Phenytoin plasma levels after intraoperative administration, for the prevention of post-craniotomy seizures
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Summary
Since in a previous study (preliminary report) (18) the iv. administration of 15 mg × kg−1 of phenytoin (PNT) over 30 min in men produced toxic levels (25μg/ml), a smallerr iv. dose of 7 mg×kg−1 was given during anaesthesia to 80 patients under going craniotomy, for the prevention of post-operative seizures.
Plasma PNT concentrations were studied in 22 patients before its iv. infusion 20min, 40min, and 1, 2, 3, 5, 8 and 12 hours later.
Mean serum phenytoin levels were 9.3,31.9,27.8,25.5,19.4,17.2, 15.4 and 19.2* μg/ml respectively.
In this study it appeared that although the initial dose was 50% smaller than before, toxic levels were still encountered one hour after PNT administration (therapeutic range 10–25 μg/ml). Bearing in mind that in both our studies PNT appeared to have approximately the same efficacy in seizure prevention (from 95–97%), we suggest, that 7–10mg × kg−1 would be adequate if administered as an intraoperative iv. infusion over an hour and that whenever possible serial serum levels should be monitored.
Keywords
phenytoin craniotomy post-operative seizuresPreview
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