oseltamivir phosphate

oseltamivir phosphate

Tamiflu

Pharmacologic class: Viral neuro-aminidase inhibitor

Therapeutic class: Antiviral

Pregnancy risk category C

Action

Inhibits influenza virus neuraminidase, altering viral particle aggregation and decreasing viral release from infected cells

Availability

Capsules: 30 mg, 45 mg, 75 mg

Powder for oral suspension: 12 mg/ml

Indications and dosages

➣ To prevent influenza type A

Adults and children older than age 13: 75 mg P.O. daily for 10 days, starting within 2 days of exposure; 75 mg P.O. daily during community outbreak of influenza for up to 6 weeks

Children ages 1 and older weighing more than 40 kg (88 lb): 75 mg P.O. daily for 10 days, starting within 2 days of exposure; continue dosing during community outbreak of influenza for up to 6 weeks

Children ages 1 and older weighing more than 23 kg up to 40 kg (more than 51 lb up to 88 lb): 60 mg P.O. daily for 10 days, starting within 2 days of exposure; continue dosing during community outbreak of influenza for up to 6 weeks

Children ages 1 and older weighing more than 15 kg up to 23 kg (33 lb up to 51 lb): 45 mg P.O. daily for 10 days, starting within 2 days of exposure; continue dosing during community outbreak of influenza for up to 6 weeks

Children ages 1 and older weighing 15 kg (33 lb) or less: 30 mg P.O. daily for 10 days, starting within 2 days of exposure; continue dosing during community outbreak of influenza for up to 6 weeks

➣ Treatment of influenza type A

Adults and children older than age 13: 75 mg P.O. b.i.d. for 5 days, starting within 2 days of symptom onset

Children ages 1 and older who weigh more than 40 kg (88 lb): 75 mg P.O. b.i.d. for 5 days, starting within 2 days of symptom onset

Children ages 1 and older who weigh more than 23 kg and up to 40 kg (51 to 88 lb): 60 mg P.O. b.i.d. for 5 days, starting within 2 days of symptom onset

Children ages 1 year and older who weigh more than 15 kg and up to 23 kg (33 to 51 lb): 45 mg P.O. b.i.d. for 5 days, starting within 2 days of symptom onset

Children ages 1 and older who weigh less than 15 kg (33 lb): 30 mg P.O. b.i.d. for 5 days, starting within 2 days of symptom onset

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug or its components

Precautions

Use cautiously in:

• chronic cardiac or renal disease, respiratory disorders

• elderly patients

• pregnant or breastfeeding patients

• children younger than age 1 (safety and efficacy not established).

Administration

• For flu treatment, give first dose at onset of symptoms. For flu prevention, give within 2 days of exposure.

Adverse reactions

CNS: headache, dizziness, fatigue, insomnia, unusual behavior, confusion

GI: nausea, vomiting, diarrhea

Respiratory: cough, bronchitis

Skin: epidermal necrolysis, erythema multiforme, Stevens-Johnson syndrome

Other: hypersensitivity reactions (including anaphylaxis)

Interactions

None significant

Patient monitoring

☞ Monitor patient closely for allergic reaction or severe rash; discontinue drug immediately if these occur.

• Closely monitor patient for unusual behavior or confusion.

• Monitor respiratory status. Watch for signs and symptoms of secondary infection.

Patient teaching

• Instruct patient to take as soon as flu symptoms occur and to complete entire course of therapy.

• Advise patient to take with food or milk to minimize GI irritation.

• Tell patient to prepare oral solution by adding water to powder and shaking well.

☞ Instruct patient or caregiver to discontinue drug and seek immediate medical attention if rash or swelling of lips, face, or throat occurs

• Instruct patient or caregiver to report change in behavior.

• Caution patient not to share drug with others, even if they have similar symptoms.

• Instruct patient to consult prescriber before taking other drugs.

• As appropriate, review all other significant adverse reactions.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved

oseltamivir phosphate

A prodrug of oseltamivir carboxylate, an inhibitor of neuraminidase enzymes on the surface of influenza viruses. These enzymes are essential for the release of the viruses from infected cells and thus the proliferation throughout the body. The drug is used to treat and prevent influenza A and B. A brand name is Tamiflu. Resistance to this drug from mutations of the neuraminidase gene was reported in 2003.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005