Effect of vigabatrin on the pharmacokinetics of carbamazepine.
OBJECTIVE
To evaluate a possible interaction between vigabatrin and carbamazepine in epileptic patients.


METHODS
Steady-state serum concentrations of carbamazepine with and without vigabatrin were compared. The study group consisted of 15 patients (eight females, seven males, and mean age 31 +/- 12 years), with refractory partial epilepsy. They received vigabatrin as add-on therapy. Patients received carbamazepine monotherapy for at least 6 months and the carbamazepine-vigabatrin combination for at least 3 months. Blood samples were obtained in the morning, before the first daily dose and the carbamazepine plasma concentrations were analysed by fluorescence polarization immunoassay (TDx System).


RESULTS
No statistically significant differences were found in mean carbamazepine daily dose. Mean trough concentrations were 7.9 +/- 1.4 microg/mL with carbamazepine alone, and 6.5 +/- 2.0 microg/mL with carbamazepine-vigabatrin association (P < 0.03). The mean values of pharmacokinetic parameters were: level/dose ratio (L/D) = 0.59 +/- 0.20 vs. 0.45 +/- 0.15 (P < 0.05) and plasma clearance (Cl) = 78.5 +/- 25.8 vs. 105.8 +/- 38.9 mL/h/kg (P < 0.05), with carbamazepine alone and carbamazepine-vigabatrin combination, respectively.


CONCLUSIONS
Vigabatrin produced a statistically significant increase in the plasma clearance of carbamazepine when the two drugs were given simultaneously.
Sánchez-Alcaraz
A
A
Departament of Pharmacy, Hospital de La Ribera, Alzira, Valencia, Spain. asanchez@hospital-ribera.com
Quintana
Ma B
MB
López
E
E
Rodríguez
I
I
Llopis
P
P
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002220:Carbamazepine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D004827:Epilepsy / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020888:Vigabatrin / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use
D000927:Anticonvulsants; D002220:Carbamazepine; D020888:Vigabatrin