Single dose comparison of the relative bioavailability of phenytoin suspension and extended capsules.
There is presently only one preparation of phenytoin approved for once-daily dosing--extended phenytoin sodium capsules. We have observed many hospitalized patients switched from either this preparation or the intravenous form of phenytoin to phenytoin oral suspension. The bioavailability and single dose pharmacokinetics of extended phenytoin sodium capsules (Dilantin Kapseals) and phenytoin oral suspension (Dilantin oral suspension) were compared in seven healthy adult volunteers. Each subject was administered both three 100-mg Dilantin Kapseals (276 mg free acid) and 11 ml (275 mg) Dilantin-125 oral suspension in a randomized cross-over design with a 1-week washout period between preparations. Blood samples were drawn over 78 h after the administration of each preparation for determination of serum phenytoin concentration. In addition, total urinary output was collected for 48 h. Statistical analysis consisted of a comparison of the area under the curve (AUC) from time zero to 48 h and time-to-peak concentration using a two-tailed paired t test at a level of significance of p less than 0.05. The total alpha level was 0.10. No significant differences were found between the two preparations. The power of detecting a 15% difference in AUC was 0.80, and the power of detecting a 5-h difference in time to peak was 0.52. Following is a summarization of the pharmacokinetic parameters (capsules mean +/- 1 SD; suspension mean +/- 1 SD).(ABSTRACT TRUNCATED AT 250 WORDS)
D000328:Adult; D001682:Biological Availability; D002214:Capsules; D005260:Female; D006801:Humans; D008297:Male; D010672:Phenytoin / Q000008:administration & dosage / Q000378:metabolism* / Q000627:therapeutic use; D013535:Suspensions
D002214:Capsules; D013535:Suspensions; D010672:Phenytoin