Interindividual and Intraindividual Variation of Methylphenidate Concentrations in Serum and Saliva of Patients With Attention-Deficit/Hyperactivity Disorder
Abstract
Therapeutic drug monitoring is becoming increasingly important in psychiatric therapy, especially in children. However, for several reasons, it cannot yet be implemented as a daily routine in clinical or outpatient settings. To evaluate new, noninvasive procedures, blood and saliva (oral fluid) samples were collected from patients with attention-deficit/hyperactivity disorder (ADHD) who were also being administered methylphenidate (MPH). The study's main purposes were to correlate MPH concentrations in serum and saliva between subjects and to analyze intraindividual variation of serum concentration. Thirty-six patients with ADHD (27 children and 9 adults) on MPH medication were included for drug analysis. MPH and its major metabolite ritalinic acid were quantified using liquid chromatography-tandem mass spectrometry measurements. The following correlations were investigated: (1) between drug concentrations in serum and saliva, and (2) between pH value and saliva to serum concentration ratio. Furthermore, the mean intraindividual MPH-concentration fluctuation in saliva under constant frame conditions was analyzed. After quantification, MPH concentrations were approximately 5 times higher in the saliva than in the serum, whereas ...Continue Reading
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