Existing pharmacovigilance post-market surveillance system relies on reporting of adverse drug reactions to national databases in real-time and post-marketing safety studies. Quantitative evaluation of incidence, prevalence trends, and patterns of use from reporting data is problematic due to under-reporting and missing data on exposure. The absence of rates of occurrence is especially problematic if drugs are used off-label, in populations they were not intended for, or in combination with other medications.
PMS – post-market surveillance, ICSR – individual case safety report, PSUR – periodic safety update report, NI studies – non-interventional studies, PASS – post-authorization safety studies
Signal detection in drug safety relies heavily on the review of individual case reports and case series and disproportionality analysis of data reported ADR databases. The creation of other signal detection methods besides disproportionality statistics is a matter for ongoing research. The foundational concept for many disproportionality methods is the proportional reporting ratio (PRR), which means the degree of disproportionate reporting of an adverse event for a product of interest compared to this same event for all other products in the database. The statistical association does not imply causality. Change-point analysis (CPA) detects changes in either the slope or variability in a time series or sequence in vast databases. Text mining is used to analyze unstructured data.
Post-market safety events as a public health challenge
The difference between pharmacovigilance and quality management systems in inpatient and outpatient healthcare settings is the nature and purpose of the information collected. While pharmacovigilance systems are designed to collect data on adverse drug reactions, the quality management systems were developed to collect information that measures the quality of care, which is all adverse experiences relating to drugs, including transcribing and dispensing errors. The highest number of adverse drug events in inpatient settings are attributed to insulins, anticoagulants, and opioid analgesics.
Adverse Drug Events:
"All harms that occur during medical care directly caused by the drug including medication errors, ADRs, allergic reactions, and overdoses"
Adverse Drug Reaction:
"Harm directly caused by a drug at normal doses."
Medication Error:
"Inappropriate use of a drug that may or may not result in harm."
System responsiveness: safety withdrawals
In the period from 2001 to 2010, the FDA approved 183 novel pharmaceuticals and 39 biologics. One-third of the newly approved therapeutics was affected by at least one post-market safety event: 3 withdrawals, 61 boxed warnings, and 59 safety communications. The most affected groups were psychiatric medications and biologics.
Onakpoya and colleagues identified 462 products that were withdrawn for safety reasons in the period from 1950 to 2014 in at least one country. The team also evaluated the quality of evidence that led to these withdrawals. In 72% of cases, the supporting evidence that led to market withdrawal consisted of anecdotal reports (level 4). Less than 10% of the identified products were withdrawn worldwide, and 39% in one country only. The authors argue that there is insufficient research into the evidence that leads to market withdrawals. The interval between first detection and authorization withdrawal did not significantly shorten since 1953.
Level 4 evidence is routinely used to make high-impact decisions, including product withdrawals. The average time from the detection of a safety signal to eventual product withdrawal on safety grounds is six years. This time lag did not substantially improve since the 1950s.
Post-authorization safety studies
The FDA may require a post-approval study as a condition of a premarket approval (PMA), humanitarian device exception (HDE), or product development protocol (PDP) application. The objective of such a study is to ensure continued safety and efficacy of marketed drugs, biologics, and devices. Post-marketing commitments (PMCs) are studies or clinical trials that a sponsor has agreed to conduct after the product launch. Post-marketing requirements (PMRs) are studies that are required under the law. These studies can be mandated under FDAAA can be required to assess a known serious relating to the use of the drug, assess signals of serious risk, and identify unexpected serious risks.
- Post-marketing studies/clinical trials of drugs approved under the accelerated approval program (Accelerated approval requirements: 21 CFR 314.510 and 21 CFR 601.41)
- Deferred pediatric studies required under the Pediatric Research Equity Act (21 CFR 314.55(b); 601.27(b)
- Studies/clinical trials under the Animal Efficacy Rule (21 CFR 314.610(b)(1) and 601.91(b)(1))
- Drugs: Database of post-approval drug studies lists 306 ongoing PMC and PMR studies
- Devices: Database of post-approval studies of medical devices contains 248 studies
As of December 20, 2017, 874 Phase IV, Observational studies were listed in the ClinicalTrial.gov registry. Results are available in a mere 69 of the 626 completed studies and for 11 of the 61 terminated studies. The situation is very similar for interventional studies. Of the more than 23.000 phase IV interventional studies found in the database, only less than 4000 have results available to the public. The majority of post-marketing studies do not have published results at all, or the results come long after completion of the study.
Real-World Evidence (RWE) that is of sufficient quality will enhance the information environment in the post-authorization phase of the drug life cycle and augment understanding of the benefit-risk profile of marketed drugs.
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