Fostemsavir is an attachment inhibitor used in adult patients with multidrug-resistant HIV-1 infection and must be used in combination with other antiretroviral drugs. Its dosing method, management of missed doses, and special dosage adjustments directly affect efficacy and safety. The following explains this from three aspects.

I. Dosing Method: Twice Daily, With or Without Food

1.Standard Dosing Frequency

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

Fixing morning and evening doses helps establish a routine and reduce missed doses.

2.With or Without Food

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

If gastrointestinal discomfort occurs, it may be taken with food to relieve symptoms.

3.Swallow Whole

Tablets should be swallowed whole and must not be chewed, crushed, or split, to avoid affecting release and absorption.

II. Management of Missed Doses

1.Take as Soon as Remembered

If a dose is missed, it should be taken as soon as remembered.

After taking the missed dose, continue the next dose as originally scheduled; the dose does not need to be doubled.

2.When the Next Dose Is Near

If the next dose is almost due, skip the missed dose and take the next dose at the original time.

Do not take two tablets at once to make up for a missed dose.

3.Avoid Repeated Missed Doses

Repeated missed doses can cause fluctuations in plasma concentrations and increase the risk of resistance.

Using reminder tools or linking dosing to daily activities is recommended.

III. Dosage Adjustment and Precautions

1.Hepatic and Renal Function and Dosage

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

Use with caution in patients with severe hepatic impairment, and the risks and benefits should be assessed.

2.Adjustments Related to Drug Interactions

Concomitant use of Fostemsavir with strong CYP3A inducers can significantly reduce its exposure and should be avoided.

When used with certain antiretroviral drugs or metabolic enzyme inhibitors, whether to adjust the regimen should be evaluated according to the prescribing information.

3.Special Populations

Use during pregnancy and lactation should weigh the benefits and risks, and a specialist should be consulted.

Safety and effectiveness in children have not been fully established, and individualized dosing should follow body weight and guidelines.

4.Adherence and Monitoring

Maintaining regular twice-daily dosing is key to sustaining viral suppression.

Viral load and immune indicators should be monitored regularly during treatment, and medical attention should be sought promptly if persistent missed doses or adverse reactions occur.