Drug products: Pro-Epanutin®
ATC code: N03AB05
Substances: fosphenytoin, fosphenytoin sodium
Fosphenytoin is a pro-drug of phenytoin and the anticonvulsant effect can thus be attriubuted to phenytoin.
Physiologic changes during pregnancy may alter plasma concentration of fosphenytoin and an increase of seizure frequency may occur in pregnant women.
Fosphenytoin can affect the metabolism of oral contraceptives and additional contraception should be used.
According to the original manufacturer, sex has no significant impact on fosphenytoin pharmacokinetics [1, 2]. One study investigated the effects of age and sex on phenytoin pharmacokinetics using isotopes of phenytoin or fosphenytoin administrated IV or IM while patients remained on their oral maintenance regimen. Adult and elderly patients (39 men, 24 women) were given a single injection of 100 mg phenytoin or fosphenytoin, and serial blood samples were collected up to 196 hours after the dose. There was no difference between men and women in phenytoin clearance, distribution volume or elimination half-life . Phenytoin pharmacokinetics is altered during pregnancy and an increase of seizure frequency may occur in pregnant women. For appropriate dose adjustment in pregnant women, periodic measurement of plasma phenytoin concentrations may be valuable .
Fosphenyotin is a prodrug of phenytoin and accordingly, its anticonvulsant effects are attributable to phenytoin .
No studies with a clinically relevant sex analysis regarding adverse effects of fosphenytoin have been found.
Fosphenytoin may affect the metabolism of estrogens and progestogens. Thus, the effect of these can be reduced. Additional contraceptive method should be used . Swedish users, please consult Janusmed Interactions(Janusmed interaktioner).
Swedish users, please consult Janusmed Drugs and Birth Defects(Janusmed fosterpåverkan).
Date of litterature search: 2013-03-11
Reviewed by: Expertrådet för neurologiska sjukdomar, Ellen Vinge
Approved by: Mia von Euler