Legal and economic identification and assessment of pharmacy substitution in narrow therapeutic index drugs, on the example of epileptic medications in Poland

Currently in Poland there is neither regulation aiming at framing the complexity of substitution process arising at pharmacy level, nor further guidelines depending on drug category. FDA describes a narrow therapeutic index drug (NTI) in the 21 Code of Federal Regulations 320.33(c) and highlights that safe and effective use of such drug products require careful titration and patient monitoring. In major therapeutic areas disadvantages of the generic substitution are irrelevant or minor in comparison to the economic benefit. In epilepsy, a number of experts and professional bodies have recommended caution with generic substitution of drugs used in this condition. Aim of the study is to legally and economically identify and assess drug sub-stitution occurrence in Polish background among selected narrow therapeutic index drugs used in epilepsy. Paper is divided into two sections: first is retrospective based and tackles the data received from the National Health Fund; whereas second section takes under consideration questionnaire based results gained during medical history being collect-ed with the patients. Basing on most commonly substituted substance in epilepsy: carbamazepine, the maximum single difference in cost in substitution at the pharmacy was identified around the level of 1.7 PLN, and maximum extra pay at the same level. Ob-served/reported changes, ADRs, discomfort were provided based on the question-naire. The study highlights the necessity of planning process and evaluation of cur-rent market regulations.