Pharmacokinetic evaluation of twice-daily extended-release carbamazepine (CBZ) and four-times-daily immediate-release CBZ in patients with epilepsy.
OBJECTIVE
A new capsule dosage form of carbamazepine (CBZ) has been developed, consisting of three different types of beads (immediate-release, extended-release, and enteric-release) that may be taken sprinkled on food or swallowed for easy administration. We compared the pharmacokinetics of the extended-release dosage form of CBZ (Carbatrol capsules) twice daily with the conventional immediate-release formulation of CBZ four times daily.


METHODS
The randomized, double-blind, two-way, cross-over study was conducted at two sites, with a planned sample size of 24 adult patients with epilepsy. Each treatment was administered for 2 weeks. At the end of the 2-week period, blood samples were obtained hourly for a 24-h period.


RESULTS
The 90% confidence intervals (CI) of the ratio of the means of the extended-release formulation twice daily to the immediate-release formulation four times daily were within the range of 0.80-1.25 for each of the pharmacokinetic parameters for CBZ and for the summation of CBZ and CBZ-epoxide (CBZ-E). There was no difference in the frequency of seizures between treatment (p = 0.103).


CONCLUSIONS
Our results demonstrate that extended-release CBZ twice daily was bioequivalent to immediate-release CBZ four times daily, with regard to CBZ levels and summation of CBZ and CBZ-E levels, based on the pharmacokinetic parameters evaluated. Substituting one formulation for the other did not cause patients to have a significant change in seizure frequency.
Garnett
W R
WR
Department of Pharmacy, Virginia Commonwealth University Medical College of Virginia, Richmond 23298-0533, USA.
Levy
B
B
McLean
A M
AM
Zhang
Y
Y
Couch
R A
RA
Rudnic
E M
EM
Pellock
J M
JM
Belendiuk
G W
GW
D000293:Adolescent; D000328:Adult; D002220:Carbamazepine / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics*; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004827:Epilepsy / Q000097:blood / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013810:Therapeutic Equivalency
D003692:Delayed-Action Preparations; D002220:Carbamazepine