Plasma concentrations of vigabatrin in epileptic patients.
OBJECTIVE
To measure plasma concentrations of vigabatrin in a group of 30 adult epileptic patients with complex partial seizures (CPS) refractory to conventional antiepileptic drugs. With a view to better defining the drug's dose-response relationships in the presence of concomitant alternative antiepileptic drugs.


METHODS
High-performance liquid chromatographic analysis of blood samples drawn at steady-state trough levels from patients receiving vigabatrin.


RESULTS
The steady-state plasma concentrations of vigabatrin showed marked interpatient variability (CV = 59.5%). The mean concentration was 42 +/- 25 micrograms/ml (range 11.5-102.7 micrograms/ml). Nineteen patients (63%) had plasma levels between 20 and 60 micrograms/ml. The plasma clearance of vigabatrin ranged from 0.24 to 1.37 ml/min/kg (mean +/- SD = 0.74 +/- 0.40 ml/min/kg), with a median value of 0.64 ml/min/kg. Concomitant treatment with carbamazepine increased the plasma clearance of vigabatrin from 0.59 ml/min/kg (monotherapy), 0.54 ml/min/kg (co-treated with phenobarbital) and 0.41 ml/min/kg (co-treated with valproic acid) to 0.92 ml/min/kg.


CONCLUSIONS
Vigabatrin plasma levels show wide interpatient variability, and co-administration with carbamazepine increases vigabatrin's clearance. While there is no relationship between plasma level and anti-epileptic effect, abnormally high levels of the drug may increase toxicity.
Sánchez-Alcaraz
A
A
Department of Pharmacy, Arnau de Vilanova Hospital, Valencia, Spain.
Quintana
B
B
Rodriguez
I
I
López
E
E
D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage / Q000097:blood*; D002220:Carbamazepine / Q000008:administration & dosage / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D017029:Epilepsy, Complex Partial / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020888:Vigabatrin; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood
D000927:Anticonvulsants; D002220:Carbamazepine; D005680:gamma-Aminobutyric Acid; D020888:Vigabatrin