fostemsavir tromethamine: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
fostemsavir tromethamine: clinical details
Prescribing considerations
- Restrict use to experienced HIV clinicians.
- Confirm HIV-1 Group M infection and consider viral subtype and susceptibility; activity is reduced against CRF01_AE and absent against HIV-2 and HIV-1 Groups O and N.
- Review prescribed, non-prescribed and herbal products for strong CYP3A induction, transporter interactions and QT risk.
- Consider cardiac history and concurrent medicines associated with torsade de pointes.
Contraindications and cautions
- Hypersensitivity to fostemsavir tromethamine or an excipient.
- Concomitant strong CYP3A inducers, including rifampicin, carbamazepine, phenytoin, mitotane, enzalutamide and St John’s wort.
Monitoring
- HIV-1 RNA, clinical response, adherence and virological failure
- New infection or inflammatory symptoms associated with immune reconstitution
- Liver chemistry, particularly with hepatitis B or C coinfection
- Renal, hepatic and muscle laboratory markers when clinically indicated
- ECG or cardiac assessment when QT-prolongation risk is relevant
Clinical pharmacology
Fostemsavir is hydrolysed at the intestinal surface to temsavir. Temsavir binds envelope gp120 and blocks CD4-receptor engagement. It is metabolised mainly through esterase hydrolysis and secondarily through CYP3A4.
Formulation and product differences
- The UK product is a prolonged-release oral tablet.
- The tablet must be swallowed whole and not chewed, crushed or split.
fostemsavir tromethamine preparations and strengths
Modified-release tablet
Route: Oral
Strengths: 600 mg
fostemsavir tromethamine interactions
A full review of medicines and herbal products is essential because interactions may reduce HIV control or increase adverse effects.
Strong CYP3A inducers, including rifampicin, carbamazepine, phenytoin, mitotane, enzalutamide and St John’s wort
Contraindicated because they can substantially reduce temsavir exposure and cause loss of virological response.
Elbasvir with grazoprevir
Not recommended because grazoprevir exposure may rise, increasing the risk of raised liver enzymes.
Atorvastatin, rosuvastatin, simvastatin, pitavastatin and fluvastatin
Exposure may increase, requiring careful selection, titration and adverse-effect monitoring.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.