Thursday October 22, 2009

Q: What's the basic difference between Phenytoin and Fosphenytoin?

Answer:

Phenytoin (Dilantin) is not water soluble, and must be solubilized in propylene glycol carrier with pH 12 to prepare IV form; therefore, cannot be given more than 50 mg/min without risk of significant hypotension and cardiac arrhythmias. Also major risk of potential irritation at IV site and vascular compromise of infused limb.

Fosphenytoin (Cerebyx) is a phosphorylated phenytoin prodrug. Highly water-soluble and therefore easier to administer than phenytoin. Enzymatically converted to phenytoin after mean 8 min and therefore can be administered more rapidly than standard phenytoin.