Hyzaar and Phenytek

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.

Ask your doctor before using phenytoin together with losartan. Using these medications together may cause losartan to be less effective. You may need a dose adjustment or your blood pressure checked more often if you take 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: Coadministration with phenytoin may decrease the plasma concentrations of the active metabolite of losartan, known as E3174. In 16 healthy volunteers administered phenytoin (4 mg/kg/day, up to 400 mg/day) and losartan (50 mg once a day) for 10 days, the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of E3174 were reduced by over 60% compared to when losartan was administered alone. In the 14 patients with wild-type CYP450 2C9, the mean losartan AUC was increased by 29% and oral clearance reduced by 29%. In contrast, 2 patients with a variant allele for the isoenzyme demonstrated a 30% reduction in losartan AUC and a 47% increase in its oral clearance. Based on these data, the investigators propose that phenytoin may affect non-2C9 pathways for losartan in individuals with wild-type CYP450 2C9 (approximately 65% of Caucasians and over 95% of Africans and Asians) but may induce clearance of losartan and E3174 in individuals with the variant allele. Losartan did not affect the pharmacokinetics of phenytoin.

MANAGEMENT: Because E3174 is responsible for most of the therapeutic effects of losartan, significant reduction in its concentration in the circulation could affect overall clinical efficacy of the drug, although that has not been tested. Until further data are available, pharmacologic response to losartan should be monitored more closely following initiation, discontinuation, or change of dosage of phenytoin.

Hyzaar

Generic Name: hydrochlorothiazide / losartan

Brand name: Hyzaar

Synonyms: n.a.

What is Hyzaar?

Phenytek

Generic Name: phenytoin

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

Synonyms: n.a.

What is Phenytek?