Fostemsavir is a novel antiretroviral drug for the treatment of HIV-1 infection, indicated for adult patients with multiply drug-resistant HIV-1 who have experienced treatment failure.

Precautions for Fostemsavir Administration

Indications and Contraindications

Indications: Reserved exclusively for adult patients with multiply drug-resistant HIV-1 infection, and must be used in combination with other antiretroviral drugs.

Absolute contraindications: Patients with a known allergy to fostemsavir or any component of its formulation.

Prohibited concurrent use: Concomitant use with strong CYP3A inducers (e.g., rifampicin, carbamazepine, St. John’s wort, etc.) is strictly forbidden. Such combinations can significantly reduce the plasma concentration of temsavir (the active metabolite of fostemsavir), leading to treatment failure.

Dosage and Administration

Fixed dosage: 600 mg per dose, twice daily. The tablets must be swallowed whole (chewing or splitting is not allowed).

Effect of food: A high-fat meal may increase absorption, while a standard meal has no significant impact. It is recommended to take the medication at regular, consistent times.

Administration in Special Populations

Hepatic or renal impairment: No dose adjustment is required for patients with mild to severe hepatic or renal impairment. Patients with end-stage renal disease do not need a supplementary dose after dialysis.

Pregnancy and lactation: Data on use during pregnancy are limited. The potential benefits and risks must be carefully weighed, and patients should be enrolled in the Antiretroviral Pregnancy Registry (APR).

Lactation: Use during lactation is contraindicated to avoid mother-to-child transmission of HIV and potential risks to the infant.

Drug Interactions

Drugs requiring cautious concurrent use:

Drugs that prolong the QT interval (e.g., certain antiarrhythmic agents): May increase the risk of torsades de pointes (a life-threatening ventricular tachycardia).

Statins (e.g., rosuvastatin): Should be initiated at the lowest dose, and symptoms of myopathy should be monitored closely.

Estrogen-containing contraceptives: The daily estrogen dose must be ≤ 30 μg to prevent the risk of thrombosis.

Fostemsavir Monitoring During Administration

Efficacy Monitoring

Viral load and CD4 cell count: Measure at baseline and regularly after the start of treatment to evaluate the antiviral effect.

Resistance testing: Conduct genotypic resistance testing promptly if treatment failure occurs.

Cardiac Monitoring

Electrocardiogram (ECG): Perform at baseline and regularly during treatment to assess the QT interval, especially when the drug is used concomitantly with other QT-prolonging medications.

Symptom observation: Seek immediate medical attention if symptoms such as palpitations or syncope occur.