European Regulatory Agencies e.g. EMEA define what generic product is. It is a medicinal product essentially similar to an original product i.e. which has the same qualitative and quantitative composition in active substances, the same pharmaceutical form, and whose bioequivalence with the reference product has been demonstrated by appropriate bioavailability studies. It means that generic should be almost identical to an innovator product and everyone knows it is almost impossible. Therefore, precise quantitative criteria are necessary to set the borderline for dissimilarity that could be accepted regarding drug safety and efficacy. The majority of generics of generally acting drugs require for registration purposes bioequivalence studies thus this is statistical acceptance for bioavailability parameters what creates the door onto a market. The simplest study design is: single dose, 2-period, 2-sequence, crossover bioequivalence study in young (18-55 y.) healthy volunteers in fasting state, if necessary the design becomes more complex including food effect testing and multiple dosing. In general, Registration Agencies require for proving average bioequivalence, 90% confidence intervals for AUC and Cmax ratios (test/reference) within 0.80-1.25 for log-transformed data. That means generic product is acceptable differing up to 20% from the reference product in 90% of subjects. That door seems to be too wide for a few percent of drugs which are "narrow therapeutic index" and/or "critical dose" drugs. It is obvious that because of clear economic reasons, the manufacturer introducing generic drug is doing only what is necessary for successful registration of the product i.e. the simplest, the shortest and the cheapest study. Such a situation may provoke the collision of interest between patient's safety and interest of generic companies. Therefore the task for Registration Agencies is to create and to obey clear rules for introducing generic products on the market taking into account that bioequivalence requirements must be related to specifi c drug.

Keywords: intellectual disability (mental retardation), Metabolism syndrome, Transplantation