspensions are available.

Recommended Dosage for Influenza Treatment:

The treatment with influenza must be initiated within 48 hours of administration of Oseltamivir.

1) Adults and Adolescents (13 Years of Age and Above)

The recommended oral dosage of Oseltamivir for managing influenza in adults and adolescents 13 years and above is 75 mg twice daily. One 75 mg capsule or an oral suspension of 12.5 mL can be taken twice daily for five days.

2) Pediatric Patients (Two Weeks to 12 Years of Age):

Usually, prophylaxis is recommended in pediatric patients for ten days after close contact with the infected person and up to six weeks at the time of a community outbreak. The table mentioned below describes the recommended oral dosage and prophylactic dosage of Oseltamivir for the treatment of influenza in pediatric patients according to the patient’s body weight:

Oseltamivir oral dosage recommendations in children for influenza treatment and prophylaxis

oseltamivir-oral-dosage

Recommended Dosage for Influenza Prophylaxis:

The post-exposure prophylaxis with Oseltamir must be initiated within 48 hours after close contact with an infected individual. In addition, seasonal prophylaxis must be started during a community outbreak.

1) Adults and Adolescents (13 Years of Age and Above):

The recommended prophylactic dosage of Oseltamivir for adults and adolescents 13 years old and above is 75 mg orally once daily for ten days after contracting an infected person and up to six weeks during a community outbreak. Immunocompromised patients can take the drug for up to 12 weeks.

2) Drug Dosage in Patients With Renal Impairment:

The table below describes the dosage recommendations for the prophylaxis and treatment of influenza in adults suffering from different stages of renal impairment:

dosage-for-prophylaxis-and-treatment-of-influenza

General Information About Influenza:

Influenza or flu is an infectious respiratory condition caused by the influenza virus type A and B. It can affect the nose, lungs, and throat and cause mild or severe illness. The condition sometimes becomes so severe that it becomes difficult for the patient to survive. One of the best ways to prevent influenza is by getting vaccinated every year. It spreads rapidly in crowded areas like schools and nursing homes. Pregnant females, children under five years of age, and elderly patients with chronic medical conditions are more likely to suffer from influenza. Usually, the incubation period lasts for two days, but it might range from one to four days.

Signs and Symptoms of Influenza:

The signs and symptoms of influenza are listed below:

  1. Fever.

  2. Muscle aches.

  3. Chills.

  4. Sweats.

  5. Headache.

  6. Persistent dry cough.

  7. Shortness of breath.

  8. Weakness.

  9. Tiredness.

  10. Runny nose.

  11. Nasal congestion.

  12. Sore throat.

  13. Pain in the eyes.

  14. Vomiting.

  15. Diarrhea.

For Patients:

What Is Oseltamivir?

Oseltamivir is a prescription medication used to treat influenza in children two weeks of age or above who have had the symptoms of influenza for not more than two days. It also prevents influenza in children one year of age and above. It is not known if Oseltamivir is effective in:

  • People who start taking the drug after two days of experiencing influenza symptoms.

  • The treatment of influenza in people with chronic heart problems or respiratory difficulties.

  • The treatment of influenza in children less than two weeks of age.

  • Prevention of influenza in children less than one year of age.

Oseltamivir does not prevent or treat infections caused by viruses other than the influenza virus. However, the drug does not prevent bacterial infection that is usually accompanied by influenza. The drug is also not recommended for patients with end-stage renal disease who are not on dialysis.

What Should the Patient Inform the Doctor Before Taking Oseltamivir?

Before taking Oseltamivir, the patient must inform the doctor if he or she has

  1. Kidney problems.

  2. Problems in swallowing Oseltamivir capsules.

  3. A history of fruit sugar or fructose intolerance. Oseltamivir contains sorbitol and can cause stomach problems and diarrhea in people with fructose intolerance.

  4. Other underlying medical conditions.

  5. Conceived or planning to conceive. As per the information available, Oseltamivir does not elevate the risk of birth defects.

  6. Breastfed or planning to breastfeed the baby. Oseltamivir can pass from the mother’s milk to the baby in small quantities.

  7. Taken or is consuming any over-the-counter drugs, vitamin and herbal supplements, and prescription drugs.

  8. Allergy to the drug or any of its ingredients.

How Should the Patient Take Oseltamivir?

