We conducted a 3-phase, double-blind, placebo-controlled, parallel study design of osmotic-release oral system (OROS)-methylphenidate (MPH) in adults (19-60 years of age) with attention deficit/hyperactivity disorder as classified by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Phase 1 of the study was a 6-week, acute efficacy trial (n = 223), phase 2 was a 24-week, double-blind continuation study of responders (n = 96), and phase 3 was a double-blind, placebo-controlled, 4-week discontinuation study (n = 23). The mean daily dosage at phase 1 endpoint was 78.4 +/- 31.7 mg (0.97 +/- 0.32 mg/kg) OROS-MPH and 96.6 +/- 26.5 mg (1.16 +/- 0.19 mg/kg) placebo (P < 0.0001). Clinical response at phase 1 endpoint was significantly greater in the OROS-MPH group (62%, n = 67 vs 37%, n = 41; P < 0.001) and was maintained throughout 24 weeks of double-blind treatment. With double-blind, placebo-controlled discontinuation, however, there was no statistically significant difference in the rate of relapse between OROS-MPH responders randomized to placebo and those randomized to continue active treatment (18%, n = 2 vs 0%, n = 0; P = 0.1). As expected, decreased appetite, insomnia, being tense/jittery, mucosal dryness, and neurological symptoms were statistically significantly associated with OROS-MPH treatment. More work is needed to be conducted with larger samples being followed to study completion to better understand the long- lasting impact of pharmacotherapy for adult attention-deficit/hyperactivity disorder.
