Analysis of hair for drugs has been increasingly utilized, and being progressively admitted by the courts to support evidences in forensic and drug related cases. The present study was designed to determine the time course of carbamazepine in hair and serum of rats after a single administration of different doses, to find the correlation between the dose and levels of the drug in hair and serum and to evaluate the relationship between serum and hair levels of carbamazepine in rats to be applied clinically later on .To determine the time course of carbamazepine in hair, sixty rats were divided into three equal groups. Each rat in the first, second and third groups were orally given a single dose of carbamazepine equals to one, five and ten times the therapeutic dose respectively. Hair and serum samples were analyzed by high performance liquid chromatography before and at 1, 2, 3, 4, 5, 6, 9, 12, 24 hours and daily for 15 days after carbamazepine administration. In the first group, carbamazepine could be detected in hair after four hours of its administration, reached maximum after nine hours, and then gradually declined. The drug could not be detected after 5 days of administration. The same course in the second group, but with higher concentration than the first group. It could not be detected after eight days. In the third group, the drug could be detected in hair after one hour of its administration, reached maximum after four hours, and then gradually decreased until it could not be detected after eight days of administration. The results showed that time course was affected by the dose and there was a significant correlation between the dose and concentration in hair (r = 0.5, P<0.0004). The drug could be detected in hair at a time when concentrations in other biological specimens (blood and urine) are not detectable.
To evaluate the relationship between serum and hair levels of carbamazepine ,120 albino rats of both sexes were divided into two portions: the first was the treated group (80 rats) , subdivided into four equal groups ( 20 rats each ) were given the therapeutic oral dose of carbamazepine once daily for one, two, three and four months respectively. The second portion was the control group (40 rats) divided into four groups (10 rats each) each group was corresponding to a treated group. The results showed a significant correlation between carbamazepine levels in serum and that in hair in the first, second and fourth groups and a non significant correlation in the third group. The concentration of the drug in serum and hair increased with the time of administration in the first three months and decreased in both of them in the fourth month. It could be concluded that hair analysis is a useful mean for long -term monitoring of carbamazepine.