Fosphenytoin. Pharmacoeconomic implications of therapy.

Advantages and disadvantages of Fosphenytoin. Advantages. More rapid intravenous administration than phenytoin and no need for an in-line filter. May be administered by intramuscular injection. Lower potential for local tissue and cardiac toxicity than phenytoin. Associated with less pain and phlebitis at the injection site, fewer reductions in infusion rate and fewer changes of administration site because of injection site complications than phenytoin. Benefits in terms of ease of administration and improved tolerability vs phenytoin have pharmacoeconomic implications which may translate into an overall cost advantage. Disadvantages. Approximately 10-fold higher acquisition cost vs phenytoin. Fosphenytoin is a parenterally administered prodrug of phenytoin, used in the treatment of patients with seizures. Advantages of fosphenytoin over phenytoin include more rapid intravenous administration, no need for an intravenous filter, and a lower potential for local tissue and cardiac toxicity. Unlike phenytoin, fosphenytoin may also be administered by intramuscular injection. Pharmacoeconomic data from a small study of patients with acute seizures in a US emergency department showed an overall cost advantage of fosphenytoin over phenytoin, despite a considerably greater acquisition cost of fosphenytoin. The main cost drivers for phenytoin therapy were treatment costs associated with adverse events. In view of the limited pharmacoeconomic data currently available, it is in the interests of individual institutions to conduct their own formal pharmacoeconomic studies applying local cost data and patterns of clinical practise to determine whether fosphenytoin should replace phenytoin on their formularly list.