Tamiflu
Tamiflu - General Information
An acetamido cyclohexene that is a structural homolog of sialic acid and inhibits neuraminidase. [PubChem]
Pharmacology of Tamiflu
Tamiflu is an antiviral drug, a neuraminidase inhibitor used in the treatment and prophylaxis of both influenza A and influenza B. Tamiflu is a prodrug (usually administered as phosphate), it is hydrolysed hepatically to the active metabolite, the free carboxylate of oseltamivir (GS4071). Like zanamivir, oseltamivir acts as a transition-state analogue inhibitor of influenza neuraminidase.
Tamiflu for patients
Patients should be instructed to begin treatment with TAMIFLU as soon as possible from the first appearance of flu symptoms. Similarly, prevention should begin as soon as possible after exposure, at the recommendation of a physician.
Patients should be instructed to take any missed doses as soon as they remember, except if it is near the next scheduled dose (within 2 hours), and then continue to take TAMIFLU at the usual times.
TAMIFLU is not a substitute for a flu vaccination. Patients should continue receiving an annual flu vaccination according to guidelines on immunization practices.
Tamiflu Interactions
Information derived from pharmacology and pharmacokinetic studies of oseltamivir suggests that clinically significant drug interactions are unlikely.
Oseltamivir is extensively converted to oseltamivir carboxylate by esterases, located predominantly in the liver. Drug interactions involving competition for esterases have not been extensively reported in literature. Low protein binding of oseltamivir and oseltamivir carboxylate suggests that the probability of drug displacement interactions is low.
In vitro studies demonstrate that neither oseltamivir nor oseltamivir carboxylate is a good substrate for P450 mixed-function oxidases or for glucuronyl transferases.
Cimetidine, a non-specific inhibitor of cytochrome P450 isoforms and competitor for renal tubular secretion of basic or cationic drugs, has no effect on plasma levels of oseltamivir or oseltamivir carboxylate.
Clinically important drug interactions involving competition for renal tubular secretion are unlikely due to the known safety margin for most of these drugs, the elimination characteristics of oseltamivir carboxylate (glomerular filtration and anionic tubular secretion) and the excretion capacity of these pathways. Coadministration of probenecid results in an approximate twofold increase in exposure to oseltamivir carboxylate due to a decrease in active anionic tubular secretion in the kidney. However, due to the safety margin of oseltamivir carboxylate, no dose adjustments are required when coadministering with probenecid.
Coadministration with amoxicillin does not alter plasma levels of either compound, indicating that competition for the anionic secretion pathway is weak.
In six subjects, multiple doses of oseltamivir did not affect the single-dose pharmacokinetics of acetaminophen.
Tamiflu Contraindications
TAMIFLU is contraindicated in patients with known hypersensitivity to any of the components of the product.
Additional information about Tamiflu
Tamiflu Indication: For the treatment of uncomplicated acute illness due to influenza infection in patients 1 year and older who have been symptomatic for no more than 2 days. Also for the prophylaxis of influenza in adult patients and adolescents 13 years and older.
Mechanism Of Action: Tamiflu is an ethyl ester prodrug requiring ester hydrolysis for conversion to the active form, oseltamivir carboxylate. The proposed mechanism of action of oseltamivir is inhibition of influenza virus neuraminidase with the possibility of alteration of virus particle aggregation and release.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Oseltamivir
Synonyms: Oseltamivir phosphate
Drug Category: Antiviral Agents; Enzyme Inhibitors
Drug Type: Small Molecule; Approved
Other Brand Names containing Oseltamivir: Tamiflu;
Absorption: Readily absorbed from the gastrointestinal tract after oral administration with a bioavailability of 75%.
Toxicity (Overdose): At present, there has been no experience with overdose. Single doses of up to 1000 mg of oseltamivir have been associated with nausea and/or vomiting. Mean LD (intravenous, mouse) = 100 mg/kg.
Protein Binding: Oseltamivir carboxylate: low (3%), Oseltamivir free base: 42%.
Biotransformation: Extensively converted to oseltamivir carboxylate by esterases located predominantly in the liver. Neither oseltamivir nor oseltamivir carboxylate is a substrate for, or inhibitor of, cytochrome P450 isoforms. At least 75% of an oral dose reaches the systemic circulation as oseltamivir carboxylate.
Half Life: 1 to 3 hours in most subjects after oral administration.
Dosage Forms of Tamiflu: Capsule Oral
Powder, for suspension Oral
Powder, for suspension Oral
Capsule Oral
Chemical IUPAC Name: ethyl (3R,4R,5S)-4-acetamido-5-amino-3-pentan-3-yloxycyclohexene-1-carboxylate
Chemical Formula: C16H28N2O4
Oseltamivir on Wikipedia: https://en.wikipedia.org/wiki/Oseltamivir
Organisms Affected: Influenza Virus
