Fostemsavir is a novel HIV-1 gp120-directed attachment inhibitor and a component of antiretroviral combination therapy. It provides a crucial treatment option for patients who have failed conventional therapies.
Precautions for Fostemsavir Administration
Key Points of Dosage Regimen
Dosage: 600 mg each time, twice daily (approximately 12 hours apart).
Dosage Form: 600 mg extended-release tablets. The tablets must be swallowed whole and should not be chewed, crushed, or split.
Dietary Effects: Fostemsavir can be taken with food or on an empty stomach. However, a high-fat meal increases drug exposure by 81%.
Missed Dose Management: If a dose is missed, take it as soon as you remember. Do not take a double dose to make up for the missed one.
Medication Use in Special Populations
Pregnancy: Currently available data are insufficient. The use of Fostemsavir during pregnancy requires a careful balance of benefits and risks. It is recommended that patients be enrolled in the Antiretroviral Pregnancy Registry.
Lactation: Mothers infected with HIV should not breastfeed to prevent virus transmission to the infant.
Hepatic Impairment: No dosage adjustment is needed for patients with mild to severe hepatic impairment.
Renal Impairment: No dosage adjustment is required for patients with renal impairment, including those undergoing hemodialysis.
Elderly Patients: Elderly patients are more prone to QT interval prolongation, so Fostemsavir should be used with caution in this population.
Concomitant Medications to Avoid
QT Interval-Prolonging Drugs: Concurrent use with drugs known to induce Torsades de Pointes may increase the risk of arrhythmias.
Statins: Concomitant use may increase the exposure of statins such as rosuvastatin and atorvastatin. Treatment with these statins should start at the lowest dose, and adverse reactions should be monitored.
Direct-Acting Antiviral (DAA) Agents for HCV: Concurrent use may increase the concentrations of grazoprevir or voxilaprevir. It is recommended to switch to alternative HCV treatment regimens.
Concomitant Medications Requiring Dosage Adjustment
Oral Contraceptives: The daily dose of ethinyl estradiol in oral contraceptives should not exceed 30 μg. Extra caution is needed, especially for patients with risk factors for thromboembolism.
Methadone/Buprenorphine: Concomitant use may increase the concentrations of these opioids. Adverse reactions related to opioids should be closely monitored.
Monitoring for Fostemsavir Therapy
Basic Monitoring Items
Virologic Response: Measure HIV-1 RNA levels every 4-8 weeks during the initial phase of treatment. Once the condition is stable, monitor every 3-6 months.
Immune Reconstitution Assessment: Regularly monitor changes in CD4+ cell count.
Electrocardiogram (ECG) Monitoring: For patients with risk factors for QT interval prolongation, perform ECGs before starting treatment and at regular intervals during treatment.
Liver Function: Monitor alanine transaminase (ALT) and aspartate transaminase (AST) levels at baseline and regularly during treatment, especially in patients coinfected with hepatitis B virus (HBV) or hepatitis C virus (HCV).
Special Monitoring Scenarios
Immune Reconstitution Inflammatory Syndrome (IRIS): During the initial phase of treatment, be alert to inflammatory reactions associated with latent infections (such as Mycobacterium avium complex [MAC], cytomegalovirus [CMV], Pneumocystis jirovecii pneumonia [PCP], and tuberculosis [TB]).
Hepatitis Reactivation: When anti-HBV treatment is discontinued, enhanced monitoring of liver function is necessary.
Adverse Drug Reactions: Focus on common adverse reactions, including nausea (incidence: 10%), diarrhea (4%), and headache (4%).