  1. The patient must take Oseltamivir, as mentioned by the doctor.

  2. Oseltamivir can be taken with or without food. However, the chances of stomach upset are low if Oseltamivir is taken with food.

  3. If he misses the dose, the patient must take Oseltamivir as soon as possible. However, the patient must avoid taking the missed dose of the drug two hours or less before the next dose. Take the next dose of Oseltamivir at the scheduled time. Do not take two doses of the drug simultaneously.

  4. If the patient is unable to swallow the Oseltamivir capsules or the oral suspension is not available, the doctor might instruct the patient to mix the contents of the capsule with corn syrup, caramel toppings, chocolate syrup, or light brown sugar.

  5. The patient must read the “Instructions for use” leaflet before taking the drug.

What Are Some of the Possible Side Effects of Oseltamivir?

Oseltamivir can cause the following serious side effects:

  • Serious Dermatologic Reactions - Oseltamivir can cause serious allergic and skin reactions, so the patient must seek medical attention under the following circumstances:

    • Skin rashes.

    • Hives.

    • Skin peels and blisters.

    • Sores and blisters in the oral cavity.

    • Itching.

    • Swelling of the face, lips, eyes, throat, or tongue.

    • Breathing troubles.

    • Chest pain.

    • Tightness of the chest.

  • Behavioral Changes - Children are most likely to develop problems related to the nervous system, including abnormal behavior and death. The parents must inform the doctor if the child presents with the following symptoms:

    • Confusion.

    • Speech problems.

    • Shaky movements.

    • Seizures.

    • Starts hearing sounds or seeing things that do not exist (hallucinations).

  • Common Side Effects -The common side effects of Oseltamivir are listed below:

How Should the Patient Store the Drug?

  1. Oseltamivir capsules must be stored at room temperature between 68 to 77 degrees Fahrenheit.

  2. Oseltamivir oral suspension must be stored in a refrigerator for 17 days between 36 to 46 degrees Fahrenheit.

  3. Oseltamivir oral suspension can also be stored for ten days at room temperature between 68 to 77 degrees Fahrenheit.

  4. The patient must safely dispose of the unused Oseltamivir that is no longer needed and remains unused.

  5. Oseltamivir and other medications must be kept out of reach of children.

General Information Regarding the Safety and Effective Use of Oseltamivir:

The patient might be given medications for reasons other than those mentioned in the patient information leaflet. Hence, the patient must avoid consuming Oseltamivir for a condition for which it was not recommended. Also, the drug must not be administered to people even if they have similar symptoms. The patient must obtain information about the drug from the doctor and the pharmacist before taking it.

How Should the Patient Take Oseltamivir Oral Suspension?

  • Step 1 - Shake the Oseltamivir oral suspension bottle before use.

  • Step 2 - Open the bottle by moving the child-resistant bottle cap downwards and twisting it in the direction of the arrow.

  • Step 3 - Use an appropriate oral dosing dispenser to measure the oral suspension so that the patient takes the correct drug dose.

  • Step 4 - Take the drug orally after measuring it from the oral dosing dispenser.

  • Step 5 - Make sure the bottle is closed with a child-resistant cap after every use.

  • Step 6 - The oral dosing dispenser must be rinsed under running water. It should be air dried after every use.

How Can the Patient Mix the Contents of the Oseltamivir Capsule With Sweetened Liquids if Directed by His Doctor or Pharmacist?

For mixing the contents of the Oseltamivir capsule with sweetened liquids, he might need the following:

  • The prescribed dose of the Oseltamivir capsules.

  • A bowl.

  • Sweetened liquids dissolve in water, including regular or sugar-free chocolate syrup, caramel topping, corn syrup, and light brown sugar.

  • Step 1 - The patient must first open the prescribed dose of Oseltamivir capsules in a bowl.

  • Step 2 - Add a small quantity of the sweetened liquids into the contents of the capsule.

  • Step 3 - Stir the contents and give the entire dose to the patient.

For Doctors:

Description:

Oseltamivir phosphate is a neuraminidase inhibitor that is available in the following forms:

  • Capsules comprising 30 mg, 45 mg, and 75 mg of the drug for oral use.

