Reassessing the lower end of the phenytoin therapeutic range: a review of the literature.
OBJECTIVE
To critically review available data on the effective lower end of the phenytoin therapeutic range for the treatment of seizure disorders.


METHODS
Relevant articles were identified from an English-language search of MEDLINE 1982-1992. Additional references were found in bibliographies of these articles.


METHODS
We reviewed articles that included data on serum phenytoin concentrations (SPCs) and seizure control. Data on concurrent anticonvulsants, seizure diagnosis, and seizure severity were extracted when available.


RESULTS
The original study defining the phenytoin therapeutic range as 10-20 mg/L is analyzed; it was based on a small, homogeneous sample that cannot be generalized to a more diverse epileptic population. Many studies report patients obtaining seizure control with SPCs below 10 mg/L. Studies including a range of seizure diagnoses and severity have a larger variability in effective SPCs; however, effective SPCs are reproducible.


CONCLUSIONS
The therapeutic range of phenytoin is defined on an individual basis. Some patients, especially those with infrequent, primary tonic-clonic seizures, may be controlled with phenytoin concentrations below the recognized reference range of 10-20 mg/L.
Hayes
G
G
Atascadero State Hospital, CA.
Kootsikas
M E
ME
D000927:Anticonvulsants / Q000627:therapeutic use; D002986:Clinical Trials as Topic; D006801:Humans; D010672:Phenytoin / Q000097:blood / Q000627:therapeutic use*; D012640:Seizures / Q000188:drug therapy*
D000927:Anticonvulsants; D010672:Phenytoin