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Adverse Reaction (“Side Effect”)

Noxious and unintended reaction to a medicinal product, in which there is a possible causal link between the adverse occurrence and the use of the medicinal product.

All the situations resulting from the use of the medicinal product in accordance with the Summary of Product Characteristics (SmPC) or the Package Leaflet (PL) are considered adverse reactions, as well as those that result from the use outside the terms described in the SmPC or PL, medication errors, misuse or abuse, or result from occupational exposure (as a result of the professional activity).

Note: A "medication error" is defined as any unintentional error in the prescribing, dispensing, or administration of a medicinal product.

The persistent or sporadic, intentional excessive use of a medicinal product which is accompanied by harmful physical or psychological effects is considered a "abuse of a medicinal product". The improper use of a medicinal product, i.e., where the medicinal product is intentionally and inappropriately used not in accordance with the SmPC or PL is defined as "misuse".

In the reporting of an adverse reaction is still important to distinguish two concepts easily confused: intensity and seriousness.


The intensity or severity is based on the intensity of the adverse reaction, being classified as mild, moderate and severe.


Seriousness is related to the evolution/outcome of the adverse reaction, being defined by the criteria described for a serious adverse reaction.

Serious Adverse Reaction

Any adverse reaction that results in death, is life-threatening, requires in-patient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability or incapacity or is a congenital anomaly/birth defect. The healthcare professional may consider an adverse reaction as a serious adverse reaction despite it does not meet any of the above criteria (important medical event).