  • A powder for oral suspension, which, after constitution with water, contains 6 mg per mL of the Oseltamivir base.

Oseltamivir is available as a white crystalline solid under the chemical name (3R,4R,5S)-4-acetylamino-5-amino 3(1-ethylpropoxy)-1-cyclohexene-1-carboxylic acid, ethyl ester, phosphate (1:1). The chemical formula of the drug is C16H28N2O4. The molecular weight of the Oseltamivir free base is 312.4 and 410.4 for Oseltamivir free salt.

Indications and Usage:

1) Management of Influenza:

Oseltamivir is specifically indicated for the treatment of acute and uncomplicated illnesses caused by influenza A and B virus in patients two weeks old and above who have remained symptomatic for more than 48 hours.

2) Influenza Prophylaxis:

Oseltamivir is also indicated for influenza prophylaxis in patients one-year-old and above.

Contraindications:

Oseltamivir is contraindicated in patients who demonstrate hypersensitivity reactions to any of the ingredients of the drug. Patients with severe allergic reactions usually present with the following:

  1. Toxic epidermal necrolysis.

  2. Stevens-Johnson syndrome.

  3. Erythema multiformae.

Limitations of Use:

  • Patients using the drug must remember that it is not a substitute for the annual influenza vaccine.

  • Influenza viruses undergo changes from time to time. The effectiveness might get reduced due to the emergence of resistance substitutions. Sometimes, other factors, like the changes in the virulence of the virus, might affect the clinical benefits of the drug. Hence, Oseltamivir must be prescribed only after studying the drug susceptibility pattern.

  • Oseltamivir is specifically not recommended for patients with end-stage renal disease and not undergoing dialysis.

Chemical Taxonomy:

chemical-taxonomy

Clinical Pharmacology:

Microbiology:

Mechanism of Action:

Oseltamivir is an ethyl ester prodrug that requires ester hydrolysis to convert into its active form, Oseltamivir carboxylate. The active form of the drug is an influenza virus neuraminidase inhibitor that mainly affects the release of viral particles. Studies report that the median IC50 values of the drug against the influenza A/H1N1, influenza B, and influenza A/H3N2 clinical isolates were 2.5 nM, 60 nM, and 0.96 nM, respectively. These results were obtained during the neuraminidase assay done with a fluorescently labeled MUNANA substrate.

Antiviral Activity:

Cell culture was done to evaluate the antiviral activity of Oseltamivir against the laboratory strains and the clinical isolates of the influenza virus. Variations were noted in the concentrations of Oseltamivir required for the inhibition of the influenza virus in the cell culture. However, nothing has been known about the relationship between antiviral activity in cell culture, inhibitory activity, and the inhibition of viral replication in humans.

Resistance:

Cell Culture Studies -Isolates of the influenza virus having reduced susceptibility to Oseltamivir carboxylate have been recovered by the passage of the virus in cell culture in the presence of increasing concentrations of Oseltamivir. In addition, amino acid substitution helps confer the reduced susceptibility of the influenza virus in the hemagglutination proteins or viral neuraminidase.

Clinical Studies:

During the community surveillance studies and treatment with Oseltamivir, reduced susceptibility isolates have been obtained. Hemagglutination substitutions in conjunction with other resistance substitutions might be responsible for the reduced susceptibility to Oseltamivir. Patients who were not treated with Oseltamivir demonstrated circulating influenza stains and neuraminidase resistance substitutions. About 99 % of the patients had Oseltamivir resistance-associated substitution H275Y.

Cross-Resistance:

Cross-resistance between Zanamivir and Oseltamivir was observed in neuraminidase biochemical assay. However, no information is available related to the single amino acid substitution that could confer cross-resistance between Oseltamivir and the drugs belonging to M2 ion channel inhibitors, including Amantadine and Rimantadine. However, it is possible that the virus carries a neuraminidase inhibitor associated-substitution in M2 and becomes resistant to the other two classes of inhibitors.

Immune Response:

No studies have been conducted to know about the interaction of Oseltamivir and the influenza vaccine. However, during the experimental and naturally acquired influenza, no changes in the humoral immune response were noted during treatment with Oseltamivir.

