Acute drug prescribing to children on chronic antiepilepsy therapy and the potential for adverse drug interactions in primary care

Aims To investigate the extent of acute coprescribing in primary care to children on chronic antiepileptic therapy, which could give rise to potentially harmful drug-drug interactions. Design Acute coprescribing to children on chronic antiepileptic drug therapy in primary care was assessed in 178 324 children aged 0-17 years for the year 1 November 1999 to 31 October 2000. Computerized prescribing data were retrieved from 161 representative general practices in Scotland. Setting One hundred and sixty-one general practices throughout Scotland. Results During the study year 723 (0.41%) children chronically prescribed antiepileptic therapy were identified. Fourteen antiepileptic agents were prescribed, with carbamazepine, sodium valproate and lamotrigine accounting for 80% of the total. During the year children on chronic antiepileptic therapy were prescribed 4895 acute coprescriptions for 269 different medicines. The average number of acute coprescriptions for non-epileptic drug therapy were eight, 11, six, and six for the 0-1, 2-4, 5-11, and 12-17-year-olds, respectively. Of these acute coprescriptions 72 (1.5%) prescribed to 22 (3.0%) children were identified as a potential source of clinically serious interactions. The age-adjusted prevalence rates for potentially serious coprescribing were 86, 26, 22, and 33/1000 children chronically prescribed antiepileptic therapy in the 0-1, 2-4, 5-11, and 12-17-year-old age groups, respectively. The drugs most commonly coprescribed which could give rise to such interactions were antacids, erythromycin, ciprofloxacin, theophylline and the low-dose oral contraceptive. For 10 (45.5%0 of the 20 children identified at risk of a potentially clinically serious adverse drug interaction, the acute coprescription was prescribed off label because of age or specific contraindication/warning. Conclusions In primary care, 3.0% of children on chronic antiepileptic therapy are coprescribed therapeutic agents, which could give rise to clinically serious drug-drug interactions.