Abstract
Therapeutic drug monitoring is used to ensure that medications are prescribed and
administered according to safe doseage advice and for the purpose of achieving
the desired therapeutic effects in patients. Several methods are used to perform
therapeutic drug monitoring. However, there is insufficient evidence to
currently support therapeutic drug monitoring of Valproic acid using salivary
samples. The aim of this paper is to determine the feasibility of using salivary
samples as a substitute for plasma samples for therapeutic drug monitoring of
Valproic acid. In this study a total of 23 patients participated, with the mean
age of 33.39. Salivary and plasma samples were collected and analysed to
determine the peak and trough concentrations of Valproic acid for comparison
between the two methods. Calibrated LC- MS/ MS was used to measure Valproic acid
levels. Statistical analyses were performed using ANOVA test and ethical
approval was obtained prior to sample collection. The results showed that saliva
Valproic acid levels were less than that of plasma levels. There was no
significant correlation between saliva and plasma level of Valproic acid
(P>0.05). However, there was a significant correlation between the area under
the curve for both saliva and plasma Valproic acid (P<0.05). Creatinine
clearance was significantly correlated with peak plasma levels of Valproic acid
(P<0.05). Albumin was significantly correlated with plasma levels of Valproic
acid. There was also a significantly positive and moderate relationship between
Log Saliva Cmax and Log plasma free Valproic acid concentration (r=0.76,
p<0.018). In conclusion, saliva samples can be used as a substitute for
plasma samples in the therapeutic drug monitoring of Valproic acid.
Keywords
therapeutic drug monitoring - salivary excretion classification system - valproic acid