Composition of Oseltamivir:

Active Ingredients - Oseltamivir phosphate.

Inactive Ingredients:

  • Oseltamivir Capsules - Croscarmellose sodium, Sodium stearyl fumarate, pregelatinized starch, Povidone K30, and talc.

  • 30 mg Capsule Shell - Gelatin, titanium dioxide, yellow iron oxide, and red iron oxide.

  • 45 mg Capsule Shell - Black iron oxide, titanium dioxide, and gelatin.

  • 75 mg Capsule Shell - Gelatin, black iron oxide, red iron oxide, yellow iron oxide, and titanium dioxide.

  • Oseltamivir Oral Suspension - Monosodium citrate, tutti frutti flavoring, sodium benzoate, sorbitol, titanium dioxide, saccharin sodium, and xanthan gum.

Pharmacokinetics:

Absorption and Bioavailability:

After the hepatic esterases have absorbed the drug from the gastrointestinal tract, it is converted into Oseltamivir carboxylate. It has been noted that 75% of the drug reaches the systemic circulation as Oseltamivir carboxylate, whereas 5% reaches Oseltamivir. The plasma concentration of the drug remained proportional for doses up to 500 mg. However, no variations were noted in the peak plasma concentration when the drug was administered with food.

Distribution:

The volume of distribution of the active form of Oseltamivir was noted in the range of 23 to 26 liters after it was administered intravenously in 24 patients. The binding of the drug to human plasma protein is around 42 % which is not sufficient enough to cause any clinically significant displacement-based drug reactions.

Elimination:

More than 90 % of the absorbed Oseltamivir is eliminated after conversion into its active metabolite. The plasma concentrations of the drug declined with a half-life of one to three hours in most patients after oral administration. Oseltamivir is eliminated unchanged in the urine after complete metabolism.

Metabolism:

Oseltamivir is primarily converted into its active metabolite with the help of the esterases located in the liver. However, the active metabolite named Oseltamivir carboxylate remains intact and is not metabolized further.

Excretion:

About 99% of the drug is eliminated by renal excretion. The renal clearance rate (18.8 L per hour) exceeds the glomerular filtration rate. This indicates that glomerular filtration is accompanied by tubular secretion.

Patients with Renal Impairment: The table below describes the population-derived pharmacokinetic parameters when the patients with renal impairment were administered Oseltamivir 100 mg.

patients-with-renal-impairmen

Drug Interactions:

Though Oseltamivir is actively converted into Oseltamivir carboxylate present in the liver, nothing has been known about the drug interactions or competition for esterases. As the drug has low plasma protein binding, studies suggest that the chances of drug displacement interactions are low. No clinically significant changes were noted when the following drugs were coadministered with Oseltamivir:

  • Probenecids.

  • Amoxicillin.

  • Acetaminophen.

  • Aspirin.

  • Cimetidine.

  • Antacids include Magnesium and Aluminum hydroxide.

  • Rimantadine.

  • Amantadine.

  • Warfarin.

Non-Clinical Toxicology:

Carcinogenesis, Impairment of Fertility, and Mutagenesis:

When Oseltamivir 400 to 500 mg per kg and its active form, Oseltamivir carboxylate, were administered in animals during the 2-year carcinogenicity study, no statistically significant effects were observed. During the Ames test and human lymphocyte chromosome assay with or without the enzymatic assay, it was discovered that Oseltamivir is non-mutagenic. However, mutagenicity was found to be positive in the Syrian Hamster Embryo (SHE) transfer test. However, the prodrug did not produce any mutagenic effects in both tests. During the fertility studies on animals, Oseltamivir 50, 250, and 1500 mg per kg per day were given to rats, but the drug did not produce any effect on fertility.

Dosage Forms and Strengths:

Oseltamivir Capsules:

  1. Available as 30 mm or 30 mg Free Base Equivalent to the Phosphate Salt - Hard gelatin, light yellow, with “ROCHE” printed on one side and “30 mg” embossed on the other side.

  2. Available as 45 mg or 45 mg Free Base Equivalent to the Phosphate Salt - Hard gelatin, gray, with “ROCHE” printed on one side and “45 mg” embossed on the other side.

