Journal article

Plasma concentrations of unbound phenytoin in the management of epilepsy.

CJ Kilpatrick, S Wanwimolruk, LM Wing

Br J Clin Pharmacol | Published : 1984


In 46 epileptic patients the range of the unbound fraction of phenytoin in plasma measured by ultrafiltration (at 37 degrees C) and tracer-labelling with [14C]-phenytoin was 6.7%-33.3% with a median of 11.9%. The total and unbound phenytoin plasma concentrations were significantly correlated (r = 0.93, P less than 0.001), but in six patients the unbound concentration fell on or outside the 90% predictability limits for a single value. In all patients the unbound concentration reflected the clinical status of the patient equally or better than the total concentration. An inverse relationship was found between the plasma albumin concentration (within the normal reference range) and the phenyto..

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