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

Author(s): Babaei A, Eslamai MH

Affiliation(s): Department of Pharmacology, Yazd University of Medical Sciences, Yazd, Iran. A_BABAII@yahoo.com

Publication date & source: 2007-02, Int J Clin Pharmacol Ther., 45(2):121-5.

Publication type:

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.