[영문]BACKGROUND: Although stimulant therapy is commonly discontinued earlyin adults with attention-deficit/hyperactivity disorder (ADHD), the factors thatcontribute to continuity of stimulant therapy remain largely unknown.OBJECTIVE: To (1) compare the continuity of methylphenidate (MPH) therapyamong adults who use immediate-release methylphenidate (IR-MPH) forADHD with adults who use extended-release methylphenidate (ER-MPH)formulations, and (2) examine some of the methodological issues involved inresearch with administrative claims for ADHD.METHODS: An analysis of pharmacy and medical claims for 75 US managedcare plans representing approximately 55 million beneficiaries for dates ofservice from January 1, 2000 through December 31, 2004. Patients had to beadults (aged 18 to 64 years) who had 1 or more outpatient medical claims forADHD (International Classification of Diseases, Ninth Revision, Clinical Modificationcode 314.xx) during the study period and who had initiated ER-MPH orIR-MPH treatment for ADHD. The study cohorts did not have a pharmacy claimfor MPHs, amphetamines, pemoline, or atomoxetine for 6 months precedingthe first (index) MPH pharmacy claim. Stimulant treatment episodes weredefined to start on the index date and terminate on the last date supplied ofthe index medication. Episodes of treatment were also defined as terminatedif there was a gap of ≥30 days between the end of the days supplied onthe pharmacy claim and the date of the next pharmacy claim for the indexmedication.RESULTS: Less than one third (30.0%) of the adult patients who wereprescribed MPH had 1 or more medical claims with a diagnosis code forADHD. For the adult MPH patients with at least 1 medical claim with adiagnosis code for ADHD, the patients who initiated therapy with ER-MPH(N = 2,833) were significantly younger, were more likely to be male, and wereless likely to be treated by a psychiatrist than were the patients who initiatedtherapy with IR-MPH (N = 2,289). Only 50.5% (n =1,156) of IR-MPH patientsand 61.4% (n =1,739) of ER-MPH patients had more than 1 pharmacy claimfor the index MPH medication. Adults treated with ER-MPH also had asignificantly longer median duration of treatment with the index medication(ER-MPH: 68 days, 95% confidence interval [CI], 65-71 days vs. IR-MPH 39days, 95% CI, 33-52 days). Controlling for group differences in age, gender,treatment by a psychiatrist, recently prescribed psychotropic medications,treated mental disorders, emergency mental health treatment, and inpatientmental health care, ER-MPH initiation was associated with an average 27%longer duration of treatment than with IR-MPH (survival time ratio: 1.27,95% CI, 1.20-1.35).CONCLUSION: In management of adult ADHD, use of ER-MPH formulationswas associated with a longer median duration of the initially prescribedmedication than was use of IR-MPH. It is unknown whether the observedabsolute unadjusted difference of 29 days in median length of therapy isclinically important.