Evaluation of therapeutic drug level monitoring of phenobarbital, phenytoin and carbamazepine in Iranian epileptic patients.

OBJECTIVE

The antiepileptic drugs phenobarbital, phenytoin and carbamazepine are widely used for the treatment of partial and tonic-clonic seizures. Large inter-individual differences in pharmacokinetics of these drugs, and the intermittent nature of epileptic attacks, increase the need for therapeutic drug level monitoring of these drugs.

MATERIAL AND METHODS

In this study, data from the therapeutic drug monitoring of phenobarbital, carbamazepine and phenytoin in 328 epileptic patients were evaluated. Serum levels of drugs were determined in a University Department of Pharmacology by high-performance liquid chromatography.

RESULTS

In this study, approximately 56% of patients were treated with 1; 30% with 2; and 14% with 3 antiepileptic drugs. In patients receiving 1 antiepileptic drug, the percentages treated with phenobarbital, carbamazepine and phenytoin were 41, 38 and 21%, respectively. In patients who received carbamazepine, serum levels in 40% of the patients were in the range of 4-8 microg/ml and more than in the range 4-12 microg/ml in 74% of the patients. In phenobarbital-treated patients, serum levels in 73% of the patients were in therapeutic range of 10-40 microg/ml, and about 44% of phenytoin-treated patients had serum levels in therapeutic range of 10-20 microg/ml. Approximately 50% of carbamazepine- and phenytoin-treated patients and approximately 70% of phenobarbital-treated patients were completely controlled. The frequency of concentrations within the therapeutic ranges decreased in patients using more than 1 antiepileptic drug. In patients who received both phenobarbital and sodium valproate, serum levels of phenobarbital were significantly (p < 0.05) greater than in patients who were taking this drug in combination with carbamazepine or phenytoin.

CONCLUSION

Our results indicate that serum levels of antiepileptic drugs, and the percentage of patients with complete seizure control are comparable with results obtained in other populations in previous studies.