Fostemsavir is an HIV-1 attachment inhibitor used in adult patients with multidrug-resistant HIV-1 infection and must be used in combination with other antiretroviral drugs. The following briefly describes it from three aspects: dosage and administration, efficacy, and precautions.

I. Dosage and Administration

1.Standard Dose

The recommended dose is one tablet twice daily, at an interval of approximately 12 hours.

It may be taken with food or on an empty stomach; food does not affect its overall exposure.

2.Method of Administration

Tablets should be swallowed whole and must not be chewed, crushed, or split.

Fixing morning and evening dosing times is recommended to reduce missed doses.

3.Management of Missed Doses

Take it as soon as remembered; if the next dose is almost due, skip the missed dose and do not double the dose.

4.Dosage Adjustment

Dosage adjustment is generally not required for mild to moderate hepatic or renal impairment.

It is contraindicated in patients with severe hepatic impairment (Child-Pugh Class C).

II. Efficacy

1.Mechanism of Action

Fostemsavir is a prodrug that is metabolized to its active component, which binds to HIV-1 gp120 and blocks viral attachment to host CD4 cells.

It retains activity against multidrug-resistant HIV-1 strains, offering a new option for treatment-experienced patients.

2.Clinical Effects

Combined with background antiretroviral therapy, it can significantly reduce viral load and increase CD4 cell counts.

It is suitable for adult patients with prior failure of multiple treatment lines and severe resistance.

3.Ensuring Efficacy

Efficacy depends on regular dosing and an effective combination regimen; missed doses can lead to viral rebound and resistance.

III. Precautions

1.Contraindications and Interactions

Concomitant use with strong CYP3A4 inducers (such as rifampin, carbamazepine, phenytoin, and St. John's wort) is prohibited to avoid decreased plasma concentrations and loss of efficacy.

It is contraindicated in patients with severe hepatic impairment.

2.Hepatic Function Monitoring

Hepatic function monitoring should be strengthened in patients with mild to moderate hepatic impairment, and elevated transaminases or jaundice should be evaluated promptly.

3.Special Populations

Use during pregnancy and lactation should weigh the benefits and risks; it is not recommended during lactation.

Safety and effectiveness in children have not been fully established, and individualized dosing is required.

4.Adherence

Regular twice-daily dosing is key to maintaining viral suppression; repeated missed doses increase the risk of resistance.

Viral load and immune indicators should be monitored regularly during treatment.