Fostemsavir is an HIV-1 gp120-directed attachment inhibitor, indicated for the treatment of adult patients with HIV-1 infection that is resistant to multiple drugs.

How to Use Fostemsavir

Administration Regimen

Dosage: 600 mg (1 tablet) each time, taken orally twice a day.

Administration Method: Swallow the tablet whole; do not chew, crush, or split it.

Effect of Food: It can be taken with food or on an empty stomach. However, a high-fat meal may increase drug absorption (AUC increases by approximately 81%), so it is recommended to maintain consistency in medication administration to avoid fluctuations in blood drug concentration.

Precautions for Fostemsavir Dosage Adjustment

Contraindicated Conditions

It is contraindicated in patients allergic to fostemsavir or any of its components.

Concurrent use with potent CYP3A inducers (such as rifampicin, carbamazepine, St. John's wort, etc.) is prohibited, as these drugs can significantly reduce the blood concentration of temsavir (the active metabolite), leading to treatment failure.

Drugs Requiring Cautious Concurrent Use

Drugs that Prolong QT Interval: Fostemsavir may prolong the QT interval at supratherapeutic doses (2400 mg). When used concurrently with other drugs that cause QT prolongation, close monitoring of the electrocardiogram (ECG) is required.

Statins: Dosage adjustment of statins (such as rosuvastatin, atorvastatin) may be necessary to avoid adverse reactions.

Oral Contraceptives: The daily dose of contraceptives containing ethinyl estradiol should not exceed 30 mcg to reduce the risk of thrombosis.

Fostemsavir Use in Special Populations

Patients with Hepatic or Renal Impairment

Hepatic Impairment: No dosage adjustment is required for mild to severe hepatic impairment (Child-Pugh Class A/B/C), but monitoring of transaminases is necessary (especially in patients with concurrent hepatitis B or C infection).

Renal Impairment: No dosage adjustment is required for patients with renal impairment, including those with end-stage renal disease undergoing hemodialysis. Hemodialysis only removes approximately 12.3% of the drug.

Pregnancy and Lactation

Pregnancy: Available animal data do not show teratogenicity, but human data are limited.

Lactation: HIV-infected patients should avoid breastfeeding to prevent virus transmission and potential adverse effects of the drug on infants.

Elderly Patients

Elderly patients (aged ≥ 65 years) may be more prone to QT prolongation due to comorbidities or drug interactions, so individualized assessment is required.

Pediatric and Adolescent Patients

The efficacy of fostemsavir in patients under 18 years of age has not been established, and its use is not recommended.