This section provides information on some of the major concepts within pharmacovigilance related to pharmaceutical products for human use.
Pharmacovigilance has been defined by the World Health Organisation as “The science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other possible drug-related problem”
Adverse Events & Adverse Reactions
The ICH E2A guideline describes Adverse Events as any “untoward medical occurrence” which happens to either a patient or a subject in a clinical investigation when a pharmaceutical product has been given to that person1. This encompasses any signs which are unfavourable and unexpected for the patient or subject, including any abnormal laboratory findings. These could be symptoms or a diseases temporally associated with the use of a medicinal product, and do not have to have been previously associated with that product. Neither do they have to have a known causal relationship with the course of treatment.
ICH E2A characterises Adverse Reactions according to the stage of the medicinal product’s life cycle. If the product has not yet been marketed, Adverse Reactions are any “noxious and unintended responses”1 to the product at any dose. The effect of this classification is to reasonably establish that a relationship between the product and the reaction “cannot be ruled out”1. Once the product has been placed on the market, “Adverse Reactions” encompass responses which are again “noxious and unintended” but occur at the established routine dosages which have been defined for use in humans to prevent, diagnose, or treat disease or modify “physiological function”1. However, some more recent definitions include responses to doses and uses outside those recommended.
Serious Adverse Events (SAEs)
As the names implies, these are “any untoward medical occurrence” that:
Is a threat to life
Results in inpatient hospitalisation
Prolongs an existing hospital stay
Results in persistent or significant disability or incapacity
Results in a congenital anomaly or birth defect
Events that require intervention to prevent the patient or subject experiencing any of the outcomes listed above or otherwise jeopardise the patient are also to be classed as serious, depending on their nature. In some cases expedited reporting will clearly be appropriate. In the EU, suspected transmission of an infectious agent also constitutes a serious adverse event.
Suspected Adverse Drug Reaction (ADRs)
This term is discussed in ICH E2A and ICH E2D, it covers those events where there is the reasonable possibility the event is a direct result of taking the product. Inevitably most serious drug reactions are treated as being “suspected” rather than “confirmed” since they would need some kind of additional evidence, such as “dechallenge and rechallenge” in order to be confirmed. This would mean the patient would take the drug, have the reaction, recover after the drug is withdrawn, and then take the drug again to confirm the reaction. Given the serious nature of such reactions, rechallenge as a test may be unethical, but it may happen in clinical practice.
Suspected Unexpected Serious Adverse Reactions (SUSARs) and Expected Drug Reactions
Before a product is marketed, a Suspected Unexpected Serious Adverse Reaction is any suspected adverse reaction which is serious and is not consistent with the information on adverse reactions made available in the current investigator brochure1. Once a product is marketed, unexpected reactions are are those whose nature or severity is not consistent with the undesirable effects included in the standard product information (Package Insert or Summary of Product Characteristics), although the investigator brochure could also be the reference document for post-marketing studies.
The goal of pharmacovigilance is to protect patients and the public wherever possible and to disseminate knowledge among the relevant professional communities and to patients in order to minimise risk. The information here is provided as a general introduction to the topics and in no way constitutes legal, safety or any other form of professional advice.
Reference and suggested further reading
1. Barton L.Cobert, MD. (2007). Manual of Drug Safety and Pharmacovigilance. Massachusetts: Jones and Bartlett.