K K Jain MD (Dr. Jain is a consultant in neurology and has no relevant financial relationships to disclose.)
Originally released February 23, 1999; last updated January 23, 2020; expires January 23, 2023

This article includes discussion of fosphenytoin, FOS, Cerebyx (old proprietary name), and Prodilantin (old proprietary name). The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Historical note and terminology

Fosphenytoin sodium is a water-soluble prodrug intended for parenteral administration. Its active metabolite is phenytoin. Unlike phenytoin, fosphenytoin does not require propylene glycol and high alkalinity to bring it into solution. Fosphenytoin is rapidly and completely absorbed after intramuscular or intravenous administration. Intravenous fosphenytoin produces fewer local side effects than intravenous phenytoin and has not been associated with serious cardiovascular adverse events. Therefore, it is a useful replacement for parenteral phenytoin. Fosphenytoin was approved by the United States Food and Drug Administration in 1996.

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