  3. Available as 75 mg or 75 mg Free Base Equivalent to the Phosphate Salt - Hard gelatin, gray or light yellow, with “ROCHE” printed on one side and “75 mg” embossed on the other side.

Oseltamivir Oral Suspension: 6 mg per mL.

Available as a white powder that is reconstituted.

Warnings and Precautions for Oseltamivir:

  • Severe Dermatologic and Hypersensitivity Reactions - Patients with allergic skin conditions, hypersensitivity reactions, and other anaphylactic reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and erythema multiforme, must avoid taking this drug.

  • Neuropsychiatric Problems - Abnormal behavior and delirium have been reported after the drug was launched on the market. Some of these events have turned fatal. However, most of these events were reported during clinical practice, so nothing has been known about their frequency. These events were commonly reported among children and had an abrupt onset and rapid resolution. However, the contribution of Oseltamivir to all these events has not been established. The patients must be carefully monitored after the treatment with Oseltamivir for delusion, hallucinations, and abnormal behavior.

  • Bacterial Infections - Nothing has been known about the efficacy of OSeltamivir against pathogens other than the influenza virus. Serious bacterial infections usually initiate with influenza-like symptoms or might occur as a complication of influenza. Oseltamivir has not been known to prevent such bacterial infections.

  • Fructose Intolerance - Fructose is not beneficial for the ones diagnosed with hereditary fructose intolerance. A single dose of OSeltamivir 75 mg delivers 2 grams of sorbitol which is the daily limit for patients suffering from hereditary fructose intolerance. As a result, these patients tend to experience diarrhea and dyspepsia.

What Are the Possible Adverse Reactions of Oseltamivir?

The following adverse reactions were observed in the patients during the clinical trial and after the drug was launched on the market:

  • General Disorders:

    • Swelling of the tongue or face.

    • Allergy.

    • Pain.

    • Anaphylactic reactions.

    • Hypothermia.

  • Dermatologic or Subcutaneous Tissue Disorders:

  • Gastrointestinal Disorders:

    • Nausea.

    • Vomiting.

    • Gastrointestinal bleeding.

    • Hemorrhagic colitis.

  • Cardiac Disorders:

    • Arrhythmia.

  • Hepatobiliary Problems:

  • Nervous System Problems:

    • Seizures.

  • Metabolism and Nutrition-Related Disorders:

    • Aggravation of diabetes.

  • Psychiatric Disorders:

    • Delirium.

    • Hallucinations.

    • Abnormal behavior.

    • Anxiety.

    • Altered consciousness.

    • Agitation.

    • Confusion.

    • Nightmares.

Interactions With Other Drugs:

Influenza Vaccine:

  1. Live Attenuated Vaccine - The interaction of Oseltamivir with the live attenuated influenza vaccine has not been evaluated. However, the patients must not be given the vaccine two weeks before or 48 hours after the administration of Oseltamivir. This is because Oseltamivir has the potential to reduce the efficacy of the live vaccine virus and the live attenuated influenza vaccine.

  2. Inactivated Influenza Vaccine - Inactivated influenza vaccine can be administered at any time, irrespective of the administration of Oseltamivir.

Preparation and Storage of Constituted Oseltamivir Oral Suspension:

The drug must be constituted by following the steps listed below:

  • Tap the bottle containing Oseltamivir powder repeatedly to loosen the powder.

  • Use a graduated cylinder to measure 55 mL of water.

  • Add the measured amount of water for the constitution into the bottle.

  • Close the bottle tightly with a child-resistant cap and shake it well for 15 seconds.

  • Hence, the constituted oral solution comprises 360 mg of Oseltamivir base per 60 mL of the volume. The solution is white colored and tutti-frutti flavored. The patient must use this solution within 17 days when stored in a refrigerator at 2 to 8 degrees Celsius. The solution must be used within ten days if stored at room temperatures of 25 degrees Celsius.

  • The patient must use an oral dosing dispenser to measure the required volume of the drug in milliliters.

Emergency Preparation of Oral Suspension From Oseltamivir 75 MG Capsules:

Emergency preparation instructions are given to the patient to provide them with enough Oseltamivir for a 5-day treatment course for influenza. Follow the steps mentioned below:

Step 1 - Calculate the dosage of Oseltamivir to be administered to the patient using the chart mentioned below:

oseltamivir-dosage

Step 2 - The preparation of the drug must be done using one of the below-mentioned vehicles:

  • Cherry syrup.

