Pharmacovigilance is the scientific study of medicinal products intended to treat a particular disease or indication for humans. It aims to establish drug safety profiles; knowledge about efficacy; metabolism and excretion; and other important clinical information. Within the EU and elsewhere, the regulatory authorities require all new medicinal products to have successfully completed a series of clinical trails before being granted a Marketing Authorisation which allows them to go on sale. This article explains some key points about the need for clinical trials and studies after the drug reached the market.
Pre-Marketing Clinical Studies Have Their Limitations
During the phase before a Marketing Authorisation is granted, clinical studies could have involved up to 10,000 patients. However, this is not always the case: it is also possible for the study size to have been much smaller. For example, ‘orphan drugs’ are those intended to treat relatively rare diseases. There may be cases where these drugs have been studied using smaller trials, with perhaps only dozens to hundreds of patients taking part.
Although pre-marketing trials must have been conducted in an extremely rigorous manner in order to meet EU drug safety regulations, they nonetheless have their limitations. The number of patients involved in even the largest trial means that uncommon and rare adverse reactions are statistically unlikely to have been detected with any certainty. The trials are able to produce important data but for example, at 5% probability level the absence of an adverse reaction within a study of 10,000 patients produces a true rate of occurrence of less than 1 in 3,333.
Pre-Marketing Trials May Not Include All Patient Groups
It could be that clinical trials did not include all the patient groups for whom the drug would be prescribed to. An example here could be studies involving patients with a maximum age of 60 years participating in clinical trials before the drug goes on sale, and subsequent prescribing to older patients once it reaches the market. There are a number of issues which could be relevant within this example. This patient group could be taking numerous other prescribed medications; they could present variations of metabolism and body mass index in comparison to younger patients; and they could present with a heightened sensitivity to certain types of medication. There could be issues around food intake, for example, if these patients are unable to follow a regularly timed meal schedule for any reason. Although there may have been some investigation into issues of polypharmacy, metabolism, the effects of food intake and so on during the pre-marketing studies, it could be that this particular patient group were not included in those studies.
Once the drug has been placed onto the market, the first 500,000 to 1,000,000 patients who take the new drug represent the first large scale safety test. Nurses, doctors and pharmacists around the world report suspected adverse reactions as spontaneous reports. They may do so via the regulatory agencies; national pharmacovigilance centres; or directly to the pharmaceutical companies. If a pharmaceutical company receives one of these reports, it must report it to the regulatory authorities. This will be generally within a 15 day timescale, subject to national and international laws.
Please note it is impossible to provide an exhaustive description of this topic within this short article; readers are therefore advised that this information cannot be considered as any type of professional advice.
by
Akshaya Srikanth
Pharm.D Resident
India
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