Home Drug Guide Fosamprenavir Calcium

Drug Guide

Generic Name

Fosamprenavir Calcium

Brand Names Lexiva

Classification

Therapeutic: Antiretroviral Agent, Protease Inhibitor

Pharmacological: Protease Inhibitor

FDA Approved Indications

Treatment of HIV-1 infection in combination with other antiretroviral agents

Mechanism of Action

Fosamprenavir is a prodrug of amprenavir; it inhibits the HIV-1 protease enzyme, preventing viral maturation and production of infectious viral particles.

Dosage and Administration

Adult: 600 mg orally twice daily in combination with other antiretrovirals

Pediatric: Not approved for pediatric use

Geriatric: Use with caution; adjust based on tolerability and renal function

Renal Impairment: Use with caution; renal function should be monitored, dose adjustments may be necessary

Hepatic Impairment: Use with caution; consider hepatic function prior to initiation

Pharmacokinetics

Absorption: Improved with food, especially high-fat meals

Distribution: Wide distribution volume; crosses placenta

Metabolism: Primarily via CYP3A4 with some contribution from other CYP enzymes

Excretion: Primarily via feces (as unchanged drug and metabolites), minimal renal excretion

Half Life: Approximately 7-11 hours after administration

Contraindications

Hypersensitivity to Fosamprenavir or amprenavir
Concurrent use with certain medications metabolized by CYP3A4 leading to increased toxicity

Precautions

Use with caution in patients with hepatic impairment, allergic reactions, or with a history of QT prolongation or arrhythmias

Adverse Reactions - Common

Nausea (Common)
Diarrhea (Common)
Headache (Common)

Adverse Reactions - Serious

Allergic reactions (including rash, Stevens-Johnson syndrome) (Rare)
QT prolongation and arrhythmias (Rare)
Hepatotoxicity (Rare)

Drug-Drug Interactions

Rifampin, St. John’s Wort (reduces efficacy)
Drugs that are CYP3A4 substrates, inhibitors, or inducers

Drug-Food Interactions

High-fat meals increase absorption but should not be relied upon to alter effect significantly

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for signs of hypersensitivity, rash, hepatotoxicity, and cardiac effects; review concomitant medications for interactions

Diagnoses:

Risk for toxicity related to drug interactions or hepatic impairment

Implementation: Administer with food, assess liver function tests regularly, monitor for adverse effects

Evaluation: Assess viral load and CD4 counts to monitor efficacy; observe for adverse reactions

Patient/Family Teaching

Take medication with food to enhance absorption
Do not alter dose or discontinue without medical advice
Report signs of allergic reactions or severe side effects promptly
Maintain regular follow-up appointments for monitoring

Special Considerations

Black Box Warnings:

Potential for hepatotoxicity and severe skin reactions

Genetic Factors: None specific

Lab Test Interference: May interfere with laboratory tests for cholesterol and lipid levels

Overdose Management

Signs/Symptoms: Nausea, vomiting, dizziness, abdominal pain

Treatment: Supportive care; gastric lavage may be considered; no specific antidote

Storage and Handling

Storage: Store at room temperature, 20-25°C (68-77°F); protect from moisture and light

Stability: Stable for the duration of the indicated shelf life when stored properly