Effect of felbamate on phenytoin and carbamazepine serum concentrations.
Felbamate (FBM) is a novel antiepileptic drug (AED) undergoing clinical trials in the United States. During a double-blind, cross-over clinical trial, patients received concomitant phenytoin (PHT) and carbamazepine (CBZ). Dosages of PHT and CBZ were adjusted to maintain serum concentrations +/- 20 and +/- 25% of baseline values. All patients required a PHT dosage decrease of 10-30% during active FBM treatment to maintain stable concentrations. CBZ serum concentrations decreased significantly in patients receiving active FBM. The mean decrease was 1.3 micrograms/ml and occurred in 30 of 32 patients. Therefore, FBM apparently causes a bidirectional effect on the serum concentrations of PHT and CBZ when all three drugs are taken concomitantly.
Graves
N M
NM
College of Pharmacy, University of Minnesota, Minneapolis 55455.
Holmes
G B
GB
Fuerst
R H
RH
Leppik
I E
IE
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage / Q000494:pharmacology*; D002220:Carbamazepine / Q000008:administration & dosage / Q000097:blood*; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D004827:Epilepsy / Q000097:blood / Q000188:drug therapy*; D000078328:Felbamate; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D048448:Phenylcarbamates; D010672:Phenytoin / Q000008:administration & dosage / Q000097:blood*; D011409:Propylene Glycols / Q000008:administration & dosage / Q000494:pharmacology*; D014481:United States
D000927:Anticonvulsants; D048448:Phenylcarbamates; D011409:Propylene Glycols; D002220:Carbamazepine; D010672:Phenytoin; D000078328:Felbamate