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Ribax contains Oseltamivir Phosphate, which is the prodrug of oseltamivir carboxylate, a potent selective inhibitor of the enzyme neuraminidase of influenza A and B viruses. Viral neuraminidase is important for the entry of the virus into the uninfected cell and for release of newly formed viral particles from infected cells, and for further spread of the infectious virus by the body.

Oseltamivir carboxylate inhibits influenza virus infection, replication, and pathogenicity.

Therapeutic indications

Treatment and prevention of influenza.

Pharmacokinetics and pharmacodynamics

Absorption: Oseltamivir is rapidly absorbed from the digestive tract after oral administration of Oseltamivir phosphate. The plasma concentrations of the active metabolite are detectable after 30 minutes, reach their maximum values ​​between 2 and 3 hours after the dose and greatly exceed (> 20 times) the plasma concentrations of the prodrug. At least 75% of an oral dose reaches the general circulation as an active metabolite. Plasma concentrations of the active metabolite are dose proportional and do not vary when administered with food. Distribution: The active metabolite reaches all places affected by influenza infection: lung tissue, bronchoalveolar lavage fluid, nasal mucosa, middle ear and trachea. The degree of binding of the prodrug to human plasma proteins is 42%. These values ​​are insufficient to provoke important pharmacological interactions. Metabolism: Oseltamivir phosphate is extensively transformed into its active metabolite by the action of liver esterases. Neither oseltamivir nor its active metabolite are substrates or inhibitors of the isoenzymes of the cytochrome P450 system. Elimination: The absorbed oseltamivir is eliminated mainly (> 90%) by biotransformation in its active metabolite. This, for its part, is not metabolized, and is eliminated in the urine. Peak plasma concentrations of the active metabolite drop with a half-life of 6 to 10 hours in most people. The active metabolite is almost completely eliminated (> 99%) by renal excretion. Its renal clearance (18.8 l / h) is superior to glomerular filtration (7.5 l / h), which indicates that, in addition to glomerular filtration, there is also a mechanism for tubular secretion. Less than 20% is eliminated in the faeces.

Pharmacokinetics in special populations:

Renal insufficiency: The administration of 100 mg of oseltamivir twice a day, for five days to patients with renal insufficiency of various degrees, shows that the exposure to the active metabolite is inversely proportional to the deterioration of the renal function. No dose adjustment is necessary in patients with creatinine clearance greater than 30 ml / min. In patients whose creatinine clearance is 10 to 30 ml / min, it is recommended to reduce the dose to 75 mg oseltamivir once daily for 5 days. Hepatic impairment: No significant increase in exposure to oseltamivir or its active metabolite is expected in patients with mild or moderate hepatic impairment. Safety and pharmacokinetics have not been studied in patients with severe hepatic impairment. Elderly: exposure to the active metabolite of 25-35%. The half-life values ​​observed in the elderly are similar to those recorded in young adults. No dosage adjustment of oseltamivir is required for either treatment or prevention of influenza in elderly patients.

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Side effects

Oseltamivir is generally well tolerated. Adverse effects occur in about 1% of adult patients and include gastrointestinal effects such as nausea, vomiting, diarrhea, abdominal pain; Headache, bronchitis, insomnia and vertigo have also been observed. These reactions are usually transient and generally occur after the first dose.


Contraindicated in hypersensitivity to oseltamivir phosphate or any component of the formulation.


Neuropsychiatric events such as seizure and delirium have been reported during the administration of oseltamivir in influenza patients, predominantly in children and adolescents. It is unknown whether these effects are drug related. Influenza patients throughout the treatment period should be closely monitored for any abnormal symptoms.

Pregnancy and lactation:

There is insufficient data on pregnant women treated with oseltamivir, therefore it should only be used during pregnancy when the expected benefits justify the risk to the fetus. Oseltamivir and the active metabolite pass into the milk of rats. It is not known whether they also pass into human breast milk, therefore it should be used when the benefits to the nursing mother justify the risks to the breastfed child.

Drug interactions

Cimetidine does not alter the plasma concentrations of oseltamivir or its active metabolite. Concomitant use of oseltamivir with probenecid may increase the exposure of oseltamivir carboxylate, as a consequence of a decrease in its active tubular secretion in the kidney; however, given the wide margin of safety of the active metabolite, no dose adjustment is necessary when oseltamivir phosphate is administered simultaneously. Co-administration of amoxicillin does not change the plasma concentrations of either drug, indicating that they do not compete. The administration of oseltamivir together with paracetamol does not alter the plasma concentrations of any. Oseltamivir can be used concomitantly with the vaccine containing the inactivated influenza virus.

Similarly, it can be administered with ACE inhibitors, thiazide diuretics, antibiotics, H2 receptor antagonists, beta-blockers, sympathomimetics, opioids, corticosteroids, inhaled bronchodilators, and pain relievers. No changes in the type or frequency of adverse effects are observed as a result of co-administration with oseltamivir.

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Each capsule contains:

Oseltamivir Phosphate    98.527 mg

(Equivalent to 75 mg of Oseltamivir)

C.S. excipients    1 capsule

Posology and  administration



Ribax can be taken with or without food; however, in some patients it can improve their tolerability if taken with food. Influenza treatment: Treatment should be started within two days of the onset of flu symptoms. Adults and adolescents ≥ 13 years: the recommended oral dose is 75 mg twice a day, for 5 days. Influenza prevention: adults and adolescents ≥ 13 years: the recommended dose of Ribax for the prevention of influenza after contact with an infected person is 75mg once a day for 10 days. Treatment should be started within two days of contact. The recommended dose for prevention during a community influenza outbreak is 75mg once a day. Safety and efficacy are proven for up to six weeks. Protection is maintained for as long as administration lasts.

Special dosage schedules: patients with renal impairment: influenza treatment: no dose adjustment is necessary in patients with creatinine clearance greater than 30 ml / min. In patients whose creatinine clearance is 10-30 ml / min, it is recommended to reduce the dose to Ribax 75 mg once daily for 5 days. Prevention of influenza: In patients with a creatinine clearance between 10 and 30 ml / min who are receiving Ribax, it is recommended to reduce the dose to a 75 mg capsule every third day or alternatively 30 mg once a day.

Patients with hepatic impairment: neither treatment nor prevention of influenza with Ribax requires dosage adjustment in patients with mild or moderate hepatic impairment. The safety and pharmacokinetics in patients with severe liver damage have not been studied. Elderly: neither treatment nor prevention of influenza with Ribax requires dosage adjustment in elderly patients. Children: Safety and efficacy in children younger than 1 year of age have not been determined.


Box containing a blister with 10 capsules.

Storage Recommendations

Store below 30 °C. Protected from humidity.


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