Methylphenidate for the treatment of apathy in Alzheimer disease: prediction of response using dextroamphetamine challenge.

Apathy is a common behavioral symptom of Alzheimer's disease (AD), being present in up to 70% of patients. Apathy in AD and non-AD populations has been associated with dysfunction in the dopaminergic brain reward system, suggesting that pharmacotherapeutic targeting of this system may be an effective treatment for apathy in AD. We therefore performed a randomized, double-blind, placebo-controlled crossover trial of methylphenidate in a sample of 13 apathetic AD patients (6 men, 7 women; age mean 77.9 years [SD, 7.8 years]; Mini Mental Status Examination score, 19.9 [SD, 4.7]). Patients were treated with methylphenidate (10 mg PO twice a day) or an identical placebo in two 2-week phases separated by a 1-week placebo washout. All patients participated in a dextroamphetamine challenge test (one 10-mg oral dose) before treatment with methylphenidate to gauge the functional integrity of the dopamine brain reward system. Overall, patients demonstrated greater improvement with methylphenidate compared with placebo according to Apathy Evaluation Scale total change scores (end of treatment - baseline: Wilcoxon Z = -2.00; P = 0.047). However, a significantly greater proportion of patients experienced at least 1 adverse event with methylphenidate compared with placebo (3 vs 1; chi = 4.33, P = 0.038). Two patients experienced serious adverse events with methylphenidate, consisting of delusions, agitation, anger, irritability, and insomnia, which resolved upon discontinuation of the medication. Response to methylphenidate was associated with increases in inattention on a continuous performance task after dextroamphetamine challenge. Psychostimulants may be effective in treating features of apathy in AD, and dopaminergic changes may predict response.