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Epilepsia. 1998 Mar;39(3):274-9.

Pharmacokinetic evaluation of twice-daily extended-release carbamazepine (CBZ) and four-times-daily immediate-release CBZ in patients with epilepsy.

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  • 1Department of Pharmacy, Virginia Commonwealth University Medical College of Virginia, Richmond 23298-0533, USA.



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.


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.


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).


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.

[PubMed - indexed for MEDLINE]
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