engleski

Therapeutic drug monitoring of carbamazepine and valproate in patients with antipsychotic coadministration

Background Numerous interactions between antiepileptics and antipsychotics have been described in literature. This preliminary research aims at showing the concentrations of carbamazepine and valproic acid in relation with a daily dose of a drug coadministred along with antipsychotics (haloperidol, clozapine, phenotiazine, risperidon, olanzapine). Methods The first group of patients (N=20, average 44y) was on therapy with carbamazepine and antipsychotics and the second group (N=40, average 40y) was on therapy with sodium valproate and antipsychotics. They were also divided into the groups according to the daily dose of the administered antiepileptic. Therapeutic interval for carbamazepine is 25, 4 umol/L-50, 8 umol/L and for valproic acid 347umol/L-697umol/L) Results Carbamazepine concentration in patients who were administered a dose of 400mg/d was below the therapeutic interval in 2/6 patients, and in 3/7 patients who were administered a dose of 600mg/d. The valproic acid concentration in patients who were administered a dose of 500mg/d and 900mg/d of valproate was below the therapeutic interval in 4/9 patients and in 2/9 patients respectively. It was established that there is no correlation between a daily dose of drug and the carbamazepine concentration in blood (r=0.2978, p=0.2300) while there is a good correlation with valproic acid (r=0.4061, p=0.0093). Conclusion Although there is no correlation between a dose of drug and the concentration in blood, determining the concentration of antiepileptic in blood contributes to the evaluation of therapeutic effect and facilitates the regulation of a dose of the drug. Therapeutic intervals determined for most antiepileptics are a useful guide to help clinicians when the concentration of drug is considerably below or above the expected values.

therapeutic drug monitoring; carbamazepine; valproate

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