Fostemsavir is an HIV-1 gp120-directed attachment inhibitor. It is indicated for use in adult patients with multiply drug-resistant HIV-1 infection, in combination with other antiretroviral agents.

How to Use Fostemsavir

Dosage and Administration Frequency

The recommended dose of Fostemsavir is 600 mg (1 tablet) taken orally twice daily. It can be administered with or without food.

The tablet must be swallowed whole; chewing, crushing, or splitting it is not allowed, as this would destroy the sustained-release structure and affect the drug's efficacy.

Medication Timing and Adherence

It is recommended to take the medication at fixed times (e.g., once in the morning and once in the evening) to maintain a stable plasma drug concentration.

If a dose is missed, it should be taken as soon as possible. However, doubling the dose to make up for the missed one is not permitted.

Requirements for Combined Medication Use

Fostemsavir must be used in combination with other active antiretroviral agents to optimize therapeutic efficacy and reduce the risk of drug resistance.

Commonly used clinical combinations include Dolutegravir or Darunavir, among others.

Dosage Adjustment of Fostemsavir

Situations Not Requiring Dosage Adjustment

Renal impairment: No dosage adjustment is needed for patients with mild to severe renal impairment or those undergoing hemodialysis.

Hepatic impairment: Patients with Child-Pugh Class A, B, or C hepatic impairment should use the conventional dose.

Absolute Contraindications

It is contraindicated in patients with a known hypersensitivity to Fostemsavir or any of its components.

Concomitant use with strong CYP3A inducers (such as Rifampicin, Carbamazepine, St. John's Wort, etc.) is prohibited. This is because such combinations can significantly reduce the plasma concentration of the active ingredient temsavir, leading to treatment failure.

Drugs Requiring Cautious Concomitant Use

QT interval-prolonging drugs: High doses of Fostemsavir (2400 mg per dose) may prolong the QT interval. When used concomitantly with other arrhythmogenic drugs, close monitoring of the electrocardiogram (ECG) is necessary.

Statins: Treatment with statins should be initiated at the lowest dose, and monitoring for muscle toxicity is required (for example, the exposure to Rosuvastatin may increase by 69%).

Fostemsavir Use in Special Populations

Pregnancy and Lactation

Pregnancy: Available animal studies have not shown teratogenicity, but data in humans are limited. It is recommended to use the Antiretroviral Pregnancy Registry (APR) to monitor fetal outcomes.

Lactation: HIV-1-infected patients should avoid breastfeeding to prevent virus transmission.

Patients with Concurrent Hepatitis Virus Infection

Patients coinfected with HBV (hepatitis B virus) or HCV (hepatitis C virus) may experience elevated liver enzymes. Regular monitoring of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) is required.

Discontinuation of anti-hepatitis B drugs may lead to HBV reactivation; therefore, effective anti-HBV treatment should be maintained.

Pediatrics and Adolescents

The efficacy of Fostemsavir in patients under 18 years of age has not been established, and its use is not recommended for this population at this time.