Psillakis T.^*, Tsatsakis A.M.^*, Daskalakis G.^**, Kalpaxidu E.^**, Petrutsu S.^**, Cliafas G.^**, Stefis A.^**

^* Toxicology Laboratory, Medical School, University of Crete, Stavrakia, Iraklion, PO Box 1393, 71409 Crete, Greece
^** General Hospital of Rhodes, Erythrou Sravrou 5, 85100 Rhodes, Greece

The aim of the study was to determine whether or not phenytoin is incorporated into the hair of patients under long term treatment in measurable amounts and whether this incorporation depends on the dosage. Such information would be valuable to physicians in order to evaluate past medical history and for various other purposes.
Methods. Several procedures including liquid-liquid extractions after hair dissolution were studied in order to determine the optimal sample preparation prior to immunoassay analysis performed in Abbott TDx instrument. The linear regression equation and the percent recovery in recovery experiments are given. The scalp hair samples were cut in two or three segments, 2 cm length each, from hair root.
Results. Phenytoin levels in the segments of scalp hair of fourteen patients (eight male and six female), aged from fourteen to seventy seven years old were ranging: a) 1^st: 2.86 to 40.47 µg/g (mean 14.53 µg/g), b) 2^nd: 3.28 to 35.47 µg/g (mean 13.80 µg/g) and c) 3^rd: 3.24 to 27.08 µg/g (mean 17.56 µg/g) The phenytoin blood concentration was ranging from 0.21 to 15.57 µg/ml (mean 5.77 µg/ml). Generally, the experiments showed reduction of drug concentrations from the 1^st to the other segments. This is due to the drug degradation to its metabolites over time or to the drug extraction from the hair by washing with hair cosmetics.
Conclusions. The levels were found to be dependent on the dosage of the drug. Higher levels of phenytoin were monitored when increased doses of drug were administered to the patients. The levels were found to be dependent on the patients' colour hair too, but didn't depend on drug blood concentrations.