Trends in antiepileptic drug utilisation in UK primary care 1993-2008: cohort study using the General Practice Research Database.

PURPOSE: To describe changes in utilisation of antiepileptic drugs (AED) by people with epilepsy in the United Kingdom during 1993-2008. METHODS: Cohort study of 63,586 participants with epilepsy and prescribed AEDs from 434 UK family practices. Prescriptions for different AEDs and AED combinations were evaluated by calendar year, gender and age group. RESULTS: Total follow-up was 361,207 person-years, with 282,080 person-years treated with AEDs and 79,126 person-years untreated. AED monotherapy accounted for 72.6% of treated person years of follow-up. Carbamazepine and valproates were among the most commonly used medications throughout 1993-2008. Phenytoin accounted for 39.5% of treated person-years in 1993 declining to 18.3% by 2008. Use of barbiturates declined from 14.3% in 1993 to 6.0% in 2008. In contrast between 1993 and 2008 there were substantial increases in the use of lamotrigine (2.0% to 17.0%) and to a lesser extent levetiracetam (0% to 8.6%). Newer AEDs were more frequently prescribed to younger participants, especially women aged 15-44 years, while older adults were more likely to be prescribed longer established AEDs. In 1993, 201 different AED combinations were prescribed, increasing to 500 different combinations in 2008. Combinations of sodium valproate and carbamazepine were frequent throughout, while sodium valproate and lamotrigine was frequent in 2008. CONCLUSIONS: Utilisation of newer AEDs in UK primary care has increased between 1993 and 2008 with increasing use of diverse combinations of AEDs. The data quantify exposure to AEDs relevant to planning analytical pharmaco-epidemiological studies, as well as providing information to inform prescribing policies.