A study on carbamazepine levels, including estimation of 10-11 epoxy-carbamazepine and levels in free plasma and saliva.
Blood and saliva were collected from 48 children, aged three to 17 years, before a morning dose of carbamazepine and then at three, six and eight hours afterward. There was no significant difference in the ratio of 10-11 epoxy-carbamazepine to total carbamazepine for children on carbamazepine alone (0.18) and those on an additional anticonvulsant (0.19). 11 children were studied on their first day of therapy. Though four of them achieved levels of total carbamazepine which would have given a readily measurable 10-11 epoxide on the above ratio, 10 of the 11 consistently had levels less than 4 mumol/l. This may be of help in detecting non-compliance. For 16 children free carbamazepine also was estimated and there was an over-all correlation coefficient of 0.85 between saliva and free-drug levels. The proportion of free to total carbamazepine varied between 19 and 54 per cent. There was a significantly higher proportion of free drug at the pre-dose sampling time than at other times. Protein binding of carbamazepine therefore is very variable and saliva estimations can contribute usefully to the monitoring of drug levels.
D000293:Adolescent; D002220:Carbamazepine / Q000031:analogs & derivatives* / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D012463:Saliva / Q000378:metabolism*
D002220:Carbamazepine; C012227:carbamazepine epoxide