Intrapatient variation in antiepileptic drug plasma concentration after generic substitution vs stable brand-name drug regimens.

Generic substitution of antiepileptic drugs (AEDs) is still a matter of controversy and concern among clinicians and patients. We aimed to assess intrasubject variation in plasma concentrations of lamotrigine (LTG), levetiracetam (LEV) and topiramate (TPM) after generic substitution compared with a stable brand-name drug regimen in a population of patients with epilepsy. A retrospective analysis was performed on prospectively collected and stored data from our therapeutic drug monitoring (TDM) database for the years 2009-2014. The main outcome variable was the proportion of patients who, after switching from branded to generic formulations, showed a greater than ±20% change in AED plasma concentrations compared to the proportion of control patients showing a change in AED plasma concentrations of the same extent while receiving stable branded formulations over repeated TDM tests. Fifty patients on LTG, 27 on LEV and 16 on TPM showing at least one TDM test while receiving generic products fulfilled the inclusion/exclusion criteria for the analysis and were compared with 200 control patients for LTG, 120 for LEV and 80 for TPM. The proportion of patients showing an intrasubject change greater than ±20% in AED plasma concentrations was similar in the brand name vs generic group compared with the control one for LTG (22% vs 33%) and LEV (44% vs 38%), while it was higher in the control group for TPM (41% vs 6%, p<0.01). These are the first data in the literature about the within-patient variation in steady-state plasma concentrations of a series of stable treatments with brand-name AEDs in a real clinical setting. In conclusion, a significant interday variability in intrapatient LTG, LEV and TPM plasma concentrations can be observed even in patients stabilized with the same brand name product over time. This suggests that any change in plasma AED concentration and possible related clinical effects after generic substitution may be not necessarily related to the switch. Our results should be confirmed by large, prospective, blinded, randomized controlled studies in people with epilepsy.

Expanded Access Programme: looking for a common definition.

Therapeutic use of an unauthorised drug (or of an authorised drug for an unauthorised indication) for patients with a life-threating disease is permitted outside a clinical trial as an Expanded Access Programme (EAP).The regulations regarding EAPs is not the same all over the world. For example, the recommendation of the European Medicines Agency (EMA) in EU countries also includes within EAPs patients who have been treated in a clinical trial and who wish to continue the treatment. Nevertheless, the patients treated in a clinical trial could have the option of continuing treatment for an extended period in an Open-label Extension study, aimed to generate long-term data on efficacy, safety, tolerability and administration.The aims of this paper - based on the difficulties and incoherence encountered by an Italian Ethic Committee (EC) during the authorisation process of EAPs - are: understanding the origin of this misclassification by analysing differences and similarities among USA, European and Italian regulations concerning EAPs; and showing difficulties in classifying international study protocols as a consequence of the lack of harmonisation of definitions.We performed a critical review of the current USA, European and Italian regulations and we analysed some practical cases by retrieving protocols from Clinicaltrials.gov and the Italian Clinical Trials Registry (OsSC) containing in the title the keywords 'Expanded Access Programme', "'Expanded Access', 'Open-label Extension study' or 'Early Access'.We observed that the Food and Drug Administration ( FDA) definition of EAP is very clear while the EMA definition is similar to that of an Open-label Extension study. This lack of a clear definition generates misclassification and it is possible to find an EAP with an efficacy or safety endpoint; or an EAP managed as a clinical trial; or an EAP classified in Clinical Trials Registries as a phase II, III or IV clinical trial.The internationalisation of the studies requires a harmonisation on a global level of legislation and definitions to eliminate misclassification of protocols. For this reason, the authors suggest that: a) the EMA definition should be harmonised with the FDA definition of EAPs, b) European regulation, even if optional, should be adopted in a compulsory way by national regulations. Moreover, separate registries for both EAPs and clinical trials should be organised.