  • Ora-sweet.

  • Sugar-free.

  • Simple syrup.

The table below lists the amount of water and vehicle required to prepare the oral suspension of the drug for the treatment and prophylaxis and treatment of influenza:

treatment of influenza

Step 3 - Follow the instructions mentioned below for preparing 75 mg Oseltamivir capsules to synthesize the oral suspension (6 mg per mL):

  • Take a measured amount of water in the polyethylene terephthalate (PET) or a glass bottle. Other bottles must not be used for the constitution as they might alter the properties of the drug.

  • Separate the cap and the capsule body and pour its contents into the PET or glass bottle.

  • Swirl the mixture for two minutes to allow adequate wetting of the Oseltamivir powder.

  • Add the specified amount of the vehicle to the suspension bottle.

  • Use a child-resistant cap to close the bottle and shake it for 30 seconds before use to allow its complete dissolution. This also helps in the homogenous distribution of the dissolved drug.

  • Provide necessary instructions to the patient regarding the safe disposal of the unused portion of the drug after the completion of the therapy.

  • The prepared oral suspension can be refrigerated for five weeks or stored at controlled room temperatures for five days.

How Is Oseltamivir Supplied or Handled?

Oseltamivir Capsules:

Oseltamivir 30 mg capsules are usually light yellow and hard gelatin capsules with “ROCHE” printed on one side and 30 mg on the other. The 45 mg and 75 mg capsules are grey or light yellow hard gelatin capsules available in the blister packages of ten.

Storage of Oseltamivir:

The capsules are usually stored at 25 degrees Celsius.

Oseltamivir Oral Suspension:

It is supplied as a white powder in a glass bottle and is mixed with water. A tutti-frutti flavored oral suspension is obtained after the powder has been constituted. Each bottle provides a volume of 60 mL equivalent to 360 mg Oseltamivir base.

Storage:

Store the constituted suspension in the refrigerator at 2 to 8 degrees Celsius.

Use of Oseltamivir in Specific Populations:

Pregnancy:

It is a pregnancy category C drug. Not much information is available regarding the effect of Oseltamivir in pregnant females. The published epidemiological data suggests that Oseltamivir, taken in any trimester, does not cause any clinically significant effects. However, these studies cannot be relied upon because of the small sample size and different comparison groups.

Disease-Associated Risks:

Pregnant females are likely to develop complications due to influenza, including preterm delivery, low birth weight, stillbirth, and maternal death.

Nursing Mothers:

Based on the available data, Oseltamivir and its active form are present in small quantities in human milk. However, no evidence of toxicity was reported in the breastfed infants.

Pediatric Population:

Influenza Treatment:

The following information is available regarding the safety and efficacy of Oseltamivir for the management of influenza in children two weeks to 17 years of age:

  1. The safety and efficacy of Oseltamivir were noted in patients 13 to 17 years of age during the well-controlled clinical trials.

  2. A double-blind placebo-controlled trial was done on 452 patients, one to 12 years old. During the trial, Oseltamivir 2 mg per kg was administered within 48 hours of the onset of symptoms. The trial results favored the administration of the drug in these patients.

Influenza Prophylaxis:

Randomized, double-blind, and placebo-controlled trials suggest that Oseltamivir can be safely administered for influenza prophylaxis in patients one to 17 years old.

Geriatric Use:

Three double-blind and placebo-controlled trials were done on 4765 patients. About 20 % of these patients were above 65 years and did not demonstrate any changes related to the safety and efficacy of the drug. People of the geriatric age group can safely use oseltamivir for influenza prevention. This is because 719 elderly patients who took the drug for 42 days did not present with any side effects.

Renal Impairment:

Patients with renal impairment presented with elevated blood levels of Oseltamivir than the ones with normal kidney functions. Therefore, dose adjustments must be done for such patients. Patients with end-stage renal disease must be carefully monitored after the administration of Oseltamivir.

Note - Nothing has been known about the safety and efficacy of the drug in patients with chronic cardiac or respiratory diseases or immunocompromised conditions.

