Trend and area variation in amphetamine prescription usage among children and adolescents in Michigan

The increased use of stimulant medications for children and teenagers is an ongoing issue of professional and public concern. Unlike methylphenidate, the growth of prescriptions and patterns of utilization of amphetamines for pediatric populations have not been well documented. The study objectives were to describe the trends of amphetamine prescription utilization among pediatric age groups in Michigan and to compare area variations. A population-based computerized data set from the state of Michigan was used to extract all outpatient prescriptions for Schedule II amphetamines dispensed from 1990 to 1997. The prescribing rates by age groups and by counties were computed with the projected population size of corresponding years, and mapped and analyzed with spatial statistical methods. Counties that did not conform to the global spatial dependence pattern in the prescription rate were identified using Moran scatter plot. A total of 236,661 outpatient prescriptions for amphetamines were dispensed in Michigan during the time frame, including less than 1% for methamphetamine, 24.5% for amphetamine, and 74.8% for dextroamphetamine. The prescribing rate was highest among children 10-14 years old (380 prescriptions per 10,000 people) in 1997, followed by children 5-9 years old (253 prescriptions per 10,000). Over the 8-year period, the prescribing rates of amphetamines increased significantly, ranging from 380% for children 2-4 years to 817% for teenagers older than 14 years. The rates among counties ranged from 60 to 1648 per 10,000 children 5-14 years old, with the highest prescribing rates in the northwestern regions of Michigan. Although spatial dependence explained 36% of the variance, the area variations that are unaccounted for are still considerable. In conclusion, there were substantial increases and unexplained area variations in amphetamine usage in Michigan during the study period. Both phenomena require awareness and evaluation from researchers, policy makers, clinicians, and the public.