Nurses Compass
Drug Guide
Fostemsavir Tromethamine
Classification
Therapeutic: Antiretroviral agent for HIV-1 infection
Pharmacological: Entry inhibitor (gp120 binding inhibitor)
FDA Approved Indications
- Treatment of HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant HIV-1 infection failing their current antiretroviral regimen
Mechanism of Action
Fostemsavir is a prodrug that is converted into the active moiety, temsavir, which binds directly to the gp120 subunit of the HIV-1 envelope glycoprotein. This prevents the virus from attaching and entering CD4+ T cells, thereby inhibiting viral entry.
Dosage and Administration
Adult: 600 mg twice daily taken with food
Pediatric: Not established
Geriatric: No specific dose adjustment provided, use with caution
Renal Impairment: No specific dose adjustment recommended, but monitor closely
Hepatic Impairment: No specific dose adjustment provided, use with caution
Pharmacokinetics
Absorption: Rapidly absorbed, food increases absorption
Distribution: Wide distribution, binds to plasma proteins
Metabolism: Primarily hepatic via CYP3A enzymes
Excretion: Primarily fecal and urinary pathways
Half Life: Approximately 7 hours
Contraindications
- Known hypersensitivity to fostemsavir or any component of the formulation
Precautions
- Use with caution in patients with hepatic impairment, monitor for signs of hepatic toxicity
- Potential for drug interactions, especially with CYP3A inducers or inhibitors
Adverse Reactions - Common
- Nausea (≥10%)
- Headache (≥10%)
- Fatigue (≥10%)
Adverse Reactions - Serious
- Liver enzyme elevations (Less common)
- Hypersensitivity reactions (Rare)
- Drug interactions leading to virologic failure (Serious but less common)
Drug-Drug Interactions
- CYP3A inducers (e.g., rifampin, carbamazepine) decrease fostemsavir levels
- CYP3A inhibitors (e.g., ketoconazole, clarithromycin) increase levels
Drug-Food Interactions
- No significant interactions reported
Drug-Herb Interactions
- No formal data, caution advised when combining with herbal supplements
Nursing Implications
Assessment: Monitor for adverse effects, hepatic function, and potential drug interactions
Diagnoses:
- Risk for infection due to HIV
- Potential for drug interactions
Implementation: Administer with food, educate patient on importance of adherence and monitoring for adverse effects
Evaluation: Assess virologic response, adverse reactions, and liver function tests periodically
Patient/Family Teaching
- Take medication with food as directed
- Report any signs of allergic reactions or severe side effects immediately
- Maintain regular follow-up appointments for lab monitoring
- Use contraception if applicable, as directed by provider
Special Considerations
Black Box Warnings:
- No black box warnings at this time
Genetic Factors: No specific genetic considerations identified
Lab Test Interference: May affect hepatic function tests and viral load assessments
Overdose Management
Signs/Symptoms: Potential for gastrointestinal symptoms, hypersensitivity reactions, or other adverse effects
Treatment: Supportive care, monitor vitals, and provide symptomatic management; no specific antidote
Storage and Handling
Storage: Store at room temperature, 20°C to 25°C (68°F to 77°F)
Stability: Stable for at least 24 months when stored properly