Generics are favoured by those responsible for healthcare costs [2]. The argument is that the generic compound is identical to the originator medicine, based on bioequivalence studies [3]. This implies that the generic compound will give identical efficacy and tolerability to the originator compound, upon which it is based. However, this may not be the case, especially with illnesses, such as epilepsy. This is due to the fact that the drugs used to treat epilepsy have a narrow therapeutic index [1].

Drugs with a narrow therapeutic index (NTI) are defined by a narrow distance between the dosage that induces a desired effect and that dosage which already has a toxic effect [4].

Generics substitution has become common place, within healthcare delivery, because of the anticipated financial benefits [5]. While the proponents of generic prescribing claim equivalence [5], this may not prove valid as the salt, adopted for the generic drug modification, as part of the formulation of the active ingredient contained within the originator medication, may exert altered characteristics [6]. The excipient, which carries the active compound, within the new formulation, and which is considered inactive, may alter its bioavailability and efficacy [7].

It follows that the economic consideration is not always realized, due to other considerations, such as efficacy or adverse events which may result in increased use of healthcare resources [5, 8]. When reviewing 30 articles related to the use of generics, most reported side effects were related to neurological diseases, especially epilepsy [5]. The authors identified the potential impacts of generics substitution which may include three main categories: patient attitudes and adherence; clinical and safety outcomes; and cost and resource utilization [5]. While generics substitution may represent an appropriate alternative to a brand-name originator product, in the management of some conditions, this may not always be the case [5].

This has clear implications for illnesses which have a NTI, where there is a restricted therapeutic range for efficacy, resulting in either too low a dose or unwanted adverse effects, should the blood levels exceed the narrow therapeutic range [4, 9]. This has particular relevance when considering anti-seizure medications (ASMs) because it may result in there being either too much or little ASM available. This in turn may result in altered seizure control, which may lead to break through seizures, which may affect driving for employment and trigger a domino effect with social consequences [10, 11].

While generics substitution may result in cost savings with respect to medication expenses, it could also result in increases in the total cost of health care, due to increased physician visits or hospitalizations [7]. It may also cause significant socio-economic consequences for those in whom the generics substitute caused breakthrough seizures which resulted in such unforeseen consequences as road traffic accidents [12, 13].

The author therefore concludes that it follows that the mandated use of generics prescriptions of active ingredients, especially when adopting electronic prescribing, may not achieve its desired goal. It is imperative to be aware of the potential downside of carte blanche acceptance of generics prescribing, and substitution of brand-name drugs, as a means of cost containment within the wider healthcare system.

Conflict of interest
The author of the research paper [1] declared that there was no conflict of interest.

Abstracted by Professor Roy G Beran, Neurology Department, Liverpool Hospital, Liverpool, Australia.

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