In brief
A conference abstract describing the first stage of our study of children on high-dose stimulants: the clinical characteristics of the children whom the NSW Ministry of Health had authorised to receive doses above the usual maximum, compared with children on regular doses from the same practice over 2003 to 2016.
Abstract
Introduction: The maximum doses of stimulants used for treating ADHD are based on convention rather than scientific data. The NSW prescribing criteria define high dose (HD) as: methylphenidate >2mg/kg or >108mg/day; dexamphetamine >1mg/kg or >50mg/day; lisdexamfetamine >70mg/day. HD can be prescribed on application to the NSW Ministry of Health (MoH), given supporting documentation of efficacy from an independent observer. In the studied practice the treatment dose was prescribed on clinical grounds. The aim of this study is to describe the clinical characteristics of children authorised by the NSW MoH to receive HD stimulants and compare them to those on regular doses (RD).
Methods: Clinical records of children treated with HD stimulant were compared with those of controls prescribed RD. Controls had a prescription on the same day that a study child commenced HD, identified using a database of prescription records. The data spanned 2003–2016, including children from a public hospital clinic and private consulting rooms. Categorical data were compared using chi-square and continuous data using independent samples t-tests. Growth data were analysed in age and sex specific z-scores.
Results: There were 51 HD and 119 RD children. The HD children were more likely than RD children to have oppositional defiant disorder (ODD) (82% vs 55%, p=0.001), and started medication at a younger age (6.4±1.7 years vs 8.3±2.8 years, p<0.001). Of the HD children, 46 had trialled HD methylphenidate: maximum dose 82.1±33.1mg/day, 2.3±0.4mg/kg/day. All had documented evidence of improvement on HD from an independent observer. HD children were more likely to take risperidone (37% vs 16%, p=0.002) but not other psychotropic drugs. Dose reductions were necessitated in 33% (n=17) HD and 27% of RD children (p=0.2); the commonest reason in HD children was worsening behaviour (n=7). The HD children grew significantly slower in height and weight (change in height z-score −0.43±0.55 vs −0.09±0.58, p<0.001, change in weight z-score −0.56±0.81 vs −0.19±0.67, p=0.002) over a treatment period of 5.1±3.0 and 4.2±3.2 years respectively. No child had a dose reduction due to hypertension.
Conclusions: Compared with RD, children on HD stimulant showed evidence of greater impairment. They started treatment at a younger age and had a higher prevalence of ODD. Over an average treatment period of >4 years, they showed a greater decline in z-scores for height and weight. Dose reductions due to side effects happened no more frequently than in children on standard doses.