Clinical Trials:

Treatment of Influenza:

Two double-blind, randomized, and placebo-controlled trials were done on 1355 patients with influenza. The trial participants had a fever (100 degrees Fahrenheit), one respiratory symptom, and one systemic symptom, including myalgia, malaise, fatigue, or headache. In addition, the patients were randomized to receive Oseltamivir for five days.

Trial Results:

The trial results showed that people who took Oseltmavir got rid of their symptoms 1.3 days earlier than those who took the placebo.

Frequently Asked Questions

1.

What Is the Use of the Drug Oseltamivir?

Oseltamivir treats infections caused by flu viruses such as influenza A, influenza B, and swine influenza A. It helps to reduce flu symptoms such as fever, headache, cough, weakness, sore throat, and stuffy or runny nose. 

2.

Which Type of Influenza Is Treated by the Drug Oseltamivir?

Oseltamivir is a prodrug of Oseltamivir carboxylate used to treat infections caused by the influenza virus A and B. It is a potent and selective inhibitor of the neuraminidase glycoprotein. This inhibitor is responsible for the replication of influenza A and B viruses.

3.

When Should the Drug Oseltamivir Be Administered?

Oseltamivir drug is used to reduce flu symptoms such as headache, cough, fever, and sore throat, whereas it is not used to treat throat infection.

4.

Is the Drug Oseltamivir Safe?

In children and teenagers, oseltamivir may cause irritation agitation, and show some abnormal behaviors, which might result in injury. Therefore, the iris must consult the doctor for any side effects after administering the drug.

5.

When Should Oseltamivir Drugs Be Avoided?

Oseltamivir should not be given to children younger than two weeks old. It should not be used if the individual is allergic to it. It should be avoided during pregnancy as it may cause complications leading to birth defects, preterm babies, etc. 
 

6.

What Is the Dosage of Oseltamivir Drug?

Oseltamivir is used for the treatment of flu, and in adults and teenagers, the dosage of the drug is 75 milligrams twice a day, one in the morning and one in the evening.

7.

What Is the Rating of the Drug Oseltamivir?

Oseltamivir has a rating of six out of ten population and has 51% positive experience with the drug while 37% negative experience.

8.

What Type of Drug Is Oseltamivir?

Oseltamivir is an antiviral drug administered orally for treatment and prophylaxis of influenza A and B virus in adults and children above one year.

9.

For How Many Days Is Oseltamivir Drug Taken?

Oseltamivir is taken twice daily in the morning and night for five days to treat flu, whereas to prevent the flu, oseltamivir is taken once daily for ten days as directed by the doctor.

10.

Can Oseltamivir Cause Liver Toxicity?

Oseltamivir can cause mild liver injury; no reports or studies show that using oseltamivir can cause acute liver failure.

11.

Which Treatment Is Oseltamivir Drug Administered?

Oseltamivir is administered to treat uncomplicated influenza A and B viruses in adults and children older than one year or age.

12.

Does The Immune System Get Affected With Oseltamivir?

The symptoms of influenza are reduced by administering the drug oseltamivir, and it inhibits the release of pro-inflammatory cytokines, which reduces the immune response. 

13.

What Is the Recovery Time of Influenza by Intake of Drug Oseltamivir?

The recovery rate from major symptoms of influenza is usually 3-7 days, but when oseltamivir is administered, recovery time is shortened by 1 to 2 days.
Dr. Rajesh Gulati
Dr. Rajesh Gulati

Family Physician

Tags:

oseltamivirantiviral drugs
Community Banner Mobile
By subscribing, I agree to iCliniq's Terms & Privacy Policy.

Source Article ArrowMost popular articles

Do you have a question on

antiviral drugs

Ask a doctor online

*guaranteed answer within 4 hours

Disclaimer: No content published on this website is intended to be a substitute for professional medical diagnosis, advice or treatment by a trained physician. Seek advice from your physician or other qualified healthcare providers with questions you may have regarding your symptoms and medical condition for a complete medical diagnosis. Do not delay or disregard seeking professional medical advice because of something you have read on this website. Read our Editorial Process to know how we create content for health articles and queries.

This website uses cookies to ensure you get the best experience on our website. iCliniq privacy policy