Value of 99mTc-TRODAT-1 SPECT to predict clinical response to methylphenidate treatment in adults with attention deficit hyperactivity disorder.

Background In a previous study, binding of 99m Tc-TRODAT-1 to the dopamine transporter (DAT) was found to be higher in patients with attention deficit hyperactivity disorder (ADHD) as compared to healthy controls. Aim To determine whether the degree of 99m Tc-TRODAT-1 binding to the striatal DAT may have a predictive role on the response to methylphenidate (MPH) in patients with ADHD. Methods Twenty-two adult patients suffering from ADHD underwent a brain SPECT scan with 99m Tc-TRODAT-1. After the scan patients received MPH, individually medicated up to 60 mg·day -1 . Severity of illness was estimated using the Clinical Global Impression (CGI-S) Scale before treatment Ten weeks after the beginning of MPH treatment the improvement in global symptoms was rated by the Clinical Global Improvement Scale (CGI-I). Results Before treatment 17/22 patients with ADHD presented with higher striatal DAT binding as compared to age-matched healthy controls (+23.8%; P<0.01). After treatment with MPH a significant improvement of ADHD symptoms was demonstrated by the CGI-I in 16 of these 17 patients (CGI-S before: 4.8; CGI-I after MPH: 1.9; P<0.01). Five patients showed reduced DAT binding prior to therapy (-14.4%; P=0.04); these patients did not respond to MPH therapy (CGI-S before: 4.5; CGI-I after MPH: 4.2; P=0.40). Conclusion Our findings suggest that ADHD patients with primarily elevated binding of 99m Tc-TRODAT-1 to the striatal DAT responded better to therapy with MPH as compared to those with normal or low DAT binding. Consequently, our results - even if obtained on a small collective indicate that measurement of DAT may be an important prognostic predictor for therapy response to MPH.