Dilantin Kapseals and Fosamprenavir

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Using phenytoin together with fosamprenavir may alter the effects of both medications. Contact your doctor if your condition worsens. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

MONITOR: In the absence of ritonavir as a pharmacokinetic booster, coadministration of amprenavir or fosamprenavir with phenytoin may result in decreased plasma concentrations of amprenavir. The proposed mechanism is phenytoin induction of amprenavir metabolism via CYP450 3A4. In contrast, when ritonavir is present, phenytoin levels may be decreased due to induction of CYP450 2C9 metabolism by ritonavir. In a pharmacokinetic study involving 14 subjects, coadministration of phenytoin (300 mg once a day) in combination with fosamprenavir plus ritonavir (700 mg and 100 mg twice a day, respectively) for 10 days resulted in a 20% reduction in phenytoin peak plasma concentration (Cmax), a 22% reduction in systemic exposure (AUC), and a 29% reduction in trough plasma concentration (Cmin). Amprenavir AUC and Cmin increased by approximately 20%.

MANAGEMENT: Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic antiretroviral drug levels, amprenavir and fosamprenavir should be used cautiously with phenytoin if ritonavir is not coadministered as a boosting agent. Antiretroviral response should be monitored more closely whenever phenytoin is added to or withdrawn from therapy, and the antiretroviral regimen adjusted as necessary. However, if ritonavir is also prescribed, the potential for reduced therapeutic effects of phenytoin should be considered. Phenytoin dosage may need to be increased if patient demonstrates subtherapeutic phenytoin levels or experiences loss of seizure control. No change in the dosages of fosamprenavir (or amprenavir) and ritonavir is necessary during coadministration with phenytoin.

Dilantin Kapseals

Generic Name: phenytoin

Brand name: Dilantin, Phenytek, Dilantin Infatabs, Phenytoin Sodium, Prompt

Synonyms: Dilantin

What is Dilantin Kapseals?

Fosamprenavir

Generic Name: fosamprenavir

Brand name: Lexiva, Telzir

Synonyms: n.a.

What is Fosamprenavir?